Comments on a faint old stellar system at 150 kpc
نویسنده
چکیده
Context. Recent study of SDSS J1257+3419 has revealed that this stellar system is either a faint and small dwarf galaxy or a faint and widely extended globular cluster. Aims. In this short note, the author suggests that this system is one of the smallest dwarf spheroidals (dSphs) in the Milky Way. Methods. We re-examine some observational quantities of this object and check whether it can be bound system. Results. As a result, we find the mass of SDSS J1257+3419 is the lowest of dSphs in the Milky Way, and its mass density is typical of dSphs. Important is that the tidal radius of SDSS J1257+3419 is much larger than its half-light radius. That is, this very small dSph can be bound by its own gravity.
منابع مشابه
Discovery of a Faint Old Stellar System at 150 kpc
We report the detection of a faint old stellar system at (α, δ) = (194.29 • , 34.32 •) (SDSS J1257+3419), based on the spatial distribution of bright red-giant branch stars in the Sloan Digital Sky Survey Data Release 4. SDSS J1257+3419 has a half-light radius of 38 ± 12 pc and an absolute integrated V-magnitude of M V = −4.8 +1.4 −1.0 mag at a heliocentric distance of 150 ± 15 kpc. A compariso...
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