SUB-KILOPARSEC ALMA IMAGING OF COMPACT STAR-FORMING GALAXIES AT z ∼ 2.5: REVEALING THE FORMATION OF DENSE GALACTIC CORES IN THE PROGENITORS OF COMPACT QUIESCENT GALAXIES

We present spatially resolved Atacama Large Millimeter/submillimeter Array (ALMA) 870 μm dust continuum maps of six massive, compact, dusty star-forming galaxies at z ∼ 2.5. These galaxies are selected for their small rest-frame optical sizes ( kpc) and high stellar mass densities that suggest that they are direct progenitors of compact quiescent galaxies at z ∼ 2. The deep observations yield high far-infrared (FIR) luminosities of and star formation rates (SFRs) of SFR = 200–700 M⊙ yr−1, consistent with those of typical star-forming “main sequence” galaxies. The high spatial resolution (FWHM ∼ 0.″12–0.″18) ALMA and Hubble Space Telescope photometry are combined to construct deconvolved, mean radial profiles of their stellar mass and (UV+IR) SFR. We find that the dusty, nuclear IR–SFR overwhelmingly dominates the bolometric SFR up to r ∼ 5 kpc, by a factor of over 100× from the unobscured UV–SFR. Furthermore, the effective radius of the mean SFR profile ( kpc) is ∼30% smaller than that of the stellar mass profile. The implied structural evolution, if such nuclear starburst last for the estimated gas depletion time of Δt = ±100 Myr, is a 4× increase of the stellar mass density within the central 1 kpc and a 1.6× decrease of the half-mass–radius. This structural evolution fully supports dissipation-driven, formation scenarios in which strong nuclear starbursts transform larger, star-forming progenitors into compact quiescent galaxies.

[1]  C. Carollo,et al.  Evolution of density profiles in high-z galaxies: compaction and quenching inside-out , 2015, 1509.00017.

[2]  J. Dunlop,et al.  SXDF-ALMA 1.5 arcmin2 DEEP SURVEY: A COMPACT DUSTY STAR-FORMING GALAXY AT z = 2.5 , 2015, 1508.05950.

[3]  A. V. D. Wel,et al.  FORMING COMPACT MASSIVE GALAXIES , 2015, 1506.03085.

[4]  J. Dunlop,et al.  THE SCUBA-2 COSMOLOGY LEGACY SURVEY: ALMA RESOLVES THE BRIGHT-END OF THE SUB-MILLIMETER NUMBER COUNTS , 2015, 1505.05152.

[5]  G. Zamorani,et al.  Evidence for mature bulges and an inside-out quenching phase 3 billion years after the Big Bang , 2015, Science.

[6]  Guillermo Barro,et al.  Compaction and quenching of high-z galaxies in cosmological simulations: blue and red nuggets , 2014, 1412.4783.

[7]  Research Center for the Early Universe,et al.  COMPACT STARBURSTS IN z ∼ 3 ?> –6 SUBMILLIMETER GALAXIES REVEALED BY ALMA , 2014, The Astrophysical Journal.

[8]  V. Springel,et al.  The formation of massive, compact galaxies at z = 2 in the Illustris simulation , 2014, 1411.0667.

[9]  A. Fontana,et al.  STELLAR MASSES FROM THE CANDELS SURVEY: THE GOODS-SOUTH AND UDS FIELDS , 2014, 1412.5180.

[10]  Max Pettini,et al.  STRONG NEBULAR LINE RATIOS IN THE SPECTRA of z ∼ 2–3 STAR FORMING GALAXIES: FIRST RESULTS FROM KBSS-MOSFIRE , 2014, 1405.5473.

[11]  S. Wuyts,et al.  DENSE CORES IN GALAXIES OUT TO z = 2.5 IN SDSS, UltraVISTA, AND THE FIVE 3D-HST/CANDELS FIELDS , 2014, 1404.4874.

[12]  D. Wake,et al.  3D-HST+CANDELS: THE EVOLUTION OF THE GALAXY SIZE–MASS DISTRIBUTION SINCE z = 3 , 2014, 1404.2844.

[13]  A. Dekel,et al.  Wet Disc Contraction to Galactic Blue Nuggets and Quenching to Red Nuggets , 2013, 1310.1074.

[14]  Christopher E. Moody,et al.  CANDELS+3D-HST: COMPACT SFGs AT z ∼ 2–3, THE PROGENITORS OF THE FIRST QUIESCENT GALAXIES , 2013, 1311.5559.

[15]  B. Lundgren,et al.  A CANDELS–3D-HST SYNERGY: RESOLVED STAR FORMATION PATTERNS AT 0.7 < z < 1.5 , 2013, 1310.5702.

[16]  A. Cimatti,et al.  The deepest Herschel-PACS far-infrared survey: number counts and infrared luminosity functions from combined PEP/GOODS-H observations , 2013, 1303.4436.

[17]  H. Rix,et al.  THE RADIAL DISTRIBUTION OF STAR FORMATION IN GALAXIES AT z ∼ 1 FROM THE 3D-HST SURVEY , 2013, 1301.0320.

[18]  E. Pellegrini,et al.  THE CO-TO-H2 CONVERSION FACTOR AND DUST-TO-GAS RATIO ON KILOPARSEC SCALES IN NEARBY GALAXIES , 2012, 1212.1208.

