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Slitless Spectroscopy Source Detection Using YOLO Deep Neural Network
Authors:
Xiaohan Chen,
Man I Lam,
Yingying Zhou,
Hongrui Gu,
Jinzhi Lai,
Zhou Fan,
Jing Li,
Xin Zhang,
Hao Tian
Abstract:
Slitless spectroscopy eliminates the need for slits, allowing light to pass directly through a prism or grism to generate a spectral dispersion image that encompasses all celestial objects within a specified area. This technique enables highly efficient spectral acquisition. However, when processing CSST slitless spectroscopy data, the unique design of its focal plane introduces a challenge: photo…
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Slitless spectroscopy eliminates the need for slits, allowing light to pass directly through a prism or grism to generate a spectral dispersion image that encompasses all celestial objects within a specified area. This technique enables highly efficient spectral acquisition. However, when processing CSST slitless spectroscopy data, the unique design of its focal plane introduces a challenge: photometric and slitless spectroscopic images do not have a one-to-one correspondence. As a result, it becomes essential to first identify and count the sources in the slitless spectroscopic images before extracting spectra. To address this challenge, we employed the You Only Look Once (YOLO) object detection algorithm to develop a model for detecting targets in slitless spectroscopy images. This model was trained on 1,560 simulated CSST slitless spectroscopic images. These simulations were generated from the CSST Cycle 6 and Cycle 9 main survey data products, representing the Galactic and nearby galaxy regions and the high galactic latitude regions, respectively. On the validation set, the model achieved a precision of 88.6% and recall of 90.4% for spectral lines, and 87.0% and 80.8% for zeroth-order images. In testing, it maintained a detection rate >80% for targets brighter than 21 mag (medium-density regions) and 20 mag (low-density regions) in the Galactic and nearby galaxies regions, and >70% for targets brighter than 18 mag in high galactic latitude regions.
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Submitted 12 October, 2025;
originally announced October 2025.
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Diffuse Ionized Gas in the Anti-center of the Milky Way
Authors:
Shiming Wen,
Wei Zhang,
Lin Ma,
Yunning Zhao,
Man I. Lam,
Chaojian Wu,
Juanjuan Ren,
Jianjun Chen,
Yuzhong Wu,
Guozhen Hu,
Yonghui Hou,
Yongheng Zhao,
Hong Wu
Abstract:
Using data from the LAMOST Medium-Resolution Spectroscopic Survey of Nebulae, we create a sample of 17,821 diffuse ionized gas (DIG) spectra in the anti-center region of the Milky Way, by excluding fibers in the directions of H II regions and supernova remnants. We then analyze the radial and vertical distributions of three line ratios ([N II]/H$α$, [S II]/H$α$, and [S II]/[N II]), as well as the…
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Using data from the LAMOST Medium-Resolution Spectroscopic Survey of Nebulae, we create a sample of 17,821 diffuse ionized gas (DIG) spectra in the anti-center region of the Milky Way, by excluding fibers in the directions of H II regions and supernova remnants. We then analyze the radial and vertical distributions of three line ratios ([N II]/H$α$, [S II]/H$α$, and [S II]/[N II]), as well as the oxygen abundance.
[N II]/H$α$ and [S II]/H$α$ do not exhibit a consistent, monotonic decrease with increasing Galactocentric distance (R$_{gal}$). Instead, they show enhancement within the interarm region, positioned between the Local Arm and the Perseus Arm. [S II]/[N II] has a radial gradient of 0.1415 $\pm$ 0.0646 kpc$^{-1}$ for the inner disk (8.34 $ < R_{gal} < $ 9.65 kpc), and remains nearly flat for the outer disk ($R_{gal} > $ 9.65 kpc). In the vertical direction, [N II]/H$α$, [S II]/H$α$, and [S II]/[N II] increase with increasing Galactic disk height ($|z|$) in both southern and northern disks.
Based on the N2S2H$α$ method, which combines [S II]/[N II] and [N II]/H$α$, we estimate the oxygen abundance. The oxygen abundance exhibits a consistent radial gradient with R$_{gal}$, featuring a slope of -0.0559 $\pm$ 0.0209 dex kpc$^{-1}$ for the inner disk and a similar slope of -0.0429 $\pm$ 0.0599 dex kpc$^{-1}$ for the outer disk. A single linear fitting to the entire disk yields a slope of -0.0317 $\pm$ 0.0124 dex kpc$^{-1}$. In the vertical direction, the oxygen abundance decreases with increasing $|z|$ in both southern and northern disks.
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Submitted 7 December, 2024;
originally announced December 2024.
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The Velocity Aberration Effect of the CSST Main Survey Camera
Authors:
Hui-Mei Feng,
Zi-Huang Cao,
Man I Lam,
Ran Li,
Hao Tian,
Xin Zhang,
Peng Wei,
Xin-Feng Li,
Wei Wang,
Hugh R. A. Jones,
Mao-Yuan Liu,
Chao Liu
Abstract:
In this study, we conducted simulations to find the geometric aberrations expected for images taken by the Main Survey Camera (MSC) of the Chinese Space Station Telescope (CSST) due to its motion. As anticipated by previous work, our findings indicate that the geometric distortion of light impacts the focal plane's apparent scale, with a more pronounced influence as the size of the focal plane inc…
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In this study, we conducted simulations to find the geometric aberrations expected for images taken by the Main Survey Camera (MSC) of the Chinese Space Station Telescope (CSST) due to its motion. As anticipated by previous work, our findings indicate that the geometric distortion of light impacts the focal plane's apparent scale, with a more pronounced influence as the size of the focal plane increases. Our models suggest that the effect consistently influences the pixel scale in both the vertical and parallel directions. The apparent scale variation follows a sinusoidal distribution throughout one orbit period. Simulations reveal that the effect is particularly pronounced in the center of the Galaxy and gradually diminishes along the direction of ecliptic latitude. At low ecliptic latitudes, the total aberration leads to about 0.94 pixels offset (a 20-minute exposure) and 0.26 pixels offset (a 300-second exposure) at the edge of the field of view, respectively. Appropriate processings for the geometric effect during the CSST pre- and post-observation phases are presented.
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Submitted 23 August, 2024;
originally announced August 2024.
