A blind CO detection of a distant red galaxy in the HS1700+64 protocluster.

We report the blind detection of ^(12)CO emission from a distant red galaxy, HS1700.DRG55. We have used the IRAM Plateau de Bure Interferometer WideX, with its 3.6 GHz of instantaneous dual-polarization bandwidth, to target ^(12)CO(3–2) from galaxies lying in the protocluster at z = 2.300 in the field HS1700+64. If indeed this line in DRG55 is ^(12)CO(3–2), its detection at 104.9 GHz indicates zCO = 2.296. None of the other eight known z ∼ 2.30 protocluster galaxies lying within the primary beam (PB) are detected in ^(12)CO, although the limits are ∼2 × worse towards the edge of the PB where several lie. The optical/near-IR magnitudes of DRG55 (R_AB > 27, KAB = 22.3) mean that optical spectroscopic redshifts are difficult with 10-m-class telescopes, but near-IR redshifts would be feasible. The 24-μm-implied star formation rate (210 M_⊙ yr^−1), stellar mass (∼10^11 M_⊙) and ^(12)CO line luminosity (3.6 × 10^10 K km s^−1  pc^2) are comparable to other normal ^(12)CO-detected star-forming galaxies in the literature, although the galaxy is some ∼2 mag (∼6 ×) fainter in the rest-frame UV than ^(12)CO-detected galaxies at z > 2. The detection of DRG55 in ^(12)CO complements three other ^(12)CO detected UV-bright galaxies in this protocluster from previous studies, and suggests that many optically faint galaxies in the protocluster may host substantial molecular gas reservoirs, and a full blind census of ^(12)CO in this overdense environment is warranted.

[1]  S. Longmore,et al.  EXCITATION CONDITIONS IN THE MULTI-COMPONENT SUBMILLIMETER GALAXY SMM J00266+1708 , 2014, 1411.0700.

[2]  A. Strom,et al.  THE Lyα PROPERTIES OF FAINT GALAXIES AT z ∼ 2–3 WITH SYSTEMIC REDSHIFTS AND VELOCITY DISPERSIONS FROM KECK-MOSFIRE , 2014, 1408.3638.

[3]  Ichi Tanaka,et al.  EVIDENCE FOR A GAS-RICH MAJOR MERGER IN A PROTO-CLUSTER AT z = 2.5 , 2014, 1403.0040.

[4]  H. Rix,et al.  A MOLECULAR LINE SCAN IN THE HUBBLE DEEP FIELD NORTH , 2013, 1312.6364.

[5]  E. I. Robson,et al.  THE SCUBA-2 COSMOLOGY LEGACY SURVEY: ULTRALUMINOUS STAR-FORMING GALAXIES IN A z = 1.6 CLUSTER , 2013, 1312.3329.

[6]  Edinburgh,et al.  An ALMA survey of sub-millimetre Galaxies in the Extended Chandra Deep Field South: the far-infrared properties of SMGs , 2013, 1310.6362.

[7]  K. Gebhardt,et al.  ANCIENT LIGHT FROM YOUNG COSMIC CITIES: PHYSICAL AND OBSERVATIONAL SIGNATURES OF GALAXY PROTO-CLUSTERS , 2013, 1310.2938.

[8]  B. Weiner,et al.  PHIBSS: MOLECULAR GAS CONTENT AND SCALING RELATIONS IN z ∼ 1–3 MASSIVE, MAIN-SEQUENCE STAR-FORMING GALAXIES , 2012, 1211.5743.

[9]  D. Elbaz,et al.  EVIDENCE FOR A WIDE RANGE OF ULTRAVIOLET OBSCURATION IN z ∼ 2 DUSTY GALAXIES FROM THE GOODS-HERSCHEL SURVEY , 2012, 1209.2707.

[10]  P. P. van der Werf,et al.  BLIND DETECTIONS OF CO J = 1–0 IN 11 H-ATLAS GALAXIES AT z = 2.1–3.5 WITH THE GBT/ZPECTROMETER , 2012, 1204.4706.

[11]  C. Steidel,et al.  FILAMENTARY LARGE-SCALE STRUCTURE TRACED BY SIX Lyα BLOBS AT z = 2.3 , 2011, 1109.2167.

