TY - JOUR
T1 - A NEW MILKY WAY SATELLITE DISCOVERED in the SUBARU/HYPER SUPRIME-CAM SURVEY
AU - Homma, Daisuke
AU - Chiba, Masashi
AU - Okamoto, Sakurako
AU - Komiyama, Yutaka
AU - Tanaka, Masayuki
AU - Tanaka, Mikito
AU - Ishigaki, Miho N.
AU - Akiyama, Masayuki
AU - Arimoto, Nobuo
AU - Garmilla, José A.
AU - Lupton, Robert H.
AU - Strauss, Michael A.
AU - Furusawa, Hisanori
AU - Miyazaki, Satoshi
AU - Murayama, Hitoshi
AU - Nishizawa, Atsushi J.
AU - Takada, Masahiro
AU - Usuda, Tomonori
AU - Wang, Shiang Yu
N1 - Funding Information:
the National Central University of Taiwan, the Space Telescope Science Institute, the National Aeronautics and Space Administration under Grant No. NNX08AR22G issued through the Planetary Science Division of the NASA Science Mission Directorate, the National Science Foundation under Grant No.AST-1238877, the University of Maryland, and Eotvos Lorand University (ELTE).
Publisher Copyright:
© 2016. The American Astronomical Society. All rights reserved..
PY - 2016/11/20
Y1 - 2016/11/20
N2 - We report the discovery of a new ultra-faint dwarf satellite companion of the Milky Way (MW) based on the early survey data from the Hyper Suprime-Cam Subaru Strategic Program. This new satellite, Virgo I, which is located in the constellation of Virgo, has been identified as a statistically significant (5.5σ) spatial overdensity of star-like objects with a well-defined main sequence and red giant branch in the color-magnitude diagram. The significance of this overdensity increases to 10.8σ when the relevant isochrone filter is adopted for the search. Based on the distribution of the stars around the likely main-sequence turnoff at r ∼ 24 mag, the distance to Virgo I is estimated as 87 kpc, and its most likely absolute magnitude calculated from a Monte Carlo analysis is M V = -0.80.9 mag. This stellar system has an extended spatial distribution with a half-light radius of pc, which clearly distinguishes it from a globular cluster with comparable luminosity. Thus, Virgo I is one of the faintest dwarf satellites known and is located beyond the reach of the Sloan Digital Sky Survey. This demonstrates the power of this survey program to identify very faint dwarf satellites. This discovery of Virgo I is based only on about 100 square degrees of data, thus a large number of faint dwarf satellites are likely to exist in the outer halo of the MW.
AB - We report the discovery of a new ultra-faint dwarf satellite companion of the Milky Way (MW) based on the early survey data from the Hyper Suprime-Cam Subaru Strategic Program. This new satellite, Virgo I, which is located in the constellation of Virgo, has been identified as a statistically significant (5.5σ) spatial overdensity of star-like objects with a well-defined main sequence and red giant branch in the color-magnitude diagram. The significance of this overdensity increases to 10.8σ when the relevant isochrone filter is adopted for the search. Based on the distribution of the stars around the likely main-sequence turnoff at r ∼ 24 mag, the distance to Virgo I is estimated as 87 kpc, and its most likely absolute magnitude calculated from a Monte Carlo analysis is M V = -0.80.9 mag. This stellar system has an extended spatial distribution with a half-light radius of pc, which clearly distinguishes it from a globular cluster with comparable luminosity. Thus, Virgo I is one of the faintest dwarf satellites known and is located beyond the reach of the Sloan Digital Sky Survey. This demonstrates the power of this survey program to identify very faint dwarf satellites. This discovery of Virgo I is based only on about 100 square degrees of data, thus a large number of faint dwarf satellites are likely to exist in the outer halo of the MW.
KW - Local Group
KW - galaxies: dwarf
KW - galaxies: individual (Virgo)
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U2 - 10.3847/0004-637X/832/1/21
DO - 10.3847/0004-637X/832/1/21
M3 - Article
AN - SCOPUS:84996588195
VL - 832
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 1
M1 - 21
ER -