Dust temperature and CO → H2 conversion factor variations in the SFR-M∗ plane

Deep Herschel PACS/SPIRE imaging and 12 CO(2−1) line luminosities from the IRAM Plateau de Bure Interferometer are combined for a sample of 17 galaxies at z > 1 from the GOODS-N field. The sample includes galaxies both on and above the main sequence (MS) traced by star-forming galaxies in the SFR-M∗ plane. The far-infrared data are used to derive dust masses, Mdust, following the Draine & Li (2007, ApJ, 657, 810) models. Combined with an empirical prescription for the dependence of the gas-to-dust ratio on metallicity (δGDR(μ0)), the CO luminosities and Mdust values are used to derive for each galaxy the CO-to-H2 conversion factor, αCO. Like in the local Universe, the value of αCO is a factor of ∼5 smaller in starbursts compared to normal star-forming galaxies (SFGs). We additionally uncover a relation between αCO and dust temperature (Tdust; αCO decreasing with increasing Tdust )a s obtained from modified blackbody fits to the far-infrared data. While the absolute normalization of the αCO(Tdust) relation is uncertain, the global trend is robust against possible systematic biases in the determination of Mdust, δGDR(μ0) or metallicity. Although we cannot formally distinguish between a step and a smooth evolution of αCO with the dust temperature, we can unambiguously conclude that in galaxies of near-solar metallicity, a critical value of Tdust = 30 K can be used to determine whether the appropriate αCO is closer to the “starburst” value (1.0 M� (K km s −1 pc 2 ) −1 ,w henTdust > 30 K) or closer to the Galactic value (4.35 M� (K km s −1 pc 2 ) −1 , when Tdust < 30 K). This indicator has the great advantage of being less subjective than visual morphological classifications of mergers/SFGs, which can be difficult at high z because of the clumpy nature of SFGs. Using Tdust to select the appropriate αCO is also more indicative of ISM conditions than a fixed LIR criterion. In the absence of far-infrared data, the offset of a galaxy from the star formation main sequence (i.e., Δlog (SSFR)MS = log[SSFR(galaxy)/SSFRMS(M∗,z)]) can be used to identify galaxies requiring the use of an αCO conversion factor lower than the Galactic value (i.e., when Δlog (SSFR)MS 0. 3d ex).

[1]  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.

[2]  C. Kramer,et al.  LOW CO LUMINOSITIES IN DWARF GALAXIES , 2012, 1203.4231.

[3]  L. Hernquist,et al.  How to distinguish starbursts and quiescently star-forming galaxies: the ‘bimodal’ submillimetre galaxy population as a case study , 2012, 1203.1318.

[4]  L. Ho,et al.  TWO POPULATIONS OF MOLECULAR CLOUDS IN THE ANTENNAE GALAXIES , 2012, 1203.1327.

[5]  P. P. van der Werf,et al.  THE MOLECULAR GAS IN LUMINOUS INFRARED GALAXIES. II. EXTREME PHYSICAL CONDITIONS AND THEIR EFFECTS ON THE Xco FACTOR , 2012, 1202.1803.

[6]  A. Cimatti,et al.  A Herschel view of the far-infrared properties of submillimetre galaxies , 2012, 1202.0761.

[7]  D. Elbaz,et al.  GOODS-HERSCHEL AND CANDELS: THE MORPHOLOGIES OF ULTRALUMINOUS INFRARED GALAXIES AT z ∼ 2 , 2011, 1110.4057.

[8]  A. Cimatti,et al.  THE IMPACT OF EVOLVING INFRARED SPECTRAL ENERGY DISTRIBUTIONS OF GALAXIES ON STAR FORMATION RATE ESTIMATES , 2011, 1106.1186.

[9]  B. Groves,et al.  HERSCHEL FAR-INFRARED AND SUBMILLIMETER PHOTOMETRY FOR THE KINGFISH SAMPLE OF NEARBY GALAXIES , 2011, 1112.1093.

