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Star formation at the edge of the Local Group: a rising star formation history in the isolated galaxy WLM

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journal contribution
posted on 2023-05-20, 08:33 authored by Albers, SM, Weisz, DR, Andrew ColeAndrew Cole, Dolphin, AE, Skillman, ED, Williams, BF, Boylan-Kolchin, M, Bullock, JS, Dalcanton, JJ, Hopkins, PF, Leaman, R, McConnachie, AW, Vogelsberger, M, Wetzel, A
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 (⁠0.5𝑟) and outer field (⁠0.7𝑟⁠) 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) ∼ 105−107M⊙⁠). 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.⁠


Publication title

Monthly Notices of the Royal Astronomical Society










School of Natural Sciences


Blackwell Publishing Ltd

Place of publication

9600 Garsington Rd, Oxford, England, Oxon, Ox4 2Dg

Rights statement

Copyright 2019 The Author(s) This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2019. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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Expanding knowledge in the physical sciences