Northern Galactic Molecular Cloud Clumps in Hi-GAL: Clump and Star Formation within Clouds

Abstract

We investigate how the properties of Galactic giant molecular clouds (GMCs) and their denser substructures (clumps) correlate with the local star formation rate. We trace clouds using the ${}^{12}$CO(3-2) transition, as observed by the CO High Resolution Survey (COHRS). We identify their constituent clumps using thermal dust emission, as observed by the Herschel infrared GALactic plane survey (Hi-GAL). We estimate star formation rates in these clouds using 70 $\mu$m emission. In total, we match 3,674 clumps to 473 clouds in position-position-velocity space spanning the Galactic longitude range $10^{\circ }<\ell <56^{\circ }$. We find that more massive clouds produce more clumps and more massive clumps. These clumps have average number densities an order of magnitude greater than their host clouds. We find a mean clump mass fraction of $0.20_{-0.10}^{+0.13}$. This mass fraction weakly varies with mass and mass surface density of clouds, and shows no clear dependence on the virial parameter and line width of the clouds. The average clump mass fraction is only weakly dependent upon Galactocentric radius. Although the scatter in our measured properties is significant, the star formation rate for clouds is independent of clump mass fraction. However, there is a positive correlation between the depletion times for clouds and clump mass fraction. We find a star formation efficiency per free fall time of ${\epsilon }_{\mathrm{ff}}=0.15\%$ for GMCs but ${\epsilon }_{\mathrm{ff}}=0.37\%$ for clumps.

arXiv commentAccepted to ApJ

References in corpus (63)

• Astropy: A Community Python Package for Astronomy
• The Global Schmidt Law in Star Forming Galaxies
• Star Formation in the Milky Way and Nearby Galaxies
• Theory of Star Formation
• Interstellar Dust Grains
• The Photodetector Array Camera and Spectrometer (PACS) on the Herschel Space Observatory
• The Herschel-SPIRE instrument and its in-flight performance
• The CO-to-H2 Conversion Factor
• Infrared Emission from Interstellar Dust. IV. The Silicate-Graphite-PAH Model in the Post-Spitzer Era
• The Neutral Atomic Phases of the ISM in the Galaxy
• Cold Dark Clouds: The Initial Conditions for Star Formation
• The Star Formation Rate and Dense Molecular Gas in Galaxies
• Calibrating Extinction-Free Star Formation Rate Diagnostics with 33GHz Free-Free Emission in NGC6946
• On the Star Formation Rates in Molecular Clouds
• Molecular Gas and Star Formation in Nearby Disk Galaxies
• The Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey
• Dust-Corrected Star Formation Rates of Galaxies. II. Combinations of Ultraviolet and Infrared Tracers
• Hi-GAL: the Herschel infrared Galactic Plane Survey
• Determining Star Formation Rates for Infrared Galaxies
• The Universality of the Stellar IMF
• Forming Realistic Late-Type Spirals in a LCDM Universe: The Eris Simulation
• The Star Formation Law in Atomic and Molecular Gas
• The Calibration of Monochromatic Far-Infrared Star Formation Rate Indicators
• Variations in the Galactic star formation rate and density thresholds for star formation
• Toward a Unification of Star Formation Rate Determinations in the Milky Way and Other Galaxies
• Bias-free Measurement of Giant Molecular Cloud Properties
• The Mass Distribution and Lifetime of Prestellar Cores in Perseus, Serpens, and Ophiuchus
• Star Formation Rates in Molecular Clouds and the Nature of the Extragalactic Scaling Relations
• The present-day star formation rate of the Milky-Way determined from Spitzer detected young stellar objects
• Hi-GAL, the Herschel infrared Galactic Plane Survey: photometric maps and compact source catalogues. First data release for Inner Milky Way: +68°> l > -70°
• The Bolocam Galactic Plane Survey -- II. Catalog of the Image Data
• Star Formation Relations in Nearby Molecular Clouds
• The Scale Dependence of the Molecular Gas Depletion Time in M33
• The link between turbulence, magnetic fields, filaments, and star formation in the Central Molecular Zone cloud G0.253+0.016
• Properties of Hi-GAL clumps in the inner Galaxy]{The Hi-GAL compact source catalogue. I. The physical properties of the clumps in the inner Galaxy ($-71.0^{\circ }<\ell <67.0^{\circ }$)
• Comparing Star Formation on Large Scales in the c2d Legacy Clouds: Bolocam 1.1 mm Dust Continuum Surveys of Serpens, Perseus, and Ophiuchus
• Star formation rates and efficiencies in the Galactic Centre
• The properties of the ISM in disc galaxies with stellar feedback
• Variations in the Star Formation Efficiency of the Dense Molecular Gas across the Disks of Star-Forming Galaxies
• Breakdown of Kennicutt-Schmidt Law at GMC Scales in M33
• Molecular Cloud Evolution IV: Magnetic Fields, Ambipolar Diffusion, and the Star Formation Efficiency
• The Bolocam Galactic Plane Survey. VII. Characterizing the Properties of Massive Star-Forming Regions
• The Star Formation Efficiency per Free Fall Time in Nearby Galaxies
• The EMPIRE Survey: Systematic Variations in the Dense Gas Fraction and Star Formation Efficiency from Full-Disk Mapping of M51
• Turbulence sets the initial conditions for star formation in high-pressure environments
• Quantifying Observational Projection Effects Using Molecular Cloud Simulations
• A 50 pc scale view of star formation efficiency across NGC 628
• Graph-based interpretation of the Molecular Interstellar Medium Segmentation
• The Bolocam Galactic Plane Survey. XIV. Physical Properties of Massive Starless and Star Forming Clumps
• Star Formation Relations in the Milky Way
• The Dense Gas Mass Fraction of Molecular Clouds in the Milky Way
• Testing Larson's relationships in massive clumps
• The integrated properties of the molecular clouds from the JCMT CO(3-2) High Resolution Survey
• Star formation towards the Scutum tangent region and the effects of Galactic environment
• Do Giant Molecular Clouds Care About the Galactic Structure?
• The Bolocam Galactic Plane Survey. X. A Complete Spectroscopic Catalog of Dense Molecular Gas Observed toward 1.1 mm Dust Continuum Sources with 7.5 <= l <= 194 degrees
• The Bolocam Galactic Plane Survey. VIII. A Mid-Infrared Kinematic Distance Discrimination Method
• The Bolocam Galactic Plane Survey. XII. Distance Catalog Expansion Using Kinematic Isolation of Dense Molecular Cloud Structures With 13CO(1-0)
• The prevalence of star formation as a function of Galactocentric radius
• Molecular Cloud-scale Star Formation in NGC 300
• The Parsec-Scale Relationship Between I_CO and A_V in Local Molecular Clouds
• Northern Galactic Molecular Cloud Clumps in Hi-GAL: Dense Gas Map and Environmental Trends
• A Galactic Molecular Cloud Clump Catalog from Hi-GAL Data: Method and Initial Results Comparison to BGPS

Cited by in corpus (1)

• Spatially Resolved Star Formation relations in local LIRGs along the complete merger sequence