[10]  E. Ostriker,et al.  A general model for the CO–H2 conversion factor in galaxies with applications to the star formation law , 2011, 1110.3791.

[11]  Reinhard Genzel,et al.  THE zCOSMOS–SINFONI PROJECT. I. SAMPLE SELECTION AND NATURAL-SEEING OBSERVATIONS , 2011, 1109.5952.

[12]  D. Elbaz,et al.  GOODS-HERSCHEL: GAS-TO-DUST MASS RATIOS AND CO-TO-H2 CONVERSION FACTORS IN NORMAL AND STARBURSTING GALAXIES AT HIGH-z , 2011, 1109.1140.

[13]  A. Cimatti,et al.  THE LESSER ROLE OF STARBURSTS IN STAR FORMATION AT z = 2 , 2011, 1108.0933.

[14]  Joana M. Oliveira,et al.  THE STATE OF THE GAS AND THE RELATION BETWEEN GAS AND STAR FORMATION AT LOW METALLICITY: THE SMALL MAGELLANIC CLOUD , 2011, 1107.1717.

[15]  F. Bournaud,et al.  Studying the spatially resolved Schmidt-Kennicutt law in interacting galaxies: the case of Arp 158 , 2011, 1107.0969.

[16]  A. Koekemoer,et al.  GALAXY STRUCTURE AND MODE OF STAR FORMATION IN THE SFR–MASS PLANE FROM z ∼ 2.5 TO z ∼ 0.1 , 2011, 1107.0317.

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

[18]  B. Magnelli,et al.  PACS Evolutionary Probe (PEP) – a Herschel key program , 2011, 1106.3285.

[19]  A. Cimatti,et al.  Building the cosmic infrared background brick by brick with Herschel/PEP. ⋆ , 2011, 1106.3070.

[20]  B. Weiner,et al.  THE METALLICITY DEPENDENCE OF THE CO → H2 CONVERSION FACTOR IN z ⩾ 1 STAR-FORMING GALAXIES , 2011, 1106.2098.

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

[22]  E. Ostriker,et al.  The CO-H2 Conversion Factor in Disc Galaxies and Mergers , 2011, 1104.4118.

[23]  R. Klessen,et al.  Modelling CO emission – II. The physical characteristics that determine the X factor in Galactic molecular clouds , 2011, 1104.3695.

[24]  R. Giovanelli,et al.  COLD GASS, an IRAM legacy survey of molecular gas in massive galaxies - II. The non-universality of the molecular gas depletion time-scale , 2011, 1104.0019.

[25]  R. Giovanelli,et al.  COLD GASS, an IRAM legacy survey of molecular gas in massive galaxies – I. Relations between H2, H i, stellar content and structural properties , 2011, 1103.1642.

[26]  Norikazu Mizuno,et al.  THE CO-TO-H2 CONVERSION FACTOR FROM INFRARED DUST EMISSION ACROSS THE LOCAL GROUP , 2011, 1102.4618.

[27]  I. Smail,et al.  ON THE EVOLUTION OF THE MOLECULAR GAS FRACTION OF STAR-FORMING GALAXIES , 2011, 1102.3694.

[28]  D. Elbaz,et al.  Evolution of the dusty infrared luminosity function from z = 0 to z = 2.3 using observations from Spitzer , 2011, 1101.2467.

[29]  H. Rix,et al.  THE STAR FORMATION HISTORY OF MASS-SELECTED GALAXIES IN THE COSMOS FIELD , 2010, 1011.6370.

[30]  Astronomy,et al.  SMA OBSERVATIONS OF GOODS 850−11 AND GOODS 850−13: FIRST EXAMPLES OF MULTIPLE SUBMILLIMETER SOURCES RESOLVED BY AN INTERFEROMETER , 2010, 1012.1071.

