Showing 1–50 of 254 results for author: Sun, Y

Understanding Pulsar Wind Nebulae with the SKA

Authors: Joseph D. Gelfand, C. -Y. Ng, B. Posselt, Mallory S. E. Roberts, Subir Bhattacharyya, Shi Dai, Rene Breton, Benjamin Stappers, Andrea Possenti, Jason Hessels, Yifan Sun, Moaz Abdelmaguid

Abstract: Produced by the interaction between the ``pulsar wind'' powered by the rotational energy of a neutron star and its surroundings, the study of pulsar wind nebulae (PWNe) provides vital insight into the physics of neutron star magnetospheres and ultra-relativistic outflows. Spatially-resolved studies of the continuum and polarized radio emission of these sources are vital for understanding the produ… ▽ More Produced by the interaction between the ``pulsar wind'' powered by the rotational energy of a neutron star and its surroundings, the study of pulsar wind nebulae (PWNe) provides vital insight into the physics of neutron star magnetospheres and ultra-relativistic outflows. Spatially-resolved studies of the continuum and polarized radio emission of these sources are vital for understanding the production of $e^\pm$ in the magnetospheres of neutron stars, the acceleration of these particles to $\gtrsim10^{15}~{\rm eV}$ energies, and the propagation of these particles within the PWN as well as the surrounding interstellar medium. The significant improvements in sensitivity, dynamic range, timing capabilities offered by the Square Kilometer Array have the potential to significantly improve our understanding of the origin of some of the highest energy particles produced in the Milky Way. △ Less

Submitted 17 December, 2025; originally announced December 2025.

Comments: 14 pages

How is Cold Gas Loaded into Galactic Nuclear Outflows?

Authors: Yang Su, Xin Liu, Shiyu Zhang, Ji Yang, Yan Sun, Shaobo Zhang, Fujun Du, Xin Zhou, Qing-Zeng Yan, Xuepeng Chen

Abstract: The origin of the multiphase gas within the Fermi/eROSITA bubbles is crucial for understanding Galactic Center (GC) feedback. We use HI4PI data to investigate the kinematics and physical properties of high-velocity clouds (HVCs) toward the GC. Our results reveal that the HVCs exhibit a distinct asymmetric distribution, closely associated with the bar-driven tilted dust lanes and the distorted over… ▽ More The origin of the multiphase gas within the Fermi/eROSITA bubbles is crucial for understanding Galactic Center (GC) feedback. We use HI4PI data to investigate the kinematics and physical properties of high-velocity clouds (HVCs) toward the GC. Our results reveal that the HVCs exhibit a distinct asymmetric distribution, closely associated with the bar-driven tilted dust lanes and the distorted overshooting streams. We propose that powerful nuclear outflows interact with these gas-rich, off-plane structures, striping and entraining cold gas from the outer Galactic regions (R_GC~0.5--1.7 kpc) rather than solely from the region of the central molecular zone (CMZ; R_GC<0.3 kpc). In this scenario, as the Galactic bar drives gas inflows along the dust lanes, nuclear outflows simultaneously break through the CMZ, sweeping up and ablating cold gas from the boundary layer of these pre-existing structures. This process naturally accounts for the observed high turbulence, complex spectral signatures, and anomalous spatial-kinematic gas patterns, as well as multiwavelength asymmetries of the bubbles. The HVCs are accelerated to about 230--340 km/s over a dynamical time of ~3--6 Myr. When the multiphase, inhomogeneous composition of the gas is included, the estimated gas outflow rate reaches ~1 Msun/yr. This value is comparable to the bar-driven inflow rate, indicating a tightly coupled gas cycle in the inner Galaxy. Our research highlights the critical role of bar-driven gas dynamics and nuclear feedback in the secular evolution of the Milky Way, offering a valuable paradigm for investigating gas cycles in external galaxies. △ Less

Submitted 15 December, 2025; originally announced December 2025.

Comments: To appear in ApJ. Comments welcome!

VLBI astrometry of radio stars to link radio and optical celestial reference frames III: 11 radio stars

Authors: Jingdong Zhang, Bo Zhang, Shuangjing Xu, Xiaofeng Mai, Mark J. Reid, Pengfei Jiang, Wen Chen, Fengchun Shu, Jinling Li, Lang Cui, Xingwu Zheng, Yan Sun, Zhaoxiang Qi

Abstract: The alignment between the radio-based International Celestial Reference Frame (ICRF) and the optical Gaia Celestial Reference Frame (Gaia-CRF) is critical for multi-waveband astronomy, yet systematic offsets at the optical bright end (G<13) limit their consistency. While radio stars offer a potential link between these frames, their utility has been restricted by the scarcity of precise Very Long… ▽ More The alignment between the radio-based International Celestial Reference Frame (ICRF) and the optical Gaia Celestial Reference Frame (Gaia-CRF) is critical for multi-waveband astronomy, yet systematic offsets at the optical bright end (G<13) limit their consistency. While radio stars offer a potential link between these frames, their utility has been restricted by the scarcity of precise Very Long Baseline Interferometry (VLBI) astrometry. In this study, we present new VLBI astrometry of 11 radio stars using the Very Long Baseline Array (VLBA), expanding the existing sample with positions, parallaxes, and proper motions measured. All 11 radio stars were detected, for 10 of which parallaxes and proper motions can be estimated, reaching a precision level of <1% in the best cases. These new samples greatly contribute to the link between ICRF and Gaia-CRF at the optical bright end. △ Less

Submitted 15 December, 2025; originally announced December 2025.

Comments: Submitted to MNRAS

Measurement of the cosmic ray nickel energy spectrum from 10 GeV/n to 2 TeV/n with the DAMPE

Authors: F. Alemanno, Q. An, P. Azzarello, F. C. T. Barbato, P. Bernardini, X. J. Bi, H. V. Boutin, I. Cagnoli, M. S. Cai, E. Casilli, J. Chang, D. Y. Chen, J. L. Chen, Z. F. Chen, Z. X. Chen, P. Coppin, M. Y. Cui, T. S. Cui, I. De Mitri, F. de Palma, A. Di Giovanni, T. K. Dong, Z. X. Dong, G. Donvito, J. L. Duan , et al. (123 additional authors not shown)

Abstract: Nickel, one of the most stable elements alongside iron, is the most abundant heavy element beyond iron in cosmic rays. With DAMPE's excellent charge resolution and broad energy range, a high-precision energy spectrum provides valuable insights into the acceleration sources of heavy nuclei and their propagation through the interstellar medium. In this analysis, we report the direct measurement of c… ▽ More Nickel, one of the most stable elements alongside iron, is the most abundant heavy element beyond iron in cosmic rays. With DAMPE's excellent charge resolution and broad energy range, a high-precision energy spectrum provides valuable insights into the acceleration sources of heavy nuclei and their propagation through the interstellar medium. In this analysis, we report the direct measurement of cosmic-ray nickel spectrum from 10 GeV/n to 2 TeV/n with nine years of flight data. The nickel spectrum is consistent with a single power law with spectral index -2.60 +/- 0.03 from 40 GeV/n to 1 TeV/n. This work provides an accurate measurement of differential flux of nickel with kinetic energy extending to TeV/n for the first time. △ Less

Submitted 12 December, 2025; originally announced December 2025.

The Milky Way Imaging Scroll Painting Survey: Data Release 1

Authors: Ji Yang, Qing-Zeng Yan, Yang Su, Shaobo Zhang, Xin Zhou, Yan Sun, Yiping Ao, Xuepeng Chen, Zhiwei Chen, Fujun Du, Min Fang, Yan Gong, Zhibo Jiang, Shengyu Jin, Binggang Ju, Chong Li, Yingjie Li, Yi Liu, Dengrong Lu, Chunsheng Luo, Yuehui Ma, Ruiqing Mao, Jixian Sun, Chen Wang, Hongchi Wang , et al. (10 additional authors not shown)

Abstract: We present the first data release (DR1) of the Milky Way Imaging Scroll Painting (MWISP) survey, a mapping in the J=(1-0) transition lines of 12CO, 13CO, and C18O toward the northern Galactic plane during 2011-2022. The MWISP survey was conducted using the PMO 13.7 m telescope at a spatial resolution of approximately 50" and a velocity resolution of 0.16 km/s at 115 GHz. DR1 fully covered 2310 squ… ▽ More We present the first data release (DR1) of the Milky Way Imaging Scroll Painting (MWISP) survey, a mapping in the J=(1-0) transition lines of 12CO, 13CO, and C18O toward the northern Galactic plane during 2011-2022. The MWISP survey was conducted using the PMO 13.7 m telescope at a spatial resolution of approximately 50" and a velocity resolution of 0.16 km/s at 115 GHz. DR1 fully covered 2310 square degrees within the Galactic longitude (l) and latitude (b) range of 9.75 deg =< l =< 229.75 deg and |b| =< 5.25 deg. The surveyed area was divided into cell units of 30'x30' for practical purposes and On-The-Fly (OTF) mapping was performed toward each target cell unit. The data were regridded into a regular 3D datacube in l-b-V_LSR with a pixel size of 30" in l-b axes and 0.16 km/s in theV_LSR axis. The median rms noise is 0.47 K, 0.25 K, and 0.25 K for 12CO, 13CO, and C18O, respectively. The equivalent 3 sigma sensitivity in 12CO luminosity is approximately 0.23 K km/s, making MWISP the most sensitive survey of its kind. In this paper, we describe the survey data, including the calibration, data cleaning, data mosaic processes, and the data products. The final mosaicked data cubes contain about 3.33x10^7 spectra (pixels) for each CO isotopologue line. Color composite images, made from the intensities of the isotopologue lines, and some concise descriptions are provided. We constructed a molecular cloud catalog based on the mosaicked 12CO data cube using the clustering algorithm DBSCAN, detecting 103,517 molecular clouds, 10,790 of which exhibit 13CO emission and 304 of which show C18O emission. Based on the histogram of voxel brightness temperature, we estimated a total 12CO flux of 7.69+/-0.38x10^7 K km/s arcmin^2, 82% of which is captured by the DBSCAN algorithm. The data, together with the cloud sample, provide unique information on molecular gas in the northern Milky Way. △ Less

Submitted 10 December, 2025; v1 submitted 9 December, 2025; originally announced December 2025.

Comments: Accepted for publication in ApJS. MWISP DR1 link: https://doi.org/10.57760/sciencedb.27351

JADES: Low Surface Brightness Galaxies at 0.4 < z < 0.8 in GOODS-S

Authors: Tristen Shields, Marcia Rieke, Kevin Hainline, Jakob M. Helton, Andrew J. Bunker, Courtney Carreira, Emma Curtis-Lake, Daniel J. Eisenstein, Benjamin D. Johnson, Pierluigi Rinaldi, Brant Robertson, Christina C. Williams, Christopher N. A. Willmer, Yang Sun

Abstract: Low surface brightness galaxies (LSBs) are an important class of galaxies that allow us to broaden our understanding of galaxy formation and test various cosmological models. We present a survey of low surface brightness galaxies at $0.4 < z_{\rm phot} < 0.8$ in the GOODS-S field using JADES data. We model LSB surface brightness profiles, identifying those with $\barμ_{\rm eff} > 24$ mag arcsec… ▽ More Low surface brightness galaxies (LSBs) are an important class of galaxies that allow us to broaden our understanding of galaxy formation and test various cosmological models. We present a survey of low surface brightness galaxies at $0.4 < z_{\rm phot} < 0.8$ in the GOODS-S field using JADES data. We model LSB surface brightness profiles, identifying those with $\barμ_{\rm eff} > 24$ mag arcsec$^{-2}$ in the F200W JWST/NIRCam filter. We study the spatial distribution, number density, Sérsic profile parameters, and rest-frame colours of these LSBs. We compare the photometrically-derived star formation histories, mass-weighted ages, and dust attenuations of these galaxies with a high surface brightness (HSB) sample at similar redshift and a lower redshift ($z_{\rm phot} < 0.4$) LSB sample, all of which have stellar masses $\lesssim 10^8 M_{\odot}$. We find that both the high and the low redshift LSB samples have low star formation (SFR$_{100} \lesssim 0.01$ $M_{\odot}$ yr$^{-1}$) compared with the HSB sample (SFR$_{100} \gtrsim 0.01$ $M_{\odot}$ yr$^{-1}$). The star formation histories show that the LSBs and HSBs possibly come from the same progenitors at $z \gtrsim 2$, though the histories are not well constrained for the LSB samples. The LSBs appear to have minimal dust, with most of our LSB samples showing $A_V < 1$ mag. JWST has pushed our understanding of LSBs beyond the local Universe. △ Less

Submitted 21 November, 2025; originally announced November 2025.

JW-Flare: Accurate Solar Flare Forecasting Method Based on Multimodal Large Language Models

Authors: Mingfu Shao, Hui Wang, Yuyang Li, Jiaben Lin, Jifeng Liu, Baolin Tan, Juan Guo, Yin Zhang, Jing Huang, Jiangtao Su, Yingzi Sun, Haiqing Xu, Jie Chen, Suo Liu, Yuanyong Deng, Liyue Tong, Yang Bai, Cunshi Wang, Kaifan Ji, Yuqing Zhou

Abstract: Solar flares, the most powerful explosive phenomena in the solar system, may pose significant hazards to spaceborne satellites and ground-based infrastructure. Despite decades of intensive research, reliable flare prediction remains a challenging task. Large Language Models, as a milestone in artificial intelligence, exhibit exceptional general knowledge and next-token prediction capabilities. Her… ▽ More Solar flares, the most powerful explosive phenomena in the solar system, may pose significant hazards to spaceborne satellites and ground-based infrastructure. Despite decades of intensive research, reliable flare prediction remains a challenging task. Large Language Models, as a milestone in artificial intelligence, exhibit exceptional general knowledge and next-token prediction capabilities. Here we introduce JW-Flare, the first Multimodal Large Language Models (MLLMs) explicitly trained for solar flare forecasting through fine-tuning on textual physic parameters of solar active regions and magnetic field images. This method demonstrates state-of-the-art (SOTA) performance for large flares prediction on the test dataset. It effectively identifies all 79 X-class flares from 18,949 test samples, yielding a True Skill Statistic (TSS) of 0.95 and a True Positive Rate (TPR) of 1.00, outperforming traditional predictive models. We further investigate the capability origins of JW-Flare through explainability experiments, revealing that solar physics knowledge acquired during pre-training contributes to flare forecasting performance. Additionally, we evaluate models of different parameter scales, confirming the Scaling_Law of Large Language Models in domain-specific applications, such as solar physics. This study marks a substantial advance in both the scale and accuracy of solar flare forecasting and opens a promising avenue for AI-driven methodologies in broader scientific domains. △ Less

Submitted 11 November, 2025; originally announced November 2025.

