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Star formation at the edge of the Local Group: a rising star formation history in the isolated galaxy WLM
Name
1909.04040.pdf
Description
Submitted version
Size
6.17 MB
Format
Adobe PDF
Checksum (MD5)
5bc06282d7e9f54f61ad235a48166beb
Author(s)
Albers, Saundra M
Weisz, Daniel R
Cole, Andrew A
Dolphin, Andrew E
Skillman, Evan D
Williams, Benjamin F
Boylan-Kolchin, Michael
Bullock, James S
Dalcanton, Julianne J
Hopkins, Philip F
Journal
Monthly Notices of the Royal Astronomical Society
Publisher
Oxford University Press (OUP)
Version
Original manuscript
Abstract
© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society We present the star formation history (SFH) of the isolated (D ∼ 970 kpc) Local Group dwarf galaxy Wolf-Lundmark-Melotte (WLM) measured from colour-magnitude diagrams (CMDs) constructed from deep Hubble Space Telescope imaging. Our observations include a central (0.5 rh) and outer field (0.7 rh) that reach below the oldest main-sequence turn-off. WLM has no early dominant episode of star formation: 20 per cent of its stellar mass formed by ∼12.5 Gyr ago (z ∼ 5). It also has an SFR that rises to the present with 50 per cent of the stellar mass within the most recent 5 Gyr (z < 0.7). There is evidence of a strong age gradient: the mean age of the outer field is 5 Gyr older than the inner field despite being only 0.4 kpc apart. Some models suggest such steep gradients are associated with strong stellar feedback and dark-matter core creation. The SFHs of real isolated dwarf galaxies and those from the Feedback in Realistic Environment suite are in good agreement for M*(z = 0) ∼ 107-109M☉, but in worse agreement at lower masses (M*(z = 0) ∼ 105-107 M☉). These differences may be explainable by systematics in the models (e.g. reionization model) and/or observations (HST field placement). We suggest that a coordinated effort to get deep CMDs between HST/JWST (crowded central fields) and WFIRST (wide-area halo coverage) is the optimal path for measuring global SFHs of isolated dwarf galaxies.
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DOI of Published Version
10.1093/MNRAS/STZ2903
