Hyper Wide Field Imaging of the Local Group Dwarf Irregular Galaxy IC 1613: An Extended Component of Metal-poor Stars

Ragadeepika Pucha, Jeffrey L. Carlin, Beth Willman, Jay Strader, David J. Sand, Keith Bechtol, Jean P. Brodie, Denija Crnojević, Duncan A. Forbes, Christopher Garling, Jonathan Hargis, Annika H.G. Peter, Aaron J. Romanowsky

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


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 ∼ 108 M o). 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.

Original languageEnglish (US)
Article number104
JournalAstrophysical Journal
Issue number2
StatePublished - Aug 1 2019


  • galaxies: dwarf
  • galaxies: halos
  • galaxies: stellar content
  • galaxies: structure

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


Dive into the research topics of 'Hyper Wide Field Imaging of the Local Group Dwarf Irregular Galaxy IC 1613: An Extended Component of Metal-poor Stars'. Together they form a unique fingerprint.

Cite this