Numerical Calibration of the HCN$-$Star Formation Correlation

Abstract

HCN(1$-$0) emission traces dense gas and correlates very strongly with star formation rates (SFRs) on scales from small Milky Way clouds to whole galaxies. The observed correlation offers strong constraints on the efficiency of star formation in dense gas, but quantitative interpretation of this constraint requires a mapping from HCN emission to gas mass and density. In this paper we provide the required calibration by postprocessing high-resolution simulations of dense, star-forming clouds to calculate their HCN emission ($L_{\mathrm{HCN}}$) and to determine how that emission is related to the underlying gas density distribution and star formation efficiency. We find that HCN emission traces gas with a luminosity-weighted mean number density of $0.8-1.7\times 10^4{\mathrm{cm}}^{-3}$ and that HCN luminosity is related to mass of dense gas of $\gtrsim 10^4{\mathrm{cm}}^{-3}$ with a conversion factor of ${\alpha }_{\mathrm{HCN}}\approx 14{\mathrm{M}}_{\odot }/(\mathrm{K}\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{pc}}^2)$. We also measure a new empirical relationship between the SFR per global mean freefall time (${\epsilon }_{\mathrm{ff}}$) and the SFR$-$HCN relationship, $\mathrm{SFR}/L_{\mathrm{HCN}}=2.0\times 10^{-7}({\epsilon }_{\mathrm{ff}}/0.01{)}^{1.1}{\mathrm{M}}_{\odot }{\mathrm{yr}}^{-1}/(\mathrm{K}\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{pc}}^2)$. The observed SFR$-$HCN correlation strongly constrains ${\epsilon }_{\mathrm{ff}}\approx 1\%$ with a factor of $\sim 3$ systematic uncertainty. The scatter in ${\epsilon }_{\mathrm{ff}}$ from cloud to cloud within the Milky Way is a factor of a few. We conclude that $L_{\mathrm{HCN}}$ is an effective tracer of dense gas and that the IR$-$HCN correlation is a significant diagnostic of the microphysics of star formation in dense gas.

References in corpus (61)

• Star Formation in the Milky Way and Nearby Galaxies
• An atomic and molecular database for analysis of submillimetre line observations
• A Multi-Code Analysis Toolkit for Astrophysical Simulation Data
• A General Theory of Turbulence-Regulated Star Formation, From Spirals to ULIRGs
• The Stellar IMF from Turbulent Fragmentation
• The Star Formation Rate and Dense Molecular Gas in Galaxies
• Comparing the statistics of interstellar turbulence in simulations and observations: Solenoidal versus compressive turbulence forcing
• The Star Formation Rate of Turbulent Magnetized Clouds: Comparing Theory, Simulations, and Observations
• On the Star Formation Rates in Molecular Clouds
• Slow Star Formation in Dense Gas: Evidence and Implications
• Analytical theory for the initial mass function: CO clumps and prestellar cores
• A Universal, Local Star Formation Law in Galactic Clouds, Nearby Galaxies, High-Redshift Disks, and Starbursts
• The Critical Density and the Effective Excitation Density of Commonly Observed Molecular Dense Gas Tracers
• HCN Survey of Normal Spiral, IR-luminous and Ultraluminous Galaxies
• The Star Formation Rate of Supersonic MHD Turbulence
• Rotational quenching of CO due to H${}_2$ collisions
• Modeling Collapse and Accretion in Turbulent Gas Clouds: Implementation and Comparison of Sink Particles in AMR and SPH
• On the Star Formation Efficiency of Turbulent Magnetized Clouds
• Star Formation Efficiencies and Lifetimes of Giant Molecular Clouds in the Milky Way
• Investigating the Cosmic-Ray Ionization Rate in the Galactic Diffuse Interstellar Medium through Observations of H3+
• Connecting Dense Gas Tracers of Star Formation in our Galaxy to High-z Star Formation
• One-Point Probability Distribution Functions of Supersonic Turbulent Flows in Self-Gravitating Media
• Star Formation Rates in Molecular Clouds and the Nature of the Extragalactic Scaling Relations
• Low Virial Parameters in Molecular Clouds: Implications for High Mass Star Formation and Magnetic Fields
• What determines the density structure of molecular clouds ? A case study of Orion B with Herschel
• Inefficient star formation through turbulence, magnetic fields and feedback
• Star Formation Relations in Nearby Molecular Clouds
• The Properties of Massive, Dense, Clumps: Mapping Surveys of HCN and CS
• The link between turbulence, magnetic fields, filaments, and star formation in the Central Molecular Zone cloud G0.253+0.016
• Star formation laws in Luminous Infrared Galaxies. New observational constraints on models
• Modeling jet and outflow feedback during star cluster formation
• The Relationship Between Molecular Gas Tracers and Kennicutt-Schmidt Laws
• A robust numerical scheme for highly compressible magnetohydrodynamics: Nonlinear stability, implementation and tests
• Variations in the Star Formation Efficiency of the Dense Molecular Gas across the Disks of Star-Forming Galaxies
• Evidence of enhanced star formation efficiency in luminous and ultraluminous infrared galaxies
• Observational Evidence of Dynamic Star Formation Rate in Milky Way Giant Molecular Clouds
• Rapid Molecular Cloud and Star Formation: Mechanisms and Movies
• Cloud Scale ISM Structure and Star Formation in M51
• The EMPIRE Survey: Systematic Variations in the Dense Gas Fraction and Star Formation Efficiency from Full-Disk Mapping of M51
• Molecular Star Formation Rate Indicators in Galaxies
• Testing the universality of the star formation efficiency in dense molecular gas
• Star Formation Relations in the Milky Way
• DESPOTIC -- A New Software Library to Derive the Energetics and SPectra of Optically Thick Interstellar Clouds
• Millimeter-Wave Line Ratios and Sub-beam Volume Density Distributions
• The origin of physical variations in the star formation law
• The rate and latency of star formation in dense, massive clumps in the Milky Way
• Optical Depth Estimates and Effective Critical Densities of Dense Gas Tracers in the Inner Parts of Nearby Galaxy Discs
• HCN and HCO+ emission in the disk of M31
• Dense Molecular Gas: A Sensitive Probe of Stellar Feedback Models
• An Evolutionary Model for Collapsing Molecular Clouds and Their Star Formation Activity. II. Mass Dependence of the Star Formation Rate
• Linking Dense Gas from the Milky Way to External Galaxies
• Spatially-Resolved Dense Molecular Gas and Star Formation Rate in M51
• On the effective turbulence driving mode of molecular clouds formed in disc galaxies
• Dense Gas Fraction and Star Formation Efficiency Variations in the Antennae Galaxies
• The Green Bank Telescope Maps the Dense, Star-Forming Gas in the Nearby Starburst Galaxy M82
• Relationship between turbulence energy and density variance in the Solar neighbourhood molecular clouds
• The driving of turbulence in simulations of molecular cloud formation and evolution
• Predicting HCN, HCO+, multi-transition CO, and dust emission of star-forming galaxies From local spiral and ultraluminous infrared galaxies to high-z star-forming and submillimeter galaxies
• Minimal HCN emission from Molecular Clouds in M33
• Spatially Resolved Chemistry in Nearby Galaxies III. Dense Molecular Gas in the Inner Disk of the LIRG IRAS 04296+2923
• Star Formation in Massive Clusters via Bondi Accretion