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All-sky Guide Star Catalog for CSST
Authors:
Hui-Mei Feng,
Zi-Huang Cao,
Man I Lam,
Ran Li,
Hao Tian,
Da-Yi Yin,
Yuan-Yu Yang,
Xin Zhang,
Dong-Wei Fan,
Yi-Qiao Dong,
Xin-Feng Li,
Wei Wang,
Long Li,
Hugh R. A. Jones,
Yi-Han Tao,
Jia-Lu Nie,
Pei-Pei Wang,
Mao-Yuan Liu,
He-jun Yang,
Chao Liu
Abstract:
The China Space Station Telescope (CSST) is a two-meter space telescope with multiple back-end instruments. The Fine Guidance Sensor (FGS) is an essential subsystem of the CSST Precision Image Stability System to ensure the required absolute pointing accuracy and line-of-sight stabilization. In this study, we construct the Main Guide Star Catalog for FGS. To accomplish this, we utilize the informa…
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The China Space Station Telescope (CSST) is a two-meter space telescope with multiple back-end instruments. The Fine Guidance Sensor (FGS) is an essential subsystem of the CSST Precision Image Stability System to ensure the required absolute pointing accuracy and line-of-sight stabilization. In this study, we construct the Main Guide Star Catalog for FGS. To accomplish this, we utilize the information about the FGS and object information from the Gaia Data Release 3. We provide an FGS instrument magnitude and exclude variables, binaries, and high proper motion stars from the catalog to ensure uniform FGS guidance capabilities. Subsequently, we generate a HEALPix index, which provides a hierarchical tessellation of the celestial sphere, and employ the Voronoi algorithm to achieve a homogeneous distribution of stars across the catalog. This distribution ensures adequate coverage and sampling of the sky. The performance of the CSST guide star catalog was assessed by simulating the field of view of the FGS according to the CSST mock survey strategy catalog. The analysis of the results indicates that this catalog provides adequate coverage and accuracy. The catalog's performance meets the FGS requirements, ensuring the functioning of the FGS and its guidance capabilities.
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Submitted 3 June, 2024;
originally announced June 2024.
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Evolved Massive Stars at Low-metallicity VII. the Lower Mass Limit of Red Supergiant Population in the Large Magellanic Cloud
Authors:
Ming Yang,
Bo Zhang,
Biwei Jiang,
Jian Gao,
Yi Ren,
Shu Wang,
Man I Lam,
Hao Tian,
Changqing Luo,
Bingqiu Chen,
Jing Wen
Abstract:
The precise definition of the lower mass limit of red supergiant stars (RSGs) is an open question in astrophysics and does not attract too much attention. Here we assemble a spectroscopic evolved cool star sample with 6,602 targets, including RSGs, asymptotic giant branch stars, and red giant branch stars, in the Large Magellanic Cloud based on \textit{Gaia} DR3 and SDSS-IV/APOGEE-2. The reference…
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The precise definition of the lower mass limit of red supergiant stars (RSGs) is an open question in astrophysics and does not attract too much attention. Here we assemble a spectroscopic evolved cool star sample with 6,602 targets, including RSGs, asymptotic giant branch stars, and red giant branch stars, in the Large Magellanic Cloud based on \textit{Gaia} DR3 and SDSS-IV/APOGEE-2. The reference spectrum of each stellar population is built according to the quantile range of relative intensity ($1\%\sim99\%$). Five different methods, e.g., chi-square ($χ^2$), cosine similarity (CS), machine learning (ML), equivalent width (EW), and line ratio (LR), are used in order to separate different stellar populations. The ML and $χ^2$ provide the best and relatively consistent prediction of certain population. The derived lower limit of the RSG population is able to reach to the $\rm K_S$-band tip of red giant branch ($\rm K_S~$$\approx12.0$ mag), indicating a luminosity as low as about $10^{3.5}~L_{\sun}$, which corresponds to a stellar radius only about $100~R_{\sun}$. Given the mass-luminosity relation of $L/L_\sun =f(M/M_\sun)^3$ with $f\approx15.5\pm3$ and taking into account of the mass loss of faint RSGs up to now, the minimal initial mass of the RSG population would be about $6.1\pm0.4~M_\sun$, which is much lower than the traditional threshold of $8~M_\sun$ for the massive stars. This is the first spectroscopic evidence, indicating that the lower mass limit of RSG population is around $6~M_\sun$. However, the destinies of such faint RSGs are still elusive and may have large impact on the stellar evolutionary and supernova models.
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Submitted 28 January, 2024;
originally announced January 2024.
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Evolved Massive Stars at Low-metallicity V. Mass-Loss Rate of Red Supergiant Stars in the Small Magellanic Cloud
Authors:
Ming Yang,
Alceste Z. Bonanos,
Biwei Jiang,
Emmanouil Zapartas,
Jian Gao,
Yi Ren,
Man I Lam,
Tianding Wang,
Grigoris Maravelias,
Panagiotis Gavras,
Shu Wang,
Xiaodian Chen,
Frank Tramper,
Stephan de Wit,
Bingqiu Chen,
Jing Wen,
Jiaming Liu,
Hao Tian,
Konstantinos Antoniadis,
Changqing Luo
Abstract:
We assemble the most complete and clean red supergiant (RSG) sample (2,121 targets) so far in the Small Magellanic Cloud (SMC) with 53 different bands of data to study the MLR of RSGs. In order to match the observed spectral energy distributions (SEDs), a theoretical grid of 17,820 Oxygen-rich models (``normal'' and ``dusty'' grids are half-and-half) is created by the radiatively-driven wind model…
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We assemble the most complete and clean red supergiant (RSG) sample (2,121 targets) so far in the Small Magellanic Cloud (SMC) with 53 different bands of data to study the MLR of RSGs. In order to match the observed spectral energy distributions (SEDs), a theoretical grid of 17,820 Oxygen-rich models (``normal'' and ``dusty'' grids are half-and-half) is created by the radiatively-driven wind model of the DUSTY code, covering a wide range of dust parameters. We select the best model for each target by calculating the minimal modified chi-square and visual inspection. The resulting MLRs from DUSTY are converted to real MLRs based on the scaling relation, for which a total MLR of $6.16\times10^{-3}$ $M_\odot$ yr$^{-1}$ is measured (corresponding to a dust-production rate of $\sim6\times10^{-6}$ $M_\odot$ yr$^{-1}$), with a typical MLR of $\sim10^{-6}$ $M_\odot$ yr$^{-1}$ for the general population of the RSGs. The complexity of mass-loss estimation based on the SED is fully discussed for the first time, indicating large uncertainties based on the photometric data (potentially up to one order of magnitude or more). The Hertzsprung-Russell and luminosity versus median absolute deviation diagrams of the sample indicate the positive relation between luminosity and MLR. Meanwhile, the luminosity versus MLR diagrams show a ``knee-like'' shape with enhanced mass-loss occurring above $\log_{10}(L/L_\odot)\approx4.6$, which may be due to the degeneracy of luminosity, pulsation, low surface gravity, convection, and other factors. We derive our MLR relation by using a third-order polynomial to fit the sample and compare our result with previous empirical MLR prescriptions. Given that our MLR prescription is based on a much larger sample than previous determinations, it provides a more accurate relation at the cool and luminous region of the H-R diagram at low-metallicity compared to previous studies.
