ON THE EVOLUTION OF THE MOLECULAR GAS FRACTION OF STAR-FORMING GALAXIES

By James E. Geach, I. Smail, S. M. Moran, L. MacArthur, C. Lagos, A. Edge. 2011

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We present IRAM Plateau de Bure interferometric detections of CO (J = 1 → 0) emission from a 24 μm-selected sample of star-forming galaxies at z = 0.4. The galaxies have polycyclic aromatic hydrocarbon 7.7 μm-derived star formation rates of SFR ∼30–60 M☉ yr−1 and stellar masses M⋆ ∼ 1011 M☉. The CO (J = 1 → 0) luminosities of the galaxies imply that the disks still contain a large reservoir of molecular gas, contributing ∼20% of the baryonic mass, but have star formation “efficiencies” similar to local quiescent disks and gas-dominated disks at z ∼ 1.5–2. We reveal evidence that the average molecular gas fraction has undergone strong evolution since z ∼ 2, with fgas ∝ (1 + z)∼2±0.5. The evolution of fgas encodes fundamental information about the relative depletion/replenishment of molecular fuel in galaxies and is expected to be a strong function of halo mass. We show that the latest predictions for the evolution of the molecular gas fraction in semi-analytic models of galaxy formation within a ΛCDM universe are supported by these new observations.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/f5996381608782389fd6ed569bda12d9b818ebd2