Comments: 12 pages, 5 figures

JADES Dark Horse: demonstrating high-multiplex observations with JWST/NIRSpec dense-shutter spectroscopy in the JADES Origins Field

Authors: Francesco D'Eugenio, Erica J. Nelson, Daniel J. Eisenstein, Roberto Maiolino, Stefano Carniani, Jan Scholtz, Mirko Curti, Christopher N. A. Willmer, Andrew J. Bunker, Jakob M. Helton, Ignas Juodžbalis, Fengwu Sun, Sandro Tacchella, Santiago Arribas, Alex J. Cameron, Stéphane Charlot, Emma Curtis-Lake, Kevin Hainline, Benjamin D. Johnson, Brant Robertson, Christina C. Williams, Chris Willott, William M. Baker, Jacopo Chevallard, A. Lola Danhaive , et al. (17 additional authors not shown)

Abstract: We present JWST/NIRSpec dense-shutter spectroscopy (DSS). This novel observing strategy with the NIRSpec micro-shutter assembly (MSA) deliberately permits a high number of controlled spectral overlaps to reach extreme multiplex while retaining the low background of slit spectroscopy. In a single configuration over the JADES Origins Field we opened shutters on all faint (F444W<30 mag) z… ▽ More We present JWST/NIRSpec dense-shutter spectroscopy (DSS). This novel observing strategy with the NIRSpec micro-shutter assembly (MSA) deliberately permits a high number of controlled spectral overlaps to reach extreme multiplex while retaining the low background of slit spectroscopy. In a single configuration over the JADES Origins Field we opened shutters on all faint (F444W<30 mag) z$_{\rm phot}$>3 candidates in the MSA, prioritising emission-line science and rejecting only bright continuum sources. Using 33.6 and 35.8 ks on-source in G235M and G395M, we observed a single mask with ~850 sources, obtaining secure spectroscopic redshifts for ~540 galaxies over 2.5<z<8.9. The per-configuration target density in DSS mode is 4-5x higher than standard no- and low-overlap MSA strategies (<200 sources), with no loss in redshift precision or accuracy. Line-flux sensitivities are 30 percent lower at fixed exposure time, matching the expected increase in background noise, but the gain in survey speed is 5x in our setup, more than justifying the penalty. The measured line sensitivity exceeds NIRCam WFSS by a minimum factor of ~5 (i.e. ~25 in exposure time) at $λ$~4 $μ$m, demonstrating that controlled overlap is a compelling method to gain deep, wide-band spectra for large samples. Crucially, we envisage the MSA could deliver even higher target allocation densities than what used here. We derive Balmer-line based SFRs, gas-phase metallicities (including a large sample suitable for strong-line calibrations), and identify rare sources (mini-quenched systems and broad-line AGN). This approach is immediately applicable wherever deep imaging enables robust pre-selection and astrometry, providing an efficient method to obtain large samples of faint emission-line galaxies, a compelling middle ground between the completeness of slitless surveys and the sensitivity and bandwidth of NIRSpec/MSA. △ Less

Submitted 13 October, 2025; originally announced October 2025.

Comments: 22 pages, 21 figures, 2 tables. Submitted to MNRAS

Investigating the Influence of Radiative Feedback in Bright-Rimmed Cloud 44

Authors: Rishi C, Neelam Panwar, Thomas J. Haworth, Yan Sun, Saurabh Sharma, R. K. Yadav, D. K. Ojha, H. P. Singh, Jessy Jose, Ajay Kumar Singh, Jincen Jose, Shubham Yadav

Abstract: Radiative feedback from massive stars plays a central role in the evolution of molecular clouds and the interstellar medium. This paper presents a multi-wavelength analysis of the bright-rimmed cloud, BRC 44, which is located at the periphery of the Hii region Sh2-145 and is excited by the massive stars in the region. We use a combination of archival and newly obtained infrared data, along with ne… ▽ More Radiative feedback from massive stars plays a central role in the evolution of molecular clouds and the interstellar medium. This paper presents a multi-wavelength analysis of the bright-rimmed cloud, BRC 44, which is located at the periphery of the Hii region Sh2-145 and is excited by the massive stars in the region. We use a combination of archival and newly obtained infrared data, along with new optical observations, to provide a census of young stellar objects (YSOs) in the region and to estimate stellar parameters such as age, mass etc. The spatial distribution of YSOs visible in the optical wavelength suggests that they are distributed in separate clumps compared to the embedded YSOs and are relatively older. Near-Infrared (NIR) spectroscopy of four YSOs in this region using the TANSPEC mounted on the 3.6m Devasthal Optical Telescope (DOT) confirms their youth. From Spectral Energy Distribution (SED) fitting, most of the embedded YSO candidates are in their early stage of evolution, with the majority of them in their Class II and some in Class I stage. The relative proper motions of the YSOs with respect to the ionizing source are indicative of the rocket effect in the BRC. The 12CO, 13CO, and C18O observations with the Purple Mountain Observatory are used to trace the distribution of molecular gas in the region. A comparison of the cold molecular gas distribution with simple analytical model calculations shows that the cloud is in the compression stage, and massive stars may be influencing the formation of young embedded stars in the BRC region due to radiative feedback. △ Less

Submitted 9 October, 2025; originally announced October 2025.

Comments: 28 pages, 11 figures. Accepted for publication in ApJ

Confirming Near- to Mid-IR Photometrically-Identified Obscured AGNs in the JWST era

Authors: George H. Rieke, Yang Sun, Jianwei Lyu, Christopher N. A. Willmer, Yongda Zhu, Pierluigi Rinaldi, Meredith A. Stone, Kevin N. Hainline, Pablo G. Perez-Gonzalez

Abstract: We evaluate the underlying assumptions for the identification of Active Galactic Nuclei (AGNs) through near- and mid-infrared photometry and spectral energy distribution (SED) fitting out to z ~ 3. For massive galaxies, log(M) > 9.5, our high resolution spectra of the rest optical range generally confirm the results of SED fitting, which relies primarily on excesses above the stellar emission betw… ▽ More We evaluate the underlying assumptions for the identification of Active Galactic Nuclei (AGNs) through near- and mid-infrared photometry and spectral energy distribution (SED) fitting out to z ~ 3. For massive galaxies, log(M) > 9.5, our high resolution spectra of the rest optical range generally confirm the results of SED fitting, which relies primarily on excesses above the stellar emission between 1 and 6 microns to identify AGN. However, the method is undermined if the redshift used for the SED fitting is incorrect. Low mass galaxies, log(M) < 9:5, can contain relatively warm dust that emits in the 4 - 6 micron range. We show that the potential contamination of AGN samples by purely star forming low-mass galaxies can be avoided by the use of the infrared properties of Haro 11 as a limiting star-forming SED template. However, relatively few star forming galaxies emit as strongly in the 3 - 6 micron range as this template, so this could result in missing some obscured AGNs to avoid a minor contamination. Including the behavior of the galaxies at rest lamda ~ 13.5 microns can mitigate this problem and yield more complete samples of bona fide AGN. JWST/MIRI supports this approach out to z ~ 0.6. △ Less

Submitted 8 October, 2025; originally announced October 2025.

Comments: ApJ, in press

JADES Data Release 4 -- Paper II: Data reduction, analysis and emission-line fluxes of the complete spectroscopic sample

Authors: J. Scholtz, S. Carniani, E. Parlanti, F. D'Eugenio, E. Curtis-Lake, P. Jakobsen, A. J. Bunker, A. J. Cameron, S. Arribas, W. M. Baker, S. Charlot, J. Chevellard, C. Circosta, M. Curti, Q. Duan, D. J. Eisenstein, K. Hainline, Z. Ji, B. D. Johnson, G. C. Jones, N. Kumari, R. Maiolino, M. V. Maseda, M. Perna, P. G. Pérez-González , et al. (16 additional authors not shown)

Abstract: We present the fourth data release of JADES, the JWST Advanced Deep Extragalactic Survey, providing deep spectroscopic observations in the two GOODS fields. A companion paper presents the target selection, spectroscopic redshifts and success rates, and in this paper, we discuss the data reduction and present emission line flux measurements. The spectroscopy in this work consists of medium-depth, d… ▽ More We present the fourth data release of JADES, the JWST Advanced Deep Extragalactic Survey, providing deep spectroscopic observations in the two GOODS fields. A companion paper presents the target selection, spectroscopic redshifts and success rates, and in this paper, we discuss the data reduction and present emission line flux measurements. The spectroscopy in this work consists of medium-depth, deep and ultradeep NIRSpec/MSA spectra of 5,190 targets, covering the spectral range $0.6\text{--}5.5$~\mum and observed with both the low-dispersion prism ($R=30\text{--}300$) and all three medium-resolution gratings ($R=500\text{--}1,500$). We describe the data reduction, analysis and description of the data products included in this data release. In total, we measured 3,297 robust redshifts out of 5,190 targets, spanning a redshift range from $z=0.5$ up to $z=14.2$, including 974 at $z>4$. This data release includes 1-d and 2-d fully reduced spectra with 3 and 5 pixel extractions, with slit-loss corrections and background subtraction optimized for point sources. Furthermore, we provide redshifts and $S/N>5$ emission-line flux catalogues for the prism and grating spectra, as well as new guidelines to use these data products. Lastly, we are launching a new JADES Online Database, designed to enable quick selection and browsing of this data release. Altogether, these data provide the largest statistical sample to date to characterise the properties of galaxy populations across Cosmic time. △ Less

Submitted 1 October, 2025; originally announced October 2025.

Comments: Submitted to MNRAS. Data available to download at https://jades.herts.ac.uk/DR4/ with access to the JADES online database at https://jades.herts.ac.uk/search/. arXiv admin note: text overlap with arXiv:2404.06531

JADES: The Star Formation and Dust Attenuation Properties of Galaxies at 3<z<7

Authors: Charity Woodrum, Irene Shivaei, Joris Witstok, Aayush Saxena, Charlotte Simmonds, Jan Scholtz, Rachana Bhatawdekar, Andrew J. Bunker, Stéfano Carniani, Stephane Charlot, Mirko Curti, Emma Curtis-Lake, Jacopo Chevallard, Francesco D'Eugenio, Kevin Hainline, Jakob M. Helton, Roberto Maiolino, Michele Perna, Pierluigi Rinaldi, Brant Robertson, Amber Straughn, Yang Sun, Sandro Tacchella, Christina C. Williams, Chris Willott , et al. (1 additional authors not shown)

Abstract: We present the star formation and dust attenuation properties for a sample of 602 galaxies at redshifts $\rm{3<z<7}$, as part of the JADES survey. Our analysis is based on measurements of the $\rm{H}α/\rm{H}β$ Balmer Decrement using medium resolution (R$\sim$1000) spectroscopic observations with the JWST/NIRSpec Micro-Shutter Assembly. Stellar masses and star formation rates (SFRs) are inferred wi… ▽ More We present the star formation and dust attenuation properties for a sample of 602 galaxies at redshifts $\rm{3<z<7}$, as part of the JADES survey. Our analysis is based on measurements of the $\rm{H}α/\rm{H}β$ Balmer Decrement using medium resolution (R$\sim$1000) spectroscopic observations with the JWST/NIRSpec Micro-Shutter Assembly. Stellar masses and star formation rates (SFRs) are inferred with \texttt{Prospector} using deep multi-band imaging. We utilize the Balmer decrement to measure dust-corrected H$α$-based SFRs, taking into account the subsolar metallicities observed in galaxies at high redshift. We confirm, with our large sample size, that the correlation between the Balmer decrement and stellar mass is already established out to $z\sim7$. We find that the relation between the Balmer decrement and stellar mass does not significantly evolve from the local universe to $z\sim7$. We investigate the UV slope as a function of the Balmer optical depth and find that the best-fit correlation for our high redshift sample is sSFR dependent and significantly different at high redshift when compared to galaxies at $z\approx 0$ and $z \approx 2$. For the highest sSFR galaxies in our sample, there is no significant correlation between the UV slope and Balmer optical depth. This is evidence that the UV slope should be used with great caution to correct for dust in high redshift galaxies. △ Less

Submitted 30 September, 2025; originally announced October 2025.

Comments: 13 pages, 5 figures, submitted to ApJ

Constraining inhomogeneous energy injection from annihilating dark matter and primordial black holes with 21-cm cosmology

Authors: Yitian Sun, Joshua W. Foster, Julian B. Muñoz

Abstract: The cosmic dawn 21-cm signal is a highly sensitive probe of any process which injects energy into the intergalactic medium, enabling novel searches for anomalous energy injection by through dark matter interactions. In addition to modifying the global 21-cm signal, these processes would leave distinct imprints on the frequency-resolved 21-cm power spectrum with a morphology jointly set by the time… ▽ More The cosmic dawn 21-cm signal is a highly sensitive probe of any process which injects energy into the intergalactic medium, enabling novel searches for anomalous energy injection by through dark matter interactions. In addition to modifying the global 21-cm signal, these processes would leave distinct imprints on the frequency-resolved 21-cm power spectrum with a morphology jointly set by the time- and spatial-dependence of energy emission and absorption. In this work, we extend the DM21cm code package, which models the effects of spatially inhomogeneous energy emission and deposition on 21-cm cosmology, to study three well-motivated scenarios which 21-cm measurements are particularly well-suited to probe: dark matter annihilation through $p$-wave processes, the Hawking radiation of light primordial black holes, and energetic emission from accreting solar-mass primordial black holes. We project sensitivities to each of these scenarios, demonstrating that leading or near leading sensitivity to each can be achieved through 21-cm probes. We also make public our updates to the DM21cm code package that enable it to accommodate energy injection processes for general continuum spectra with arbitrary spatial and temporal dependence in an accompanying release. △ Less

Submitted 26 September, 2025; originally announced September 2025.