[31]  R. Klessen,et al.  Modelling CO emission – I. CO as a column density tracer and the X factor in molecular clouds , 2010, 1011.2019.

[32]  C. Conselice,et al.  Origins of the extragalactic background at 1 mm from a combined analysis of the AzTEC and MAMBO data in GOODS-N , 2010, 1009.2503.

[33]  F. Bertoldi,et al.  MOST SUBMILLIMETER GALAXIES ARE MAJOR MERGERS , 2010, 1009.2495.

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

[35]  R. Teyssier,et al.  ISM properties in hydrodynamic galaxy simulations: turbulence cascades, cloud formation, role of gravity and feedback , 2010, 1007.2566.

[36]  A. Cimatti,et al.  The dust content of high-z submillimeter galaxies revealed by Herschel , , 2010, 1005.5678.

[37]  F. Walter,et al.  COLD MOLECULAR GAS IN MASSIVE, STAR-FORMING DISK GALAXIES AT z = 1.5 , 2010, 1005.4965.

[38]  A. Cimatti,et al.  Far-infrared properties of submillimeter and optically faint radio galaxies , 2010, 1005.1154.

[39]  A. Cimatti,et al.  The first Herschel view of the mass-SFR link in high-z galaxies , 2010, 1005.1089.

[40]  A. Cimatti,et al.  Dissecting the cosmic infra-red background with Herschel/PEP , 2010, 1005.1073.

[41]  F. Mannucci,et al.  A fundamental relation between mass, SFR and metallicity in local and high redshift galaxies , 2010, 1005.0006.

[42]  Christopher F. McKee,et al.  THE DARK MOLECULAR GAS , 2010, 1004.5401.

[43]  B. Weiner,et al.  A study of the gas–star formation relation over cosmic time , 2010, 1003.5180.

[44]  D. Elbaz,et al.  DIFFERENT STAR FORMATION LAWS FOR DISKS VERSUS STARBURSTS AT LOW AND HIGH REDSHIFTS , 2010, 1003.3889.

[45]  D. Padgett,et al.  Specific star formation and the relation to stellar mass from 0 < z < 2 as seen in the far-infrared at 70 and 160 μm , 2010, 1003.2446.

[46]  S. Glover,et al.  On the relationship between molecular hydrogen and carbon monoxide abundances in molecular clouds , 2010, 1003.1340.

[47]  R. Davé,et al.  IMAGING THE MOLECULAR GAS IN A SUBMILLIMETER GALAXY AT z = 4.05: COLD MODE ACCRETION OR A MAJOR MERGER? , 2010, 1002.3838.

[48]  J. Hjorth,et al.  RAPID DUST PRODUCTION IN SUBMILLIMETER GALAXIES AT z > 4? , 2010, 1002.2636.

[49]  Jean-Luc Starck,et al.  FERMI OBSERVATIONS OF CASSIOPEIA AND CEPHEUS: DIFFUSE GAMMA-RAY EMISSION IN THE OUTER GALAXY , 2009, 0912.3618.

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

[51]  G. Magdis,et al.  On the stellar masses of IRAC detected Lyman Break Galaxies at z∼ 3 , 2009, 0909.3950.

[52]  D. Weinberg,et al.  The n ature of submillimetre galaxies in cosmological hydrodynamic simulations , 2009, 0909.4078.

[53]  D. Clements,et al.  The submillimetre properties of ultraluminous infrared galaxies , 2009, 0911.3593.

[54]  Laboratoire d'Astrophysique de Marseille,et al.  RADIAL DISTRIBUTION OF STARS, GAS, AND DUST IN SINGS GALAXIES. II. DERIVED DUST PROPERTIES , 2009, 0909.2658.

[55]  E. Brinks,et al.  HERACLES: THE HERA CO LINE EXTRAGALACTIC SURVEY , 2009, 0905.4742.