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• Star Clusters Across Cosmic Time
• A Unified Model for Galactic Discs: Star Formation, Turbulence Driving, and Mass Transport
• Interacting galaxies on FIRE-2: The connection between enhanced star formation and interstellar gas content
• EMPIRE: The IRAM 30-m Dense Gas Survey of Nearby Galaxies
• Low-J CO Line Ratios From Single Dish CO Mapping Surveys and PHANGS-ALMA
• On The Nature of Variations in the Measured Star Formation Efficiency of Molecular Clouds
• Dense gas is not enough: environmental variations in the star formation efficiency of dense molecular gas at 100pc scales in M51
• Short-lived radioisotopes in meteorites from Galactic-scale correlated star formation
• The MALATANG Survey: the L_gas-L_IR correlation on sub-kiloparsec scale in six nearby star-forming galaxies as traced by HCN J=4-3 and HCO^+ J=4-3
• Do Spectroscopic Dense Gas Fractions Track Molecular Cloud Surface Densities?
• Slow Star Formation in the Milky Way: Theory Meets Observations
• A Simple Non-equilibrium Feedback Model for Galaxy-Scale Star Formation: Delayed Feedback and SFR Scatter
• Towards a radially-resolved semi-analytic model for the evolution of disc galaxies tuned with machine learning
• The ALMOND Survey: Molecular cloud properties and gas density tracers across 25 nearby spiral galaxies with ALMA
• The density structure of supersonic self-gravitating turbulence
• Chronostar: a novel Bayesian method for kinematic age determination. I. Derivation and application to the β Pictoris Moving Group
• Kiloparsec-scale Variations in the Star Formation Efficiency of Dense Gas: the Antennae Galaxies (NGC 4038/39)
• The Global Star-Formation Law by Supernova Feedback
• The centres of M83 and the Milky Way: opposite extremes of a common star formation cycle
• The Life Cycle of the Central Molecular Zone. II: Distribution of atomic and molecular gas tracers
• PRUSSIC I - a JVLA survey of HCN/HCO+/HNC (1-0) emission in z$\sim$3 dusty galaxies: Low dense-gas fractions in high-redshift star-forming galaxies
• Dense-gas tracers and carbon isotopes in five 2.5<z<4 lensed dusty star forming galaxies from the SPT SMG sample
• The Catalogue for Astrophysical Turbulence Simulations (CATS)
• On the density regime probed by HCN emission
• Extreme Variation in Star Formation Efficiency Across a Compact, Starbursting Disk Galaxy
• Planck's Dusty GEMS. VIII. Dense-gas reservoirs in the most active dusty starbursts at z~3
• Determining Star Formation Thresholds from Observations
• Tracers of Dense Gas in the Outer Galaxy
• Reconstructing three-dimensional densities from two-dimensional observations of molecular gas
• Cold Molecular Gas in Merger Remnants. II. The properties of dense molecular gas
• Does the HCN/CO ratio trace the star-forming fraction of gas? I. A comparison with analytical models of star formation
• Predicting HCN, HCO + , multi-transition CO, and dust emission of star-forming galaxies: Constraining the properties of resolved gas and dust disks of local spiral galaxies
• Understanding biases in measurements of molecular cloud kinematics using line emission
• PRUSSIC III -- ALMA and NOEMA survey of dense gas in high-redshift star-forming galaxies
• A 260 pc resolution ALMA map of HCN(1-0) in the galaxy NGC 4321
• Gas phase Elemental abundances in Molecular cloudS (GEMS). X. Observational effects of turbulence on the chemistry of molecular clouds
• Does the HCN/CO ratio trace the star-forming fraction of gas? II. Variations in CO and HCN Emissivity
• Star formation in cloud cores -- simulations and observations of dense molecular cores and the formation of solar mass stars
• The MALATANG survey: Dense gas distribution on sub-kiloparsec scales across the disk of M82