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Submitted 4 April, 2023;
originally announced April 2023.
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The wide-field, multiplexed, spectroscopic facility WEAVE: Survey design, overview, and simulated implementation
Authors:
Shoko Jin,
Scott C. Trager,
Gavin B. Dalton,
J. Alfonso L. Aguerri,
J. E. Drew,
Jesús Falcón-Barroso,
Boris T. Gänsicke,
Vanessa Hill,
Angela Iovino,
Matthew M. Pieri,
Bianca M. Poggianti,
D. J. B. Smith,
Antonella Vallenari,
Don Carlos Abrams,
David S. Aguado,
Teresa Antoja,
Alfonso Aragón-Salamanca,
Yago Ascasibar,
Carine Babusiaux,
Marc Balcells,
R. Barrena,
Giuseppina Battaglia,
Vasily Belokurov,
Thomas Bensby,
Piercarlo Bonifacio
, et al. (190 additional authors not shown)
Abstract:
WEAVE, the new wide-field, massively multiplexed spectroscopic survey facility for the William Herschel Telescope, will see first light in late 2022. WEAVE comprises a new 2-degree field-of-view prime-focus corrector system, a nearly 1000-multiplex fibre positioner, 20 individually deployable 'mini' integral field units (IFUs), and a single large IFU. These fibre systems feed a dual-beam spectrogr…
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WEAVE, the new wide-field, massively multiplexed spectroscopic survey facility for the William Herschel Telescope, will see first light in late 2022. WEAVE comprises a new 2-degree field-of-view prime-focus corrector system, a nearly 1000-multiplex fibre positioner, 20 individually deployable 'mini' integral field units (IFUs), and a single large IFU. These fibre systems feed a dual-beam spectrograph covering the wavelength range 366$-$959\,nm at $R\sim5000$, or two shorter ranges at $R\sim20\,000$. After summarising the design and implementation of WEAVE and its data systems, we present the organisation, science drivers and design of a five- to seven-year programme of eight individual surveys to: (i) study our Galaxy's origins by completing Gaia's phase-space information, providing metallicities to its limiting magnitude for $\sim$3 million stars and detailed abundances for $\sim1.5$ million brighter field and open-cluster stars; (ii) survey $\sim0.4$ million Galactic-plane OBA stars, young stellar objects and nearby gas to understand the evolution of young stars and their environments; (iii) perform an extensive spectral survey of white dwarfs; (iv) survey $\sim400$ neutral-hydrogen-selected galaxies with the IFUs; (v) study properties and kinematics of stellar populations and ionised gas in $z<0.5$ cluster galaxies; (vi) survey stellar populations and kinematics in $\sim25\,000$ field galaxies at $0.3\lesssim z \lesssim 0.7$; (vii) study the cosmic evolution of accretion and star formation using $>1$ million spectra of LOFAR-selected radio sources; (viii) trace structures using intergalactic/circumgalactic gas at $z>2$. Finally, we describe the WEAVE Operational Rehearsals using the WEAVE Simulator.
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Submitted 31 October, 2023; v1 submitted 7 December, 2022;
originally announced December 2022.
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Searching Water Megamasers By Using Mid-infrared Spectroscopy (I): Possible Mid-infrared Indicators
Authors:
Man I Lam,
C. Jakob Walcher,
Feng Gao,
Ming Yang,
Huan Li,
Lei Hao
Abstract:
Water megamasers at 22 GHz with a gas disk configuration in galaxies provide the most precise measurements of supermassive black hole masses, as well as independent constraints on the Hubble constant in the nearby universe. The existence of other maser types, such as jet or outflow masers, represents another tracer for AGN science. However, the detection rate of water megamasers in galaxies is ext…
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Water megamasers at 22 GHz with a gas disk configuration in galaxies provide the most precise measurements of supermassive black hole masses, as well as independent constraints on the Hubble constant in the nearby universe. The existence of other maser types, such as jet or outflow masers, represents another tracer for AGN science. However, the detection rate of water megamasers in galaxies is extremely low. Over 40 years, only $\sim$ 160 galaxies are found to harbour maser emission, and $\sim$ 30\% of them show features in their maser emission that indicate a disk-like geometry. Therefore, increasing the detection rate of masers is a crucial task to allow expanding on maser studies. We present a comparison of mid-infrared spectroscopic data between a maser galaxy sample and a Seyfert 2 control sample. We find that maser galaxies show significant peculiarities in their mid-infrared spectra: (1) Maser galaxies tend to present stronger silicate absorption at $τ$ 9.7 $μ$m than the control sample, (2) PAH 11.3 $μ$m emission in maser galaxies is much weaker than in the control sample, (3) spectral indices at 20-30 $μ$m are steeper in maser galaxies than in the control sample and tend to be mid-infrared enhanced population. We conclude that there may be good indicators in mid-infrared and far-infrared which could differentiate maser and non-maser Seyfert 2 galaxies. Upcoming infrared facilities, such as the James Webb Space Telescope, may be able to exploit these and other useful criteria and tracers for water megamaser observations.
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Submitted 20 July, 2021;
originally announced July 2021.
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Evolved Massive Stars at Low-metallicity IV. Using 1.6 $μ$m "H-bump" to identify red supergiant stars: a case study of NGC 6822
Authors:
Ming Yang,
Alceste Z. Bonanos,
Biwei Jiang,
Man I Lam,
Jian Gao,
Panagiotis Gavras,
Grigoris Maravelias,
Shu Wang,
Xiao-Dian Chen,
Frank Tramper,
Yi Ren,
Zoi T. Spetsieri
Abstract:
We present a case study of using a novel method to identify red supergiant (RSG) candidates in NGC 6822, based on their 1.6 $μ$m "H-bump". We collected 32 bands of photometric data for NGC 6822 ranging from optical to MIR. By using the theoretical spectra from MARCS, we demonstrate that there is a prominent difference around 1.6 $μ$m ("H-bump") between low-surface-gravity (LSG) and high-surface-gr…
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We present a case study of using a novel method to identify red supergiant (RSG) candidates in NGC 6822, based on their 1.6 $μ$m "H-bump". We collected 32 bands of photometric data for NGC 6822 ranging from optical to MIR. By using the theoretical spectra from MARCS, we demonstrate that there is a prominent difference around 1.6 $μ$m ("H-bump") between low-surface-gravity (LSG) and high-surface-gravity (HSG) targets. Taking advantage of this feature, we identify efficient color-color diagrams (CCDs) of rzH and rzK to separate HSG and LSG targets from crossmatching of optical and NIR data. Moreover, synthetic photometry from ATLAS9 also give similar results. Further separating RSG candidates from the rest of the LSG candidates is done by using semi-empirical criteria on NIR CMDs and resulted in 323 RSG candidates. Meanwhile, the simulation of foreground stars from Besançon models also indicates that our selection criteria is largely free from the contamination of Galactic giants. In addition to the "H-bump" method, we also use the traditional BVR method as a comparison and/or supplement, by applying a slightly aggressive cut to select as much as possible RSG candidates (358 targets). Furthermore, the Gaia astrometric solution is used to constrain the sample, where 181 and 193 targets were selected from the "H-bump" and BVR method, respectively. The percentages of selected targets in both methods are similar as $\sim$60\%, indicating the comparable accuracy of the two methods. In total, there are 234 RSG candidates after combining targets from both methods with 140 ($\sim$60\%) of them in common. The final RSG candidates are in the expected locations on the MIR CMDs, while the spatial distribution is also coincident with the FUV-selected star formation regions, suggesting the selection is reasonable and reliable.
