Tracing the evolution of dust-obscured activity using sub-millimetre galaxy populations from STUDIES and AS2UDS
Authors:
U. Dudzevičiūtė,
I. Smail,
A. M. Swinbank,
C. -F. Lim,
W. -H. Wang,
J. M. Simpson,
Y. Ao,
S. C. Chapman,
C. -C. Chen,
D. Clements,
H. Dannerbauer,
L. C. Ho,
H. S. Hwang,
M. Koprowski,
C. -H. Lee,
D. Scott,
H. Shim,
R. Shirley,
Y. Toba
Abstract:
We analyse the physical properties of 121 SNR $\geq$ 5 sub-millimetre galaxies (SMGs) from the STUDIES 450-$μ$m survey. We model their UV-to-radio spectral energy distributions using MAGPHYS+photo-$z$ and compare the results to similar modelling of 850-$μ$m-selected SMG sample from AS2UDS, to understand the fundamental physical differences between the two populations at the observed depths. The re…
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We analyse the physical properties of 121 SNR $\geq$ 5 sub-millimetre galaxies (SMGs) from the STUDIES 450-$μ$m survey. We model their UV-to-radio spectral energy distributions using MAGPHYS+photo-$z$ and compare the results to similar modelling of 850-$μ$m-selected SMG sample from AS2UDS, to understand the fundamental physical differences between the two populations at the observed depths. The redshift distribution of the 450-$μ$m sample has a median of $z$ = 1.85 $\pm$ 0.12 and can be described by strong evolution of the far-infrared luminosity function. The fainter 450-$μ$m sample has $\sim$14 times higher space density than the brighter 850-$μ$m sample at $z$ $\lesssim$2, and a comparable space density at $z$ = 2-3, before rapidly declining, suggesting LIRGs are the main obscured population at $z$ $\sim$ 1-2, while ULIRGs dominate at higher redshifts. We construct rest-frame $\sim$ 180-$μ$m-selected and dust-mass-matched samples at $z$ = 1-2 and $z$ = 3-4 from the 450-$μ$m and 850-$μ$m samples, respectively, to probe the evolution of a uniform sample of galaxies spanning the cosmic noon era. Using far-infrared luminosity, dust masses and an optically-thick dust model, we suggest that higher-redshift sources have higher dust densities due to inferred dust continuum sizes which are roughly half of those for the lower-redshift population at a given dust mass, leading to higher dust attenuation. We track the evolution in the cosmic dust mass density and suggest that the dust content of galaxies is governed by a combination of both the variation of gas content and dust destruction timescale.
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Submitted 13 October, 2020;
originally announced October 2020.
An imperfectly passive nature: Bright sub-millimeter emission from dust-obscured star formation in the z=3.717 "passive" system, ZF20115
Authors:
J. M. Simpson,
Ian Smail,
Wei-Hao Wang,
D. Riechers,
J. S. Dunlop,
Y. Ao,
N. Bourne,
A. Bunker,
S. C. Chapman,
Chian-Chou Chen,
H. Dannerbauer,
J. E. Geach,
T. Goto,
C. M. Harrison,
H. S. Hwang,
R. J. Ivison,
Tadayuki Kodama,
C. -H. Lee,
H. -M. Lee,
M. Lee,
C. -F. Lim,
M. J. Michalowski,
D. J. Rosario,
H. Shim,
X. W. Shu
, et al. (6 additional authors not shown)
Abstract:
The identification of high-redshift massive galaxies with old stellar populations may pose challenges to some models of galaxy formation. However, to securely classify a galaxy as quiescent, it is necessary to exclude significant ongoing star formation, something that can be challenging to achieve at high redshift. In this letter, we analyse deep ALMA/870um and SCUBA-2/450um imaging of the claimed…
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The identification of high-redshift massive galaxies with old stellar populations may pose challenges to some models of galaxy formation. However, to securely classify a galaxy as quiescent, it is necessary to exclude significant ongoing star formation, something that can be challenging to achieve at high redshift. In this letter, we analyse deep ALMA/870um and SCUBA-2/450um imaging of the claimed "post-starburst" galaxy ZF-20115 at z=3.717 that exhibits a strong Balmer break and absorption lines. The far-infrared imaging reveals a luminous starburst located 0.4+/-0.1 arcsec (~3kpc in projection) from the position of the rest-frame ultra-violet/optical emission, with an obscured star-formation rate of 100 Mo/yr. This star-forming component is undetected in the rest-frame ultraviolet but contributes significantly to the lower angular resolution photometry at restframe wavelengths >3500A, significantly complicating the determination of a reliable stellar mass. Importantly, in the presence of dust obscuration, strong Balmer features are not a unique signature of a post-starburst galaxy and are indeed frequently observed in infrared-luminous galaxies. We conclude that the ZF20015 system does not pose a challenge to current models of galaxy formation and that deep sub-/millimeter observations are a prerequisite for any claims of quiescence. The multi-wavelength observations of ZF20115 unveil a complex system with an intricate and spatially-varying star-formation history. ZF20115 demonstrates that understanding high-redshift obscured starbursts will only be possible with multi-wavelength studies that include high-resolution observations, available with the JWST, at mid-infrared wavelengths.
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Submitted 12 April, 2017;
originally announced April 2017.