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Citations in the corpus

Physical Models of Galaxy Formation in a Cosmological Framework (2014, methodology): “…to high redshift from CO and dust-based methods (corrected for selection effects) indicate a rise in mH2/(mH2 +mstar) back in cosmic time to z ∼ 2, then a plateau or possibly a slight decline (Geach et al. 2011, Genzel et al. 2014, Saintonge et al. 2013, Scoville et al. 2014, Tacconi et al. 2013).”
An analytic model for the evolution of the stellar, gas and metal content of galaxies (2011, background): “Observed gas fractions for fairly massive galaxies from Tacconi et al. (2010) at z = 1.2 and 2.2 and Geach et al. (2011) at z = 0.4 are indicated, to be compared with predictions for ∼ 1012−13M⊙ halos; the model predictions are generally too low.”
Molecular hydrogen abundances of galaxies in the EAGLE simulations (2015, background): “Observational data are from Saintonge et al. (2011), Geach et al. (2011), Magdis et al. (2012), Saintonge et al. (2013) and Tacconi et al. (2013), and also refer to quantities measured for main-sequence galaxies over a range of stellar masses similar to the one chosen here.”
An ALMA survey of the SCUBA-2 CLS UDS field: physical properties of 707 sub-millimetre galaxies (2019, background): “In this model, the rapid decrease in the number density of SMGs at z 1.5–2 is explained by the decline in the molecular gas fraction in the haloes (Geach et al. 2011; Lagos et al. 2011; Tacconi et al. 2018), as well as the decrease in the number of dark matter haloes that transit above the mass…”
Cool Gas in High-Redshift Galaxies (2013, background): “A functional form of fgas ∼ 0.1× (1 + z) 2 fits the data reasonable (see also Magdis et al. 2012a; Geach et al. 2011).”
The neutral hydrogen content of galaxies in cosmological hydrodynamic simulations (2013, background): “The slow evolution in H i content contrasts to the much more rapid evolution observed in the molecular gas fraction (e.g. Tacconi et al. 2010; Geach et al. 2011), although some of that evolution may reflect uncertainties in assessing the molecular gas content from CO emission (e.g. Narayanan,…”
What drives the growth of black holes (2011, result): “This result is found despite the large increase in SFR for AGNs over z ≈ 0–3 and the global increase in the coldgas mass fraction in massive galaxies with redshift (e.g., Daddi et al., 2010; Tacconi et al., 2010; Geach et al., 2011).”
Cosmic evolution of the atomic and molecular gas contents of galaxies (2011, background): “Recently Geach et al. (2011) compared the evolution of the observed molecular-to-(stellar plus molecular mass) ratio (which approximates to the gas-to-baryonic ratio if the HI fraction is small),fgas = Mmol/(Mstellar +Mmol), with predictions for the Bow06.”
CO excitation of normal star forming galaxies out to $z=1.5$ as regulated by the properties of their interstellar medium (2014, unknown): “…of CO emission lines largely from the IRAM Plateau de Bure interferometer (Daddi et al 2008; 2010a; D10 hereafter; Tacconi et al 2010; 2013; Geach et al 2011) and confirmed by gas mass estimates obtained via the conversion of dust masses (Magdis et al 2011; 2012; Santini et al 2014;…”
THE LESSER ROLE OF STARBURSTS IN STAR FORMATION AT z = 2 (2011, background): “Observations of the CO molecular gas content of MS galaxies indicate that their star formation efficiency does not depend strongly on cosmic epoch to z ∼ 2, with the SFR increase being due to higher molecular gas fractions (Daddi et al. 2008; 2010a; Tacconi et al. 2010; Geach et al. 2011).”
THE EVOLVING INTERSTELLAR MEDIUM OF STAR-FORMING GALAXIES SINCE z = 2 AS PROBED BY THEIR INFRARED SPECTRAL ENERGY DISTRIBUTIONS (2012, background): “For the last step we have assumed that at high−z, MH2 ≫ MHI or equivalently that Mgas ≈ MH2 , as supported by both observational evidence (e.g., Daddi et al. 2010; Tacconi et al. 2010, Geach et al. 2011) and theoretical arguments (Blitz & Rosolowsky 2006; Bigiel et al. 2008, Obreschkow et al. 2009).”
The properties of the star-forming interstellar medium at z = 0.84-2.23 from HiZELS : mapping the internal dynamics and metallicity gradients in high-redshift disc galaxies. (2012, background): “…compared to the thin discs C© 2012 The Authors Monthly Notices of the Royal Astronomical Society C© 2012 RAS at R oyal O bservatory L ibrary on N ovem ber 20, 2014 http://m nras.oxfordjournals.org/ of local spirals (Daddi et al. 2010; Tacconi et al. 2010; Geach et al. 2011; Swinbank et al. 2011).”
A Herschel view of the far-infrared properties of submillimetre galaxies (2012, background): “Here, the redshift dependence, (1+ z)2.2z=2 ≡ ((1+ z)/3) 2.2, comes from the evolution of the gas fraction found in Geach et al. (2011).”
A survey of molecular gas in luminous sub-millimetre galaxies (2012, methodology): “There is a steep decrease in the mean gas fraction of galaxies below z ∼ 1, however, with median gas fractions dropping to ∼20 per cent by z ∼ 0.4 (Geach et al. 2011), and <10 per cent for typical SMGs in the local Universe (Bothwell et al. 2009).”
xCOLD GASS: The Complete IRAM 30 m Legacy Survey of Molecular Gas for Galaxy Evolution Studies (2017, background): “Improvement in instrument sensitivities and bandwidth have also made possible the investigation of the molecular gas contents of galaxies far beyond the local Universe (Tacconi et al. 2010; Daddi et al. 2010; Geach et al. 2011; Magdis et al. 2012; Magnelli et al. 2012; Bauermeister et al. 2013).”
Dusty Star Forming Galaxies at High Redshift (2014, background): “…forming galaxies (ranging from relatively quiescent BzK galaxies, forming at∼10–100M⊙ yr−1, to dusty starbursts), suggest gas fractions ranging from fgas ∼ 0.2–0.8 (e.g. Daddi et al., 2010a; Tacconi et al., 2010; Geach et al., 2011; Magdis et al., 2012b; Combes et al., 2013; Tacconi et al., 2013).”
The KMOS Redshift One Spectroscopic Survey (KROSS):dynamical properties, gas and dark matter fractions of typical z~1 star-forming galaxies (2016, unknown): “…and gas content etc. of these galaxies (e.g. Doherty et al. 2004, 2006; Bell et al. 2005, 2012; Erb et al. 2006a,b; Kassin et al. 2007, 2012; Buitrago et al. 2008; Dunne et al. 2009; Peng et al. 2010; Geach et al. 2011; van Dokkum et al. 2011; Stott et al. 2013a,b; Sobral et al. 2014).”
The Herschel view of the dominant mode of galaxy growth from z = 4 to the present day (2014, background): “…of galactic gas reservoirs yield gas fractions evolving from about 10% in the local Universe (Leroy et al. 2008) up to 60% at z 3 (Tacconi et al. 2010; Daddi et al. 2010; Geach et al. 2011; Magdis et al. 2012; Saintonge et al. 2013; Santini et al. 2014; Genzel et al. 2015; Béthermin et al. 2015).”