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Submitted 21 January, 2021;
originally announced January 2021.
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Evolved Massive Stars at Low-metallicity III. A Source Catalog for the Large Magellanic Cloud
Authors:
Ming Yang,
Alceste Z. Bonanos,
Biwei Jiang,
Jian Gao,
Panagiotis Gavras,
Grigoris Maravelias,
Shu Wang,
Xiao-Dian Chen,
Man I Lam,
Yi Ren,
Frank Tramper,
Zoi T. Spetsieri
Abstract:
We present a clean, magnitude-limited (IRAC1 or WISE1$\leq$15.0 mag) multiwavelength source catalog for the LMC. The catalog was built upon crossmatching ($1''$) and deblending ($3''$) between the SEIP source list and Gaia DR2, with strict constraints on the Gaia astrometric solution to remove the foreground contamination. The catalog contains 197,004 targets in 52 different bands including 2 ultr…
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We present a clean, magnitude-limited (IRAC1 or WISE1$\leq$15.0 mag) multiwavelength source catalog for the LMC. The catalog was built upon crossmatching ($1''$) and deblending ($3''$) between the SEIP source list and Gaia DR2, with strict constraints on the Gaia astrometric solution to remove the foreground contamination. The catalog contains 197,004 targets in 52 different bands including 2 ultraviolet, 21 optical, and 29 infrared bands. Additional information about radial velocities and spectral/photometric classifications were collected from the literature. The bright end of our sample is mostly comprised of blue helium-burning stars (BHeBs) and red HeBs with inevitable contamination of main sequence stars at the blue end. After applying modified magnitude and color cuts based on previous studies, we identify and rank 2,974 RSG, 508 YSG, and 4,786 BSG candidates in the LMC in six CMDs. The comparison between the CMDs of the LMC and SMC indicates that the most distinct difference appears at the bright red end of the optical and near-infrared CMDs, where the cool evolved stars (e.g., RSGs, AGB, and RGs) are located, which is likely due to the effect of metallicity and SFH. Further quantitative comparison of colors of massive star candidates in equal absolute magnitude bins suggests that, there is basically no difference for the BSG candidates, but large discrepancy for the RSG candidates as LMC targets are redder than the SMC ones, which may be due to the combined effect of metallicity on both spectral type and mass-loss rate, and also the age effect. The $T_{\rm eff}$ of massive star populations are also derived from reddening-free color of $(J-K_{\rm S})_0$. The $T_{\rm eff}$ ranges are $3500<T_{\rm eff}<5000$ K for RSG population, $5000<T_{\rm eff}<8000$ K for YSG population, and $T_{\rm eff}>8000$ K for BSG population, with larger uncertainties towards the hotter stars.
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Submitted 15 December, 2020;
originally announced December 2020.
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An $Hα$ Imaging Survey of the all (Ultra-)Luminous Infrared Galaxies at $Dec. \ge -30^{\circ}$ in the GOALS Sample
Authors:
Jun-Jie Jin,
Yi-Nan Zhu,
Hong Wu,
Feng-Jie Lei,
Chen Cao,
Xian-Min Meng,
Zhi-Min Zhou,
Man I Lam
Abstract:
This paper presents the result of $Hα$ imaging for luminous infrared galaxies (LIRGs) and ultra-luminous infrared galaxies (ULIRGs). \textbf{It is } a \textbf{complete subsample of Great Observatories All-sky LIRG Survery (GOALS) with $Dec. \ge -30^{\circ}$}, \textbf{and} consists 148 galaxies with $log(L_{IR}/L_{\odot}) \ge 11.0$. All the $Hα$ images were carried out using the 2.16-m telescope \t…
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This paper presents the result of $Hα$ imaging for luminous infrared galaxies (LIRGs) and ultra-luminous infrared galaxies (ULIRGs). \textbf{It is } a \textbf{complete subsample of Great Observatories All-sky LIRG Survery (GOALS) with $Dec. \ge -30^{\circ}$}, \textbf{and} consists 148 galaxies with $log(L_{IR}/L_{\odot}) \ge 11.0$. All the $Hα$ images were carried out using the 2.16-m telescope \textbf{at the Xinglong Station of the} National Astronomy Observatories, Chinese Academy of Sciences\textbf{ (NAOC),} during the year from 2006 to 2009. We obtained pure $Hα$ luminosity for each galaxy and corrected the luminosity for $[NII]$ emission, filter transmission and extinction. We also classified these galaxies based on their morphology and interaction. We found that the distribution of star-forming \textbf{regions} in these galaxies is related to this classification. As the merging process advanced, these galaxies tend to have a more compact distribution of star-forming region, higher \textbf{$L_{IR}$} and warmer IR-color ($f_{60}/f_{100}$). \textbf{These} results imply that the degree of dynamical disturbance plays an important role in determining the distribution of star-forming region.
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Submitted 23 October, 2019;
originally announced October 2019.
