METALLICITY-DEPENDENT QUENCHING OF STAR FORMATION AT HIGH REDSHIFT IN SMALL GALAXIES

By Mark R. Krumholz, A. Dekel. 2011

146 citations recorded by the source corpus.

The star formation rates (SFRs) of low-metallicity galaxies depend sensitively on the gas metallicity, because metals are crucial to mediating the transition from intermediate-temperature atomic gas to cold molecular gas, a necessary precursor to star formation. We study the impact of this effect on the star formation history of galaxies. We incorporate metallicity-dependent star formation and metal enrichment in a simple model that follows the evolution of a halo main progenitor. Our model shows that including the effect of metallicity leads to suppression of star formation at redshift z > 2 in dark halos with masses ≲ 1011 M☉, with the suppression becoming near total for halos below ∼109.5–1010 M☉. We find that at high redshift, until z ∼ 2, the SFR cannot catch up with the gas inflow rate (IR), because the SFR is limited by the free-fall time, and because it is suppressed further by a lack of metals in small halos. As a result, in each galaxy the SFR is growing in time faster than the IR, and the integrated cosmic SFR density is rising with time. The suppressed in situ SFR at high-z makes the growth of stellar mass dominated by ex situ SFR, meaning stars formed in lower mass progenitor galaxies and then accreted, which implies that the specific SFR (sSFR) remains constant with time. The intensely accreted gas at high-z is accumulating as an atomic gas reservoir. This provides additional fuel for star formation in 1010–1012 M☉ halos at z ∼ 1–3, which allows the SFR to exceed the instantaneous IR, and may enable an even higher outflow rate. At z < 1, following the natural decline in IR with time due to the universal expansion, the SFR and sSFR are expected to drop. We specify the expected dependence of sSFR and metallicity on stellar mass and redshift. At a given z, and below a critical mass, these relations are predicted to be flat and rising, respectively. Our model predictions qualitatively match some of the puzzling features in the observed star formation history.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/69b6d7c2c0cdaf454d62ad03d9e6a47676bc37fe