Comments: 25 pages, 10 figures. Code available at https://github.com/yitiansun/DM21cm

Investigation of hadronic cross sections of cosmic ray carbon and oxygen on BGO from 200 GeV to 10 TeV energy at the DAMPE experiment

Authors: F. Alemanno, Q. An, P. Azzarello, F. C. T. Barbato, P. Bernardini, X. J. Bi, H. Boutin, I. Cagnoli, M. S. Cai, E. Casilli, E. Catanzani, J. Chang, D. Y. Chen, J. L. Chen, Z. F. Chen, Z. X. Chen, P. Coppin, M. Y. Cui, T. S. Cui, Y. X. Cui, I. De Mitri, F. de Palma, A. Di Giovanni, T. K. Dong, Z. X. Dong , et al. (122 additional authors not shown)

Abstract: The Dark Matter Particle Explorer (DAMPE) has made significant progress in measuring the fluxes of cosmic rays. These new measurements are pivotal in advancing our understanding of the origins and propagation mechanisms of cosmic rays. The bismuth germanium oxide (BGO) calorimeter plays a crucial role in these measurements, particularly in the precise determination of cosmic ray fluxes. However, f… ▽ More The Dark Matter Particle Explorer (DAMPE) has made significant progress in measuring the fluxes of cosmic rays. These new measurements are pivotal in advancing our understanding of the origins and propagation mechanisms of cosmic rays. The bismuth germanium oxide (BGO) calorimeter plays a crucial role in these measurements, particularly in the precise determination of cosmic ray fluxes. However, for a calorimetric experiment like DAMPE, uncertainties in hadronic models persist as a major barrier in achieving more accurate measurements of fluxes of cosmic ray nuclei. This study centers on the measurement of the inelastic hadronic cross sections of carbon and oxygen nuclei interacting with BGO crystals target over an extensive energy range, spanning from 200 GeV to 10 TeV. For carbon nuclei interacting with the BGO target, the measurements of the cross sections have achieved a total relative uncertainty of less than 10% below 8 TeV for carbon, and below 3 TeV for oxygen. For oxygen nuclei, the same level of precision was attained below 3 TeV. Additionally, we compare the experimental results with Geant4 and FLUKA simulations to validate the accuracy and consistency of these simulation tools. Through comprehensive analysis of the inelastic hadronic interaction cross sections, this research provides validation for the hadronic interaction models used in DAMPE's cosmic-ray flux measurements. △ Less

Submitted 21 September, 2025; originally announced September 2025.

Scientific Objectives of the Xue-shan-mu-chang 15-meter Submillimeter Telescope

Authors: XSMT Project Collaboration Group, Yiping Ao, Jin Chang, Zhiwei Chen, Xiangqun Cui, Kaiyi Du, Fujun Du, Yan Gong, Zhanwen Han, Gregory Herczeg, Luis C. Ho, Jie Hu, Yipeng Jing, Sihan Jiao, Binggang Ju, Jing Li, Xiaohu Li, Xiangdong Li, Lingrui Lin, Zhenhui Lin, Daizhong Liu, Dong Liu, Guoxi Liu, Zheng Lou, Dengrong Lu , et al. (26 additional authors not shown)

Abstract: Submillimeter astronomy is poised to revolutionize our understanding of the Universe by revealing cosmic phenomena hidden from optical and near-infrared observations, particularly those associated with interstellar dust, molecular gas, and star formation. The Xue-shan-mu-chang 15-meter submillimeter telescope (XSMT-15m), to be constructed at a premier high-altitude site (4813 m) in Qinghai, China,… ▽ More Submillimeter astronomy is poised to revolutionize our understanding of the Universe by revealing cosmic phenomena hidden from optical and near-infrared observations, particularly those associated with interstellar dust, molecular gas, and star formation. The Xue-shan-mu-chang 15-meter submillimeter telescope (XSMT-15m), to be constructed at a premier high-altitude site (4813 m) in Qinghai, China, marks a major milestone for Chinese astronomy, establishing the China mainland's first independently developed, world-class submillimeter facility. Equipped with state-of-the-art instruments, XSMT-15m will address a diverse range of frontier scientific questions spanning extragalactic astronomy, Galactic structure, time-domain astrophysics, and astrochemistry. In synergy with current and forthcoming observatories, XSMT-15m will illuminate the formation and evolution of galaxies, unravel the physical and chemical processes shaping the interstellar medium, and explore transient phenomena in the submillimeter regime. These capabilities will advance our understanding across extragalactic astronomy, Galactic ecology, astrochemistry, and time-domain astrophysics, inaugurating a new era for submillimeter research in China and the northern hemisphere. △ Less

Submitted 17 September, 2025; originally announced September 2025.

Comments: Accepted by Science China Physics, Mechanics & Astronomy

Quasar Radiative Feedback May Suppress Galaxy Growth on Intergalactic Scales at $z = 6.3$

Authors: Yongda Zhu, Eiichi Egami, Xiaohui Fan, Fengwu Sun, George D. Becker, Christopher Cain, Huanqing Chen, Anna-Christina Eilers, Yoshinobu Fudamoto, Jakob M. Helton, Xiangyu Jin, Maria Pudoka, Andrew J. Bunker, Zheng Cai, Jaclyn B. Champagne, Zhiyuan Ji, Xiaojing Lin, Weizhe Liu, Hai-Xia Ma, Zheng Ma, Roberto Maiolino, George H. Rieke, Marcia J. Rieke, Pierluigi Rinaldi, Yang Sun , et al. (5 additional authors not shown)

Abstract: We present observational evidence that intense ionizing radiation from a luminous quasar suppresses nebular emission in nearby galaxies on intergalactic scales at $z=6.3$. Using JWST/NIRCam grism spectroscopy from the SAPPHIRES and EIGER programs, we identify a moderate but statistically significant decline in [O\,\textsc{iii}]\,$\lambda5008$ luminosity relative to the UV continuum (… ▽ More We present observational evidence that intense ionizing radiation from a luminous quasar suppresses nebular emission in nearby galaxies on intergalactic scales at $z=6.3$. Using JWST/NIRCam grism spectroscopy from the SAPPHIRES and EIGER programs, we identify a moderate but statistically significant decline in [O\,\textsc{iii}]\,$\lambda5008$ luminosity relative to the UV continuum ($L_{5008}/L_{1500}$) among galaxies within $\sim$ 7 comoving Mpc (cMpc) of the quasar J0100$+$2802, the most UV-luminous quasar known at this epoch ($M_{1450}=-29.26$). While $L_{1500}$ remains roughly constant with transverse distance, $L_{5008}$ increases significantly, suggesting suppression of very recent star formation toward the quasar. The effect persists after controlling for completeness, local density, and UV luminosity, and correlates with the projected photoionization-rate profile $Γ_{\mathrm{qso}}$. A weaker but directionally consistent suppression in $L_{5008}/L_{1500}$ is also observed along the line of sight. The transverse suppression radius ($\sim$ 7 cMpc) implies a recent radiative episode with a cumulative duration $\sim$ 3.1 Myr, shorter than required for thermal photoheating to dominate and thus more naturally explained by rapid H$_2$ photodissociation and related radiative processes. Environmental effects alone appear insufficient to explain the signal. Our results provide direct, geometry-based constraints on large-scale quasar radiative feedback and recent quasar lifetimes. △ Less

Submitted 19 November, 2025; v1 submitted 29 August, 2025; originally announced September 2025.

Comments: Accepted for publication in The Astrophysical Journal Letters (ApJL); to be presented at AAS 247

IGR J17091-3624: Newly Formed Periodic Dips and Multiwavelength Activity During the 2025 Outburst

Authors: Zikun Lin, Yanan Wang, Shuyuan Wei, Yongkang Sun, Long Ji, Samaporn Tinyanont, Meng Sun, Song Wang, Diego Altamirano, Douglas J. K. Buisson, Wenxiong Li, Qian Chen, Jifeng Liu, Shuang-Nan Zhang, Wei Wang, Zhen Guo, Pathompong Butpan, Rungrit Anutarawiramkul

Abstract: The black hole low-mass X-ray binary (LMXB) candidate IGR J17091-3624 experienced a hard-state-only outburst in 2025. In this paper, we show that IXPE detected a series of intermittent X-ray dips, spanning a total interval of ~1 day. Subsequent observations with NICER, EP, NuSTAR, and Swift reveal that these dips recur with a period of 2.83$\pm$0.07 days and are accompanied by an increase in spect… ▽ More The black hole low-mass X-ray binary (LMXB) candidate IGR J17091-3624 experienced a hard-state-only outburst in 2025. In this paper, we show that IXPE detected a series of intermittent X-ray dips, spanning a total interval of ~1 day. Subsequent observations with NICER, EP, NuSTAR, and Swift reveal that these dips recur with a period of 2.83$\pm$0.07 days and are accompanied by an increase in spectral hardness. This is the first time such quasi-periodic dipping behavior has been observed in this target since discovery. Our spectral analysis shows that the dips can be explained by obscuration from an ionized absorber characterized by an ionization parameter of $logξ$ ~1-3 erg cm s$^{-1}$ and an equivalent hydrogen column density of $N^{\rm zxipcf}_{\rm H}$~(1-30)$\times10^{22}$ cm$^{-2}$. The periodic reappearance of the absorber is likely caused by obscuring material located in the outer accretion disk, modulated by the binary orbital period. If confirmed, this period would suggest that the donor star in IGR J17091-3624 has deviated from the standard main-sequence evolutionary path and is likely a (partially) stripped giant. In the optical band, no significant periodicity or correlation with the X-ray dips was detected, whereas the radio counterpart exhibited a flat to steep spectrum, in contrast to the inverted spectrum typically observed during the hard state of LMXBs. △ Less

Submitted 19 December, 2025; v1 submitted 24 August, 2025; originally announced August 2025.

Comments: 17 pages, 10 figures, 1 tables

Molecular Gas Distribution toward the Inner and Outer Galaxy Revealed by MWISP -- the Galactic Longitude 45°--60°and 120°--130°

Authors: Xin Zhou, Ji Yang, Yan Sun, Qing-Zeng Yan, Lixia Yuan, Yang Su, Xuepeng Chen, Shaobo Zhang

Abstract: Molecular clouds (MCs) are cradles of star and planet formation, thereby playing an important role in the evolution of galaxies. Based on the unbiased Milky Way Imaging Scroll Painting (MWISP) survey data of $^{12}$CO, $^{13}$CO, and C$^{18}$O (J=1--0) line emission in two regions toward the inner and outer Galaxy, i.e. the G50 ($44.75°\le l \le 60.25°$) and G120 ($119.75°\le l \le 130.25°$) regio… ▽ More Molecular clouds (MCs) are cradles of star and planet formation, thereby playing an important role in the evolution of galaxies. Based on the unbiased Milky Way Imaging Scroll Painting (MWISP) survey data of $^{12}$CO, $^{13}$CO, and C$^{18}$O (J=1--0) line emission in two regions toward the inner and outer Galaxy, i.e. the G50 ($44.75°\le l \le 60.25°$) and G120 ($119.75°\le l \le 130.25°$) regions, the distribution of molecular gas is studied. Both regions have Galactic latitudes of $|b| \le 5.25°$. A catalog containing 24724 MCs is constructed from the data. In our proximity, several molecular structures with large angular scales and small velocity dispersions are discovered, resembling curtains of mist. Beyond the nearby molecular gas, a clear aggregation of MCs along coherent structures in the Galactic plane is visible, sketching spiral arm structures. Nevertheless, the aggregation of MCs is also detected in the inter-arm region between the Perseus and Outer arms in the G50 region. The Galactic molecular disk in this inter-arm region is found to be thinner than that in the adjacent spiral arm region. In addition, the thickness of the Galactic molecular disk examined here is found to be correlated with the warp of it, indicating their homologous origins. The molecular disk has a typical thickness of ~220 pc in the inner Galaxy. Moreover, the dispersion of the MC systemic velocity decreases with increasing galactocentric radius, resulting in lower kinematic distance uncertainties at larger radii. However, the Perseus arm segment in the G120 region exhibits a relatively large cloud-to-cloud velocity dispersion and split components in its MC velocity distribution. △ Less

Submitted 20 August, 2025; originally announced August 2025.

Comments: 29 pages, 16 figures, 2 table, accepted for publication in The Astronomical Journal

SMILES Data Release II: Probing Galaxy Evolution during Cosmic Noon and Beyond with NIRSpec Medium-Resolution Spectra

Authors: Yongda Zhu, Nina Bonaventura, Yang Sun, George H. Rieke, Stacey Alberts, Jianwei Lyu, Irene Shivaei, Jane E. Morrison, Zhiyuan Ji, Eiichi Egami, Jakob M. Helton, Marcia J. Rieke, Pierluigi Rinaldi, Fengwu Sun, Christopher N. A. Willmer

Abstract: We present the second data release of the Systematic Mid-Infrared Instrument (MIRI) Legacy Extragalactic Survey (SMILES), focusing on JWST/NIRSpec medium-resolution spectroscopy of galaxies across cosmic time. This release includes spectroscopic observations of 166 galaxies spanning $0 < z < 7.5$, sampling star-forming galaxies, quiescent systems, and active galactic nuclei (AGN), with an emphasis… ▽ More We present the second data release of the Systematic Mid-Infrared Instrument (MIRI) Legacy Extragalactic Survey (SMILES), focusing on JWST/NIRSpec medium-resolution spectroscopy of galaxies across cosmic time. This release includes spectroscopic observations of 166 galaxies spanning $0 < z < 7.5$, sampling star-forming galaxies, quiescent systems, and active galactic nuclei (AGN), with an emphasis on galaxies at cosmic noon ($z \sim 1$-3). We describe the target selection strategy, the observational setup with the G140M/F100LP and G235M/F170LP gratings, and the data calibration process. The final data products include the reduced spectra, redshift catalog, emission-line catalogs produced with \texttt{GELATO} for emission-line galaxies and \texttt{pPXF} fits for quiescent systems, and ancillary spectral energy distribution (SED) fit results derived from multi-band photometry. The SMILES NIRSpec dataset enables investigations of obscured AGN, multi-phase outflows, ionizing properties, and the role of environment in galaxy evolution. △ Less

Submitted 9 December, 2025; v1 submitted 17 August, 2025; originally announced August 2025.