[19]  Daniel Foreman-Mackey,et al.  emcee: The MCMC Hammer , 2012, 1202.3665.

[20]  Chien Y. Peng,et al.  STRUCTURAL PARAMETERS OF GALAXIES IN CANDELS , 2012, 1211.6954.

[21]  C. Conselice,et al.  THE DEPENDENCE OF QUENCHING UPON THE INNER STRUCTURE OF GALAXIES AT 0.5 ⩽ z < 0.8 IN THE DEEP2/AEGIS SURVEY , 2012, 1210.4173.

[22]  D. Elbaz,et al.  THE EVOLVING INTERSTELLAR MEDIUM OF STAR-FORMING GALAXIES SINCE z = 2 AS PROBED BY THEIR INFRARED SPECTRAL ENERGY DISTRIBUTIONS , 2012, 1210.1035.

[23]  Carnegie,et al.  CANDELS: THE PROGENITORS OF COMPACT QUIESCENT GALAXIES AT z ∼ 2 , 2012, 1206.5000.

[24]  G. Brammer,et al.  THE STAR FORMATION MASS SEQUENCE OUT TO z = 2.5 , 2012, 1205.0547.

[25]  J. Newman,et al.  SMOOTH(ER) STELLAR MASS MAPS IN CANDELS: CONSTRAINTS ON THE LONGEVITY OF CLUMPS IN HIGH-REDSHIFT STAR-FORMING GALAXIES , 2012, 1203.2611.

[26]  Marijn Franx,et al.  SIZES AND SURFACE BRIGHTNESS PROFILES OF QUIESCENT GALAXIES AT z ∼ 2 , 2011, 1111.3361.

[27]  Jordi Cepa,et al.  ON STAR FORMATION RATES AND STAR FORMATION HISTORIES OF GALAXIES OUT TO z ∼ 3 , 2011, 1106.5502.

[28]  S. Ravindranath,et al.  CANDELS: THE COSMIC ASSEMBLY NEAR-INFRARED DEEP EXTRAGALACTIC LEGACY SURVEY—THE HUBBLE SPACE TELESCOPE OBSERVATIONS, IMAGING DATA PRODUCTS, AND MOSAICS , 2011, 1105.3753.

[29]  D. Calzetti,et al.  GOODS–Herschel: an infrared main sequence for star-forming galaxies , 2011, 1105.2537.

[30]  M. C. Cooper,et al.  High molecular gas fractions in normal massive star-forming galaxies in the young Universe , 2010, Nature.

[31]  Garth D. Illingworth,et al.  AN ULTRA-DEEP NEAR-INFRARED SPECTRUM OF A COMPACT QUIESCENT GALAXY AT z = 2.2 , 2009, 0905.1692.

[32]  Daniel Ceverino,et al.  FORMATION OF MASSIVE GALAXIES AT HIGH REDSHIFT: COLD STREAMS, CLUMPY DISKS, AND COMPACT SPHEROIDS , 2009, 0901.2458.

[33]  B. Weiner,et al.  DETERMINING STAR FORMATION RATES FOR INFRARED GALAXIES , 2008, 0810.4150.

[34]  C. Conselice,et al.  Exploring the Evolutionary Paths of the Most Massive Galaxies since z ~ 2 , 2008, 0807.1069.

[35]  P. Hopkins,et al.  A Cosmological Framework for the Co-Evolution of Quasars, Supermassive Black Holes, and Elliptical Galaxies. I. Galaxy Mergers and Quasar Activity , 2007, 0706.1243.

[36]  B. Draine,et al.  Infrared Emission from Interstellar Dust. IV. The Silicate-Graphite-PAH Model in the Post-Spitzer Era , 2006, astro-ph/0608003.

[37]  H. Rix,et al.  Toward an Understanding of the Rapid Decline of the Cosmic Star Formation Rate , 2005, astro-ph/0502246.

[38]  G. Bruzual,et al.  Stellar population synthesis at the resolution of 2003 , 2003, astro-ph/0309134.

[39]  G. Chabrier Galactic Stellar and Substellar Initial Mass Function , 2003, astro-ph/0304382.

[40]  L. Ho,et al.  Detailed Structural Decomposition of Galaxy Images , 2002, astro-ph/0204182.

[41]  D. Elbaz,et al.  Interpreting the Cosmic Infrared Background: Constraints on the Evolution of the Dust-enshrouded Star Formation Rate , 2001, astro-ph/0103067.

[42]  G. Helou,et al.  The Infrared Spectral Energy Distribution of Normal Star-forming Galaxies: Calibration at Far-Infrared and Submillimeter Wavelengths , 2000, astro-ph/0011014.

[43]  A. Kinney,et al.  The Dust Content and Opacity of Actively Star-forming Galaxies , 1999, astro-ph/9911459.

[44]  Jr.,et al.  STAR FORMATION IN GALAXIES ALONG THE HUBBLE SEQUENCE , 1998, astro-ph/9807187.

[45]  S. White,et al.  The formation of galactic discs , 1997, astro-ph/9707093.

[46]  S. M. Fall,et al.  Formation and rotation of disc galaxies with haloes , 1980 .