PHANGS-MUSE: the HII region luminosity function of local star-forming galaxies

Abstract

We use an unprecedented sample of about 23,000 HII regions detected at an average physical resolution of 67pc in the PHANGS-MUSE sample to study the extragalactic HII region Ha luminosity function (LF). Our observations probe the star-forming disk of 19 nearby spiral galaxies with low inclination and located close to the star formation main sequence at z=0. The mean LF slope $\alpha$ in our sample is =1.73 with a $\sigma$ of 0.15. We find that $\alpha$ decreases with the galaxy's star formation rate surface density and argue that this is driven by an enhanced clustering of young stars at high gas surface densities. Looking at the HII regions within single galaxies we find that no significant variations occur between the LF of the inner and outer part of the star-forming disk, whereas the LF in the spiral arm areas is shallower than in the inter-arm areas for six out of the 13 galaxies with clearly visible spiral arms. We attribute these variations to the spiral arms increasing the molecular clouds arm--inter-arm mass contrast and find suggestive evidence that they are more evident for galaxies with stronger spiral arms. Furthermore, we find systematic variations in $\alpha$ between samples of HII regions with high and low ionization parameter q and argue that they are driven by the aging of HII regions.

arXiv commentAccepted in A&A. Main text: 19 pages, 11 Figures, 4 Tables. Catalog including 23301 HII regions will be available in electronic form at the CDS upon official publication

References in corpus (102)