Comments: Accepted for publication in ApJ. The data products can be found at https://github.com/ydzhuastro/smiles_dr2 before publishing on STScI/MAST; DR1 (MIRI) can be found at https://github.com/staceyalberts/JWST-SMILES and http://dx.doi.org/10.17909/et3f-zd57

CU-JADE: A Method for Traversing Extinction Jumps along the Line of Sight

Authors: Shiyu Zhang, Yang Su, Xuepeng Chen, Min Fang, Fujun Du, Shaobo Zhang, Qing-Zeng Yan, Xin Liu, Miaomiao Zhang, Yan Sun, Ji Yang

Abstract: Although interstellar dust extinction serves as a powerful distance estimator, the solar system's location within the Galactic plane complicates distance determinations, especially for molecular clouds (MCs) at varying distances along the line of sight (LoS). The presence of complex extinction patterns along the LoS introduces degeneracies, resulting in less accurate distance measurements to overl… ▽ More Although interstellar dust extinction serves as a powerful distance estimator, the solar system's location within the Galactic plane complicates distance determinations, especially for molecular clouds (MCs) at varying distances along the line of sight (LoS). The presence of complex extinction patterns along the LoS introduces degeneracies, resulting in less accurate distance measurements to overlapping MCs in crowded regions of the Galactic plane. In this study, we develop the CUSUM-based Jump-point Analysis for Distance Estimation (CU-JADE), a novel method designed to help mitigate these observational challenges. The key strengths of CU-JADE include: (1) sensitivity to detect abrupt jumps in Distance-$A_λ$ ($D$-$A$) datasets, (2) minimal systematic errors as demonstrated on both mock and observed data, and (3) the ability to combine CUSUM analysis with multiwavelength data to improve the completeness of distance measurements for nearby gas structures, even for extinction values as low as $ΔA_{V} \gtrsim 0.15$ mag. By combining CO survey data with a large sample of stars characterized by high-precision parallaxes and extinctions, we uncovered the multilayered molecular gas distribution in the high-latitude Cepheus region. We also determined accurate distances to MCs beyond the Cygnus Rift by analyzing the intricate structure of gas and extinction within the Galactic plane. Additionally, we constructed a full-sky 3D extinction map extending to 4 kpc, which provides critical insights into dense interstellar medium components dominated by molecular hydrogen. These results advance our understanding of the spatial distribution and physical properties of MCs across the Milky Way. △ Less

Submitted 20 August, 2025; v1 submitted 23 July, 2025; originally announced July 2025.

Comments: To be published in AJ (doi: 10.3847/1538-3881/adf49b)

Beyond the Dot: an LRD-like nucleus at the Heart of an IR-Bright Galaxy and its implications for high-redshift LRDs

Authors: Pierluigi Rinaldi, George H. Rieke, Zihao Wu, Carys J. E. Gilbert, Fabio Pacucci, Luigi Barchiesi, Stacey Alberts, Stefano Carniani, Andrew J. Bunker, Rachana Bhatawdekar, Francesco D'Eugenio, Zhiyuan Ji, Benjamin D. Johnson, Kevin Hainline, Vasily Kokorev, Nimisha Kumari, Edoardo Iani, Jianwei Lyu, Roberto Maiolino, Eleonora Parlanti, Brant E. Robertson, Yang Sun, Cristian Vignali, Christina C. Williams, Christopher N. A. Willmer , et al. (1 additional authors not shown)

Abstract: Little Red Dots (LRDs) are compact, red sources discovered by JWST at high redshift ($z \gtrsim 4$), marked by distinctive "V-shaped" spectral energy distributions (SEDs) and often interpreted as rapidly accreting AGNs. Their evolution remains unclear, as identifying counterparts at lower redshifts is challenging. We present WISEA J123635.56+621424.2 (here dubbed {\it the Saguaro}), a $z=2.0145$ g… ▽ More Little Red Dots (LRDs) are compact, red sources discovered by JWST at high redshift ($z \gtrsim 4$), marked by distinctive "V-shaped" spectral energy distributions (SEDs) and often interpreted as rapidly accreting AGNs. Their evolution remains unclear, as identifying counterparts at lower redshifts is challenging. We present WISEA J123635.56+621424.2 (here dubbed {\it the Saguaro}), a $z=2.0145$ galaxy in GOODS-North, as a possible analog of high-redshift LRDs and a potential missing link in their evolutionary path toward lower-redshift systems. It features a compact LRD-like nucleus surrounded by a face-on spiral host. Its connection to LRDs includes that: (1) its nuclear spectrum shows a clear "V-shaped" SED; and (2) when redshifted to $z=7$, surface brightness dimming makes the host undetectable, thus mimicking an LRD. This suggests that high-redshift LRDs may be embedded in extended hosts. To test this, we stack rest-frame UV images of 99 photometrically selected LRDs, revealing faint, diffuse emission. Stacking in redshift bins reveals mild radial growth, consistent with the expected galaxy size evolution. A simple analytic model confirms that surface brightness dimming alone can explain their compact appearance. Lastly, we show that {\it the Saguaro} is not unique by describing similar objects from the literature at $z\lesssim3.5$. Taken together, our results support a scenario in which LRDs may not be a distinct population, but could be the visible nuclei of galaxies undergoing a short-lived, AGN-dominated evolutionary phase, with their compact, red appearance driven largely by observational biases. △ Less

Submitted 23 July, 2025; originally announced July 2025.

Comments: 26 pages, 8 plots, and 2 tables. Sudmitted to ApJ. Comments are welcome!

Lunar Orbital VLBI Experiment: motivation, scientific purposes and status

Authors: Xiaoyu Hong, Weiren Wu, Qinghui Liu, Dengyun Yu, Chi Wang, Tao Shuai, Weiye Zhong, Renjie Zhu, Yonghui Xie, Lihua Zhang, Liang Xiong, Yuhua Tang, Yongliao Zou, Haitao Li, Guangli Wang, Jianfeng Xie, Changbin Xue, Hao Geng, Juan Zhang, Xiaojing Wu, Yong Huang, Weimin Zheng, Lei Liu, Fang Wu, Xiuzhong Zhang , et al. (25 additional authors not shown)

Abstract: The Lunar Orbital VLBI Experiment (LOVEX) is a scientific component of the Chinese Lunar Exploration Project (CLEP) Chang'E-7. The spaceborne component of LOVEX is implemented onboard the relay satellite QueQiao-2, which was launched on 2024 March 20, and later placed into an elliptical selenocentric orbit. The LOVEX-specific payload consists of an X-band cryogenic receiver, a hydrogen maser frequ… ▽ More The Lunar Orbital VLBI Experiment (LOVEX) is a scientific component of the Chinese Lunar Exploration Project (CLEP) Chang'E-7. The spaceborne component of LOVEX is implemented onboard the relay satellite QueQiao-2, which was launched on 2024 March 20, and later placed into an elliptical selenocentric orbit. The LOVEX-specific payload consists of an X-band cryogenic receiver, a hydrogen maser frequency standard, and VLBI data formatting and acquisition electronics. Several components of the QueQiao-2 nominal onboard instrumentation, such as the 4.2-meter antenna, the data storage device, and the downlink communication system, contribute to the overall spaceborne VLBI instrumentation. This allows us to form a space radio telescope capable of co-observing with Earth-based radio telescopes in VLBI mode. In this space VLBI system, the length of the baseline extends up to approximately 380,000 km. This paper presents the LOVEX scientific objectives, architecture, instrumentation, pre-launch tests, in-flight verification and calibration, and the first in-flight detections of interferometric response (''fringes'') achieved through observations of the quasar AO 0235+164 and the Chang'E-6 orbital module, positioned at the Sun-Earth Lagrange point L2. These initial results demonstrate the successful performance of LOVEX, verifying its capability for both astronomical and spacecraft tracking observations at ultra-long VLBI baselines. △ Less

Submitted 22 July, 2025; originally announced July 2025.

Comments: Accepted for publication in Science China: Physics, Mechanics & Astronomy

Journal ref: SCIENCE CHINA Physics, Mechanics & Astronomy, vol. 69, No. 1, 219511, January 2026

The $z=7.08$ quasar ULAS J1120+0641 May Never Reach a "Normal" Black Hole to Stellar Mass Ratio

Authors: Meredith A. Stone, George H. Rieke, Jianwei Lyu, Michael K. Florian, Kevin N. Hainline, Yang Sun, Yongda Zhu

Abstract: JWST observations of quasars in the Epoch of Reionization have revealed that many lie in host galaxies that are severely undermassive relative to the supermassive black holes. It is unclear how these systems will evolve to the tight local relation between stellar mass and black hole mass. We search for companions around the z=7.08 quasar ULAS J1120+0641 using JWST/NIRCam narrow, medium, and wide-b… ▽ More JWST observations of quasars in the Epoch of Reionization have revealed that many lie in host galaxies that are severely undermassive relative to the supermassive black holes. It is unclear how these systems will evolve to the tight local relation between stellar mass and black hole mass. We search for companions around the z=7.08 quasar ULAS J1120+0641 using JWST/NIRCam narrow, medium, and wide-band photometry to identify [O III] emitters at the quasar redshift, and explore the potential for growth of the host galaxy through future mergers. We find 22 sources near the quasar's redshift across our two 4.4 arcmin$^2$ fields, indicating that environment of ULAS J1120+0641 is strongly overdense in z~7.1 galaxies relative to the field. We estimate the potential future mass budget of the quasar host galaxy by summing the current stellar and gas masses of the quasar host and surrounding galaxies, correcting for incompleteness and selection effects. With no further black hole growth, ULAS J1120+0641 is unlikely to reach a $M_{\mathrm{BH}}/M_*$ ratio less than ~2.5% at z=0, still much higher than typical for local galaxies. However, such systems -- a quiescent black hole in a low-luminosity galaxy -- may have escaped detection locally if they are sufficiently distant. △ Less

Submitted 15 August, 2025; v1 submitted 17 July, 2025; originally announced July 2025.

Comments: 23 pages, 8 figures plus 4 in appendix. Replacing with revised version after submitting to ApJ, comments welcome

Unveiling the nature and fate of the almost-dark cloud AGC 226178 through HI mapping

Authors: Yu-Zhu Sun, Hong-Xin Zhang, Elias Brinks, Rory Smith, Fujia Li, Minsu Kim, Se-Heon Oh, Zesen Lin, Jaebeom Kim, Weibin Sun, Tie Li, Patrick Côté, Alessandro Boselli, Lijun Chen, Pierre-Alain Duc, Sanjaya Paudel, Matthew A. Taylor, Kaixiang Wang, Enci Wang, Lanyue Zhang, Yinghe Zhao

Abstract: The origin of extragalactic, almost dark HI clouds with extreme gas-to-stellar mass ratios remains poorly understood. We investigate the nature and fate of the "almost dark" cloud AGC 226178, projected within the Virgo cluster, with an HI-to-stellar mass ratio of ~1000. We present deep single-dish HI mapping from the Five-hundred-meter Aperture Spherical Telescope (FAST), complemented by high-reso… ▽ More The origin of extragalactic, almost dark HI clouds with extreme gas-to-stellar mass ratios remains poorly understood. We investigate the nature and fate of the "almost dark" cloud AGC 226178, projected within the Virgo cluster, with an HI-to-stellar mass ratio of ~1000. We present deep single-dish HI mapping from the Five-hundred-meter Aperture Spherical Telescope (FAST), complemented by high-resolution interferometric data from the Very Large Array (VLA), as part of the Atomic gas in Virgo Interacting Dwarf galaxies (AVID) project. These observations provide the highest-quality HI analysis to date of such a cloud, combining resolution and sensitivity. FAST data reveal a short, low-velocity tail toward the dwarf galaxy VCC 2034, previously proposed as a possible origin for AGC 226178. However, VCC 2034 shows a line-of-sight asymmetric HI feature and cometary morphology indicating a stripping event unrelated to AGC 226178. VLA data reveal a velocity gradient across AGC 226178 and a clumpy internal structure. The velocity dispersion exceeds the thermal linewidth, implying turbulence or unresolved motions. The cloud cannot be gravitationally bound by atomic gas alone. The resolved HI clumps follow standard HI mass-star formation rate and mass-size relations, with those forming stars reaching surface densities above the threshold for self-shielding. We conclude that AGC 226178 is a free-floating HI cloud of unknown origin. The system appears to be in the process of disintegration. It is likely located well outside the Virgo cluster, as the preservation of its extended HI morphology within the cluster environment would otherwise require a substantial reservoir of unseen molecular gas with a mass exceeding that of the observed HI content. While confinement pressure from the hot intracluster medium may aid its stability, it is unlikely to be the dominant factor preventing its disruption. △ Less

Submitted 31 July, 2025; v1 submitted 29 June, 2025; originally announced June 2025.

Comments: 18 pages, 14 figures. Accepted for Publication in A&A

Journal ref: A&A 701, A73 (2025)

The MALATANG survey: Dense gas distribution on sub-kiloparsec scales across the disk of M82

Authors: Jian-Fa Wang, Yu Gao, Qing-Hua Tan, Xue-Jian Jiang, Li Ji, Zhi-Yu Zhang, Jun-Zhi Wang, Jun-Feng Wang, R. Thomas Greve, Yan Jiang, Ashley Bemis, Elias Brinks, Aeree Chung, J. Malcolm Currie, Richard de Grijs, Taotao Fang, C. Luis Ho, Bumhyun Lee, Satoki Matsushita, Michał Michałowski, Soojong Pak, Panomporn Poojon, G. Mark Rawlings, Amelie Saintonge, Yi-Chen Sun , et al. (1 additional authors not shown)

Abstract: We present observations of HCN J=4-3 and HCO^+ J=4-3 lines obtained with the James Clerk Maxwell Telescope as part of the MALATANG survey, combined with archival HCN J=1-0 and HCO^+ J=1-0 data from the Green Bank Telescope, to study the spatial distribution and excitation conditions of dense molecular gas in the disk of M82. We detect HCN J=4-3 and HCO^+ J=4-3 emission within the central region (<… ▽ More We present observations of HCN J=4-3 and HCO^+ J=4-3 lines obtained with the James Clerk Maxwell Telescope as part of the MALATANG survey, combined with archival HCN J=1-0 and HCO^+ J=1-0 data from the Green Bank Telescope, to study the spatial distribution and excitation conditions of dense molecular gas in the disk of M82. We detect HCN J=4-3 and HCO^+ J=4-3 emission within the central region (< 500 pc) of the galaxy, while the J=1-0 emission lines exhibit a more extended spatial distribution (> 700 pc). The dense gas shows a clear double-lobed structure in both spatial distribution and kinematics, with the HCN and HCO^+ J=4-3 lines in the southwest lobe blueshifted by ~ 40 km/s relative to the J=1-0 lines. The HCN J=4-3/1-0 and HCO^+ J=4-3/1-0 line-luminosity ratios range from 0.09 to 0.53 and from 0.14 to 0.87, respectively, with mean values of 0.18 +/- 0.04 and 0.36 +/- 0.06. The HCN ratio is lower than the typical average observed in nearby star-forming galaxies, whereas the HCO^+ ratio is comparatively higher, suggesting that the high-J HCN emission in M82 is significantly sub-thermally excited. Spatially, the peak values of the J=4-3/1-0 ratios are found in the northwest region of M82, coinciding with the galaxy-scale outflow. Elevated HCN/HCO^+ ratios are also detected in roughly the same area, potentially tracing local excitation enhancements driven by the outflow. The HCN/HCO^+ J=4-3 ratio across all detected regions ranges from 0.19 to 1.07 with a mean value of 0.41 +/- 0.11, which is significantly lower than the average J=1-0 ratio of 0.76 +/- 0.08. Both ratios are significantly lower than the average values observed in nearby star-forming galaxies, which could be related to the relatively low gas density and the presence of an extended photo-dissociation region in M82. △ Less

Submitted 26 June, 2025; v1 submitted 25 June, 2025; originally announced June 2025.