[12]  F. Walter,et al.  EXTENDED COLD MOLECULAR GAS RESERVOIRS IN z ≃ 3.4 SUBMILLIMETER GALAXIES , 2011, 1105.4177.

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

[14]  Benjamin M. Tofflemire,et al.  INTERSTELLAR SONIC AND ALFVÉNIC MACH NUMBERS AND THE TSALLIS DISTRIBUTION , 2011, 1103.3299.

[15]  M. Pettini,et al.  DIFFUSE Lyα EMITTING HALOS: A GENERIC PROPERTY OF HIGH-REDSHIFT STAR-FORMING GALAXIES , 2011, 1101.2204.

[16]  R. J. Ivison,et al.  Tracing the molecular gas in distant submillimetre galaxies via CO(1-0) imaging with the EVLA , 2010, 1009.0749.

[17]  I. Smail,et al.  THE STELLAR MASS CONTENT OF SUBMILLIMETER-SELECTED GALAXIES , 2010, 1006.0238.

[18]  J. Dunlop,et al.  REVERSAL OF FORTUNE: CONFIRMATION OF AN INCREASING STAR FORMATION–DENSITY RELATION IN A CLUSTER AT z = 1.62 , 2010, 1005.5126.

[19]  B. Hoyle,et al.  THE XMM CLUSTER SURVEY: ACTIVE GALACTIC NUCLEI AND STARBURST GALAXIES IN XMMXCS J2215.9−1738 AT z = 1.46 , 2010, 1005.4692.

[20]  P. Cox,et al.  DETECTIONS OF CO MOLECULAR GAS IN 24 μm BRIGHT ULIRGs AT z ∼ 2 IN THE SPITZER FIRST LOOK SURVEY , 2010, 1003.2369.

[21]  F. Walter,et al.  FIRST REDSHIFT DETERMINATION OF AN OPTICALLY/ULTRAVIOLET FAINT SUBMILLIMETER GALAXY USING CO EMISSION LINES , 2009, 0909.3177.

[22]  I. Smail,et al.  DO SUBMILLIMETER GALAXIES REALLY TRACE THE MOST MASSIVE DARK-MATTER HALOS? DISCOVERY OF A HIGH-z CLUSTER IN A HIGHLY ACTIVE PHASE OF EVOLUTION , 2008, 0809.1159.

[23]  J. Newman,et al.  The role of environment in the mass–metallicity relation , 2008, 0805.0308.

[24]  Arjun Dey,et al.  A Significant Population of Very Luminous Dust-Obscured Galaxies at Redshift z ~ 2 , 2008, 0801.1860.

[25]  P. V. D. Okkum,et al.  ACCEPTED FOR PUBLICATION IN APJ LETTERS Preprint typeset using L ATEX style emulateapj A SIGNIFICANT POPULATION OF RED, NEAR-IR SELECTED HIGH REDSHIFT GALAXIES 1 , 2003 .

[26]  S. Ravindranath,et al.  Vigorous Star Formation with Low Efficiency in Massive Disk Galaxies at z = 1.5 , 2007, 0711.4995.

[27]  C. Steidel,et al.  Morphologies of Galaxies in and around a Protocluster at z = 2.300 , 2007, 0706.2865.

[28]  J. Starck,et al.  The reversal of the star formation-density relation in the distant universe , 2007, astro-ph/0703653.

[29]  Jia-Sheng Huang,et al.  Ultraviolet to Mid-Infrared Observations of Star-forming Galaxies at z ~ 2: Stellar Masses and Stellar Populations , 2005, astro-ph/0503485.

[30]  C. Steidel,et al.  Spectroscopic Identification of a Protocluster at z = 2.300: Environmental Dependence of Galaxy Properties at High Redshift , 2005, astro-ph/0502432.

[31]  I. Smail,et al.  A Redshift Survey of the Submillimeter Galaxy Population , 2004, astro-ph/0412573.

[32]  P. P. van der Werf,et al.  A Significant Population of Red, Near-Infrared-selected High-Redshift Galaxies , 2003, astro-ph/0303163.

[33]  Jr.,et al.  The Global Schmidt law in star forming galaxies , 1997, astro-ph/9712213.