VALIDATION OF THE EQUILIBRIUM MODEL FOR GALAXY EVOLUTION TO z ∼ 3 THROUGH MOLECULAR GAS AND DUST OBSERVATIONS OF LENSED STAR-FORMING GALAXIES

By A. Saintonge, D. Lutz, R. Genzel, B. Magnelli, R. Nordon, L. Tacconi, A. Baker, K. Bandara, S. Berta, N. F. Förster Schreiber and 4 more. 2013

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We combine IRAM Plateau de Bure Interferometer and Herschel PACS and SPIRE measurements to study the dust and gas contents of high-redshift star-forming galaxies. We present new observations for a sample of 17 lensed galaxies at z = 1.4–3.1, which allow us to directly probe the cold interstellar medium of normal star-forming galaxies with stellar masses of ∼1010 M☉, a regime otherwise not (yet) accessible by individual detections in Herschel and molecular gas studies. The lensed galaxies are combined with reference samples of submillimeter and normal z ∼ 1–2 star-forming galaxies with similar far-infrared photometry to study the gas and dust properties of galaxies in the SFR–M*–redshift parameter space. The mean gas depletion timescale of main-sequence (MS) galaxies at z > 2 is measured to be only ∼450 Myr, a factor of ∼1.5 (∼5) shorter than at z = 1 (z = 0), in agreement with a (1 + z)−1 scaling. The mean gas mass fraction at z = 2.8 is 40% ± 15% (44% after incompleteness correction), suggesting a flattening or even a reversal of the trend of increasing gas fractions with redshift recently observed up to z ∼ 2. The depletion timescale and gas fractions of the z > 2 normal star-forming galaxies can be explained under the “equilibrium model” for galaxy evolution, in which the gas reservoir of galaxies is the primary driver of the redshift evolution of specific star formation rates. Due to their high star formation efficiencies and low metallicities, the z > 2 lensed galaxies have warm dust despite being located on the star formation MS. At fixed metallicity, they also have a gas-to-dust ratio 1.7 times larger than observed locally when using the same standard techniques, suggesting that applying the local calibration of the δGDR–metallicity relation to infer the molecular gas mass of high-redshift galaxies may lead to systematic differences with CO-based estimates.

