Shell Structure in the Fornax Dwarf Spheroidal Galaxy
نویسنده
چکیده
We present initial results from a wide field photometric survey of the Fornax dwarf spheroidal (dSph) galaxy. The focus here is on a small overdensity of stars located approximately 17 (670 pc in projection) from the centre of Fornax. Based on imaging data in both V and I bands down to V ≈ 21, the dimensions of the feature are ∼1.7×3.2 (68×128 pc) with an average surface brightness of 25.8 mag/arcsec in V . A follow-up analysis using the deep B and R band data obtained by Stetson, Hesser, & Smecker-Hane (1998) indicates that the overdensity is apparently dominated by a relatively young stellar population with an age ≈ 2 Gyr, though the current data do not rule out the presence of older stars. Our preferred interpretation is that the overdensity represents shell structure in the Fornax dSph galaxy, a phenomenon previously unseen in dwarf galaxies. The shell may be the remnant of a merger with Fornax of a smaller, gas-rich system that occured approximately 2 Gyr ago. The comparitively recent star formation seen in some dSph and dE galaxies may then also be the result of infall of small relatively gas-rich systems. Subject headings: galaxies: dwarf — galaxies: individual (Fornax) — galaxies: photometry — galaxies: stellar content — galaxies: interactions — Galaxy: halo — Local Group
منابع مشابه
A Wide-Field Survey of the Fornax Dwarf Spheroidal Galaxy
The results of a photometric survey of the Fornax dwarf spheroidal galaxy are presented herein. Accurate photometry in two colours (V and I) was collected over a 10 deg area centred on the Fornax system with the aim of searching for extra-tidal structure. The data were complete to a magnitude of V = 20, or approximately one magnitude brighter than the Fornax red clump stars. Stars were selected...
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