Document Type
Article
Publication Date
July 2019
Publication Title
The Astrophysical Journal
Volume
880
Issue Number
104
First Page
1
Last Page
11
DOI
10.3847/1538-4357/ab29fb
Disciplines
Astrophysics and Astronomy | External Galaxies | Other Astrophysics and Astronomy | Physics
Abstract
Stellar halos offer fossil evidence for hierarchical structure formation. Since halo assembly is predicted to be scale-free, stellar halos around low-mass galaxies constrain properties such as star formation in the accreted subhalos and the formation of dwarf galaxies. However, few observational searches for stellar halos in dwarfs exist. Here we present gi photometry of resolved stars in isolated Local Group dwarf irregular galaxy IC 1613 (M sstarf ~ 108 M ⊙). These Subaru/Hyper Suprime-Cam observations are the widest and deepest of IC 1613 to date. We measure surface density profiles of young main-sequence, intermediate to old red giant branch, and ancient horizontal branch stars outside of 12' (~2.6 kpc; 2.5 half-light radii) from the IC 1613 center. All of the populations extend to ~24' (~5.2 kpc; 5 half-light radii), with the older populations best fit by a broken exponential in these outer regions. Comparison with earlier studies sensitive to IC 1613's inner regions shows that the density of old stellar populations steepens substantially with distance from the center; we trace the g-band effective surface brightness to an extremely faint limit of ~33.7 mag arcsec−2. Conversely, the distribution of younger stars follows a single, shallow exponential profile in the outer regions, demonstrating different formation channels for the younger and older components of IC 1613. The outermost, intermediate-age and old stars have properties consistent with those expected for accreted stellar halos, though future observational and theoretical work is needed to definitively distinguish this scenario from other possibilities.
Recommended Citation
Ragadeepika Pucha, Jeffrey Carlin, Beth Willman, Jay Strader, David Sand, Keith Bechtol, Jean Brodie, Denija Crnojević, Duncan Forbes, Christopher Garling, Jonathan Hargis, Annika Peter, and Aaron Romanowsky. "Hyper Wide Field Imaging of the Local Group Dwarf Irregular Galaxy IC 1613: An Extended Component of Metal-poor Stars" The Astrophysical Journal (2019): 1-11. https://doi.org/10.3847/1538-4357/ab29fb
Comments
This article was published in The Astrophysical Journal, volume 880, issue 104, 2019 and can also be found at this link. Copyright © 2019, American Astronomical Society. All rights reserved.
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