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The galaxy luminosity function in the LAMOST Complete Spectroscopic Survey of Pointing Area at the Southern Galactic Cap
Authors:
Pinsong Zhao,
Hong Wu,
C. K. Xu,
Ming Yang,
Fan Yang,
Yinan Zhu,
Man I Lam,
Junjie Jin,
Hailong Yuan,
Haotong Zhang,
Shiyin Shen,
Jianrong Shi,
Ali Luo,
Xuebing Wu,
Yongheng Zhao,
Yipeng Jing
Abstract:
We present optical luminosity functions (LFs) of galaxies in the $^{0.1}g$, $^{0.1}r$, and $^{0.1}i$ bands, calculated using data in $\sim 40$ $deg^{2}$ sky area of LAMOST Complete Spectroscopic Survey of Pointing Area (LaCoSSPAr) in Southern Galactic Cap. Redshifts for galaxies brighter $r = 18.1$ were obtained mainly with LAMOST. In each band, LFs derived using both parametric and non-parametric…
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We present optical luminosity functions (LFs) of galaxies in the $^{0.1}g$, $^{0.1}r$, and $^{0.1}i$ bands, calculated using data in $\sim 40$ $deg^{2}$ sky area of LAMOST Complete Spectroscopic Survey of Pointing Area (LaCoSSPAr) in Southern Galactic Cap. Redshifts for galaxies brighter $r = 18.1$ were obtained mainly with LAMOST. In each band, LFs derived using both parametric and non-parametric maximum likelihood methods agree well with each other. In the $^{0.1}r$ band, our fitting parameters of the Schechter function are $φ_{*}=(1.65\pm0.36)\times10^{-2}h^{3}Mpc^{-3}$, $M_{*}=-20.69\pm0.06$ mag, and $α=-1.12\pm0.08$, in agreements with previous studies. Separate LFs are also derived for emission line galaxies and absorption line galaxies, respectively. The LFs of absorption line galaxies show a dip at $^{0.1}r \sim 18.5$ and can be well fitted by a double-Gaussian function, suggesting a bi-modality in passive galaxies.
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Submitted 19 March, 2019;
originally announced March 2019.
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4MOST Survey Strategy Plan
Authors:
G. Guiglion,
C. Battistini,
C. P. M. Bell,
T. Bensby,
T. Boller,
C. Chiappini,
J. Comparat,
N. Christlieb,
R. Church,
M. -R. L. Cioni,
L. Davies,
T. Dwelly,
R. S. de Jong,
S. Feltzing,
A. Gueguen,
L. Howes,
M. Irwin,
I. Kushniruk,
M. I Lam,
J. Liske,
R. McMahon,
A. Merloni,
P. Norberg,
A. S. G. Robotham,
O. Schnurr
, et al. (8 additional authors not shown)
Abstract:
The current status of and motivation for the 4MOST Survey Strategy, as developed by the Consortium science team, are presented here. Key elements of the strategy are described, such as sky coverage, number of visits and total exposure times in different parts of the sky, and how to deal with different observing conditions. The task of organising the strategy is not simple, with many different surv…
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The current status of and motivation for the 4MOST Survey Strategy, as developed by the Consortium science team, are presented here. Key elements of the strategy are described, such as sky coverage, number of visits and total exposure times in different parts of the sky, and how to deal with different observing conditions. The task of organising the strategy is not simple, with many different surveys that have vastly different target brightnesses and densities, sample completeness levels, and signal-to-noise requirements. We introduce here a number of concepts that we will use to ensure all surveys are optimised. Astronomers who are planning to submit a Participating Survey proposal are strongly encouraged to read this article and any relevant 4MOST Survey articles in this issue of The Messenger such that they can optimally complement and benefit from the planned surveys of the 4MOST Consortium.
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Submitted 1 April, 2019; v1 submitted 6 March, 2019;
originally announced March 2019.
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4MOST Scientific Operations
Authors:
C. J. Walcher,
M. Banerji,
C. Battistini,
C. P. M. Bell,
O. Bellido-Tirado,
T. Bensby,
J. M. Bestenlehner,
T. Boller,
J. Brynnel,
A. Casey,
C. Chiappini,
N. Christlieb,
R. Church,
M. -R. L. Cioni,
S. Croom,
J. Comparat,
L. J. M. Davies,
R. S. de Jong,
T. Dwelly,
H. Enke,
S. Feltzing,
D. Feuillet,
M. Fouesneau,
D. Ford,
S. Frey
, et al. (43 additional authors not shown)
Abstract:
The 4MOST instrument is a multi-object spectrograph that will address Galactic and extragalactic science cases simultaneously by observing targets from a large number of different surveys within each science exposure. This parallel mode of operation and the survey nature of 4MOST require some distinct 4MOST-specific operational features within the overall operations model of ESO. The main feature…
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The 4MOST instrument is a multi-object spectrograph that will address Galactic and extragalactic science cases simultaneously by observing targets from a large number of different surveys within each science exposure. This parallel mode of operation and the survey nature of 4MOST require some distinct 4MOST-specific operational features within the overall operations model of ESO. The main feature is that the 4MOST Consortium will deliver, not only the instrument, but also contractual services to the user community, which is why 4MOST is also described as a facility. This white paper concentrates on information particularly useful to answering the forthcoming Call for Letters of Intent.
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Submitted 1 April, 2019; v1 submitted 6 March, 2019;
originally announced March 2019.
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4MOST: Project overview and information for the First Call for Proposals
Authors:
R. S. de Jong,
O. Agertz,
A. Agudo Berbel,
J. Aird,
D. A. Alexander,
A. Amarsi,
F. Anders,
R. Andrae,
B. Ansarinejad,
W. Ansorge,
P. Antilogus,
H. Anwand-Heerwart,
A. Arentsen,
A. Arnadottir,
M. Asplund,
M. Auger,
N. Azais,
D. Baade,
G. Baker,
S. Baker,
E. Balbinot,
I. K. Baldry,
M. Banerji,
S. Barden,
P. Barklem
, et al. (313 additional authors not shown)
Abstract:
We introduce the 4-metre Multi-Object Spectroscopic Telescope (4MOST), a new high-multiplex, wide-field spectroscopic survey facility under development for the four-metre-class Visible and Infrared Survey Telescope for Astronomy (VISTA) at Paranal. Its key specifications are: a large field of view (FoV) of 4.2 square degrees and a high multiplex capability, with 1624 fibres feeding two low-resolut…
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We introduce the 4-metre Multi-Object Spectroscopic Telescope (4MOST), a new high-multiplex, wide-field spectroscopic survey facility under development for the four-metre-class Visible and Infrared Survey Telescope for Astronomy (VISTA) at Paranal. Its key specifications are: a large field of view (FoV) of 4.2 square degrees and a high multiplex capability, with 1624 fibres feeding two low-resolution spectrographs ($R = λ/Δλ\sim 6500$), and 812 fibres transferring light to the high-resolution spectrograph ($R \sim 20\,000$). After a description of the instrument and its expected performance, a short overview is given of its operational scheme and planned 4MOST Consortium science; these aspects are covered in more detail in other articles in this edition of The Messenger. Finally, the processes, schedules, and policies concerning the selection of ESO Community Surveys are presented, commencing with a singular opportunity to submit Letters of Intent for Public Surveys during the first five years of 4MOST operations.