Journal ref: A&A 700, A72 (2025)

Impact of $Ξ$-Hypernuclear Constraints on Relativistic Equation of State and Properties of Hyperon Stars

Authors: Shi Yuan Ding, Xiang Dong Sun, Bao Yuan Sun, Ang Li

Abstract: Significant uncertainties persist in describing the equation of state and internal structure of hyperon stars due to the limited understanding of the mechanisms underlying hyperon interactions. Constraining the interaction parameter space through a combination of the latest astronomical observations and hypernuclear physics experiments is therefore essential. In this study, we incorporate experime… ▽ More Significant uncertainties persist in describing the equation of state and internal structure of hyperon stars due to the limited understanding of the mechanisms underlying hyperon interactions. Constraining the interaction parameter space through a combination of the latest astronomical observations and hypernuclear physics experiments is therefore essential. In this study, we incorporate experimental constraints from $Ξ$ hypernuclear physics on top of $Λ$ hyperons considered in \citet{Sun2023APJ942.55}. Specifically, based on updated measurements of hyperon separation energies from $Ξ$ hypernuclear experiments, sets of $ΞN$ effective interactions are constructed and a linear correlation between their scalar ($σ$) and vector ($ω$) coupling strength ratios is proposed as a constraint derived from $Ξ$ hypernuclear physics. Together with experimental correlations and astronomical observational data, four types of analyses are performed to constrain hyperon-nucleon interactions and the properties of hyperon stars. Compared to the vector $ω$ meson-hyperon coupling, the introduction of linear correlations in hypernuclear physics imposes a more substantial constraint on the scalar $σ$ meson-hyperon coupling, significantly enhancing its coupling strength and thereby ensuring the stiffness of the equation of state, highlighting the crucial role of hypernuclear studies in solving the hyperon puzzle problem. Consequently, a maximum mass of around $2M_{\odot}$ can be achieved with all five interactions considered in this study under the combined constraints from astronomical observations and nuclear physics. With more reliably estimated hyperon-nucleon contributions, the uncertainties in both the fractions and the threshold densities at which hyperons appear inside neutron stars are notably reduced, along with those in the mass-radius predictions. △ Less

Submitted 15 October, 2025; v1 submitted 20 June, 2025; originally announced June 2025.

Comments: 17 pages, 9 figures, 3 tables

Journal ref: Phys. Rev. D 112, 103008 (2025)

AVID: Formation and evolution of a coalesced major merger of late-type dwarf galaxies (VCC 479) on the outskirts of the Virgo cluster

Authors: Weibin Sun, Hong-Xin Zhang, Rory Smith, Elias Brinks, Patrick Côté, Se-Heon Oh, Zesen Lin, Alessandro Boselli, Laura Ferrarese, Fujia Li, Yuzhu Sun, Lijun Chen, Lanyue Zhang, Minsu Kim, Jaebeom Kim, Tie Li, Bojun Tao, Matt Taylor, Pierre-Alain Duc, Ruben Sánchez-Janssén, Yinghe Zhao, Sanjaya Paudel, Eric W. Peng, Kaixiang Wang, Stephen Gwyn , et al. (2 additional authors not shown)

Abstract: Dwarf-dwarf galaxy mergers are among the least explored aspects of dwarf galaxy pre-processing as they fall into clusters. We present the first case study of a coalesced late-type dwarf major merger (VCC 479; stellar mass $\sim\,8\,\times\,10^7\,\rm M_\odot$) that has undergone significant environmental influence, with the aim of exploring dwarf galaxy evolution under the combined effects of galax… ▽ More Dwarf-dwarf galaxy mergers are among the least explored aspects of dwarf galaxy pre-processing as they fall into clusters. We present the first case study of a coalesced late-type dwarf major merger (VCC 479; stellar mass $\sim\,8\,\times\,10^7\,\rm M_\odot$) that has undergone significant environmental influence, with the aim of exploring dwarf galaxy evolution under the combined effects of galaxy interactions and environmental processes, and understanding its relevance to the diversity of dwarf galaxies in cluster environments. Our analysis is based on VLA and FAST HI emission line mapping from the Atomic gas in Virgo Interacting Dwarf galaxies (AVID) survey. We also perform idealized hydrodynamical simulations of dwarf-dwarf mergers to help interpret the observations. We identify symmetric stellar shell structures in VCC 479, indicative of a coalesced major merger of dwarf galaxies. The galaxy features a central starburst, initiated $\sim$600 Myr ago, embedded within an exponential disk quenched $\sim$1 Gyr ago. The starburst contributes only 2.9$\pm$0.5\% of the total stellar mass, and VCC 479's global star formation rate is 0.3 dex lower than typical dwarfs of similar mass. The galaxy is highly HI deficient, with most HI gas concentrated within the central 1 kpc and little extended HI envelope. The misalignment of the HI velocity field with the stellar body is best explained by merger-triggered gas inflow, as seen in our simulations. Our analysis is consistent with a scenario that the majority of HI gas of the progenitor galaxies was removed by the cluster environment prior to the final coalescence. The merger concentrates the remaining gas toward the galaxy center, triggering a central starburst. The combined effect of environment stripping and galaxy merger has transformed VCC 479 into a blue-core dwarf undergoing morphological transition from a late-type to an early-type galaxy. △ Less

Submitted 6 July, 2025; v1 submitted 18 June, 2025; originally announced June 2025.

Comments: 18 pages, 15 figures. Accepted for Publication in A&A

Journal ref: A&A 700, A113 (2025)

OGHReS: Star formation in the Outer Galaxy II ($\ell = 180^\circ$-$280^\circ$)

Authors: J. S. Urquhart, C. Koenig, D. Colombo, A. Karska, A. Giannetti, T. J. T. Moore, A. Y. Yang, F. Wyrowski, Y. Sun, Z. Jiang, K. R. Neralwar, D. Eden, I. Grozdanova, S. Neupane, M. Figueira, E. Dann, V., S. Veena, W. -J. Kim, S. Leurini, J. Brand, M. -Y. Lee

Abstract: The Outer Galaxy High-Resolution Survey (OGHReS) covers 100 square degrees ($180^\circ < \ell < 280^\circ$) in the (2--1) transitions of three CO-isotopologues. We use the spectra to refine the velocities and physical properties to 6706 \higal\ clumps located in the OGHReS region. In a previous paper, we analysed 3584 clumps between $\ell = 250^\circ$ and $280^\circ$. Here, we cover a further 3122… ▽ More The Outer Galaxy High-Resolution Survey (OGHReS) covers 100 square degrees ($180^\circ < \ell < 280^\circ$) in the (2--1) transitions of three CO-isotopologues. We use the spectra to refine the velocities and physical properties to 6706 \higal\ clumps located in the OGHReS region. In a previous paper, we analysed 3584 clumps between $\ell = 250^\circ$ and $280^\circ$. Here, we cover a further 3122 clumps ($180^\circ < \ell < 250^\circ$) and determine reliable velocities for \withVLSR\ of these, finding good agreement with the previously assigned velocities ($\sim$80 percent within 5 \kms). We update velocities for 288 clumps and provide new values for an additional 411. Combining these with the previous results, we have velocities and physical properties for 6193 clumps (92.3 percent). The \allnonDetections\ non-detections are low surface density clumps or likely contamination by evolved stars and galaxies. Key findings: i) improved correlation between clumps and spiral arm loci, and the discovery of clumps beyond the outer arm supports the existence of a new spiral structure; ii) decreasing trend in the $L/M$-ratio consistent with less high-mass star formation in the outer Galaxy; iii) increase in the star formation fraction (SFF) in the outer Galaxy, suggesting that more clumps are forming stars despite their lower mass; iv) discrepancies in velocity assignments across different surveys that could affect $\sim$10000 clumps, especially in the fourth quadrant. △ Less

Submitted 19 May, 2025; originally announced May 2025.

Comments: 18 pages, 14 figues. Full versions of Tables 1 and 2 are only available in electronic form via CDS. arXiv admin note: text overlap with arXiv:2401.00808

Gravitationally Bound Gas Determines Star Formation in the Galaxy

Authors: Sihan Jiao, Jingwen Wu, Zhi-Yu Zhang, Neal J. Evans II, Chao-Wei Tsai, Di Li, Hauyu Baobab Liu, Yong Shi, Junzhi Wang, Qizhou Zhang, Yuxin Lin, Linjing Feng, Xing Lu, Yan Sun, Hao Ruan, Fangyuan Deng

Abstract: Stars form from molecular gas under complex conditions influenced by multiple competing physical mechanisms, such as gravity, turbulence, and magnetic fields. However, accurately identifying the fraction of gas actively involved in star formation remains challenging. Using dust continuum observations from the Herschel Space Observatory, we derived column density maps and their associated probabili… ▽ More Stars form from molecular gas under complex conditions influenced by multiple competing physical mechanisms, such as gravity, turbulence, and magnetic fields. However, accurately identifying the fraction of gas actively involved in star formation remains challenging. Using dust continuum observations from the Herschel Space Observatory, we derived column density maps and their associated probability distribution functions (N-PDFs). Assuming the power-law component in the N-PDFs corresponds to gravitationally bound (and thus star-forming) gas, we analyzed a diverse sample of molecular clouds spanning a wide range of mass and turbulence conditions. This sample included 21 molecular clouds from the solar neighborhood ($d<$500 pc) and 16 high-mass star-forming molecular clouds. For these two groups, we employed the counts of young stellar objects (YSOs) and mid-/far-infrared luminosities as proxies for star formation rates (SFR), respectively. Both groups revealed a tight linear correlation between the mass of gravitationally bound gas and the SFR, suggesting a universally constant star formation efficiency in the gravitationally bound gas phase. The star-forming gas mass derived from threshold column densities ($N_{\mbox {threshold}}$) varies from cloud to cloud and is widely distributed over the range of $\sim$1--17$\times$10$^{21}$ cm$^{-2}$ based on N-PDF analysis. But in solar neighborhood clouds, it is in rough consistency with the traditional approach using $A_{\rm V}$ $\ge$ 8 mag. In contrast, in high turbulent regions (e.g., the Central Molecular Zone) where the classical approach fails, the gravitationally bound gas mass and SFR still follow the same correlation as other high-mass star-forming regions in the Milky Way. Our findings also strongly support the interpretation that gas in the power-law component of the N-PDF is undergoing self-gravitational collapse to form stars. △ Less

Submitted 12 May, 2025; originally announced May 2025.

Comments: 23 pages, 17 figures. Submitted to A&A

Measurement of separate electron and positron spectra from 10 GeV to 20GeV with the geomagnetic field on DAMPE

Authors: DAMPE Collaboration, F. Alemanno, Q. An, P. Azzarello, F. C. T. Barbato, P. Bernardini, X. J. Bi, H. Boutin, I. Cagnoli, M. S. Cai, E. Casilli, E. Catanzani, J. Chang, D. Y. Chen, J. L. Chen, Z. F. Chen, Z. X. Chen, P. Coppin, M. Y. Cui, T. S. Cui, Y. X. Cui, I. DeMitri, F. dePalma, A. DiGiovanni, T. K. Dong , et al. (127 additional authors not shown)

Abstract: The cosmic-ray (CR) electrons and positrons in space are of great significance for studying the origin and propagation of cosmic-rays. The satellite-borne experiment DArk Matter Particle Explorer (DAMPE) has been used to measure the separate electron and positron spectra, as well as the positron fraction. In this work, the Earth's magnetic field is used to distinguish CR electrons and positrons, a… ▽ More The cosmic-ray (CR) electrons and positrons in space are of great significance for studying the origin and propagation of cosmic-rays. The satellite-borne experiment DArk Matter Particle Explorer (DAMPE) has been used to measure the separate electron and positron spectra, as well as the positron fraction. In this work, the Earth's magnetic field is used to distinguish CR electrons and positrons, as the DAMPE detector does not carry an onboard magnet. The energy range for the measurements is from 10 to 20 GeV, being currently limited at high energy by the zenith pointing orientation of DAMPE. The results are consistent with previous measurements based on the magnetic spectrometer by AMS-02 and PAMELA, while the results of Fermi-LAT seem then to be systematically shifted to larger values. △ Less

Submitted 21 August, 2025; v1 submitted 9 May, 2025; originally announced May 2025.

Comments: Accepted for publication in Chinese Physics C

The Large-scale Environments of Low-luminosity AGNs at $3.9 < z < 6$ and Implications for Their Host Dark Matter Halos from a Complete NIRCam Grism Redshift Survey

Authors: Xiaojing Lin, Xiaohui Fan, Fengwu Sun, Junyu Zhang, Eiichi Egami, Jakob M. Helton, Feige Wang, Haowen Zhang, Andrew J. Bunker, Zheng Cai, Zhiyuan Ji, Xiangyu Jin, Roberto Maiolino, Maria Anne Pudoka, Pierluigi Rinaldi, Brant Robertson, Sandro Tacchella, Wei Leong Tee, Yang Sun, Christopher N. A. Willmer, Chris Willott, Yongda Zhu

Abstract: We study the large-scale environments and clustering properties of 28 low-luminosity AGNs at $z=3.9-6$ in the GOODS-N field. Our sample, identified from the JWST NIRCam Imaging and WFSS data in CONGRESS and FRESCO surveys with either broad H$α$ emission lines or V-shape continua, are compared to 782 H$α$ emitters (HAEs) selected from the same data. These AGNs are located in diverse large-scale env… ▽ More We study the large-scale environments and clustering properties of 28 low-luminosity AGNs at $z=3.9-6$ in the GOODS-N field. Our sample, identified from the JWST NIRCam Imaging and WFSS data in CONGRESS and FRESCO surveys with either broad H$α$ emission lines or V-shape continua, are compared to 782 H$α$ emitters (HAEs) selected from the same data. These AGNs are located in diverse large-scale environments and do not preferentially reside in denser environments compared to HAEs. Their overdensity field, $δ$, averaged over (15 $h^{-1}$cMpc)$^3$, ranges from $-0.56$ to 10.56, and shows no clear correlation with broad-line luminosity, black hole (BH) masses, or the AGN fraction. It suggests that $> 10$ cMpc structures do not significantly influence BH growth. We measure the two-point cross-correlation function of AGNs with HAEs, finding a comparable amplitude to that of the HAE auto-correlation. This indicates similar bias parameters and host dark matter halo masses for AGNs and HAEs. The correlation length of field AGNs is 4.26 $h^{-1}$cMpc, and 7.66 $h^{-1}$cMpc at $3.9 < z < 5$ and $5 < z < 6$, respectively. We infer a median host dark matter halo mass of $\log (M_h/M_\odot)\approx 11.0-11.2$ and host stellar masses of $\log (M_\star/M_\odot) \approx 8.4-8.6$ by comparing with the UniverseMachine simulation. Our clustering analysis suggests that low-luminosity AGNs at high redshift reside in normal star-forming galaxies with overmassive BHs. They represent an intrinsically distinct population from luminous quasars and could be a common phase in galaxy evolution. △ Less

Submitted 12 December, 2025; v1 submitted 5 May, 2025; originally announced May 2025.