[56]  Edward B. Jenkins,et al.  A UNIFIED REPRESENTATION OF GAS-PHASE ELEMENT DEPLETIONS IN THE INTERSTELLAR MEDIUM , 2009, 0905.3173.

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

[58]  D. Thompson,et al.  STAR FORMATION AND DUST OBSCURATION AT z ≈ 2: GALAXIES AT THE DAWN OF DOWNSIZING , 2009, 0905.1674.

[59]  S. Rawlings,et al.  THE COSMIC DECLINE IN THE H2/H i RATIO IN GALAXIES , 2009, 0904.0213.

[60]  B. Magnelli,et al.  The 0.4 < z < 1.3 star formation history of the Universe as viewed in the far-infrared , 2009, 0901.1543.

[61]  R. Teyssier,et al.  Cold streams in early massive hot haloes as the main mode of galaxy formation , 2008, Nature.

[62]  L. Cowie,et al.  A Highly Complete Spectroscopic Survey of the GOODS-N Field , 2008, 0812.2481.

[63]  B. Madore,et al.  THE STAR FORMATION EFFICIENCY IN NEARBY GALAXIES: MEASURING WHERE GAS FORMS STARS EFFECTIVELY , 2008, 0810.2556.

[64]  B. Madore,et al.  THE STAR FORMATION LAW IN NEARBY GALAXIES ON SUB-KPC SCALES , 2008, 0810.2541.

[65]  Paolo Coppi,et al.  EAZY: A Fast, Public Photometric Redshift Code , 2008, 0807.1533.

[66]  M. Halpern,et al.  An AzTEC 1.1 mm Survey of the GOODS-N Field – I. Maps, Catalogue and Source Statistics , 2008, 0806.3791.

[67]  Edinburgh,et al.  A 1200-μm MAMBO survey of the GOODS-N field: a significant population of submillimetre dropout galaxies , 2008, 0806.3106.

[68]  Adam K. Leroy,et al.  The Resolved Properties of Extragalactic Giant Molecular Clouds , 2008, Proceedings of the International Astronomical Union.

[69]  S. L. Scott,et al.  Molecular Gas in the z = 1.2 Ultraluminous Merger GOODS J123634.53+621241.3 , 2008, 0805.0321.

[70]  A. Cimatti,et al.  Submillimeter Galaxies at z ~ 2: Evidence for Major Mergers and Constraints on Lifetimes, IMF, and CO-H2 Conversion Factor , 2008, 0801.3650.

[71]  K. Souccar,et al.  The AzTEC mm-wavelength camera , 2008, 0801.2783.

[72]  L. Kewley,et al.  Metallicity Calibrations and the Mass-Metallicity Relation for Star-forming Galaxies , 2008, 0801.1849.

[73]  J. Brinchmann,et al.  Metallicities and Physical Conditions in Star-forming Galaxies at z ~ 1.0-1.5 , 2008, 0801.1670.

[74]  C. McKee,et al.  Far-Infrared Spectral Energy Distributions and Photometric Redshifts of Dusty Galaxies , 2007, 0710.4142.

[75]  Benjamin D. Johnson,et al.  The UV-Optical Color Magnitude Diagram. II. Physical Properties and Morphological Evolution On and Off of a Star-forming Sequence , 2007, 0711.4823.

[76]  A. Cimatti,et al.  Multiwavelength Study of Massive Galaxies at z~2. I. Star Formation and Galaxy Growth , 2007, 0705.2831.

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

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

[79]  Caltech,et al.  The Hubble Deep Field-North SCUBA Super-map - IV. Characterizing submillimetre galaxies using deep Spitzer imaging , 2006, astro-ph/0605573.

[80]  E. Rosolowsky,et al.  The Role of Pressure in GMC Formation II: The H2-Pressure Relation , 2006, astro-ph/0605035.

[81]  C. Steidel,et al.  Hα Observations of a Large Sample of Galaxies at z ~ 2: Implications for Star Formation in High-Redshift Galaxies , 2006, astro-ph/0604388.

