The Relationship between Gas Content and Star Formation in Molecule-rich Spiral Galaxies

By Tony Wong, L. Blitz. 2001

548 citations recorded by the source corpus.

We investigate the relationship between H I, H2, and the star formation rate (SFR) using azimuthally averaged data for seven CO-bright spiral galaxies. Contrary to some earlier studies based on global fluxes, we find that ΣSFR exhibits a much stronger correlation with Σ than with Σ, as Σ saturates at a value of ~ 10 M☉ pc-2 or even declines for large ΣSFR. Hence, the good correlation between ΣSFR and the total (H I+H2) gas surface density Σgas is driven by the molecular component in these galaxies, with the observed relation between ΣSFR and Σ following a Schmidt-type law of index nmol ≈ 0.8 if a uniform extinction correction is applied or nmol ≈ 1.4 for a radially varying correction dependent on gas density. The corresponding Schmidt law indices for Σgas versus ΣSFR are 1.1 and 1.7 for the two extinction models, in rough agreement with previous studies of the disk-averaged star formation law. An alternative to the Schmidt law, in which the gas depletion timescale is proportional to the orbital timescale, is also consistent with the data if radially varying extinction corrections are applied. We find no clear evidence for a link between the gravitational instability parameter for the gas disk (Qg) and the SFR, and we suggest that Qg be considered a measure of the gas fraction. This implies that for a state of marginal gravitational stability to exist in galaxies with low gas fractions, it must be enforced by the stellar component. In regions where we have both H I and CO measurements, the ratio of H I to H2 surface density scales with radius as roughly R1.5, and we suggest that the balance between H I and H2 is determined primarily by the midplane interstellar pressure. These results favor a "law" of star formation in quiescent disks in which the ambient pressure and metallicity control the formation of molecular clouds from H I, with star formation then occurring at a roughly constant rate per unit H2 mass.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/82e0bc9b3eb47db53df3607724e3b752aa182660

