A study of the gas–star formation relation over cosmic time

By R. Genzel, L. Tacconi, J. Graciá-Carpio, A. Sternberg, M. Cooper, K. Shapiro, A. Bolatto, N. Bouché, Frédéric Bournaud, A. Burkert and 12 more. 2010

751 citations recorded by the source corpus.

We use the first systematic data sets of CO molecular line emission in z∼ 1–3 normal star-forming galaxies (SFGs) for a comparison of the dependence of galaxy-averaged star formation rates on molecular gas masses at low and high redshifts, and in different galactic environments. Although the current high-z samples are still small and biased towards the luminous and massive tail of the actively star-forming ‘main-sequence’, a fairly clear picture is emerging. Independent of whether galaxy-integrated quantities or surface densities are considered, low- and high-z SFG populations appear to follow similar molecular gas–star formation relations with slopes 1.1 to 1.2, over three orders of magnitude in gas mass or surface density. The gas-depletion time-scale in these SFGs grows from 0.5 Gyr at z∼ 2 to 1.5 Gyr at z∼ 0. The average corresponds to a fairly low star formation efficiency of 2 per cent per dynamical time. Because star formation depletion times are significantly smaller than the Hubble time at all redshifts sampled, star formation rates and gas fractions are set by the balance between gas accretion from the halo and stellar feedback. In contrast, very luminous and ultraluminous, gas-rich major mergers at both low and high z produce on average four to 10 times more far-infrared luminosity per unit gas mass. We show that only some fraction of this difference can be explained by uncertainties in gas mass or luminosity estimators; much of it must be intrinsic. A possible explanation is a top-heavy stellar mass function in the merging systems but the most likely interpretation is that the star formation relation is driven by global dynamical effects. For a given mass, the more compact merger systems produce stars more rapidly because their gas clouds are more compressed with shorter dynamical times, so that they churn more quickly through the available gas reservoir than the typical normal disc galaxies. When the dependence on galactic dynamical time-scale is explicitly included, disc galaxies and mergers appear to follow similar gas-to-star formation relations. The mergers may be forming stars at slightly higher efficiencies than the discs.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/10d065e75164c81f03093baecc297c802cc2f5f6

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In Astronomy and Astrophysics

