Connecting Dense Gas Tracers of Star Formation in our Galaxy to High-z Star Formation

By Jingwen Wu, N. Evans II, Yu Gao, P. Solomon, Y. Shirley, P. V. Vanden Bout. 2005

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Observations have revealed prodigious amounts of star formation in starburst galaxies as traced by dust and molecular emission, even at large redshifts. Recent work shows that for both nearby spiral galaxies and distant starbursts, the global star formation rate, as indicated by the infrared luminosity, has a tight and almost linear correlation with the amount of dense gas as traced by the luminosity of HCN. Our surveys of Galactic dense cores in HCN 1-0 emission show that this correlation continues to a much smaller scale, with nearly the same ratio of infrared luminosity to HCN luminosity found over 7-8 orders of magnitude in LIR, with a lower cutoff around 104.5 L☉ of infrared luminosity. The linear correlation suggests that we may understand distant star formation in terms of the known properties of local star-forming regions. Both the correlation and the luminosity cutoff can be explained if the basic unit of star formation in galaxies is a dense core, similar to those studied in our Galaxy.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/3843d64ae1bc40f8b02439ef7509eb21fb68e750

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Citations in the corpus

THE SPITZER c2d LEGACY RESULTS: STAR-FORMATION RATES AND EFFICIENCIES; EVOLUTION AND LIFETIMES (2008, background): “The results are more consistent with relations found for dense gas (Wu et al. 2005).”
On the origin of the galaxy star‐formation‐rate sequence: evolution and scatter (2009, background): “Following Blitz & Rosolowsky (2006) we assume that star formation takes place in dense molecular gas, traced by the hydrogen cyanide molecule (HCN), with a constant star formation efficiency: SFR [M pc−2 Gyr−1] = ̃SF [Gyr−1] mol,HCN [M pc−2] , (A1) where ̃SF 10−13 Gyr−1 (Gao & Solomon 2004; Wu et al”
Molecular Hydrogen and Global Star Formation Relations in Galaxies (2007, background): “In contrast, observations generally show that star formation in galaxies correlates strongly withmolecular gas, especially with the highly dense gas traced by HCN emission (Gao & Solomon 2004; Wu et al. 2005).”
STAR FORMATION RELATIONS IN NEARBY MOLECULAR CLOUDS (2014, background): “Vutisalchavakul & Evans (2013) have reexamined some of the massive dense clumps studied by Wu et al. (2005) to get better SFR by using radio continuum and integrating over the whole H II region.”
ENVIRONMENTAL DEPENDENCE OF THE KENNICUTT–SCHMIDT RELATION IN GALAXIES (2010, background): “…with the molecular gas (e.g., Wong & Blitz 2002a; Bigiel et al. 2008), especially with the densest gas traced by HCN emission (Gao & Solomon 2004; Wu et al. 2005), while it only correlates weakly, if at all, with the density of atomic gas (Wong & Blitz 2002a; Kennicutt et al. 2007; Bigiel et al.…”
What controls star formation in the central 500 pc of the Galaxy (2013, background): “Dense molecular gas as traced by HCN is found to be correlated with star formation tracers (e.g. Gao & Solomon 2004; Wu et al. 2005).”
The evolution of massive black holes and their spins in their galactic hosts (2012, background): “Assuming that star formation in galactic disks only happensinside dense molecular clouds, which are well traced by the HCN luminosity (Wu et al. 2005; Gao & Solomon 2004), we follow 4 The reservoir’s geometry is needed for instance to calculate the velocity Vc of the composite system, entering e.g.…”
Star-formation laws in luminous infrared galaxies. New observational constraints on models (2011, background): “These values are close the upper limit imposed by the maximum efficiencies measured in Galactic star-forming cores (∼3900L⊙ L′−1; Wu et al. 2005).”
THE STAR FORMATION RATE AND GAS SURFACE DENSITY RELATION IN THE MILKY WAY: IMPLICATIONS FOR EXTRAGALACTIC STUDIES (2010, background): “(17) This equation is equivalent to that shown in Wu et al. (2005), which is the fit to both massive clumps and galaxies.”
The Global Evolution of Giant Molecular Clouds. I. Model Formulation and Quasi-Equilibrium Behavior (2006, unknown): “Observations show that stars form much more slowly than the free-fall rate in GMCs (Zuckerman & Evans 1974; Rownd & Young 1999; Wong & Blitz 2002; Gao & Solomon 2004; Wu et al. 2005), and any successful GMC model must explain why this should be.”
Star Formation in the Milky Way and Nearby Galaxies (2012, background): “Wu et al. (2005b) have subsequently shown that this linear relation extends down to the scales of individual star-forming molecular clouds and dense clumps in the Galaxy.”
A UNIVERSAL, LOCAL STAR FORMATION LAW IN GALACTIC CLOUDS, NEARBY GALAXIES, HIGH-REDSHIFT DISKS, AND STARBURSTS (2011, unknown): “Heiderman et al. (2010) do not give an explicit value for tdense, but their best-fit value for objects above their threshold (their Figure 10) corresponds to tdense ≈ 80 Myr; this is similar to the value of tdense = 83 Myr obtained by Wu et al. (2005, 2010), and so we adopt it.”
Variations in the Galactic star formation rate and density thresholds for star formation (2012, background): “This suggests the linear relationship observed between the quantity of gas above the proposed extinction threshold and the SFR (Gao & Solomon 2004; Wu et al. 2005; Lada et al. 2012) extends to a larger number of more representative SF regions across the Galaxy.”
Star Formation in NGC 5194 (M51a). II. The Spatially Resolved Star Formation Law (2007, background): “Subsequent work has shown that this trend extends to other highly-extincted HII regions in other galaxies (Wu et al. 2005; Alonso-Herrero et al. 2006; Calzetti et al. 2007).”
THE PROPERTIES OF MASSIVE, DENSE CLUMPS: MAPPING SURVEYS OF HCN AND CS (2010, methodology): “As noted by Wu et al. (2005), there is a cut-off around L∼ 104.5L⊙ in the LIR-L ′ HCN1−0 correlation.”
The Relationship between Molecular Gas Tracers and Kennicutt-Schmidt Laws (2007, background): “However, they find that their correlation, which covers nearly three decades in total galactic star formation rate, is linear: LFIR ∝ LHCN. Wu et al. (2005) show that this correlation extends down to individual star-forming clumps of gas in the Milky Way, provided that their infrared luminosities ar”
STAR FORMATION RATES IN MOLECULAR CLOUDS AND THE NATURE OF THE EXTRAGALACTIC SCALING RELATIONS (2011, result): “The close correlation of the star formation rate with the mass of dense gas over these immense scales has been established in previous studies (Wu et al. 2005, Paper I).”
THE MOLECULAR GAS IN LUMINOUS INFRARED GALAXIES. II. EXTREME PHYSICAL CONDITIONS AND THEIR EFFECTS ON THE Xco FACTOR (2012, methodology): “Further evidence for a near-constant ǫg,∗ is the tight linear LIR-HCN(1-0) correlation found for individual GMCs up to entire ULIRGs (Wu et al. 2005) with HCN J=1–0 used as a dense gas mass tracer.”
xCOLD GASS: The Complete IRAM 30 m Legacy Survey of Molecular Gas for Galaxy Evolution Studies (2017, background): “The latter is particularly important to link the global, statistical studies with high resolution observations of individual clouds in the Milky Way and other very nearby galaxies (Wu et al. 2005; Buchbender et al. 2013).”