Cosmic evolution of the H2 mass density and the epoch of molecular gas

Abstract

We present new empirical constraints on the evolution of ${\rho }_{{\mathrm{H}}_2}$, the cosmological mass density of molecular hydrogen, back to $z\approx 2.5$. We employ a statistical approach measuring the average observed $850\mu \mathrm{m}$ flux density of near-infrared selected galaxies as a function of redshift. The redshift range considered corresponds to a span where the $850\mu \mathrm{m}$ band probes the Rayleigh-Jeans tail of thermal dust emission in the rest-frame, and can therefore be used as an estimate of the mass of the interstellar medium (ISM). Our sample comprises of $\approx 150,000$ galaxies in the UKIDSS-UDS field with near-infrared magnitudes $K_{\mathrm{AB}}\le 25$ mag and photometric redshifts with corresponding probability distribution functions derived from deep 12-band photometry. With a sample approximately 2 orders of magnitude larger than in previous works we significantly reduce statistical uncertainties on ${\rho }_{{\mathrm{H}}_2}$ to $z\approx 2.5$. Our measurements are in broad agreement with recent direct estimates from blank field molecular gas surveys, finding that the epoch of molecular gas coincides with the peak epoch of star formation with ${\rho }_{{\mathrm{H}}_2}\approx 2\times 10^7{\mathrm{M}}_{\odot }\mathrm{Mp}{\mathrm{c}}^{-3}$ at $z\approx 2$. We demonstrate that ${\rho }_{{\mathrm{H}}_2}$ can be broadly modelled by inverting the star-formation rate density with a fixed or weakly evolving star-formation efficiency. This 'constant efficiency' model shows a similar evolution to our statistically derived ${\rho }_{{\mathrm{H}}_2}$, indicating that the dominant factor driving the peak star formation history at $z\approx 2$ is a larger supply of molecular gas in galaxies rather than a significant evolution of the star-formation rate efficiency within individual galaxies.

Accepted for publication in ApJ

References in corpus (30)

• Cosmic Star Formation History
• The UKIRT Infrared Deep Sky Survey (UKIDSS)
• EAZY: A Fast, Public Photometric Redshift Code
• A Dust-Obscured Massive Maximum-Starburst Galaxy at a Redshift of 6.34
• An ALMA survey of Sub-millimeter Galaxies in the Extended Chandra Deep Field South: Physical properties derived from ultraviolet-to-radio modelling
• The WFCAM Science Archive
• The UKIRT Wide Field Camera ZYJHK Photometric System: Calibration from 2MASS
• The SCUBA-2 Cosmology Legacy Survey: 850um maps, catalogues and number counts
• The Subaru/XMM-Newton Deep Survey (SXDS) - II. Optical Imaging and Photometric Catalogs
• ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: Survey Description
• The Evolution of the IR Luminosity Function and Dust-obscured Star Formation in the Last 13 Billion Years
• Dynamical masses of early-type galaxies at z~2: Are they truly superdense?
• ALMA spectroscopic survey in the Hubble Ultra Deep Field: Continuum number counts, resolved 1.2-mm extragalactic background, and properties of the faintest dusty star forming galaxies
• Automated Mining of the ALMA Archive in the COSMOS Field (A3COSMOS): II. Cold Molecular Gas Evolution out to Redshift 6
• ALMA spectroscopic survey in the Hubble Ultra Deep Field: CO luminosity functions and the evolution of the cosmic density of molecular gas
• ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: Molecular gas reservoirs in high-redshift galaxies
• Dust continuum emission as a tracer of gas mass in galaxies
• The ALMA Spectroscopic Survey in the HUDF: Multi-band constraints on line luminosity functions and the cosmic density of molecular gas
• ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: Search for [CII] line and dust emission in 6<z<8 galaxies
• A Detailed Study of Gas and Star Formation in a Highly Magnified Lyman Break Galaxy at z=3.07
• An ALMA survey of submillimetre galaxies in the COSMOS field: Physical properties derived from energy balance spectral energy distribution modelling
• VLA-ALMA Spectroscopic Survey in the Hubble Ultra Deep Field (VLASPECS): Total Cold Gas Masses and CO Line Ratios for z=2-3 "Main Sequence" Galaxies
• Confirming Herschel candidate protoclusters from ALMA/VLA CO observations
• The Molecular Gas Reservoirs of $z\sim 2$ Galaxies: A comparison of CO(1-0) and dust-based molecular gas masses
• VLA imaging of 12CO J=1-0 and free-free emission in lensed submillimetre galaxies
• Recalibrating the Cosmic Star Formation History
• The IRAM/GISMO two-millimeter survey in the COSMOS field
• ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: implications for spectral line intensity mapping at millimeter wavelengths and CMB spectral distortions
• S2COSMOS: Evolution of Gas Mass with Redshift Using Dust Emission
• The Molecular Mass function of the Local Universe

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