1. P. Hopkins
2. L. Hernquist
3. R. Dav'e
4. R. Somerville
5. Volker Springel
6. A. Dekel
7. T. Naab
8. D. Narayanan

Citations in the corpus

• GOODS-Herschel: the far-infrared view of star formation in active galactic nucleus host galaxies since z ≈ 3 (2011, background): “…process driving the star formation activity, with starbursts being induced by major mergers, while internal processes (e.g., disk instabilities, turbulence) drive main-sequence star formation (e.g., Elbaz et al. 2007; Tacconi et al. 2008; Daddi et al. 2010b; Genzel et al. 2010; Elbaz et al. 2011).”
• The Star Formation Main Sequence in the Hubble Space Telescope Frontier Fields (2017, background): “These two populations have been associated with different growth mechanisms (Daddi et al. 2010; Genzel et al. 2010; Elbaz et al. 2011): MS galaxies are thought to grow on long timescales as a consequence of smooth gas accretion from the Intergalactic Medium (IGM), while MS outliers, also called…”
• MOLECULAR GAS AND STAR FORMATION IN NEARBY DISK GALAXIES (2013, background): “…(Section 4.4) and show strong evidence for lower τmoldep , i.e., more efficient star formation, in galaxy centers compared to galaxy disks - a phenomenon that we discuss in context of recent proposals for “disk” and “starburst” modes of star formation (Daddi et al. 2010; Genzel et al. 2010).”
• AGN wind scaling relations and the co-evolution of black holes and galaxies (2017, background): “…function of star-forming galaxies is exponentially cut-offed above a quenching mass M∗ ∼ 1011 M (Peng et al. 2010), the galaxy main sequence flattens above the same mass, whereas the star formation efficiency and the gas-to-star mass fraction decrease (Genzel et al. 2010, and references therein).”
• STAR FORMATION RELATIONS IN NEARBY MOLECULAR CLOUDS (2014, background): “This relation may also be useful for understanding starburst galaxies (Daddi et al. 2010; Genzel et al. 2010), but it cannot be extended to the level of molecular clouds in the MW (e.g., Krumholz et al. 2012).”
• A UNIVERSAL, LOCAL STAR FORMATION LAW IN GALACTIC CLOUDS, NEARBY GALAXIES, HIGH-REDSHIFT DISKS, AND STARBURSTS (2011, neutral): “…of the local and global star formation laws for disks as a whole has been noted by many authors (e.g. Krumholz & McKee 2005; Leroy et al. 2008; Genzel et al. 2010), and so it is impossible to decide whether the more physically meaningful star formation law is local or global if the only…”
• GAS REGULATION OF GALAXIES: THE EVOLUTION OF THE COSMIC SPECIFIC STAR FORMATION RATE, THE METALLICITY–MASS–STAR-FORMATION RATE RELATION, AND THE STELLAR CONTENT OF HALOS (2013, background): “This is longer than measurements of the consumption timescale of molecular gas at the present epoch (Young and Scoville (1991), Daddi et al (2010), Genzel et al 2010, Saintonge et al 2011b, and references therein), which are of order 1-2 Gyr, but additional atomic gas should be included, since it…”
• The baryonic assembly of dark matter haloes (2011, background): “Observationally, galaxies otherwise exhaust their fuel on time-scales ∼1–2 Gyr locally, with some evidence of even shorter gas-depletion time-scales ∼0.5 Gyr at z ∼ 2 (e.g. Genzel et al. 2010).”
• Evolution of the atomic and molecular gas content of galaxies (2013, methodology): “…through the CO line have recently become available for small samples of objects, although these samples are usually biased towards the most gasrich, actively star-forming galaxies (e.g. Genzel et al. 2010; Tacconi et al. 2010; Riechers et al. 2011; Bothwell et al. 2013; Tacconi et al. 2013).”
• Enhanced star formation rates in AGN hosts with respect to inactive galaxies from PEP-Herschel observations (2012, background): “…long duty cycles (e.g. Dekel et al. 2009),outliers are believed to undergo short and intense starbursts occurring typically during mergers1 or in dense nuclear star forming regions, which increase their SF efficiency (Daddi et al. 2010; Tacconi et al. 2010; Genzel et al. 2010; Wuyts et al. 2011).”
• A CONSTANT MOLECULAR GAS DEPLETION TIME IN NEARBY DISK GALAXIES (2011, background): “Its evolution over cosmic time informs our understanding of galaxy assembly (Daddi et al. 2010; Genzel et al. 2010).”
• The applicability of far-infrared fine-structure lines as star formation rate tracers over wide ranges of metallicities and galaxy types (2014, background): “…modes of star formation (Graciá-Carpio et al. 2011), i.e., the star-forming disk galaxies populating the main sequence in the gas-star formation diagrams and ultra-luminous gas-rich mergers with elevated levels of star formation for the same gas fractions (Daddi et al. 2010; Genzel et al. 2010).”
• Gusty, gaseous flows of FIRE: Galactic winds in cosmological simulations with explicit stellar feedback (2015, background): “The physical feedback implementation in FIRE successfully regulates mass accumulation in galaxies and provides a physical explanation for the inefficiency of star formation in galactic discs (Kennicutt 1983, 1998; Genzel et al. 2010).”
• Globular clusters as the relics of regular star formation in ‘normal’ high-redshift galaxies (2015, background): “…proceeds at high densities and pressures, withgas surface densitiesΣ = 102–103.5 M⊙ pc−2, SFR surface densities ΣSFR = 10 −1–100.5 M⊙ yr−1 kpc−2, and gas velocity dispersionsσ = 10–100 km s−1 (Genzel et al. 2010; Swinbank et al. 2012; Tacconi et al. 2013), implying pressures ofP/k > 107 K cm−3.”
• Evolution of the dust emission of massive galaxies up to z=4 and constraints on their dominant mode of star formation (2014, background): “This difference can be understood if we consider that galaxies are driven by two types of star formation activity: smooth processes fed by large reservoirs of gas in normal star-forming galaxies and boosted star-formation in gas rich mergers (Daddi et al. 2010b; Genzel et al. 2010).”
• A survey of molecular gas in luminous sub-millimetre galaxies (2012, background): “When combined with far-IR luminosities (calculated directly, or inferred from radio continuum flux observations via the far-IR/radio correlation), gas masses provide estimates of the star formation efficiencies (SFE) in SMGs (e.g. Greve et al. 2005; Daddi et al. 2010; Genzel et al. 2010).”
• THE DRIVING MECHANISM OF STARBURSTS IN GALAXY MERGERS (2010, background): “…a dual law for SF, where the integrated gas consumption timescale (ΣSFR/Σgas) is relatively low for quiescent star-forming disks and higher for starbursting ULIRGs and sub-millimeter galaxies (likely major mergers), as pointed out independently by Daddi et al. (2010a) and Genzel et al. (2010).”
• THE IMPACT OF INTERACTIONS, BARS, BULGES, AND ACTIVE GALACTIC NUCLEI ON STAR FORMATION EFFICIENCY IN LOCAL MASSIVE GALAXIES (2012, background): “Star formation in galaxies proceeds at maximum efficiency in systems undergoing major mergers (Genzel et al. 2010; Daddi et al. 2010).”