Comments: Main text 15 pages; 9 figures; Accepted by the ApJ

Abundant Population of Broad H$α$ Emitters in the GOODS-N Field Revealed by CONGRESS, FRESCO, and JADES

Authors: Junyu Zhang, Eiichi Egami, Fengwu Sun, Xiaojing Lin, Jianwei Lyu, Yongda Zhu, Pierluigi Rinaldi, Yang Sun, Andrew J. Bunker, Rachana Bhatawdekar, Jakob M. Helton, Roberto Maiolino, Zheng Ma, Brant Robertson, Sandro Tacchella, Giacomo Venturi, Christina C. Williams, Chris Willott

Abstract: We present a spectroscopic search for broad H$α$ emitters at z~3.7-6.5 in the GOODS-N field, utilizing JWST/NIRCam slitless spectroscopy from FRESCO and CONGRESS, complemented by JADES imaging. We identify 19 broad H$α$ emitters with FWHM > 1000 km/s at z~4-5.5, including 9 new sources. The black hole masses and AGN bolometric luminosities, inferred from the broad H$α$ components, indicate that mo… ▽ More We present a spectroscopic search for broad H$α$ emitters at z~3.7-6.5 in the GOODS-N field, utilizing JWST/NIRCam slitless spectroscopy from FRESCO and CONGRESS, complemented by JADES imaging. We identify 19 broad H$α$ emitters with FWHM > 1000 km/s at z~4-5.5, including 9 new sources. The black hole masses and AGN bolometric luminosities, inferred from the broad H$α$ components, indicate that most sources are accreting at ~10% of the Eddington limit. We derive their host stellar masses via SED fitting and find higher $M_{BH}/M_{*}$ ratios relative to the local $M_{BH}$-$M_{*}$ relations, consistent with previous studies. We find that 42% of the sample do not satisfy the widely-used color selection criteria for Little Red Dots (LRDs), with the majority of these sources lacking the characteristic steep red slope. A comparison of the average SEDs between our sample and LRDs selected in the same field reveals that the steep red slopes observed in some LRDs are likely due to line-boosting effects as previously suggested. Furthermore, we find that 68% of color-selected LRDs with H$α$ detections in the NIRCam/Grism spectra do not exhibit broad-line features. While the limited sensitivity of the grism spectra may hinder the detection of broad-line components in faint sources, our findings still highlight the enigmatic nature of the LRD population. △ Less

Submitted 5 May, 2025; originally announced May 2025.

Comments: Submitted to ApJ. 23 pages, 16 figures, 3 tables

Some Questions and Challenges in Measurements of Solar Magnetic Fields

Authors: Hongqi Zhang, Jiangtao Su, Xiaofan Wang, Xingming Bao, Yu Liu, Yingzi Sun, Mingyu Zhao

Abstract: Huairou Solar Observing Station of the National Astronomical Observatories of the Chinese Academy of Sciences has been in operation since 1987. Successful observations of the solar vector magnetic field have been conducted during its operation. Based on the achievements at Huairou, we analyze the methods of observing the solar magnetic field, including discussions of the approximation of the trans… ▽ More Huairou Solar Observing Station of the National Astronomical Observatories of the Chinese Academy of Sciences has been in operation since 1987. Successful observations of the solar vector magnetic field have been conducted during its operation. Based on the achievements at Huairou, we analyze the methods of observing the solar magnetic field, including discussions of the approximation of the transfer theory of the solar magnetic field in the atmosphere, wide field of view polarized observation, and some questions on the inversion of solar magnetic field data. We also present relevant challenges for further research. △ Less

Submitted 1 May, 2025; originally announced May 2025.

Pair-Instability Gap Black Holes in Population III Star Clusters: Pathways, Dynamics, and Gravitational Wave Implications

Authors: Weiwei Wu, Long Wang, Shuai Liu, Yining Sun, Ataru Tanikawa, Michiko Fujii

Abstract: The detection of the gravitational wave (GW) event GW190521 raises questions about the formation of black holes within the pair-instability mass gap (PIBHs). We propose that Population III (Pop III) star clusters significantly contribute to events similar to GW190521. We perform $N$-body simulations and find that PIBHs can form from stellar collisions or binary black hole (BBH) mergers, with the l… ▽ More The detection of the gravitational wave (GW) event GW190521 raises questions about the formation of black holes within the pair-instability mass gap (PIBHs). We propose that Population III (Pop III) star clusters significantly contribute to events similar to GW190521. We perform $N$-body simulations and find that PIBHs can form from stellar collisions or binary black hole (BBH) mergers, with the latter accounting for 90\% of the contributions. Due to GW recoil during BBH mergers, approximately 10-50% of PIBHs formed via BBH mergers escape from clusters, depending on black hole spins and cluster escape velocities. The remaining PIBHs can participate in secondary and multiple BBH formation events, contributing to GW events. Assuming Pop III stars form in massive clusters (initially 100,000 $M_\odot$) with a top-heavy initial mass function, the average merger rates for GW events involving PIBHs with 0% and 100% primordial binaries are $0.005$ and $0.017$ $\text{yr}^{-1} \text{Gpc}^{-3}$, respectively, with maximum values of $0.030$ and $0.106$ $\text{yr}^{-1} \text{Gpc}^{-3}$. If Pop III stars form in low-mass clusters (initial mass of $1000M_\odot$ and $10000 M_\odot$), the merger rate is comparable with a 100% primordial binary fraction but significantly lower without primordial binaries. We also calculate the characteristic strains of the GW events in our simulations and find that about 43.4% (LISA) 97.8% (Taiji) and 66.4% (Tianqin) of these events could potentially be detected by space-borne detectors, including LISA, Taiji, and TianQin. The next-generation GW detectors such as DECIGO, ET, and CE can nearly cover all these signals. △ Less

Submitted 28 April, 2025; originally announced April 2025.

Comments: 19 pages, 13 figures, accepted for publication in ApJ

Systematic search for blue hyper-velocity stars from LAMOST survey

Authors: Yongkang Sun, Yang Huang, Jifeng Liu, Haozhu Fu, Huawei Zhang, Yinbi Li, Cuihua Du, Jianrong Shi, Xiao Kong

Abstract: Hypervelocity stars (HVSs) represent a unique class of objects capable of escaping the gravitational pull of the Milky Way due to extreme acceleration events, such as close encounters with the supermassive black hole at the Galactic center (GC), supernova explosions in binary systems, or multi-body dynamical interactions. Finding and studying HVSs are crucial to exploring these ejection mechanisms… ▽ More Hypervelocity stars (HVSs) represent a unique class of objects capable of escaping the gravitational pull of the Milky Way due to extreme acceleration events, such as close encounters with the supermassive black hole at the Galactic center (GC), supernova explosions in binary systems, or multi-body dynamical interactions. Finding and studying HVSs are crucial to exploring these ejection mechanisms, characterizing central black holes, probing the GC environment, and revealing the distribution of dark matter in our galaxy. The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) spectroscopic surveys have so far identified four B-type unbound HVSs. To expand this sample with the second-phase LAMOST survey that started in 2018, we conducted a systematic search for early-type HVSs using the LAMOST Data Release 10. We identified 125 early-type high-velocity candidates with total velocities exceeding 300 km\,s$^{-1}$. Among them, we report ten new unbound B- and A-type hypervelocity star (HVS) candidates (designated LAMOST-HVS5 through LAMOST-HVS14), tripling the number of unbound HVSs previously identified by LAMOST. Kinematic analyses suggest that these newly discovered HVS candidates likely originated either from the Galactic Center or via dynamical interactions. Future high-resolution follow-up observations promise to refine the stellar parameters, distances, and elemental abundances of these candidates, thereby providing deeper insights into their origins and broadening their potential applications across astrophysics. △ Less

Submitted 20 April, 2025; originally announced April 2025.

Comments: 21 pages, 11 figures, accepted for publication in APJ

Extreme Neutral Outflow in a non-AGN Quiescent Galaxy at z~1.3

Authors: Yang Sun, Zhiyuan Ji, George H. Rieke, Francesco D'Eugenio, Yongda Zhu, Fengwu Sun, Xiaojing Lin, Andrew J. Bunker, Jianwei Lyu, Pierluigi Rinaldi, Christopher N. A. Willmer

Abstract: We report the discovery of a substantial sodium doublet (Na D $λλ$5890, 5896Å)-traced neutral outflow in the quiescent galaxy JADES-GS-206183 at $z=1.317$. Its JWST/NIRSpec-MSA spectrum shows a deep, blueshifted Na D absorption, revealing a neutral outflow with $v_{\rm out}=828^{+79}_{-49}\,\mathrm{km\,s^{-1}}$ and a mass outflow rate of… ▽ More We report the discovery of a substantial sodium doublet (Na D $λλ$5890, 5896Å)-traced neutral outflow in the quiescent galaxy JADES-GS-206183 at $z=1.317$. Its JWST/NIRSpec-MSA spectrum shows a deep, blueshifted Na D absorption, revealing a neutral outflow with $v_{\rm out}=828^{+79}_{-49}\,\mathrm{km\,s^{-1}}$ and a mass outflow rate of $\log(\dot{M}_{\rm out}/\mathrm{M_{\odot}\,yr^{-1}})=2.40^{+0.11}_{-0.16}$. This outflow rate exceeds that of any neutral outflows identified beyond $z\sim1$ by the same line and is comparable with those in local galaxies with intensive star formation or luminous AGN. JADES-GS-206183 is also a peculiar quiescent galaxy with a spiral$+$bar morphology, high dust attenuation ($A_V=2.27\pm0.23$ mag). Paschen $α$ (Pa$α$) emission from the FRESCO NIRCam grism confirms its low star formation rate ($\mathrm{SFR_{Paα}}=10.78\pm 0.55\,\mathrm{M_{\odot}\,yr^{-1}}$), placing it 0.5 dex below the main-sequence ($\log(\mathrm{sSFR/yr^{-1}})=-10.2$). Despite the systematics introduced by different star formation history (SFH) priors, the SED modeling, combining HST-to-NIRCam photometry with the VLT/MUSE spectrum, suggests that JADES-GS-206183 experienced an older episode of star formation 0.5-2 Gyr ago and a possible rejuvenation within recent $\sim$10 Myr. Moreover, rest-frame optical lines indicate that the current AGN activity of JADES-GS-206183, if present, is also weak. Even though we tentatively detect a broad component of the H$α$ line, it likely traces an ionized outflow rather than an AGN. The results demonstrate that the Na D outflow in JADES-GS-206183 is highly unlikely to be driven by current star formation or nuclear activity. Instead, it may represent a long-lasting fossil outflow from past AGN activity, potentially co-triggered with the early phase of rejuvenation. △ Less

Submitted 12 December, 2025; v1 submitted 20 April, 2025; originally announced April 2025.

Comments: 24 pages, 12 figure, Accepted for publication in ApJ

Molecular Clouds at the Edge of the Galaxy I. Variation of CO J=2-1/1-0 Line Ratio

Authors: C. S. Luo, X. D. Tang, C. Henkel, K. M. Menten, Y. Sun, Y. Gong, X. W. Zheng, D. L. Li, Y. X. He, X. Lu, Y. P. Ao, X. P. Chen, T. Liu, K. Wang, J. W. Wu, J. Esimbek, J. J. Zhou, J. J. Qiu, X. Zhao, J. S. Li, Q. Zhao, L. D. Liu

Abstract: The Galactic edge at Galactocentric distances of 14\,--\,22\,kpc provides an ideal laboratory to study molecular clouds in an environment that is different from the solar neighborhood, due to its lower gas density, lower metallicity, and little or no perturbation from the spiral arms. Observations of CO\,($J$\,=\,2--1) spectral lines were carried out towards 72 molecular clouds located at the Gala… ▽ More The Galactic edge at Galactocentric distances of 14\,--\,22\,kpc provides an ideal laboratory to study molecular clouds in an environment that is different from the solar neighborhood, due to its lower gas density, lower metallicity, and little or no perturbation from the spiral arms. Observations of CO\,($J$\,=\,2--1) spectral lines were carried out towards 72 molecular clouds located at the Galactic edge using the IRAM\,30\,m telescope. Combined with CO\,($J$\,=\,1--0) data from the MWISP project, we investigate the variations of $R_{21}$ across these Galactic edge clouds, with $R_{21}$ representing CO(2-1)/CO(1-0) integrated intensity ratios. These are found to range from 0.3 to 3.0 with a mean of 1.0\,$\pm$\,0.1 in the Galactic edge clouds. The proportions of very low ratio gas (VLRG; $R_{21}$\,<\,0.4), low ratio gas (LRG; 0.4\,$\le$\,$R_{21}$\,<\,0.7), high ratio gas (HRG; 0.7\,$\le$\,$R_{21}$\,<\,1.0), and very high ratio gas (VHRG; $R_{21}$\,$\ge$\,1.0) are 6.9\%, 29.2\%, 26.4\%, and 37.5\%, respectively, indicating a significant presence of high $R_{21}$ ratio molecular gas within these regions. In our Galaxy, the $R_{21}$ ratio exhibits a gradient of initial radial decline followed by a high dispersion with increasing Galacticentric distance and a prevalence for high ratio gas. There is no apparent systematic variation within the Galactocentric distance range of 14 to 22\,kpc. A substantial proportion of HRG and VHRG is found to be associated with compact clouds and regions displaying star-forming activity, suggesting that the high $R_{21}$ ratios may stem from dense gas concentrations and recent episodes of star formation. △ Less

Submitted 18 April, 2025; originally announced April 2025.

