分类： 天文学 >> 天文学 提交时间： 2023-02-19
Jack E. Birkin
Ian Smail
A. M. Swinbank
Fang Xia An
S. C. Chapman
Chian-Chou Chen
C. J. Conselice
U. Dudzevičiūtė
D. Farrah
B. Gullberg
Y. Matsuda
A. Puglisi
E. Schinnerer
D. Scott
J. L. Wardlow
P. van der Werf
摘要： We present spatially resolved kinematics of 31 ALMA-identified dust-obscured star-forming galaxies (DSFGs) at $z\sim$1.3-2.6, as traced by H$\alpha$ emission using VLT/KMOS near-infrared integral field spectroscopy from our on-going Large Programme ''KMOS-ALMA Observations of Submillimetre Sources'' (KAOSS). We derive H$\alpha$ rotation curves and velocity dispersion profiles for the DSFGs. Of the 31 sources with bright, spatially extended H$\alpha$ emission, 25 display rotation curves that are well fit by a Freeman disc model, enabling us to measure a median inclination-corrected velocity at 2.2$R_{\rm d}$ of $v_{\rm rot}$ = 190 $\pm$ 30 kms$^{-1}$ and a median intrinsic velocity dispersion of $\sigma_0$ = 87 $\pm$ 6 kms$^{-1}$ for these $\textit{disc-like}$ sources. By comparison with less actively star-forming galaxies, KAOSS DSFGs are both faster rotating and more turbulent, but have similar $v_{\rm rot}/\sigma_0$ ratios, median 2.4 $\pm$ 0.5. We suggest that $v_{\rm rot}/\sigma_0$ alone is insufficient to describe the kinematics of DSFGs, which are not kinematically ''cold'' discs, and that the individual components $v_{\rm rot}$ and $\sigma_0$ indicate that they are in fact turbulent, but rotationally supported systems in $\sim$50 per cent of cases. This turbulence may be driven by star formation or mergers/interactions. We estimate the normalisation of the stellar Tully-Fisher relation (sTFR) for the disc-like DSFGs and compare it with local studies, finding no evolution at fixed slope between $z\sim$2 and $z\sim$0. Finally, we use kinematic estimates of DSFG halo masses to investigate the stellar-to-halo mass relation, finding our sources to be consistent with shock heating and strong feedback which likely drives the declining stellar content in the most massive halos.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Marta Frias Castillo
Jacqueline Hodge
Matus Rybak
Paul van der Werf
Ian Smail
Jack Birkin
Chian-Chou Chen
Scott Chapman
Ryley Hill
Claudia del P. Lagos
Cheng-Lin Liao
Elisabete da Cunha
Gabriela Calistro Rivera
Jianhang Chen
Eric Jimenez Andrade
Eric Murphy
Douglas Scott
Mark Swinbank
Fabian Walter
Rob Ivison
摘要： We present initial results of an ongoing survey with the Karl G. Jansky Very Large Array targeting the CO($J$ = 1-0) transition in a sample of 30 submillimeter-selected, dusty star-forming galaxies at $z =$ 2-5 with existing mid--$J$ CO detections from ALMA and NOEMA, of which 17 have been fully observed. We detect CO(1-0) emission in 11 targets, along with three tentative ($\sim$1.5-2$\sigma$) detections; three galaxies are undetected. Our results yield total molecular gas masses of 6-23$\times$10$^{10}$ ($\alpha_\mathrm{CO}$/1) M$_\odot$, with gas mass fractions, $f_\mathrm{gas}$=$M_\mathrm{mol}$/($M_*$+$M_\mathrm{mol}$), of 0.1-0.8 and a median depletion time of (140$\pm$70) Myr. We find median CO excitation ratios of $r_{31}$ = 0.75$\pm$0.39 and $r_{41}$ = 0.63$\pm$0.44, with a significant scatter. We find no significant correlation between the excitation ratio and a number of key parameters such as redshift, CO(1-0) line width or $\Sigma_\mathrm{SFR}$. We only find a tentative positive correlation between $r_{41}$ and the star-forming efficiency, but we are limited by our small sample size. Finally, we compare our results to predictions from the SHARK semi-analytical model, finding a good agreement between the molecular gas masses, depletion times and gas fractions of our sources and their SHARK counterparts. Our results highlight the heterogeneous nature of the most massive star-forming galaxies at high-redshift, and the importance of CO(1--0) observations to robustly constrain their total molecular gas content and ISM properties.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Chian-Chou Chen
