The Relationship between Molecular Gas Tracers and Kennicutt-Schmidt Laws

  title={The Relationship between Molecular Gas Tracers and Kennicutt-Schmidt Laws},
  author={Mark R. Krumholz and Todd A. Thompson},
  journal={The Astrophysical Journal},
  pages={289 - 298}
We provide a model for how Kennicutt-Schmidt (KS) laws, which describe the correlation between star formation rate and gas surface or volume density, depend on the molecular line chosen to trace the gas. We show that, for lines that can be excited at low temperatures, the KS law depends on how the line critical density compares to the median density in a galaxy's star-forming molecular clouds. High critical density lines trace regions with similar physical properties across galaxy types, and… 

Figures and Tables from this paper

What Sets the Slope of the Molecular Kennicutt–Schmidt Relation?
The surface densities of molecular gas, , and the star formation rate (SFR), , correlate almost linearly on kiloparsec scales in observed star-forming (non-starburst) galaxies. We explore the origin
Molecular Star Formation Rate Indicators in Galaxies
We derive a physical model for the observed relations between star formation rate (SFR) and molecular line (CO and HCN) emission in galaxies and show how these observed relations are reflective of
The Kennicutt–Schmidt Law and Gas Scale Height in Luminous and Ultraluminous Infrared Galaxies
A new analysis of high-resolution data from the Atacama Large Millimeter/submillimeter Array for five luminous or ultraluminous infrared galaxies gives a slope for the Kennicutt–Schmidt (KS) relation
What FIREs up star formation: The emergence of the Kennicutt-Schmidt law from feedback
We present an analysis of the global and spatially resolved Kennicutt–Schmidt (KS) star formation relation in the FIRE (Feedback In Realistic Environments) suite of cosmological simulations,
The Star Formation Rate-Dense Gas Relation in the Nuclei of Nearby Galaxies
We investigate the relationship between the star formation rate (SFR) and dense molecular gas mass in the nuclei of galaxies. To do this, we utilize the observed 850 μm luminosity as a proxy for the
Star Formation Rates in Molecular Clouds and the Nature of the Extragalactic Scaling Relations
In this paper, we investigate scaling relations between star formation rates and molecular gas masses for both local Galactic clouds and a sample of external galaxies. We specifically consider
On the Appearance of Thresholds in the Dynamical Model of Star Formation
The Kennicutt–Schmidt (KS) relationship between the surface density of the star formation rate (SFR) and the gas surface density has three distinct power laws that may result from one model in which
Extreme galaxies during reionization: testing ISM and disc models
We test the ability of equilibrium galactic disc and one-zone interstellarmedium (ISM)models to describe the physical and emission properties of quasar hosts, submillimetre galaxies, and Lyman a
Constraining cloud parameters using high density gas tracers in galaxies
Far-infrared molecular emission is an important tool used to understand the excitation mechanisms of the gas in the inter-stellar medium of star-forming galaxies. In the present work, we model the
A general model for the CO–H2 conversion factor in galaxies with applications to the star formation law
The most common means of converting an observed CO line intensity into a molecular gas mass requires the use of a conversion factor (XCO). While in the Milky Way this quantity does not appear to vary


The Relationship between Gas Content and Star Formation in Molecule-rich Spiral Galaxies
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
Rotating Nuclear Rings and Extreme Starbursts in Ultraluminous Galaxies
New CO interferometer data show that the molecular gas in infrared ultraluminous galaxies is in rotating nuclear disks or rings. The CO maps yield disk radii, kinematic major axes, rotation speeds,
Connecting Dense Gas Tracers of Star Formation in our Galaxy to High-z Star Formation
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
The Star Formation Rate and Dense Molecular Gas in Galaxies
HCN luminosity is a tracer of dense molecular gas, n(H2) ≳ 3 × 104 cm-3, associated with star-forming giant molecular cloud (GMC) cores. We present the results and analysis of our survey of HCN
A General Theory of Turbulence-regulated Star Formation, from Spirals to Ultraluminous Infrared Galaxies
We derive an analytic prediction for the star formation rate in environments ranging from normal galactic disks to starbursts and ULIRGs in terms of the observables of those systems. Our calculation
The Global Schmidt law in star forming galaxies
Measurements of Hα, H I, and CO distributions in 61 normal spiral galaxies are combined with published far-infrared and CO observations of 36 infrared-selected starburst galaxies, in order to study
Molecular Gas at High Redshift
▪ Abstract The Early Universe Molecular Emission Line Galaxies (EMGs) are a population of galaxies with only 36 examples that hold great promise for the study of galaxy formation and evolution at
HCN versus HCO+ as Dense Molecular Gas Mass Tracers in Luminous Infrared Galaxies
It has recently been argued that the HCN J = 1-0 line emission may not be an unbiased tracer of dense molecular gas (n ≳ 104 cm-3) in luminous infrared galaxies (LIRGs; LFIR > 1011 L☉) and that HCO+
Star Formation Thresholds in Galactic Disks
We report the first results of a detailed study of the star formation law in a sample of 32 nearby spiral galaxies with well-measured rotation curves, H I and H2 (as traced by CO) surface density
A Search for Dense Molecular Gas in High-Redshift Infrared-Luminous Galaxies
We present a search for HCN emission from four high-redshift far-IR-luminous galaxies. Current data and models suggest that these high-z IR-luminous galaxies represent a major starburst phase in the