H {alpha} morphologies of star clusters in 16 LEGUS galaxies Constraints on H II region evolution time-scales. (2022)
Keywords :
ISM evolution - H II regions - galaxies: ISM - galaxies: star clusters: general
Abstract:The analysis of star cluster ages in tandem with the morphology of their H II regions can provide insight into the processes that clear a cluster's natal gas, as well as the accuracy of cluster ages and dust reddening derived from Spectral Energy Distribution (SED) fitting. We classify 3757 star clusters in 16 nearby galaxies according to their H{alpha} morphology (concentrated, partially exposed, no emission), using Hubble Space Telescope (HST) imaging from the Legacy ExtraGalactic Ultraviolet Survey (LEGUS). We find : (1) The mean SED ages of clusters with concentrated (1-2 Myr) and partially exposed H II region morphologies (2-3 Myr) indicate a relatively early onset of gas clearing and a short (1-2 Myr) clearing time-scale. (2) The
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Previous studies have examined correlations between H{alpha}
morphology and star cluster properties, we use imaging from the Hubble
Space Telescope (HST) to study star clusters. We build upon the sample
from Hannon et al. (2019MNRAS.490.4648H), where this study quadruples
the number of young, massive clusters. By examining all clusters
regardless of SED age, this study may prove valuable in checking the
reliability of SED-fit ages, and obtaining new insights regarding
time-scales associated with gas clearing.
The data used in this study are taken from LEGUS (Calzetti et al.
2015AJ....149...51C,
https://mast.stsci.edu/search/ui/#/hst/results?proposal_id=9796,10402,
13364 and
https://archive.stsci.edu/prepds/legus/dataproducts-public.html),
which combines WFC3 and archival ACS HST imaging to provide full
five-band NUV-U-B-V-I coverage for 50 nearby galaxies. The
LEGUS-H{alpha} follow-up survey provides coverage of the H{alpha}
emission-line with a narrow-band filter as well as a medium-band
filter sampling line-free continuum. General properties for our 16
selected galaxies including distance, position angle, inclination, and
diameter, are provided in table1.dat.
Then we extract cluster photometric data of the 21 galaxy fields (i.e
see section 2 for the procedure). Next, following the classification
process of Hannon et al. (2019MNRAS.490.4648H) (i.e see section 3). We
built H{alpha} morphology classifications for 3815 detected star
clusters as presented in the tablea1.dat.
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- J/ApJS/192/6 : A GALEX UV imaging survey of nearby galaxies (Lee+, 2011)
- J/ApJ/889/154 : LEGUS & Ha-LEGUS obs. of NGC4449 star clusters
- J/MNRAS/498/4906 : Pressure components in the central HII regions
- J/ApJS/212/1 : The WISE catalog of Galactic HII regions (Anderson+, 2014)
- J/ApJS/181/321 : Properties of Spitzer c2d dark clouds (Evans+, 2009)