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Citations in the corpus

A Redshift-independent Efficiency Model: Star Formation and Stellar Masses in Dark Matter Halos at z ≳ 4 (2018, background): “…the UV background (Barkana & Loeb 1999), stellar feedback by supernovae (Dekel & Silk 1986), radiation pressure from stars (Thompson et al. 2005; Murray et al. 2010; Hopkins et al. 2010), and suppression of the formation of molecular hydrogen in low metallicity environments (Krumholz & Dekel 2012).”
A fundamental relation between the metallicity, gas content, and stellar mass of local galaxies (2013, background): “…between these models is that Davé et al. (2012) assume an ‘equilibrium condition’, whereby the inflow rate is balanced by the sum of the star formation and outflow rates (this is sometimes referred to as the ‘reservoir’ or ‘bathtub model’ – see Bouché et al. 2010; Krumholz & Dekel 2012).”
The current status of galaxy formation (2012, background): “Metallicity-dependent star formation alleviates the high redshift problem, reducing the stellar mass that is in place early and enhancing the SSFR as needed 6 Joseph Silk1,2,3, Gary A. Mamon1 (Krumholz & Dekel, 2012).”
Constraining the galaxy–halo connection over the last 13.3 Gyr: star formation histories, galaxy mergers and structural properties (2017, background): “Previous studies have shown related figures to the panels in Figure 9 (see e.g., Firmani & Avila-Reese 2010; Krumholz & Dekel 2012; Behroozi, Wechsler & Conroy 2013b; Yang et al. 2013).”
KECK SPECTROSCOPY OF 3 < z < 7 FAINT LYMAN BREAK GALAXIES: THE IMPORTANCE OF NEBULAR EMISSION IN UNDERSTANDING THE SPECIFIC STAR FORMATION RATE AND STELLAR MASS DENSITY (2012, background): “Possibilities included the inefficient formation of molecular hydrogen in metal-poor galaxies (e.g., Robertson&Kravtsov 2008; Gnedin et al. 2009; Krumholz & Dekel 2012), or an increase in the mass outflow rate per unit star formation with redshift.”
A fundamental problem in our understanding of low-mass galaxy evolution (2012, background): “…suppresses star formation in low mass haloes at early times, potentially mitigating the need for strong feedback at later epochs, like for example very inefficient high-z star formation (Krumholz & Dekel 2012), preheating (Mo et al. 2005) or warm dark matter (as discussed in Fontanot et al. 2009).”
Four phases of angular-momentum buildup in high-z galaxies: from cosmic-web streams through an extended ring to disc and bulge (2014, background): “Therefore, the early SFR is overestimated, while the suppression of SFR in small galaxies is underestimated, resulting in excessive early star formation prior to z ∼ 3, by a factor of the order of 2.”
Evolution of density profiles in high-z galaxies: compaction and quenching inside-out (2015, background): “Currently, the code assumes a SFR efficiency per free fall time that is rather realistic, but it does not yet follow in detail the formation of molecules and the effect of metallicity on SFR (Krumholz & Dekel 2012).”
Toy models for galaxy formation versus simulations (2013, methodology): “We note that this may not be true for less massive galaxies and at higher redshifts, where feedback is likely to be more effective in suppressing star formation and accumulating a gas reservoir (e.g. Zolotov et al. 2012; Krumholz & Dekel 2012).”
Molecular and atomic gas along and across the main sequence of star-forming galaxies (2016, background): “…how it is replenished by inflows and depleted by star formation and outflows (e.g. White & Frenk 1991; Bouché et al. 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…”
The confinement of star-forming galaxies into a main sequence through episodes of gas compaction, depletion and replenishment (2015, background): “As mentioned above, the code as- MNRAS 000, 1–27 (2016) sumes a SFR efficiency per free fall time that is rather realistic, but it does not yet follow in detail the formation of molecules and the effect of metallicity on SFR (Krumholz & Dekel 2012).”
A unified model for galactic discs: star formation, turbulence driving, and mass transport (2017, methodology): “…indicate regions of transport-driven versus feedback-driven turbulence; see the main text for details. this fraction on halo mass and redshift is highly complex and substantially uncertain (e.g. Obreschkow et al. 2009; Fu et al. 2010; Lagos et al. 2011; Krumholz & Dekel 2012; Forbes et al. 2014a).”
The big problems in star formation: The star formation rate, stellar clustering, and the initial mass function (2014, background): “…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 2012).”
The z ∼ 6 Luminosity Function Fainter than −15 mag from the Hubble Frontier Fields: The Impact of Magnification Uncertainties (2016, background): “…predict a flattening in the UV LF at ∼ −13 or ∼ −15 due to less efficient atomic and molecular hydrogen cooling, respectively (Muñoz & Loeb 2011; Krumholz & Dekel 2012; Kuhlen et al. 2013; Jaacks et al. 2013; Wise et al. 2014; Liu et al. 2016; Gnedin 2016; Finlator et al. 2016), while 7…”
Great Optically Luminous Dropout Research Using Subaru HSC (GOLDRUSH). I. UV Luminosity Functions at $z \sim 4-7$ Derived with the Half-Million Dropouts on the 100 deg$^2$ Sky (2017, background): “…UV LF down to ∼ −14 mag, at around which many cosmological hydrodynamic simulations of galaxy formation predict a flattening (e.g., Muñoz & Loeb 2011; Krumholz & Dekel 2012; Kuhlen et al. 2013; Jaacks et al. 2013; Wise et al. 2014; O’Shea et al. 2015; Liu et al. 2016; Gnedin 2016; Ocvirk et…”
Physical Models of Galaxy Formation in a Cosmological Framework (2014, background): “…converting ISM gas into stars is reduced owing to the lower metallicity at early epochs which results in less efficient formation of molecular gas (Krumholz & Dekel 2012), but hydrodynamic simula- Models of Galaxy Formation 39 tions and SAMs incorporating H2 formation modeling suggest that this…”
A survey of molecular gas in luminous sub-millimetre galaxies (2012, background): “8), and the theoretically predicted fall in specific accretion rates (Krumholz & Dekel 2012).”
The Star Formation Main Sequence in the Hubble Space Telescope Frontier Fields (2017, background): “…the observations (feedback effects can modify the trend, see e.g. Davé et al. 2011b), that the effect of metallicity should be taken into account (Krumholz & Dekel 2012) and that other processes besides pure accretion are at play in assembling galaxies, such as mergers (e.g. Tasca et al.…”