Revealing the Stellar Mass and Dust Distributions of Submillimeter Galaxies at Redshift 2

Abstract

We combine high-resolution ALMA and HST/CANDELS observations of 20 submillimeter galaxies (SMGs) predominantly from the AS2UDS survey at z ≃ 2 with bright rest-frame optical counterparts (K s 22.9) to investigate the resolved structural properties of their dust and stellar components. We derive two-dimensional stellar-mass distributions that are inferred from spatial mass-to-light ratio (M/L * ) corrections based on rest-frame optical colors. Due to the high central column densities of dust in our SMGs, our mass distributions likely represent a lower limit to the true central mass density. The centroid positions between the inferred stellar-mass and the dust distributions agree within 1.1 kpc, indicating an overall good spatial agreement between the two components. The majority of our sources exhibit compact dust configurations relative to the stellar component (with a median ratio of effective radii R e,dust /R e, * = 0.6). This ratio does not change with specific star-formation rate (sSFR) over the factor of 30 spanned by our targets, sampling the locus of 'normal' main sequence galaxies up to the starburst regime, log (sSFR/sSFR MS ) ≥ 0.5. Our results imply that massive SMGs are experiencing centrally enhanced star formation unlike typical spiral galaxies in the local Universe. The sizes and stellar densities of our SMGs are in agreement with those of the passive population at z = 1.5, consistent with these systems being the descendants of z ≃ 2 SMGs.

First detection of the 448 GHz ortho-H2O line at high redshift: probing the structure of a starburst nucleus at z = 3.63

“…Nevertheless, with ALMA, Calistro Rivera et al (2018 find evidence of significant radial variation of the ISM properties in SMGs and suggest caution when interpreting single band dust continuum data. Furthermore, by measuring the structure of the dusty ISM, one can assess the stellar mass assembly history of SMGs and build a link to galaxy populations of today (e.g., Lang et al 2019). However, such observations require resolving the continuum emission in multiple bands that sample the peak of the dust spectral energy distribu-Article number, page 1 of 6 arXiv:2001.06589v1 [astro-ph.GA] 18 Jan 2020 A&A proofs: manuscript no.…”

Growth of Supermassive Black Hole Seeds in ETG Star-forming Progenitors: Multiple Merging of Stellar Compact Remnants via Gaseous Dynamical Friction and Gravitational-wave Emission

“…Actually, the structure of high-z ETG starforming progenitors is more complex. On kpc scales, both observations (e.g., Genzel et al 2011;Tadaki et al 2017aTadaki et al ,b, 2018Hodge et al 2019;Lang et al 2019;Rujopakarn et al 2019) and simulations (e.g., Bournaud et al 2014;Mandelker et al 2014Mandelker et al , 2017Oklopcic et al 2017) indicate the presence of clumps with masses 10 7 − 10 8 M and sizes of 100 − 200 kpc; note that even more massive and extended clumps can be present but are rarer, and could be real outcomes from collisions of smaller ones (e.g., Tamburello et al 2015) or apparent structures due to blending from observations with limited resolution (e.g., Tamburello et al 2017;Behrend et al 2016;Faure et al 2019, in preparation). The survival of the clumps is still a debated issue, with different simulations favoring short-lived clumps because of feedback and/or collisions (e.g., Hopkins et al 2012;Oklopcic et al 2017), or long-lived clumps that may eventually sink toward the center via gravitational torque and bar instabilities and contribute to the growth of a central bulge (e.g., Ceverino et al 2012;Bournaud et al 2014).…”

“…On sub-kpc scales star formation is likely to occur preferentially in molecular gas clouds with masses 10 6 M and radii of 10 − 20 pc. Observations show a rather smooth distribution of the stellar mass in high-z star-forming systems (e.g., Swinbank et al 2010;Hodge et al 2016;Rujopakarn et al 2016;Lang et al 2019) and in their quiescent high-z (e.g., van der Wel & van der Marel 2008; Belli et al 2017) and local descendants (e.g., Cappellari et al 2013), indicating that molecular clouds are dissolved or a substantial amount of stars can escape quite rapidly from them (typical escape timescales amount to 100 Myr). However, it could be that some compact remnants born within the cloud might remain bound to a stellar cluster originated there; this will reduce somewhat the number of remnants available for growing the central BH seed.…”

“…The idea was inspired by a wealth of recent observational evidences concerning the population of ETG progenitors; this has been discovered thanks to wide-area far-IR/sub-mm/radio surveys and shown to be responsible for the bulk of the cosmic star formation history out to z 6 (e.g., Lapi et al 2011;Gruppioni et al 2013Gruppioni et al , 2015Weiss et al 2013;Koprowski et al 2014Koprowski et al , 2016Strandet et al 2016;Novak et al 2017;Riechers et al 2017;Schreiber et al 2018;Zavala et al 2018;Wang et al 2019). Interferometric, high-resolution observations with ALMA have allowed to reveal in these galaxies large SFRs 10 2 − 10 3 M yr −1 , considerable dust amounts 10 8 − 10 9 M and huge molecular gas reservoirs 10 10 −10 11 M within a central compact region of a few kiloparsecs (e.g., Scoville et al 2014Scoville et al , 2016Ikarashi et al 2015;Simpson et al 2015;Barro et al 2016;Spilker et al 2016;Tadaki et al 2017aTadaki et al ,b, 2018Talia et al 2018;Lang et al 2019). Ensuing optical/near-IR/mid-IR followup measurements and broadband SED modeling have highlighted that these objects already comprise large stellar masses M 10 11 M , implying typical star-formation timescales τ ψ ∼ a few to several 10 8 yr, as also inferred from the so called galaxy main sequence (e.g., Elbaz et al 2007;Rodighiero et al 2011Rodighiero et al , 2015Speagle et al 2014;Popesso et al 2019;Boogaard et al 2019;Wang et al 2019).…”

S2COSMOS: Evolution of gas mass with redshift using dust emission

“…Without having much deeper magnitude-limited samples, which only exist for small area fields such as GOODS-North and GOODS-South, we cannot quantify the biases involved. However, the two obvious biases are that we will be missing highly-dust-obscured galaxies such as SMGs (Lang et al 2019;Stach et al 2019), which will be fainter because of the obscuration, and passive galaxies, which will be fainter in the rest-frame UV because of the lack of young stars. We expect a bias in the high-redshift bins toward star-forming galaxies since at a given stellar mass and redshift, these are brighter than passive galaxies and will be preferentially included in magnitude-limited samples.…”