Quantifying the decline in CO(2-1) intensity around PHANGS-HST star clusters: Constraints on molecular gas dispersal, stellar feedback, and cluster formation efficiency
Abstract
We combine the largest survey of star clusters in nearby galaxies to-date, PHANGS-HST, with maps of molecular gas maps from PHANGS-ALMA to constrain the efficiency of cluster formation and the typical timescales over which clusters become dis-associated from their natal molecular gas. We analyse 29,233 clusters in 36 galaxies using CO maps at 150 pc resolution. For each star cluster with stellar mass ≥ 103.5 M⊙, we measure the radial profiles of CO(2-1) integrated intensity and obtain local background-subtracted CO intensity, ICObkgsub, at cluster centre. We group the clusters by age and mass to quantify the dependence of ICObkgsub and corresponding molecular gas mass, Mmol, on these cluster properties. To account for the cluster mass (MSC) dependence, we also calculate the normalised mass ratio of (Mmol/MSC). We find that CO intensity varies systematically with cluster age and mass. Clusters that are spatially associated with Hα emission exhibit the highest ICObkgsub of 7.4 K km s−1, corresponding to a Mmol/MSC ratio of 82 and implying a cluster formation efficiency (εobs) of ∼ 1.2%. Young clusters without associated Hα emission show lower and age-dependent ICObkgsub and Mmol/MSC, decreasing from 1.3 K km s−1 and 15 for clusters with age 1-3 Myr, to a level ≈ 0 for clusters older than 9--10 Myr. Clusters older than 10 Myr show no statistical excess of CO intensity. We use the clusters with Hα association as initial conditions to model the impact of cluster drift and demonstrate that this is unlikely to drive the observed cluster-gas spatial disassociation on short timescales of 4-6 Myr. Instead, early stellar feedback seems likely to be the main driver.
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BibTeX
@misc{he2026quantifying,
title = {{Quantifying the decline in CO(2-1) intensity around PHANGS-HST star clusters: Constraints on molecular gas dispersal, stellar feedback, and cluster formation efficiency}},
author = {Hao He and Adam K. Leroy and Erik Rosolowsky and Janice Lee and Brad Whitmore and David Thilker and Daniel A. Dale and Frank Bigiel and Annie Hughes and Jiayi Sun and Gagandeep Anand and Ashley T. Barnes and Zein Bazzi and Médéric Boquien and Rupali Chandar and Dario Colombo and Sinan Deger and Simthembile Dlamini and Hamid Hassani and Stephan Hannon and Ralf S. Klessen and Simon C. O. Glover and Kathryn Grasha and Ivan Grasimov and Remy Indebetouw and Kirsten Larson and Lukas Neumann and Elias K. Oakes and Hsi-An Pan and Miguel Querejeta and Lise Ramambason and M. Jimena Rodríguez and Sumit K. Sarbadhicary and Eva Schinnerer and Qiushi and Tian and Leonardo Úbeda and Antonio Usero and Thomas G. Williams and Jianwen Zhou},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.31838},
eprint = {2609.31838},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.31838},
}
RIS
TY - UNPB
TI - Quantifying the decline in CO(2-1) intensity around PHANGS-HST star clusters: Constraints on molecular gas dispersal, stellar feedback, and cluster formation efficiency
AU - Hao He
AU - Adam K. Leroy
AU - Erik Rosolowsky
AU - Janice Lee
AU - Brad Whitmore
AU - David Thilker
AU - Daniel A. Dale
AU - Frank Bigiel
AU - Annie Hughes
AU - Jiayi Sun
AU - Gagandeep Anand
AU - Ashley T. Barnes
AU - Zein Bazzi
AU - Médéric Boquien
AU - Rupali Chandar
AU - Dario Colombo
AU - Sinan Deger
AU - Simthembile Dlamini
AU - Hamid Hassani
AU - Stephan Hannon
AU - Ralf S. Klessen
AU - Simon C. O. Glover
AU - Kathryn Grasha
AU - Ivan Grasimov
AU - Remy Indebetouw
AU - Kirsten Larson
AU - Lukas Neumann
AU - Elias K. Oakes
AU - Hsi-An Pan
AU - Miguel Querejeta
AU - Lise Ramambason
AU - M. Jimena Rodríguez
AU - Sumit K. Sarbadhicary
AU - Eva Schinnerer
AU - Qiushi
AU - Tian
AU - Leonardo Úbeda
AU - Antonio Usero
AU - Thomas G. Williams
AU - Jianwen Zhou
PY - 2026
DA - 2026/09/25
PB - arXiv
DO - 10.48550/arxiv.2609.31838
UR - https://arxiv.org/abs/2609.31838
AB - We combine the largest survey of star clusters in nearby galaxies to-date, PHANGS-HST, with maps of molecular gas maps from PHANGS-ALMA to constrain the efficiency of cluster formation and the typical timescales over which clusters become dis-associated from their natal molecular gas. We analyse 29,233 clusters in 36 galaxies using CO maps at 150 pc resolution. For each star cluster with stellar mass ≥ 10^3.5 M_⊙, we measure the radial profiles of CO(2-1) integrated intensity and obtain local background-subtracted CO intensity, I_CO^bkgsub, at cluster centre. We group the clusters by age and mass to quantify the dependence of I_CO^bkgsub and corresponding molecular gas mass, M_mol, on these cluster properties. To account for the cluster mass (M_SC) dependence, we also calculate the normalised mass ratio of (M_mol/M_SC). We find that CO intensity varies systematically with cluster age and mass. Clusters that are spatially associated with Hα emission exhibit the highest I_CO^bkgsub of 7.4 K km s^−1, corresponding to a M_mol/M_SC ratio of 82 and implying a cluster formation efficiency (ε_obs) of ∼ 1.2%. Young clusters without associated Hα emission show lower and age-dependent I_CO^bkgsub and M_mol/M_SC, decreasing from 1.3 K km s^−1 and 15 for clusters with age 1-3 Myr, to a level ≈ 0 for clusters older than 9--10 Myr. Clusters older than 10 Myr show no statistical excess of CO intensity. We use the clusters with Hα association as initial conditions to model the impact of cluster drift and demonstrate that this is unlikely to drive the observed cluster-gas spatial disassociation on short timescales of 4-6 Myr. Instead, early stellar feedback seems likely to be the main driver.
ER -