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Star Cluster Properties In Two Legus Galaxies Computed With Stochastic Stellar Population Synthesis Models
Univ Calif Santa Cruz, Dept Astron & Astrophys, Santa Cruz, CA 95064 USA..
Stockholm Univ, Dept Astron, Oskar Klein Ctr, SE-10691 Stockholm, Sweden..
Univ Durham, Inst Computat Cosmol, Durham DH1 3LE, England.;Univ Durham, Ctr Extragalact Astron, Dept Phys, Durham DH1 3LE, England..
Inst Astrophys Paris, F-75014 Paris, France..
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2015 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 812, no 2, 147Article in journal (Refereed) PublishedText
Abstract [en]

We investigate a novel Bayesian analysis method, based on the Stochastically Lighting Up Galaxies (slug) code, to derive the masses, ages, and extinctions of star clusters from integrated light photometry. Unlike many analysis methods, slug correctly accounts for incomplete initial mass function (IMF) sampling, and returns full posterior probability distributions rather than simply probability maxima. We apply our technique to 621 visually confirmed clusters in two nearby galaxies, NGC 628 and NGC 7793, that are part of the Legacy Extragalactic UV Survey (LEGUS). LEGUS provides Hubble Space Telescope photometry in the NUV, U, B, V, and I bands. We analyze the sensitivity of the derived cluster properties to choices of prior probability distribution, evolutionary tracks, IMF, metallicity, treatment of nebular emission, and extinction curve. We find that slug's results for individual clusters are insensitive to most of these choices, but that the posterior probability distributions we derive are often quite broad, and sometimes multi-peaked and quite sensitive to the choice of priors. In contrast, the properties of the cluster population as a whole are relatively robust against all of these choices. We also compare our results from slug to those derived with a conventional non-stochastic fitting code, Yggdrasil. We show that slug's stochastic models are generally a better fit to the observations than the deterministic ones used by Yggdrasil. However, the overall properties of the cluster populations recovered by both codes are qualitatively similar.

Place, publisher, year, edition, pages
2015. Vol. 812, no 2, 147
Keyword [en]
galaxies: individual (NGC 628, NGC 7793), galaxies: star clusters: general, methods: data analysis, methods: statistical, techniques: photometric
National Category
Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:uu:diva-270639DOI: 10.1088/0004-637X/812/2/147ISI: 000365206600059OAI: oai:DiVA.org:uu-270639DiVA: diva2:890214
Swedish Research Council, 2011-5349
Available from: 2016-01-01 Created: 2016-01-01 Last updated: 2016-01-01Bibliographically approved

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Zackrisson, Erik
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