PHANGS-HST: Globular Cluster Systems in 17 Nearby Spiral Galaxies

Abstract

We present new catalogs of likely globular clusters (GCs) in 17 nearby spiral galaxies studied as part of the PHANGS-HST Treasury Survey. The galaxies were imaged in five broad-band filters from the near-ultraviolet through the $I$ band. PHANGS-HST has produced catalogs of stellar clusters of all ages by selecting extended sources (from multiple concentration index measurements) followed by morphological classification (centrally concentrated and symmetric or asymmetric, multiple peaks, contaminant) by visually examining the V-band image and separately by a machine-learning algorithm which classified larger samples to reach fainter limits. From both cluster catalogs, we select an initial list of candidate GCs to have $B-V\ge 0.5$ and $V-I\ge 0.73$~mag, then remove likely contaminants (including reddened young clusters, background galaxies misclassified by the neural network, and chance superpositions/blends of stars) after a careful visual inspection. We find that $\approx 86$ % of the color-selected candidates classified as spherically symmetric, and $\approx 68$ of those classified as centrally concentrated but asymmetric are likely to be GCs. The luminosity functions of the GC candidates in 2 of our 17 galaxies, NGC 628 and NGC 3627, are atypical, and continue to rise at least 1~mag fainter than the expected turnover near $M_V\sim -7.4$. These faint candidate GCs have more extended spatial distributions than their bright counterparts, and may reside in the disk rather than the bulge/halo, similar to faint GCs previously discovered in M101. These faint clusters may be somewhat younger since the age-metallicity degeneracy makes it difficult to determine precise cluster ages from integrated colors once they reach $\approx 1$~Gyr.

21 pages, 12 figures

References in corpus (26)

• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• The ACS Virgo Cluster Survey. XII. The Luminosity Function of Globular Clusters in Early Type Galaxies
• A z=0 Multi-wavelength Galaxy Synthesis I: A WISE and GALEX Atlas of Local Galaxies
• Imfit: A Fast, Flexible New Program for Astronomical Image Fitting
• The PHANGS-MUSE survey -- Probing the chemo-dynamical evolution of disc galaxies
• Galaxy Groups within 3500 km s${}^{-1}$
• Distances to PHANGS Galaxies: New Tip of the Red Giant Branch Measurements and Adopted Distances
• The E-MOSAICS project: tracing galaxy formation and assembly with the age-metallicity distribution of globular clusters
• The PHANGS-JWST Treasury Survey: Star Formation, Feedback, and Dust Physics at High Angular resolution in Nearby GalaxieS
• Action Dynamics of the Local Supercluster
• Cosmicflows-3: Two Distance$-$Velocity Calculators
• PHANGS-HST: Star Cluster Spectral Energy Distribution Fitting with CIGALE
• LEGUS and Halpha-LEGUS Observations of Star Clusters in NGC 4449: Improved Ages and the Fraction of Light in Clusters as a Function of Age
• Star Cluster Classification in the PHANGS-HST Survey: Comparison between Human and Machine Learning Approaches
• Star Cluster Mass and Age Distributions of Two Fields in M83 Based on HST/WFC3 Observations
• H$\alpha$ Morphologies of Star Clusters in 16 LEGUS Galaxies: Constraints on HII region evolution timescales
• PHANGS-JWST First Results: The Dust Filament Network of NGC 628 and its Relation to Star Formation Activity
• Planetary Nebula Luminosity Function distances for 19 galaxies observed by PHANGS-MUSE
• Bright, Relatively Isolated Star Clusters in PHANGS-HST Galaxies: Aperture Corrections, Quantitative Morphologies, and Comparison with Synthetic Stellar Population Models
• Improving Star Cluster Age Estimates in PHANGS-HST Galaxies and the Impact on Cluster Demographics in NGC 628
• Luminosity functions of globular clusters in five nearby spiral galaxies using HST/ACS images
• Globular Cluster Formation in the Virgo Cluster
• Star Cluster Classification using Deep Transfer Learning with PHANGS-HST
• Constraining the epoch of reionization from the observed properties of the high-z Universe
• Two Populations of Old Star Clusters in the Spiral Galaxy M101 Based on HST/ACS Observations
• What to expect when using globular clusters as tracers of the total mass distribution in Milky Way-mass galaxies

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• Globular Cluster Counts around 700 Nearby Galaxies
• Euclid: Early Release Observations -- The star cluster systems of the Local Group dwarf galaxies IC 10 and NGC 6822
• Clusters, Clumps, Dust, & Gas (CCDG) in NGC1614: Bench-marking Cluster Demographics in Extreme Systems