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Submitted 1 April, 2019; v1 submitted 6 March, 2019;
originally announced March 2019.
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Interpreting the star formation - extinction relation with MaNGA
Authors:
Huan Li,
Stijn Wuyts,
Lei Hao,
Lin Lin,
Man I Lam,
Médéric Boquien,
Brett H. Andrews,
Donald P. Schneider
Abstract:
We investigate the resolved relation between local extinction and star formation surface density within nearby star-forming galaxies selected from the MaNGA survey. Balmer decrement measurements imply an extinction of the Hα line emission which scales approximately linearly with the logarithm of the star formation surface density: $ A_{Hα} = 0.46 \log(Σ_{SFR}) + 1.53$. Secondary dependencies are o…
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We investigate the resolved relation between local extinction and star formation surface density within nearby star-forming galaxies selected from the MaNGA survey. Balmer decrement measurements imply an extinction of the Hα line emission which scales approximately linearly with the logarithm of the star formation surface density: $ A_{Hα} = 0.46 \log(Σ_{SFR}) + 1.53$. Secondary dependencies are observed such that, at a given $Σ_{SFR}$, regions of lower metallicity and/or enhanced Hα equivalent width (EW) suffer less obscuration than regions of higher metallicity and/or lower Hα EW. Spaxels lying above the mean relation also tend to belong to galaxies that are more massive, larger and viewed under higher inclination than average. We present a simple model in which the observed trends can be accounted for by a metallicity-dependent scaling between $Σ_{SFR}$ and $Σ_{dust}$ via a super-linear Kennicutt-Schmidt relation ($n_{KS} \sim 1.47$) and a dust-to-gas ratio which scales linearly with metallicity (DGR($Z_{\odot}$) = 0.01). The relation between the resulting total dust column and observed effective extinction towards nebular regions requires a geometry for the relative distribution of Hα emitting regions and dust that deviates from a uniform foreground screen and also from an entirely homogeneous mixture of dust and emitting sources. The best-fit model features an Hα EW and galactocentric distance dependent fraction of the dust mass in a clumpy foreground screen in front of a homogeneous mixture.
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Submitted 7 January, 2019;
originally announced January 2019.
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Red supergiant stars in the Large Magellanic Cloud. II. Infrared properties and mid-infrared variability
Authors:
Ming Yang,
Alceste Z. Bonanos,
Bi-Wei Jiang,
Jian Gao,
Meng-Yao Xue,
Shu Wang,
Man I Lam,
Zoi T. Spetsieri,
Yi Ren,
Panagiotis Gavras
Abstract:
The characteristics of IR properties and MIR variability of RSGs in the LMC are analyzed based on 12 bands of NIR to MIR co-added data from 2MASS, Spitzer and WISE, and $\sim$6.6 years of MIR time-series data collected by the ALLWISE and NEOWISE-R projects. 773 RSGs candidates were compiled from the literature and verified by using the CMD, SED and MIR variability. About 15\% of valid targets in t…
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The characteristics of IR properties and MIR variability of RSGs in the LMC are analyzed based on 12 bands of NIR to MIR co-added data from 2MASS, Spitzer and WISE, and $\sim$6.6 years of MIR time-series data collected by the ALLWISE and NEOWISE-R projects. 773 RSGs candidates were compiled from the literature and verified by using the CMD, SED and MIR variability. About 15\% of valid targets in the $IRAC1-IRAC2$/$IRAC2-IRAC3$ diagram may show PAH emission. We show that arbitrary dereddening Q parameters related to the IRAC4, S9W, WISE3, WISE4, and MIPS24 bands could be constructed based on a precise measurement of MIR interstellar extinction law. Several peculiar outliers in our sample are discussed, in which one outlier might be a RSG right before the explosion or an x-AGB star in the very late evolutionary stage based on the MIR spectrum and photometry. There are 744 identified RSGs in the final sample having both the WISE1- and WISE2-band time-series data. The results show that the MIR variability is increasing along with the increasing of brightness. There is a relatively tight correlation between the MIR variability, MLR, and the warm dust or continuum, where the MIR variability is evident for the targets with $K_S-WISE3>1.0~mag$ and $WISE4<6.5~mag$, while the rest of the targets show much smaller MIR variability. The MIR variability is also correlated with the MLR for which targets with larger variability also show larger MLR with an approximate upper limit of $-6.1~M_\odot/yr^{-1}$. Both the variability and the luminosity may be important for the MLR since the WISE4-band flux is increasing exponentially along with the degeneracy of luminosity and variability. The identified RSG sample has been compared with the theoretical evolutionary models and shown that the discrepancy between observation and evolutionary models can be mitigated by considering both variability and extinction.
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Submitted 8 May, 2018;
originally announced May 2018.
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An H$α$ Imaging Survey of the Low-surface-brightness Galaxies Selected from the Fall Sky Region of the 40$\%$ ALFALFA \ion{H}{1} Survey
Authors:
Fengjie Lei,
Hong Wu,
Wei Du,
Yinan Zhu,
Man I Lam,
Zhimin Zhou,
Min He,
Junjie Jin,
Tianwen Cao,
Pinsong Zhao,
Fan Yang,
Chaojian Wu,
Hongbin Li,
Juanjuan Ren
Abstract:
We present the observed H$α$ flux and derived star formation rates (SFRs) for a fall sample of low$-$surface$-$brightness galaxies (LSBGs). The sample is selected from the fall sky region of the 40$\%$ ALFALFA {\ion{H}{1}} survey $-$ SDSS DR7 photometric data, and all the $Hα$ images were obtained using the 2.16 m telescope, operated by the National Astronomy Observatories, Chinese Academy of Scie…
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We present the observed H$α$ flux and derived star formation rates (SFRs) for a fall sample of low$-$surface$-$brightness galaxies (LSBGs). The sample is selected from the fall sky region of the 40$\%$ ALFALFA {\ion{H}{1}} survey $-$ SDSS DR7 photometric data, and all the $Hα$ images were obtained using the 2.16 m telescope, operated by the National Astronomy Observatories, Chinese Academy of Sciences. A total of 111 LSBGs were observed and $Hα$ flux was measured in 92 of them. Though almost all the LSBGs in our sample are {\ion{H}{1}}$-$rich, their SFRs derived from the extinction and filter$-$transmission$-$corrected $Hα$ flux, are less than 1$M_{\sun}$$yr^{-1}$.