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Citations in the corpus

REGULATION OF STAR FORMATION RATES IN MULTIPHASE GALACTIC DISKS: A THERMAL/DYNAMICAL EQUILIBRIUM MODEL (2010, methodology): “…correlations of the star formation rate with Σ, using either azimuthal averages over rings, or mapping with apertures down to <∼ kpc scales (e.g. Wong & Blitz 2002; Boissier et al. 2003, 2007; Heyer et al. 2004; Komugi et al. 2005; Schuster et al. 2007; Kennicutt et al. 2007; Dong et al.…”
On the Rapid Collapse and Evolution of Molecular Clouds (2007, background): “…(Elmegreen & Elmegreen 1983, 1987) or a giant molecular association (Rand & Kulkarni 1990) depending on the molecular fraction, which, in turn, depends on metallicity and pressure (Elmegreen 1993; Honma, Sofue & Arimoto 1995, Wong & Blitz 2002) and is unrelated to the cloud formation process.”
MAXIMALLY STAR-FORMING GALACTIC DISKS. I. STARBURST REGULATION VIA FEEDBACK-DRIVEN TURBULENCE (2011, background): “Molecular gas dominates mid-disk regions, but is a small fraction of the total in outer disks, where Σ and the disk’s stellar density ρ∗ are lower (Wong & Blitz 2002; Blitz & Rosolowsky 2004, 2006; Leroy et al. 2008).”
The Origin of the Mass-Metallicity Relation: Insights from 53,000 Star-forming Galaxies in the Sloan Digital Sky Survey (2004, background): “Wong & Blitz (2002) found that application of a radially-dependent attenuation c rrection to Hα produced a steeper Schmidt law, with a power law index of 1.7 (as compared to Kennicutt’s 1.4).”
Molecular Hydrogen and Global Star Formation Relations in Galaxies (2007, methodology): “While the slope of the spatially-resolved molecular gas SK relation is consistently measured to benmol ≈ 1.4 in the same systems, with a two-sigma variation ofnmol ∼ 1.2− 1.7 (Wong & Blitz 2002; Boissier et al. 2003; Heyer et al. 2004; Boissier et al. 2007; Kennicutt et al. 2007).”
The lifecycle of molecular clouds in nearby star-forming disc galaxies (2019, background): “…studies have shown that the atomic-to-molecular transition occurs at atomic gas surface densities Σgas ≈ 10 M pc−2 at near-solar metallicity (e.g. Wong & Blitz 2002; Leroy et al. 2008; Schruba et al. 2011; Krumholz 2014; Schruba et al. 2018), which is close to the critical molecular gas…”
STARS, GAS, AND DARK MATTER IN THE SOLAR NEIGHBORHOOD (2015, background): “0 pcHI thin 2S = - , is somewhat less than the maximum of about M10 observed in star-forming disk galaxies (Wong & Blitz 2002).”
On the relation between the Schmidt and Kennicutt-Schmidt star formation laws and its implications for numerical simulations (2007, background): “The KS law depends on the total gas surface density, but several studies have claimed that the exponent n ≈ 1.4 is only valid for molecular gas and that including atomic gas results in larger exponents (e.g. Wong & Blitz 2002; Heyer et al. 2004).”
Cosmic evolution of the atomic and molecular gas contents of galaxies (2011, background): “…have been measured in low stellar mass, HI-dominated dwarf and low surface brightness galaxies (e.g. Roychowdhury et al. 2009; Wyder et al. 2009), and larger SFRsin more massive galaxies with more abundant H2, such as normal spiral and starburst galaxies (e.g. Kennicutt 1998; Wong & Blitz 2002).”
The Star Formation Rate and Dense Molecular Gas in Galaxies (2003, background): “This seems to also be true in terms of the mean surface densities of the SFR and molecular gas mass for the nearest galaxies with spatially resolved observations (e.g., Wong & Blitz 2002; Rownd & Young 1999).”
Implementing molecular hydrogen in hydrodynamic simulations of galaxy formation (2012, background): “Based on the relationship between pressure and the transition from HI to H2 presented in Elmegreen (1993), Wong & Blitz (2002) hypothesized a dependency ofH2 fraction on midplane pressure for their sample of galaxies.”
The Galactic abundance gradient from Cepheids - V. Transition zone between 10 and 11 kpc (2004, background): “As was noted by Wong & Blitz (2002), CO emission can be amplified simply due to the star formation process ongoing in molecular clouds, and in this case, CO emission may trace this process rather than the H2 mass.”
Star Formation in the Milky Way and Nearby Galaxies (2012, methodology): “…analyses of the star formation law derived in this way have been carried out by numerous authors (e.g., Kennicutt 1989; Martin & Kennicutt 2001; Wong & Blitz 2002; Boissier et al. 2003; Heyer et al. 2004; Komugi et al. 2005; Schuster et al. 2007; Leroy et al. 2008; Schruba et al. 2011; Gratier…”
Cold gas properties of the Herschel Reference Survey - II. Molecular and total gas scaling relations (2014, result): “…the existence of a tight relation between the gas and the star-formation-ratesurface density, generally called Schmidt law (Schmidt 1959; Kennicutt 1998), thereby extending earlier results from Kennicutt (1989), Martin & Kennicutt (2001), and Wong & Blitz (2002) on a local cale of a few 100 pc.”
On the Origin of the Global Schmidt Law of Star Formation (2003, methodology): “This “constant efficiency” model on the scale of star forming regions is well motivated by observations (e.g., Young et al. 1996; Wong & Blitz 2002).”
THE SPATIALLY RESOLVED STAR FORMATION LAW FROM INTEGRAL FIELD SPECTROSCOPY: VIRUS-P OBSERVATIONS OF NGC 5194 (2009, background): “The saturation at 10 M⊙pc −2 has been previously observed by Wong & Blitz (2002) using azimuthally averaged data, and further confirmed to be a widespread phenomena in normal spirals by Bigiel et al. (2008) using 2D spatially resolved measurements.”
MOLECULAR GAS AND STAR FORMATION IN NEARBY DISK GALAXIES (2013, methodology): “Recent observations offer good evidence that ΣSFR relates to ΣHI and Σmol in fundamentally different ways (L08, B08 Wong & Blitz 2002; Schruba et al. 2011) and that ΣSFR is even a multivalued function of Σmol (Daddi et al. 2010; Genzel et al. 2010; Schruba et al. 2011; Saintonge et al. 2011, 2012,…”
The Molecular Gas Distribution and Schmidt Law in M33 (2003, methodology): “Martin & Kennicutt (2001) demonstrate that Q provides an accurate gauge of the gas column density at which star formation is inhibited for most of the 32 galaxies in their sample.”