Cheng-Lin Liao
Ian Smail
A. M. Swinbank
Y. Ao
A. J. Bunker
S. C. Chapman
B. Hatsukade
R. J. Ivison
Minju M. Lee
Stephen Serjeant
Hideki Umehata
Wei-Hao Wang
Y. Zhao
摘要： We introduce an ALMA band 3 spectroscopic survey, targeting the brightest submillimeter galaxies (SMGs) in the COSMOS field. Here we present the first results based on the 18 primary SMGs that have 870 $\mu$m flux densities of $S_{870}=12.4-19.3$ mJy and are drawn from a parent sample of 260 ALMA-detected SMGs from the AS2COSMOS survey. We detect emission lines in 17 and determine their redshifts to be in the range of $z=2-5$ with a median of $3.2\pm0.3$. We confirm that SMGs with brighter $S_{870}$ are located at higher redshifts. The data additionally cover five fainter companion SMGs, and we obtain line detection in one. Together with previous studies, our results indicate that for SMGs that satisfy our selection, their brightest companion SMGs are physically associated with their corresponding primary SMGs in $\ge40$% of the time, suggesting that mergers play a role in the triggering of star formation. By modeling the foreground gravitational fields, $2$. We determine that about 90% of the primary SMGs have lines that are better described by double Gaussian profiles, and the median separation of the two Gaussian peaks is 430$\pm$40 km s$^{-1}$. This allows estimates of an average baryon mass, which together with the line dispersion measurements puts our primary SMGs on the similar mass-$\sigma$ correlation found on local early-type galaxies. Finally, the number density of our $z>4$ primary SMGs is found to be $1\times10^{-6}$ cMpc$^{-3}$, suggesting that they can be the progenitors of $z\sim3-4$ massive quiescent galaxies.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Chian-Chou Chen
Zhen-Kai Gao
Qi-Ning Hsu
Cheng-Lin Liao
Yu-Han Ling
Ching-Min Lo
Wei-Hao Wang
Yu-Jan Wang
摘要： We report morphological analyses of seven submillimeter galaxies (SMGs) at $z\sim2$ using the JWST NIRCam images taken as part of the public CEERS and PRIMER surveys. Through two-dimensional surface brightness profile fittings we find evidence of bulges in all the sample SMGs, in particular at F444W filter, suggesting an ubiquitous presence of stellar bulges. The median size of these bulges at F444W is found to be 0.7$\pm$1.0 kpc and its median Sersic index is 0.7$\pm$0.9. Structures akin to spiral arms and bars are also identified, although their asymmetric shapes, tidal features, as well as evidence of nearby galaxies at consistent redshifts as those of corresponding SMGs suggest that these SMGs are undergoing dynamical interactions, likely responsible for the triggering of their star-forming activities. Via the curve-of-growth analyses we deduce half-light radii for the NIRCam wavebands, finding that sizes are significantly smaller at longer wavelengths in all cases, in particular that the median size ratio between F444W and F150W is $0.6\pm0.1$. However, we also find that F444W sizes, roughly corresponding to rest-frame $H$-band, are not smaller than those of submillimeter continuum as measured by ALMA, contrasting recent predictions from theoretical models. Our results suggest that while stellar bulges are undergoing an active formation phase in SMGs at $z\sim2$, the total stellar masses of SMGs are still dominated by their disks, not bulges.
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