Journal ref: A&A 698, A54 (2025)

The Luminosity Function and Clustering of H$α$ Emitting Galaxies at $z\approx4-6$ from a Complete NIRCam Grism Redshift Survey

Authors: Xiaojing Lin, Eiichi Egami, Fengwu Sun, Haowen Zhang, Xiaohui Fan, Jakob M. Helton, Feige Wang, Andrew J. Bunker, Zheng Cai, Daniel J. Eisenstein, Daniel T. Jaffe, Zhiyuan Ji, Xiangyu Jin, Maria Anne Pudoka, Sandro Tacchella, Wei Leong Tee, Pierluigi Rinaldi, Brant Robertson, Yang Sun, Christopher N. A. Willmer, Chris Willott, Junyu Zhang, Yongda Zhu

Abstract: We study the luminosity function (LF) and clustering properties of 888 H$α$ emitters (HAEs) at $3.75 < z < 6$ in the GOODS-N field. The sample, built from JWST CONGRESS and FRESCO NIRCam grism surveys using a novel redshift assignment algorithm, spans $\sim$62 arcmin$^2$ and reaches $L_{\rm Hα} \sim 10^{41.2} {\rm erg s^{-1}}$. We identify two prominent filamentary protoclusters at… ▽ More We study the luminosity function (LF) and clustering properties of 888 H$α$ emitters (HAEs) at $3.75 < z < 6$ in the GOODS-N field. The sample, built from JWST CONGRESS and FRESCO NIRCam grism surveys using a novel redshift assignment algorithm, spans $\sim$62 arcmin$^2$ and reaches $L_{\rm Hα} \sim 10^{41.2} {\rm erg s^{-1}}$. We identify two prominent filamentary protoclusters at $z \approx 4.41$ and $z \approx 5.19$, hosting 98 and 144 HAEs, respectively. The observed H$α$ LFs show similar shallow faint-end slopes for both protocluster and field galaxies at $z=3.75-5$, and for the protocluster at $z=5-6$ ($α\approx 1.2$ to $-1.3$). In contrast, the field LF at $z=5-6$ is much steeper ($α=-1.87_{-0.23}^{+0.30}$), suggesting that protocluster galaxies at $z > 5$ are more evolved, resembling those at $z=3.75-5$. The observed star formation rate density from H$α$, integrated down to 0.45 ${\rm M_\odot yr^{-1}}$, is $0.050^{+0.002}_{-0.003}$ and $0.046^{+0.006}_{-0.004} M_\odot {\rm yr}^{-1} {\rm Mpc}^{-3}$ at $z=3.75-5$ and $z=5-6$, with protoclusters contributing $\sim$25% and 55%, respectively. This implies that a large fraction of star formation at $z > 4$ occurs in protoclusters. We conduct the first star-formation-rate-limited 3D clustering analysis at $z > 4$. We find the filamentary protocluster geometry flattens the power-law shape of the HAE auto-correlation functions, with slopes much shallower than typically assumed. The auto-correlation function of field HAEs have correlation lengths of $r_0 = 4.61^{+1.00}_{-0.68} h^{-1}{\rm Mpc}$ at $z \approx 4-5$ and $r_0 = 6.23^{+1.68}_{-1.13} h^{-1}{\rm Mpc}$ at $z=5-6$. Comparing the observed correlation functions with the UniverseMachine simulation, we infer the dark matter (sub-)halo masses of HAEs to be $\log (M_h/M_\odot)=11.0-11.2$ at $z\approx 4-6$, with a scatter of 0.4 dex. △ Less

Submitted 12 December, 2025; v1 submitted 10 April, 2025; originally announced April 2025.

Comments: Main text 19 pages, 11 figures. Accepted by ApJ

Nuclear Winds Drive Cold Gas Outflows on Kiloparsec Scales in Reionization-Era Quasars

Authors: Yongda Zhu, Marcia J. Rieke, Luis C. Ho, Yang Sun, George H. Rieke, Feng Yuan, Tom J. L. C. Bakx, George D. Becker, Jinyi Yang, Eduardo Bañados, Manuela Bischetti, Christopher Cain, Xiaohui Fan, Yoshinobu Fudamoto, Seyedazim Hashemi, Ryota Ikeda, Zhiyuan Ji, Xiangyu Jin, Weizhe Liu, Yichen Liu, Jianwei Lyu, Hai-Xia Ma, Tsutomu T. Takeuchi, Hideki Umehata, Feige Wang , et al. (1 additional authors not shown)

Abstract: Accreting supermassive black holes (SMBHs) are thought to influence the evolution of their host galaxies through multi-phase feedback driven by powerful nuclear outflows. Although this mechanism is central to theoretical models of SMBH-galaxy co-evolution across cosmic time, direct observational evidence connecting nuclear winds to large-scale cold gas outflows remains limited, especially in the e… ▽ More Accreting supermassive black holes (SMBHs) are thought to influence the evolution of their host galaxies through multi-phase feedback driven by powerful nuclear outflows. Although this mechanism is central to theoretical models of SMBH-galaxy co-evolution across cosmic time, direct observational evidence connecting nuclear winds to large-scale cold gas outflows remains limited, especially in the early universe. Here we report statistical evidence for such a connection in a sample of luminous quasars at $z \sim 5.5$. We compare stacked [C\,{\sc ii}] 158 $μ$m emission profiles from ALMA observations, which trace galactic-scale neutral gas, for quasars with and without broad absorption lines (BALs) that indicate powerful nuclear winds on sub-kiloparsec scales. The BAL quasar stack exhibits a significant (S/N = 4.45) blueshifted broad component in the [C\,{\sc ii}] line profile, with a velocity offset of $Δv_{\rm b} = -2.1 \times 10^2\,\rm km\,s^{-1}$ and a full width at half maximum of $1.18 \times 10^3\,\rm km\,s^{-1}$, whereas the non-BAL stack shows no such feature. We estimate that a few percent to one-quarter of the nuclear wind energy may be transferred to cold neutral gas on kiloparsec scales. These results suggest that BAL winds can couple to the host galaxy's interstellar medium, providing empirical support for models of multi-phase AGN feedback. This mechanism may also contribute to the observed divers ity in $M_{\rm BH}/M_*$ among luminous quasars recently identified by JWST. △ Less

Submitted 22 July, 2025; v1 submitted 3 April, 2025; originally announced April 2025.

Comments: 17 pages, 9 figures, 1 table; re-submitted to ApJ

The Mini-SiTian Array: Imaging Processing Pipeline

Authors: Kai Xiao, Zhirui Li, Yang Huang, Jie Zheng, Haibo Yuan, Junju Du, Linying Mi, Hongrui Gu, Yongkang Sun, Bowen Zhang, Shunxuan He, Henggeng Han, Min He, Ruifeng Shi, Yu Zhang, Chuanjie Zheng, Zexi Niu, Guiting Tian, Hu Zou, Yongna Mao, Hong Wu, Jifeng Liu

Abstract: As a pathfinder of the SiTian project, the Mini-SiTian (MST) array, employed three commercial CMOS cameras, represents a next-generation, cost-effective optical time-domain survey project. This paper focuses primarily on the precise data processing pipeline designed for wide-field, CMOS-based devices, including the removal of instrumental effects, astrometry, photometry, and flux calibration. When… ▽ More As a pathfinder of the SiTian project, the Mini-SiTian (MST) array, employed three commercial CMOS cameras, represents a next-generation, cost-effective optical time-domain survey project. This paper focuses primarily on the precise data processing pipeline designed for wide-field, CMOS-based devices, including the removal of instrumental effects, astrometry, photometry, and flux calibration. When applying this pipeline to approximately 3000 observations taken in the Field 02 (f02) region by MST, the results demonstrate a remarkable astrometric precision of approximately 70--80\,mas (about 0.1\,pixel), an impressive calibration accuracy of approximately 1\,mmag in the MST zero points, and a photometric accuracy of about 4\,mmag for bright stars. Our studies demonstrate that MST CMOS can achieve photometric accuracy comparable to that of CCDs, highlighting the feasibility of large-scale CMOS-based optical time-domain surveys and their potential applications for cost optimization in future large-scale time-domain surveys, like the SiTian project. △ Less

Submitted 2 April, 2025; originally announced April 2025.

Comments: 24 pages, 17 figures, 1 table, accepted for publication in a special issue of Research in Astronomy and Astrophysics on the Mini-SiTian Array, see main results in Figures 11, 12, and 15

Searching for kilonova with the SiTian prototype telescope

Authors: Zhirui Li, Hongrui Gu, Yongkang Sun, Yang Huang, Youjun Lu, Jifeng Liu

Abstract: We simulate the optical searching of gravitational-wave electromagnetic counterpart of the binary neutron star (BNS) merger event (i.e., a kilonova) using the ground based {\it SiTian} project prototype telescope with a 5-min limiting magnitude of 22.0, triggered by LIGO and Virgo gravitational wave detectors during the ongoing O4 run. Our simulations show that an average of 0.17-0.25 kilonova eve… ▽ More We simulate the optical searching of gravitational-wave electromagnetic counterpart of the binary neutron star (BNS) merger event (i.e., a kilonova) using the ground based {\it SiTian} project prototype telescope with a 5-min limiting magnitude of 22.0, triggered by LIGO and Virgo gravitational wave detectors during the ongoing O4 run. Our simulations show that an average of 0.17-0.25 kilonova events can be observed over the entire O4 period of $\sim 2$ years in the most optimistic case we set, while no kilonova can be detected in other cases. We note that it is beneficial for {\it SiTian}'s kilonova searching by extending the exposure time to gain deeper limiting magnitude despite the rapid decline of kilonova luminosity. △ Less

Submitted 2 April, 2025; originally announced April 2025.

Comments: 16 pages, 7 figures. Accepted for publication in a special issue of Research in Astronomy and Astrophysics on the Mini-SiTian Array

The Mini-SiTian Array: first-two-year operation

Authors: Min He, Hong Wu, Liang Ge, Jian-feng Tian, Zheng Wang, Hai-yang Mu, Yu Zhang, Yang Huang, Jie Zheng, Zhou Fan, Zheng-yang Li, Hong-hui Gu, Heng-geng Han, Kai Xiao, Zhi-rui Li, Jun-jie Jin, Bei-chuan Wang, Jun Ma, Jin-hang Zou, Ying Wu, Jiu-peng Guo, Li-guo Fang, Zhi-gang Hou, Bo-wen Zhang, Yun-fei Xu , et al. (48 additional authors not shown)

Abstract: The SiTian project, designed to utilize 60 telescopes distributed across multiple sites in China, is a next-generation time-domain survey initiative. As a pathfinder for the SiTian project, the Mini-SiTian (MST) has been proposed and implemented to test the SiTian's brain and data pipeline, and to evaluate the feasibility of its technology and science cases. Mounted at the Xinglong Observatory, th… ▽ More The SiTian project, designed to utilize 60 telescopes distributed across multiple sites in China, is a next-generation time-domain survey initiative. As a pathfinder for the SiTian project, the Mini-SiTian (MST) has been proposed and implemented to test the SiTian's brain and data pipeline, and to evaluate the feasibility of its technology and science cases. Mounted at the Xinglong Observatory, the MST project comprises three 30 cm telescopes and has been operated since Nov. 2022. Each telescope of the MST possesses a large field of view, covering $2.29^{\circ}$ $\times$ $1.53^{\circ}$ FOV, and is equipped with $g'$, $r'$ and $i'$ filters, respectively. Acting as the pioneer of the forthcoming SiTian project, the MST is dedicated to the discovery of variable stars, transients, and outburst events, and has already obtained some interesting scientific results. In this paper, we will summarize the first-two-year operation of the MST project. △ Less

Submitted 2 April, 2025; originally announced April 2025.

Comments: 10 pages, 11 figures, Accepted for publication in a special issue of Research in Astronomy and Astrophysics on the Mini-SiTian Array

The Mini-SiTian Array: White Paper

Authors: Henggeng Han, Yang Huang, Beichuan Wang, Yongkang Sun, Cunshi Wang, Zhirui Li, Junjie Jin, Ningchen Sun, Kai Xiao, Min He, Hongrui Gu, Zexi Niu, Hong Wu, Jifeng Liu

Abstract: This paper outlines the scientific goals and observational strategies of the Mini-SiTian array. Mounted at Xinglong Observatory, the Mini-SiTian array consists of three 30 cm telescopes and has been in operation since 2022. The large field of view, combined with the capability for multi-band photometric observations, enables the Mini-SiTian array to perform rapid follow-up observations to identify… ▽ More This paper outlines the scientific goals and observational strategies of the Mini-SiTian array. Mounted at Xinglong Observatory, the Mini-SiTian array consists of three 30 cm telescopes and has been in operation since 2022. The large field of view, combined with the capability for multi-band photometric observations, enables the Mini-SiTian array to perform rapid follow-up observations to identify optical counterparts of gravitational waves, capture the early light curves of tidal disruption events and supernovae, and monitor stellar flares, Be star outbursts, and cataclysmic variable stars, although its limiting magnitude is not very deep. By collaborating with the Xinglong 2.16-m telescope and leveraging a real-time image processing pipeline, simultaneous photometric and spectroscopic observations could be performed to reveal their underlying physical mechanisms. The observational and research experience provide critical guidance for the implementation of the full-scale SiTian project in the future. △ Less

Submitted 2 April, 2025; originally announced April 2025.

Comments: 11 pages, 2 figures, Accepted for publication in a special issue of Research in Astronomy and Astrophysics on the Mini-SiTian Array

The Mini-SiTian Array: the mini-SiTian Realtime Image Processing pipeline (STRIP)

Authors: Hongrui Gu, Yang Huang, Yongkang Sun, Kai Xiao, Zhirui Li, Beichuan Wang, Zhou Fan, Chuanjie Zheng, Henggeng Han, Hu Zou, Wenxiong Li, Hong Wu, Jifeng Liu

Abstract: This paper provides a comprehensive introduction to the Mini-SiTian Real-Time Image Processing pipeline (STRIP) and evaluates its operational performance. The STRIP pipeline is specifically designed for real-time alert triggering and light curve generation for transient sources. By applying the STRIP pipeline to both simulated and real observational data of the Mini-SiTian survey, it successfully… ▽ More This paper provides a comprehensive introduction to the Mini-SiTian Real-Time Image Processing pipeline (STRIP) and evaluates its operational performance. The STRIP pipeline is specifically designed for real-time alert triggering and light curve generation for transient sources. By applying the STRIP pipeline to both simulated and real observational data of the Mini-SiTian survey, it successfully identified various types of variable sources, including stellar flares, supernovae, variable stars, and asteroids, while meeting requirements of reduction speed within 5 minutes. For the real observational dataset, the pipeline detected 1 flare event, 127 variable stars, and 14 asteroids from three monitored sky regions. Additionally, two datasets were generated: one, a real-bogus training dataset comprising 218,818 training samples, and the other, a variable star light curve dataset with 421 instances. These datasets will be used to train machine learning algorithms, which are planned for future integration into STRIP. △ Less

Submitted 2 April, 2025; originally announced April 2025.