LSBGs and star forming galaxies have similar {\ion{H}{1}} surface densities, but LSBGs have much lower SFRs and SFR surface densities than star$-$forming galaxies. Our results show that LSBGs deviate from the Kennicutt-Schmidt law significantly, which indicate that they have low star formation efficiency. The SFRs of LSBGs are close to average SFRs in Hubble time and support the previous arguments that most of the LSBGs are stable systems and they tend to seldom contain strong interactions or major mergers during their star formation histories.
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Submitted 7 March, 2018;
originally announced March 2018.
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The LAMOST Complete Spectroscopic Survey of Pointing Area (LaCoSSPAr) in the Southern Galactic Cap I. The Spectroscopic Redshift Catalog
Authors:
Ming Yang,
Hong Wu,
Fan Yang,
Man I Lam,
Tian-Wen Cao,
Chao-Jian Wu,
Pin-Song Zhao,
Tian-Meng Zhang,
Zhi-Min Zhou,
Xue-Bing Wu,
Yan-Xia Zhang,
Zheng-Yi Shao,
Yi-Peng Jing,
Shi-Yin Shen,
Yi-Nan Zhu,
Wei Du,
Feng-Jie Lei,
Min He,
Jun-Jie Jin,
Jian-Rong Shi,
Wei Zhang,
Jian-Ling Wang,
Yu-Zhong Wu,
Hao-Tong Zhang,
A-Li Luo
, et al. (7 additional authors not shown)
Abstract:
We present a spectroscopic redshift catalog from the LAMOST Complete Spectroscopic Survey of Pointing Area (LaCoSSPAr) in the Southern Galactic Cap (SGC), which is designed to observe all sources (Galactic and extra-galactic) by using repeating observations with a limiting magnitude of $r=18.1~mag$ in two $20~deg^2$ fields. The project is mainly focusing on the completeness of LAMOST ExtraGAlactic…
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We present a spectroscopic redshift catalog from the LAMOST Complete Spectroscopic Survey of Pointing Area (LaCoSSPAr) in the Southern Galactic Cap (SGC), which is designed to observe all sources (Galactic and extra-galactic) by using repeating observations with a limiting magnitude of $r=18.1~mag$ in two $20~deg^2$ fields. The project is mainly focusing on the completeness of LAMOST ExtraGAlactic Surveys (LEGAS) in the SGC, the deficiencies of source selection methods and the basic performance parameters of LAMOST telescope. In both fields, more than 95% of galaxies have been observed. A post-processing has been applied to LAMOST 1D spectrum to remove the majority of remaining sky background residuals. More than 10,000 spectra have been visually inspected to measure the redshift by using combinations of different emission/absorption features with uncertainty of $σ_{z}/(1+z)<0.001$. In total, there are 1528 redshifts (623 absorption and 905 emission line galaxies) in Field A and 1570 redshifts (569 absorption and 1001 emission line galaxies) in Field B have been measured. The results show that it is possible to derive redshift from low SNR galaxies with our post-processing and visual inspection. Our analysis also indicates that up to 1/4 of the input targets for a typical extra-galactic spectroscopic survey might be unreliable. The multi-wavelength data analysis shows that the majority of mid-infrared-detected absorption (91.3%) and emission line galaxies (93.3%) can be well separated by an empirical criterion of $W2-W3=2.4$. Meanwhile, a fainter sequence paralleled to the main population of galaxies has been witnessed both in $M_r$/$W2-W3$ and $M_*$/$W2-W3$ diagrams, which could be the population of luminous dwarf galaxies but contaminated by the edge-on/highly inclined galaxies ($\sim30\%$).
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Submitted 11 October, 2017;
originally announced October 2017.
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FGK 22 $μ$m Excess Stars in LAMOST DR2 Stellar Catalog
Authors:
Chao-Jian Wu,
Hong Wu,
Kang Liu,
Tan-Da Li,
Ming Yang,
Man I Lam,
Fan Yang,
Yue Wu,
Yong Zhang,
Yonghui Hou,
Guangwei Li
Abstract:
Since the release of LAMOST (the Large Sky Area Multi-Object Fiber Spectroscopic Telescope) catalog, we have the opportunity to use the LAMOST DR2 stellar catalog and \emph{WISE All-sky catalog} to search for 22 $μ$m excess candidates. In this paper, we present 10 FGK candidates which show an excess in the infrared (IR) at 22 $μ$m. The ten sources are all the newly identified 22 $μ$m excess candid…
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Since the release of LAMOST (the Large Sky Area Multi-Object Fiber Spectroscopic Telescope) catalog, we have the opportunity to use the LAMOST DR2 stellar catalog and \emph{WISE All-sky catalog} to search for 22 $μ$m excess candidates. In this paper, we present 10 FGK candidates which show an excess in the infrared (IR) at 22 $μ$m. The ten sources are all the newly identified 22 $μ$m excess candidates. Of these 10 stars, 5 stars are F type and 5 stars are G type. The criterion for selecting candidates is $K_s-[22]_{μm}\geq0.387$. In addition, we present the spectral energy distributions (SEDs) covering wavelength from optical to mid-infrared band. Most of them show an obvious excess from 12 $μ$m band and three candidates even show excess from 3.4 $μ$m. To characterize the amount of dust, we also estimate the fractional luminosity of ten 22 $μ$m excess candidates.
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Submitted 10 March, 2016;
originally announced March 2016.
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Low Surface Brightness Galaxies selected from the 40% sky area of the ALFALFA HI survey.I.Sample and statistical properties
Authors:
Wei Du,
Hong Wu,
Man I Lam,
Yinan Zhu,
Fengjie Lei,
Zhimin Zhou
Abstract:
The population of Low Surface Brightness (LSB) galaxies is crucial for understanding the extremes of galaxy formation and evolution of the universe. As LSB galaxies are mostly rich in gas (HI), the alpha.40-SDSS DR7 sample is absolutely one of the best survey combinations to select a sample of them in the local Universe. Since the sky backgrounds are systematically overestimated for galaxy images…
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The population of Low Surface Brightness (LSB) galaxies is crucial for understanding the extremes of galaxy formation and evolution of the universe. As LSB galaxies are mostly rich in gas (HI), the alpha.40-SDSS DR7 sample is absolutely one of the best survey combinations to select a sample of them in the local Universe. Since the sky backgrounds are systematically overestimated for galaxy images by the SDSS photometric pipeline, particularly for luminous galaxies or galaxies with extended low surface brightness outskirts, in this paper, we above all estimated the sky backgrounds of SDSS images in the alpha.40-SDSS DR7 sample, using a precise method of sky subtraction. Once subtracting the sky background, we did surface photometry with the Kron elliptical aperture and fitted geometric parameters with an exponential profile model for each galaxy image. Basing on the photometric and geometric results, we further calculated the B-band central surface brightness, mu_{0}(B), for each galaxy and ultimately defined a sample of LSB galaxies consisting of 1129 galaxies with mu_{0}(B) > 22.5 mag arcsec^{-2} and the minor-to-major axis ratio b/a > 0.3. This HI-selected LSB galaxy sample from the alpha.40-SDSS DR7 is a relatively unbiased sample of gas-rich and disk-dominated LSB galaxies, which is complete both in HI observation and the optical magnitude within the limit of SDSS DR7 photometric survey. We made analysis on optical and radio 21cm HI properties of this LSB galaxy sample. Additionally, we statistically investigated the environment of our LSB galaxies, and found that up to 92% of the total LSB galaxies have less than 8 neighbouring galaxies, which strongly evidenced that LSB galaxies prefer to reside in the low-density environment.
