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Universal Upper End of the Stellar Initial Mass Function in the Young and Compact LEGUS Clusters

Published version
Peer-reviewed

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Abstract

jats:titleAbstract</jats:title> jats:pWe investigate the variation in the upper end of the stellar initial mass function (uIMF) in 375 young and compact star clusters in five nearby galaxies within ∼5 Mpc. All the young stellar clusters (YSCs) in the sample have ages ≲ 4 Myr and masses above 500 jats:italicM</jats:italic> jats:sub⊙</jats:sub>, according to standard stellar models. The YSC catalogs were produced from Hubble Space Telescope images obtained as part of the Legacy ExtraGalactic UV Survey (LEGUS) Hubble treasury program. They are used here to test whether the uIMF is universal or changes as a function of the cluster’s stellar mass. We perform this test by measuring the Hjats:italicα</jats:italic> luminosity of the star clusters as a proxy for their ionizing photon rate, and charting its trend as a function of cluster mass. Large cluster numbers allow us to mitigate the stochastic sampling of the uIMF. The advantage of our approach relative to previous similar attempts is the use of cluster catalogs that have been selected independently of the presence of Hjats:italicα</jats:italic> emission, thus removing a potential sample bias. We find that the uIMF, as traced by the Hjats:italicα</jats:italic> emission, shows no dependence on cluster mass, suggesting that the maximum stellar mass that can be produced in star clusters is universal, in agreement with previous findings.</jats:p>

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Keywords

5101 Astronomical Sciences, 51 Physical Sciences

Journal Title

Astrophysical Journal

Conference Name

Journal ISSN

0004-637X
1538-4357

Volume Title

954

Publisher

American Astronomical Society