• Galactic Stellar and Substellar Initial Mass Function
• Power-law distributions in empirical data
• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• The Host Galaxies of AGN
• Star Formation in the Milky Way and Nearby Galaxies
• A large stellar evolution database for population synthesis studies. I. Scaled solar models and isochrones
• Improving the full spectrum fitting method: accurate convolution with Gauss-Hermite functions
• Using Strong Lines to Estimate Abundances in Extragalactic HII Regions and Starburst Galaxies
• Powerlaw: a Python package for analysis of heavy-tailed distributions
• HyperLEDA. III. The catalogue of extragalactic distances
• Calibrating Extinction-Free Star Formation Rate Diagnostics with 33GHz Free-Free Emission in NGC6946
• PyNeb: a new tool for analyzing emission lines. I. Code description and validation of results
• Dust-Corrected Star Formation Rates of Galaxies. II. Combinations of Ultraviolet and Infrared Tracers
• UV-extended E-MILES stellar population models: young components in massive early-type galaxies
• Galactic-Field IMFs of Massive Stars
• Nebular Emission from Star-Forming Galaxies
• An H-alpha Imaging Survey of Galaxies in the Local 11 Mpc Volume
• On the fraction of star formation occurring in bound stellar clusters
• The warm ionized medium in spiral galaxies
• The MUSE Hubble Ultra Deep Field Survey: I. Survey description, data reduction and source detection
• The Big Problems in Star Formation: the Star Formation Rate, Stellar Clustering, and the Initial Mass Function
• New calibrations for abundance determinations in HII regions
• The lifecycle of molecular clouds in nearby star-forming disc galaxies
• The PdBI Arcsecond Whirlpool Survey (PAWS): Environmental Dependence of Giant Molecular Cloud Properties in M51
• Fast and inefficient star formation due to short-lived molecular clouds and rapid feedback
• The PHANGS-MUSE survey -- Probing the chemo-dynamical evolution of disc galaxies
• Hierarchical Star Formation from the Time-Space Distribution of Star Clusters in the Large Magellanic Cloud
• SDSS-IV MaNGA: The Impact of Diffuse Ionized Gas on Emission-line Ratios, Interpretation of Diagnostic Diagrams, and Gas Metallicity Measurements
• The Luminosity Function of Star Clusters in Spiral Galaxies
• Discovery of Recent Star Formation in the Extreme Outer Regions of Disk Galaxies
• High Mass, OB Star Formation in M51 : HST Halpha and Palpha Imaging
• On the Star Formation Rate - Brightest Cluster Relation: Estimating the peak SFR in post-merger galaxies
• An uncertainty principle for star formation. I. Why galactic star formation relations break down below a certain spatial scale
• The Spatially Resolved Star Formation Law from Integral Field Spectroscopy: VIRUS-P Observations of NGC 5194
• The Physical Properties and Effective Temperature Scale of O-type Stars as a Function of Metallicity. II. Analysis of 20 More Magellanic Cloud Stars, and Results from the Complete Sample
• Modelling the Pan-Spectral Energy Distribution of Starburst Galaxies: III. Emission Line Diagnostics of Ensembles of Evolving HII Regions
• Implications for the formation of star clusters from extra-galactic star-formation rates
• Distances to PHANGS Galaxies: New Tip of the Red Giant Branch Measurements and Adopted Distances
• A Uniform Catalog of Molecular Clouds in the Milky Way
• The Survey for Ionization in Neutral-Gas Galaxies: III. Diffuse, Warm Ionized Medium and Escape of Ionizing Radiation
• Integral field spectroscopy of a sample of nearby galaxies: II. Properties of the H ii regions
• The Optical Depth of H II Regions in the Magellanic Clouds
• Probing the role of the galactic environment in the formation of stellar clusters; using M83 as a test bench
• Mapping metallicity variations across nearby galaxy disks
• A General Theory of Turbulent Fragmentation
• PHANGS CO kinematics: disk orientations and rotation curves at 150 pc resolution
• Numerical biases on IMF determinations created by binning
• Giant Molecular Cloud Catalogues for PHANGS-ALMA: Methods and Initial Results
• Stellar structures, molecular gas, and star formation across the PHANGS sample of nearby galaxies
• The ionizing stars of extragalactic H II regions
• Winds and radiation in unison: a new semi-analytic feedback model for cloud dissolution
• Star clusters near and far; tracing star formation across cosmic time
• The PHANGS-HST Survey: Physics at High Angular resolution in Nearby GalaxieS with the Hubble Space Telescope
• High Resolution Molecular Gas Maps of M33
• A tale of two DIGs: The relative role of HII regions and low-mass hot evolved stars in powering the diffuse ionised gas (DIG) in PHANGS-MUSE galaxies
• The molecular cloud lifecycle
• HIIphot: Automated Photometry of HII Regions Applied to M51
• The Spatial Evolution of Stellar Structures in the LMC
• Catalogue of the morphological features in the Spitzer Survey of Stellar Structure in Galaxies (S${}^4$G)
• Probing cluster formation under extreme conditions: massive star clusters in blue compact galaxies
• A New Catalog of HII Regions in M31
• An uncertainty principle for star formation - II. A new method for characterising the cloud-scale physics of star formation and feedback across cosmic history
• Hierarchical Star-Formation in M33: Fundamental properties of the star-forming regions
• A unified model for the maximum mass-scales of molecular clouds, stellar clusters, and high-redshift clumps
• Simulations of the star-forming molecular gas in an interacting M51-like galaxy
• The GIST Pipeline: A Multi-Purpose Tool for the Analysis and Visualisation of (Integral-field) Spectroscopic Data
• On the duration of the embedded phase of star formation
• Panchromatic Hubble Andromeda Treasury XVI. Star Cluster Formation Efficiency and the Clustered Fraction of Young Stars
• Star formation scaling relations at ~100 pc from PHANGS: Impact of completeness and spatial scale
• Panchromatic Hubble Andromeda Treasury XVIII. The High-mass Truncation of the Star Cluster Mass Function
• On the Form of the HII Region Luminosity Function
• How Galactic Environment affects the Dynamical State of Molecular Clouds and their Star Formation Efficiency
• Star cluster formation in the most extreme environments: Insights from the HiPEEC survey
• WARPFIELD 2.0: Feedback-regulated minimum star formation efficiencies of giant molecular clouds
• The ALMA view of GMCs in NGC 300: Physical Properties and Scaling Relations at 10 pc Resolution
• Populations of high-luminosity density-bounded H II regions in spiral galaxies? Evidence and implications
• Measuring the mixing scale of the ISM within nearby spiral galaxies
• Analyzing derived metallicities and ionization parameters from model-based determinations in ionized gaseous nebulae
• Which feedback mechanisms dominate in the high-pressure environment of the Central Molecular Zone?
• PHANGS-HST: Star Cluster Spectral Energy Distribution Fitting with CIGALE
• HII regions in the CALIFA survey: I. Catalog presentation
• NGC628 with SITELLE : I. Imaging Spectroscopy of 4285 HII region candidates
• The Luminosity Function of Star Clusters in 20 Star-Forming Galaxies Based on Hubble Legacy Archive Photometry
• PHANGS-HST: New Methods for Star Cluster Identification in Nearby Galaxies
• Spitzer Analysis of HII Region Complexes in the Magellanic Clouds: Determining a Suitable Monochromatic Obscured Star Formation Indicator
• The ACS Nearby Galaxy Survey Treasury. X. Quantifying the Star Cluster Formation Efficiency of Nearby Dwarf Galaxies
• Star Cluster Properties in Two LEGUS Galaxies Computed with Stochastic Stellar Population Synthesis Models
• WARPFIELD-EMP: The Self-Consistent Prediction of Emission Lines from Evolving HII Regions in Dense Molecular Clouds
• Statistical properties of HII regions in the disc of M100
• Structure and Feedback in 30 Doradus I: Observations
• HII Region Luminosity Function of the Interacting Galaxy M51
• An uncertainty principle for star formation -- III. The characteristic emission time-scales of star formation rate tracers
• Simulations of the star-forming molecular gas in an interacting M51-like galaxy: cloud population statistics
• Spaxel Analysis: Probing the Physics of Star Formation in Ultraluminous Infrared Galaxies
• The Paα Luminosity Function of HII Regions in Nearby Galaxies from HST/NICMOS
• Star Formation in HI Selected Galaxies. II. HII Region Properties
• Properties of the HII region populations of M51 and NGC 4449 from Halpha images with ACS on HST
• The organization of cloud-scale gas density structure: high resolution CO vs. 3.6 $\mu$m brightness contrasts in nearby galaxies
• Mapping electron temperature variations across a spiral arm in NGC 1672
• The Connection Between Galaxy Environment and the Luminosity Function Slopes of Star-Forming Regions
• The Galactic HII Region Luminosity Function at Radio and Infrared Wavelengths
• Physical Properties of H II Regions in M51 from Spectroscopic Observations