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Submitted 28 April, 2015;
originally announced April 2015.
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The HI dominated Low Surface Brightness Galaxy KKR17
Authors:
Man I. Lam,
Hong Wu,
Ming Yang,
Zhi-Min Zhou,
Wei Du,
Yi-Nan Zhu
Abstract:
We present new narrow-band (H$α$ and [OIII]) imagings and optical spectrophotometry of HII regions for a gas-rich low surface brightness irregular galaxy, KKR 17. The central surface brightness of the galaxy is $μ_0(B)$ = 24.15 $\pm$0.03 mag~sec$^{-2}$. The galaxy was detected by \emph{Arecibo Legacy Fast ALFA survey} (ALFALFA), and its mass is dominated by neutral hydrogen (HI) gas. In contrast,…
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We present new narrow-band (H$α$ and [OIII]) imagings and optical spectrophotometry of HII regions for a gas-rich low surface brightness irregular galaxy, KKR 17. The central surface brightness of the galaxy is $μ_0(B)$ = 24.15 $\pm$0.03 mag~sec$^{-2}$. The galaxy was detected by \emph{Arecibo Legacy Fast ALFA survey} (ALFALFA), and its mass is dominated by neutral hydrogen (HI) gas. In contrast, both the stellar masses of the bright HII and diffuse stellar regions are small. In addition, the fit to the spectral energy distribution to each region shows the stellar populations of HII and diffuse regions are different. The bright HII region contains a large fraction of O-type stars, revealing the recent strong star formation, whereas the diffuse region is dominated by median age stars, which has a typical age of $\sim$ 600 Myrs. Using the McGaugh's abundance model, we found that the average metallicity of KKR 17 is 12 + (O/H) = 8.0 $\pm$ 0.1. The star formation rate of KKR 17 is 0.21$\pm$0.04 M$_{\odot}$/yr, which is $\sim$1/5 of our Milky Way's. Based on the analysis results to young stellar clusters in HII region, it is found that the bright HII region showed two sub-components with different velocities and metallicities. This may be caused by the outflow of massive stars or merging events. However, the mechanism of triggering star formation in the HII region is still uncertain.
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Submitted 20 November, 2014;
originally announced November 2014.
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Quantifying the Heating Sources for Mid-infrared Dust Emissions in Galaxies: The Case of M 81
Authors:
Nanyao Lu,
G. J. Bendo,
A. Boselli,
M. Baes,
H. Wu.,
S. C. Madden,
I. De Looze,
A. Rémy-Ruyer,
M. Boquien,
C. D. Wilson,
M. Galametz,
M. I. Lam,
A. Cooray,
L. Spinoglio,
Y. Zhao
Abstract:
With the newly available SPIRE images at 250 and 500 micron from Herschel Space Observatory, we study quantitative correlations over a sub-kpc scale among three distinct emission components in the interstellar medium of the nearby spiral galaxy M 81 (NGC 3031): (a) $I_{8}$ or $I_{24}$, the surface brightness of the mid-infrared emission observed in the Spitzer IRAC 8 or MIPS 24 micron band, with…
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With the newly available SPIRE images at 250 and 500 micron from Herschel Space Observatory, we study quantitative correlations over a sub-kpc scale among three distinct emission components in the interstellar medium of the nearby spiral galaxy M 81 (NGC 3031): (a) $I_{8}$ or $I_{24}$, the surface brightness of the mid-infrared emission observed in the Spitzer IRAC 8 or MIPS 24 micron band, with $I_8$ and $I_{24}$ being dominated by the emissions from Polycyclic Aromatic Hydrocarbons (PAHs) and very small grains (VSGs) of dust, respectively; (b) $I_{500}$, that of the cold dust continuum emission in the Herschel SPIRE 500 micron band, dominated by the emission from large dust grains heated by evolved stars, and (c) $I_{{\rm H}α}$, a nominal surface brightness of the H$α$ line emission, from gas ionized by newly formed massive stars. The results from our correlation study, free from any assumption on or modeling of dust emissivity law or dust temperatures, present solid evidence for significant heating of PAHs and VSGs by evolved stars. In the case of M 81, about 67% (48%) of the 8 micron (24 micron) emission derives its heating from evolved stars, with the remainder attributed to radiation heating associated with ionizing stars.
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Submitted 14 October, 2014;
originally announced October 2014.
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Far-Infrared and submillimeter properties of SDSS galaxies in the Herschel ATLAS science demonstration phase field
Authors:
M. I. Lam,
H. Wu,
Y. -N. Zhu,
Z. -M. Zhou
Abstract:
Using the Herschel ATLAS science demonstration phase data crossidentified with SDSS DR7 spectra, we select 297 galaxies with F250μm > 5σ. The sample galaxies are classified into five morphological types, and more than 40% of the galaxies are peculiar/compact galaxies. The peculiar galaxies show higher far-infrared/submillimeter luminosity-to-mass ratios than the other types. We perform and analyze…
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Using the Herschel ATLAS science demonstration phase data crossidentified with SDSS DR7 spectra, we select 297 galaxies with F250μm > 5σ. The sample galaxies are classified into five morphological types, and more than 40% of the galaxies are peculiar/compact galaxies. The peculiar galaxies show higher far-infrared/submillimeter luminosity-to-mass ratios than the other types. We perform and analyze the correlations of far-infrared/submillimeter and Hα luminosities for different morphological types and different spectral types. The Spearman rank coefficient decreases and the scatter increases with the wavelength increasing from 100 μm to 500 μm. We conclude that a single Herschel SPIRE band is not good for tracing star formation activities in galaxies. AGNs contribute less to the far-infrared/submillimeter luminosities and do not show a difference from star-forming galaxies. However, the earlier type galaxies present significant deviations from the best fit of star-forming galaxies.
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Submitted 17 January, 2013;
originally announced January 2013.