Comments: 17 pages, 9 figures. Accepted for publication in a special issue of Research in Astronomy and Astrophysics on the Mini-SiTian Array

JADES and SAPPHIRES: Galaxy Metamorphosis Amidst a Huge, Luminous Emission-line Region

Authors: Francesco D'Eugenio, Jakob M. Helton, Kevin Hainline, Fengwu Sun, Roberto Maiolino, Pablo G. Pérez-González, Ignas Juodžbalis, Santiago Arribas, Andrew J. Bunker, Stefano Carniani, Emma Curtis-Lake, Eiichi Egami, Daniel J. Eisenstein, Benjamin D. Johnson, Brant Robertson, Sandro Tacchella, Christopher N. A. Willmer, Chris Willott, William M. Baker, A. Lola Danhaive, Qiao Duan, Yoshinobu Fudamoto, Gareth C. Jones, Xiaojing Lin, Weizhe Liu , et al. (10 additional authors not shown)

Abstract: We report the discovery of a remarkably large and luminous line-emitting nebula extending on either side of the Balmer-break galaxy JADES-GS-518794 at z=5.89, detected with JADES JWST/NIRCam imaging in [O III]$λλ$4959,5007 and H$α$ and spectroscopically confirmed with NIRCam/WFSS thanks to the pure-parallel SAPPHIRES programme. The end-to-end velocity offset is $Δv=830\pm130$ km s$^{-1}$. Nebulae… ▽ More We report the discovery of a remarkably large and luminous line-emitting nebula extending on either side of the Balmer-break galaxy JADES-GS-518794 at z=5.89, detected with JADES JWST/NIRCam imaging in [O III]$λλ$4959,5007 and H$α$ and spectroscopically confirmed with NIRCam/WFSS thanks to the pure-parallel SAPPHIRES programme. The end-to-end velocity offset is $Δv=830\pm130$ km s$^{-1}$. Nebulae with such large size and high luminosity (25-pkpc diameter, L[O III] = $1.2\times 10^{10}$ L$_\odot$) are routinely observed around bright quasars, unlike JADES-GS-518794. With a stellar mass of $10^{10.1}$ M$_\odot$, this galaxy is at the knee of the mass function at z=6. Its star-formation rate declined for some time (10-100 Myr prior to observation), followed by a recent (10 Myr) upturn. This system is part of a candidate large-scale galaxy overdensity, with an excess of Balmer-break galaxies compared to the field (3 $σ$). We discuss the possible origin of this nebula as material from a merger or gas expelled by an active galactic nucleus (AGN). The symmetry of the nebula, its bubble-like morphology, kinematics, high luminosity, and the extremely high equivalent width of [OIII] together favour the AGN interpretation. Intriguingly, there may be a physical connection between the presence of such a large, luminous nebula and the possible metamorphosis of the central galaxy towards quenching. △ Less

Submitted 8 July, 2025; v1 submitted 19 March, 2025; originally announced March 2025.

Comments: 21 pages, 12 figures, accepted by MNRAS

Calibration of Complementary Metal-oxide-semiconductor Sensor-based Photometry to a Few-millimagnitude Precision: The Case of the Mini-SiTian Array

Authors: Kai Xiao, Yang Huang, Haibo Yuan, Zhirui Li, Yongkang Sun, Timothy C. Beers, Min He, Jifeng Liu, Hong Wu, Yongna Mao, Bowen Huang, Mingyang Ma, Chuanjie Zheng, Hongrui Gu, Beichuan Wang, Lin Yang, Shuai Xu

Abstract: We present a pioneering achievement in the high-precision photometric calibration of CMOS-based photometry, by application of the Gaia BP/RP (XP) spectra-based synthetic photometry (XPSP) method to the mini-SiTian array (MST) photometry. Through 79 repeated observations of the $\texttt{f02}$ field on the night, we find good internal consistency in the calibrated MST $G_{\rm MST}$-band magnitudes f… ▽ More We present a pioneering achievement in the high-precision photometric calibration of CMOS-based photometry, by application of the Gaia BP/RP (XP) spectra-based synthetic photometry (XPSP) method to the mini-SiTian array (MST) photometry. Through 79 repeated observations of the $\texttt{f02}$ field on the night, we find good internal consistency in the calibrated MST $G_{\rm MST}$-band magnitudes for relatively bright stars, with a precision of about 4\,mmag for $G_{\rm MST}\sim 13$. Results from more than 30 different nights (over 3100 observations) further confirm this internal consistency, indicating that the 4\,mmag precision is stable and achievable over timescales of months. An independent external validation using spectroscopic data from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) DR10 and high-precision photometric data using CCDs from Gaia DR3 reveals a zero-point consistency better than 1\,mmag. Our results clearly demonstrate that CMOS photometry is on par with CCD photometry for high-precision results, highlighting the significant capabilities of CMOS cameras in astronomical observations, especially for large-scale telescope survey arrays. △ Less

Submitted 16 March, 2025; originally announced March 2025.

Comments: 8 pages, 6 figures, ApJL accepted, see main results in Figures 4

Gas Transfer Between the Inner 3-kpc Disk and the Galactic Central Molecular Zone

Authors: Yang Su, Shiyu Zhang, Yan Sun, Ji Yang, Fujun Du, Min Fang, Qing-Zeng Yan, Shaobo Zhang, Zhiwei Chen, Xuepeng Chen, Xin Zhou, Lixia Yuan, Yuehui Ma

Abstract: We uncovered a more tilted molecular gas structure with highly negative velocities located near the dust lane. Our observations also show that the approaching gas flows from the overshoot process are captured by the bar gravitational and then flows towards the Galactic central molecular zone (CMZ) through the bar channel. The recycling gas from the overshoot effect, in conjunction with freshly acc… ▽ More We uncovered a more tilted molecular gas structure with highly negative velocities located near the dust lane. Our observations also show that the approaching gas flows from the overshoot process are captured by the bar gravitational and then flows towards the Galactic central molecular zone (CMZ) through the bar channel. The recycling gas from the overshoot effect, in conjunction with freshly accreted gas from the inner 3-kpc disk, accumulates significantly near R_GC~1/2R_bar and R_GC~2/3R_bar regions by adopting a bar length of ~3.2--3.4kpc. Importantly, within these regions, there are frequent collisions and substantial angular momentum exchanges between gas flows with different trajectories. In this scenario, the DISSIPATION processes arising from interactions between colliding flows, together with the varying torques induced by the nonaxisymmetric bar, effectively transfer the angular momentum of viscous gas outward, thereby driving the molecular gas to settle into the CMZ within ~3 orbital periods. A long-term gas inflow with an average rate of >1.1Msun/yr, coupled with intense transient accretion events that exceed the average rate by several times due to the overshoot effect, significantly regulates the gas distribution, physical properties, and dynamical evolution of the CMZ. These findings provide robust observational evidence for elucidating the intricate dynamics of molecular gas flows towards the CMZ. Our results show that gas dynamics has a significant impact on the secular evolution of both the Milky Way and the extragalactic gas-rich galaxies. △ Less

Submitted 4 May, 2025; v1 submitted 15 March, 2025; originally announced March 2025.

Comments: Published in the ApJ, 984, 109 (2025)

Journal ref: ApJ, 984, 109 (2025)

Tentative rotation in a galaxy at z$\sim$14 with ALMA

Authors: J. Scholtz, E. Parlanti, S. Carniani, M. Kohandel, F. Sun, A. L. Danhaive, R. Maiolino, S. Arribas, R. Bhatawdekar, A. J. Bunker, S. Charlot, F. D'Eugenio, A. Ferrara, Z. Ji, Gareth C. Jones, P. Rinaldi, B. Robertson, A. Pallottini, I. Shivaei, Y. Sun, S. Tacchella, H. Übler, G. Venturi

Abstract: We re-analysed ALMA observations of the [OIII]$λ$88$μ$m emission line in JADES-GS-z14.0, so far the most distant spectroscopically confirmed galaxy at z=14.18. Our analysis shows a tentative detection of a velocity gradient of [OIII]$λ$88$μ$m using three independent tests: 1) construction of moment maps; 2) extraction of integrated spectra from a grid of apertures; and 3) spectro-astrometry in bot… ▽ More We re-analysed ALMA observations of the [OIII]$λ$88$μ$m emission line in JADES-GS-z14.0, so far the most distant spectroscopically confirmed galaxy at z=14.18. Our analysis shows a tentative detection of a velocity gradient of [OIII]$λ$88$μ$m using three independent tests: 1) construction of moment maps; 2) extraction of integrated spectra from a grid of apertures; and 3) spectro-astrometry in both the image and uv planes. We performed kinematical fitting using the KinMS code and estimated a dynamical mass of log$_{10}$(M$_{\rm dyn}$/$\rm M_\odot$)= 9.4$^{+0.8}_{-0.4}$, with the bulk of the uncertainties due to the degeneracy between dynamical mass and inclination. We measure an upper limit on the velocity dispersion ($σ_{v}$) of $<40~$ km/s~which results in an estimate of V$_{\rm rot}/σ>$ 2.5. This result, if confirmed with higher-resolution observations, would imply that kinematically cold discs are already in place at $z\sim14$. Comparison with mock observations from the SERRA cosmological simulations confirms that even low-resolution observations are capable of detecting a velocity gradient in $z>10$ galaxies as compact as JADES-GS-z14.0. This work shows that deeper ALMA or JWST/NIRSpec IFS observations with high spatial resolution will be able to estimate an accurate dynamical mass for JADES-GS-z14.0, providing an upper limit to the stellar mass of this over-luminous galaxy. △ Less

Submitted 24 October, 2025; v1 submitted 13 March, 2025; originally announced March 2025.

Comments: accepted in Submitted to MNRAS as a letter

The $M_{*}-M_{\rm BH}$ Relation Evolution from z $\sim$ 6 to the Present Epoch

Authors: Yang Sun, George H. Rieke, Jianwei Lyu, Meredith A. Stone, Zhiyuan Ji, Pierluigi Rinaldi, Christopher N. A. Willmer, Yongda Zhu

Abstract: The ratio between the stellar mass of a galaxy, $M_{*}$, and that of its central supermassive black hole (SMBH), $M_\bullet$, the ``Magorrian'' relationship, traces their coevolution. JWST observations have suggested significant evolution in $M_\bullet/M_{*}$ relative to local scaling relationships both in low-mass galaxies and in quasars at z $\ge$ 4. We test this possibility by (1) determining t… ▽ More The ratio between the stellar mass of a galaxy, $M_{*}$, and that of its central supermassive black hole (SMBH), $M_\bullet$, the ``Magorrian'' relationship, traces their coevolution. JWST observations have suggested significant evolution in $M_\bullet/M_{*}$ relative to local scaling relationships both in low-mass galaxies and in quasars at z $\ge$ 4. We test this possibility by (1) determining the preferred $M_\bullet/M_{*}$ scaling relation among those proposed locally; and (2) providing uniform host galaxy stellar mass estimates. These steps reduce the prominence of the reported evolution. We then apply Monte Carlo simulations to account for observational biases. We still find a significant increase over the local scaling relation in $M_\bullet/M_{*}$ for z $\ge$ 4 SMBHs in very low-mass galaxies ($\log(M_*/M_{\odot})<10$). However, similarly high values of $M_\bullet/M_{*}$ are also found in low mass galaxies at $z \sim$ 0.5 to 3 that may be common at cosmic noon. Nonetheless, galaxies with similar behavior are rare locally and not accounted for in the local scaling relations. In contrast, z $\sim$ 6 quasars can have $M_\bullet/M_{*}$ well above the local relation value, but they can be explained as extreme cases still within the scaling relation for their higher mass host galaxies. Black holes in some of them and in the low-mass systems may be undergoing very high accretion episodes that result in high $M_\bullet/M_{*}$ but that will be followed by quiescent periods when growth of the host drives the systems toward more typical $M_\bullet/M_{*}$ values. △ Less

Submitted 7 March, 2025; v1 submitted 5 March, 2025; originally announced March 2025.

Comments: 20 pages, 7 figures, resubmitted to ApJ based on reviewer report

"Frog-eyes" in Astronomy: Monitoring Binary Radial Velocity Variations Through A Pair of Narrow-Band Filters

Authors: Chuanjie Zheng, Yang Huang, Jifeng Liu, Hongrui Gu, Hong Wu, Youjun Lu, Yongkang Sun, Henggeng Han, Song Wang, Timothy C. Beers, Kai Xiao, Zhirui Li, Boweng Zhang, Yongna Mao, Zhengyang Li, Hangxin Ji

Abstract: Spectroscopic observations are a crucial step in driving major discoveries in the era of time-domain surveys. However, the pace of current spectroscopic surveys is increasingly unable to meet the demands of rapidly advancing large-scale time-domain surveys. To address this issue, we propose the ``Frog-eyes" system, which employs a pair of narrow-band filters: one positioned near a strong absorptio… ▽ More Spectroscopic observations are a crucial step in driving major discoveries in the era of time-domain surveys. However, the pace of current spectroscopic surveys is increasingly unable to meet the demands of rapidly advancing large-scale time-domain surveys. To address this issue, we propose the ``Frog-eyes" system, which employs a pair of narrow-band filters: one positioned near a strong absorption line to capture signals from Doppler shifts, and the other placed on the adjacent continuum to monitor intrinsic variations. The combination of observations from the two filters enables the extraction of radial velocity (RV) curves from a large sample of binary stars, and is particularly efficient for single-lined binaries (SB1), using photometric techniques. Comprehensive mock simulations on SB1 demonstrate that the binary orbital parameters can be precisely measured from the extracted RV curves for binary systems where the primary star has an effective temperature greater than 6000 K. With a typical ground-based photometric precision of approximately 0.3%, the uncertainties in the derived semi-amplitude K and eccentricity e are less than 10% and 0.1, respectively, for binary systems with K $\ge$ 30 km/s. These encouraging results are further validated by real observations of the hot subdwarf-white dwarf binary system HD 265435, using a non-specialized ``Frog-eyes" system installed on the Chinese 2.16m telescope. Once this system is properly installed on large-field-of-view survey telescopes, the rate of acquiring RV curves for binaries will approach their detection rate in leading time-domain photometric surveys. △ Less

Submitted 25 February, 2025; originally announced February 2025.

Comments: 17 pages, 11 figures, and 3 tables. Accepted for publication by SCPMA