[82]  S. Veilleux,et al.  Dynamical Properties of Ultraluminous Infrared Galaxies. I. Mass Ratio Conditions for ULIRG Activity in Interacting Pairs , 2005, astro-ph/0510670.

[83]  A. Coil,et al.  Chemical Abundances of DEEP2 Star-forming Galaxies at z~1.0-1.5 , 2005, astro-ph/0509102.

[84]  L. Cambresy,et al.  Large-scale variations of the dust optical properties in the Galaxy , 2005, astro-ph/0501444.

[85]  T. D. Matteo,et al.  Modelling feedback from stars and black holes in galaxy mergers , 2004, astro-ph/0411108.

[86]  Paul S. Smith,et al.  The Multiband Imaging Photometer for Spitzer (MIPS) , 2004 .

[87]  J. Brinkmann,et al.  The physical properties of star-forming galaxies in the low-redshift universe , 2003, astro-ph/0311060.

[88]  P. Solomon,et al.  The Star Formation Rate and Dense Molecular Gas in Galaxies , 2003, astro-ph/0310339.

[89]  J. Schaye.  Star Formation Thresholds and Galaxy Edges: Why and Where , 2004 .

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

[91]  J. Clariá,et al.  On the calibration of the COBE/IRAS dust emission reddening maps , 2003, astro-ph/0306609.

[92]  J. Surace,et al.  The IRAS Revised Bright Galaxy Sample , 2003, astro-ph/0306263.

[93]  G. Lewis,et al.  The Bivariate Luminosity-Color Distribution of IRAS Galaxies and Implications for the High-Redshift Universe , 2003, astro-ph/0301233.

[94]  L. Blitz,et al.  The Relationship between Gas Content and Star Formation in Molecule-rich Spiral Galaxies , 2001, astro-ph/0112204.

[95]  Cambridge,et al.  New Light on the Search for Low-Metallicity Galaxies , 2001, astro-ph/0110356.

[96]  D. Hartmann,et al.  The Milky Way in Molecular Clouds: A New Complete CO Survey , 2000, astro-ph/0009217.

[97]  B. Draine,et al.  Infrared Emission from Interstellar Dust Ii. the Diffuse Interstellar Medium , 2000 .

[98]  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.

[99]  F. Israel.  Extragalactic H2 and its variable relation to CO , 2000, astro-ph/0001250.

[100]  Alyssa A. Goodman,et al.  Measuring Galactic Extinction: A Test , 1999, astro-ph/9902109.

[101]  R. Genzel,et al.  Counterrotating Nuclear Disks in Arp 220 , 1998, astro-ph/9810325.

[102]  P. Solomon,et al.  Rotating Nuclear Rings and Extreme Starbursts in Ultraluminous Galaxies , 1998, astro-ph/9806377.

[103]  N. Scoville,et al.  Arcsecond Imaging of CO Emission in the Nucleus of Arp 220 , 1997 .

[104]  Simon J. E. Radford,et al.  The Molecular Interstellar Medium in Ultraluminous Infrared Galaxies , 1996, astro-ph/9610166.

[105]  B. Soifer,et al.  Molecular gas in luminous infrared galaxies , 1991 .

[106]  M. Werner,et al.  IRAS observations of an optically selected sample of interacting galaxies , 1988 .

[107]  Philip R. Maloney,et al.  I(CO)/N(H2) conversions and molecular gas abundances in spiral and irregular galaxies , 1988 .

[108]  A. R. Rivolo,et al.  Mass, luminosity, and line width relations of Galactic molecular clouds , 1987 .

[109]  F. Schloerb,et al.  Carbon monoxide as an extragalactic mass tracer , 1986 .

[110]  D. Sanders,et al.  CO detections and IRAS observations of bright radio spiral galaxies at cz equal or less than 9000 kilometers per second , 1985 .