Subfields: Astronomy and Astrophysics

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Citations in the corpus

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).”
The big problems in star formation: The star formation rate, stellar clustering, and the initial mass function (2014, background): “This is not true in present-day spirals with tdep ∼ 1 Gyr,2 or even for large star-forming galaxies up to z ∼ 3 (Saintonge et al. 2013), though it 2However, Kennicutt & Evans (2012) point out that even the Milky might have been true for their progenitors at even higher redshift (Krumholz & Dekel…”
The dust content of galaxies from z = 0 to z = 9 (2016, background): “…the decrease in dust mass can be explained by the observed and inferred decrease in the gas fraction of galaxies (e.g., Tacconi et al. 2010; Narayanan et al. 2012; Tacconi et al. 2013; Saintonge et al. 2013; Santini et al. 2014; Béthermin et al. 2015; Popping et al. 2015; Scoville et al. 2016).”
THE KMOS3D SURVEY: DESIGN, FIRST RESULTS, AND THE EVOLUTION OF GALAXY KINEMATICS FROM 0.7 ⩽ z ⩽ 2.7 (2014, background): “…out to z ∼ 2.5 (e.g., Förster Schreiber et al. 2006, 2009; Genzel et al. 2006, 2008; Shapiro et al. 2008; Epinat et al. 2009, 2012; Wuyts et al. 2011a) and the evolution of molecular gas mass fractions (e.g. Tacconi et al. 2010, 2013; Daddi et al. 2010; Saintonge et al. 2013; Genzel et al. 2014a).”
Introducing the Illustris Project: the evolution of galaxy populations across cosmic time (2014, background): “Such a qualitative behaviour has been suggested in recent z ∼ 3 data (Magdis et al. 2012; Saintonge et al. 2013), and similar limits have been set even at z ∼ 5 (Davies et al. 2010; Livermore et al. 2012), although large uncertainties still plague the measurements at such high redshifts.”
COMBINED CO AND DUST SCALING RELATIONS OF DEPLETION TIME AND MOLECULAR GAS FRACTIONS WITH COSMIC TIME, SPECIFIC STAR-FORMATION RATE, AND STELLAR MASS (2014, methodology): “19 CO 2-1, 3-2 or 4-3 detections of above main-sequence submillimeter galaxies (SMGs) between z=1.2 and 3.4, obtained with the IRAM PdBI by Greve et al. (2005), Tacconi et al. (2006, 2008) and Bothwell et al. (2013); 10.”
Evolution of Interstellar Medium, Star Formation, and Accretion at High Redshift (2017, methodology): “For MS galaxies Saintonge et al. (2013) and Genzel et al. (2015) obtain slightly lower depletion times ∼ 450 Myr and gas mass fractions ∼ 40% at z ∼ 2.8.”
EVIDENCE FOR WIDE-SPREAD ACTIVE GALACTIC NUCLEUS-DRIVEN OUTFLOWS IN THE MOST MASSIVE z ∼ 1–2 STAR-FORMING GALAXIES (2014, background): “1 log(M∗/M ) = 11.5 lensed main-sequence SFG (J0901+1814; Diehl et al. 2009; Saintonge et al. 2013), for which we obtained deep, seeing limited and AO SINFONI data.”
The evolution of the dust and gas content in galaxies (2013, background): “Finally, steep slopes for the global star formation law may be explained by the results of Saintonge et al. (2013), who claim that the gas-to-dust ratio may be 1.7 times larger at z > 2 than observed locally.”
Molecular hydrogen abundances of galaxies in the EAGLE simulations (2015, background): “It has been established that the H2-to-stellar mass ratio anticorrelates with stellar mass and that such a relation is present from z = 0 to at least z ≈ 2.5 (e.g. Saintonge et al. 2011, 2013; Tacconi et al. 2013; Bothwell et al. 2014; DessaugesZavadsky et al. 2015; Santini et al. 2014).”
The COSMOS2015 galaxy stellar mass function . Thirteen billion years of stellar mass assembly in ten snapshots (2017, background): “…increase rate of DM haloes (sMIR ≡ M−1h dMh/dt, see e.g. Neistein & Dekel 2008) evolve in a similar way, as expected if star formation is regulated by the amount of cold gas in the galaxy reservoir, which in turn depends on the inflow of DM into the halo (Lilly et al. 2013; Saintonge et al. 2013).”
The evolution of the dust temperatures of galaxies in the SFR–M∗ plane up to z ~ 2 (2013, background): “…galaxies to extend the study of the dust temperatures of MS galaxies to lower stellar masses and higher redshifts (4 × 109 < M∗ < 1011 M , 2 < z < 3), Saintonge et al. (2013) also report higher Tdust values compared to lower redshift samples, and attribute this variation to lower metallicities…”
Dusty Star Forming Galaxies at High Redshift (2014, background): “Note that recent work by Saintonge et al. (2013) suggests that the molecular gas fraction rise may plateau at redshifts z & 2.”
Physical Models of Galaxy Formation in a Cosmological Framework (2014, methodology): “…of CO (an indirect tracer of molecular hydrogen, H2) in fairly massive high redshift galaxies that the gas fraction of galaxies has decreased significantly over cosmic time since z ∼ 2 (Bothwell et al. 2013b, Genzel et al. 2014, Saintonge et al. 2013, Tacconi et al. 2010, Tacconi et al. 2013).”
Evolution of the dust emission of massive galaxies up to z=4 and constraints on their dominant mode of star formation (2014, methodology): “Saintonge et al. (2013) found an offset of a factor 1.7 for a population of lensed galaxies and discussed the possible origins of the tension between the gas content estimated from CO and from dust.”
Molecular and atomic gas along and across the main sequence of star-forming galaxies (2016, background): “…2010; Davé et al. 2011, 2012; Krumholz & Dekel 2012; Lilly et al. 2013), are well supported by observations of the redshift evolution of the molecular gascontents of galaxies (Tacconi et al. 2010, 2013; Magdis et al. 2012; ⋆ E-mail: a.saintonge@ucl.ac.uk Saintonge et al. 2013; Genzel et al. 2015).”
PHIBSS: Unified Scaling Relations of Gas Depletion Time and Molecular Gas Fractions (2017, methodology): “19 CO 2-1, 3-2 or 4-3 detections of above main-sequence submillimeter galaxies (SMGs) between z=1.2 and 3.4, obtained with the IRAM PdBI by Greve et al. (2005), Tacconi et al. (2006, 2008) and Bothwell et al. (2013).”