A NEW MILKY WAY SATELLITE DISCOVERED in the SUBARU/HYPER SUPRIME-CAM SURVEY

Daisuke Homma; Masashi Chiba; Sakurako Okamoto; Yutaka Komiyama; Masayuki Tanaka; Mikito Tanaka; Miho N. Ishigaki; Masayuki Akiyama; Nobuo Arimoto; José A. Garmilla; Robert H. Lupton; Michael A. Strauss; Hisanori Furusawa; Satoshi Miyazaki; Hitoshi Murayama; Atsushi J. Nishizawa; Masahiro Takada; Tomonori Usuda; Shiang Yu Wang

doi:10.3847/0004-637X/832/1/21

A NEW MILKY WAY SATELLITE DISCOVERED in the SUBARU/HYPER SUPRIME-CAM SURVEY

Daisuke Homma, Masashi Chiba, Sakurako Okamoto, Yutaka Komiyama, Masayuki Tanaka, Mikito Tanaka, Miho N. Ishigaki, Masayuki Akiyama, Nobuo Arimoto, José A. Garmilla, Robert H. Lupton, Michael A. Strauss, Hisanori Furusawa, Satoshi Miyazaki, Hitoshi Murayama, Atsushi J. Nishizawa, Masahiro Takada, Tomonori Usuda, Shiang Yu Wang

Research output: Contribution to journal › Article › peer-review

42 Citations (Scopus)

Abstract

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.

Original language	English
Article number	21
Journal	Astrophysical Journal
Volume	832
Issue number	1
DOIs	https://doi.org/10.3847/0004-637X/832/1/21
Publication status	Published - 2016 Nov 20

Keywords

Local Group
galaxies: dwarf
galaxies: individual (Virgo)

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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Homma, D., Chiba, M., Okamoto, S., Komiyama, Y., Tanaka, M., Tanaka, M., Ishigaki, M. N., Akiyama, M., Arimoto, N., Garmilla, J. A., Lupton, R. H., Strauss, M. A., Furusawa, H., Miyazaki, S., Murayama, H., Nishizawa, A. J., Takada, M., Usuda, T., & Wang, S. Y. (2016). A NEW MILKY WAY SATELLITE DISCOVERED in the SUBARU/HYPER SUPRIME-CAM SURVEY. Astrophysical Journal, 832(1), [21]. https://doi.org/10.3847/0004-637X/832/1/21

A NEW MILKY WAY SATELLITE DISCOVERED in the SUBARU/HYPER SUPRIME-CAM SURVEY. / Homma, Daisuke; Chiba, Masashi; Okamoto, Sakurako; Komiyama, Yutaka; Tanaka, Masayuki; Tanaka, Mikito; Ishigaki, Miho N.; Akiyama, Masayuki; Arimoto, Nobuo; Garmilla, José A.; Lupton, Robert H.; Strauss, Michael A.; Furusawa, Hisanori; Miyazaki, Satoshi; Murayama, Hitoshi; Nishizawa, Atsushi J.; Takada, Masahiro; Usuda, Tomonori; Wang, Shiang Yu.

In: Astrophysical Journal, Vol. 832, No. 1, 21, 20.11.2016.

Research output: Contribution to journal › Article › peer-review

Homma, D, Chiba, M, Okamoto, S, Komiyama, Y, Tanaka, M, Tanaka, M, Ishigaki, MN, Akiyama, M, Arimoto, N, Garmilla, JA, Lupton, RH, Strauss, MA, Furusawa, H, Miyazaki, S, Murayama, H, Nishizawa, AJ, Takada, M, Usuda, T & Wang, SY 2016, 'A NEW MILKY WAY SATELLITE DISCOVERED in the SUBARU/HYPER SUPRIME-CAM SURVEY', Astrophysical Journal, vol. 832, no. 1, 21. https://doi.org/10.3847/0004-637X/832/1/21

Homma, Daisuke ; Chiba, Masashi ; Okamoto, Sakurako ; Komiyama, Yutaka ; Tanaka, Masayuki ; Tanaka, Mikito ; Ishigaki, Miho N. ; Akiyama, Masayuki ; Arimoto, Nobuo ; Garmilla, José A. ; Lupton, Robert H. ; Strauss, Michael A. ; Furusawa, Hisanori ; Miyazaki, Satoshi ; Murayama, Hitoshi ; Nishizawa, Atsushi J. ; Takada, Masahiro ; Usuda, Tomonori ; Wang, Shiang Yu. / A NEW MILKY WAY SATELLITE DISCOVERED in the SUBARU/HYPER SUPRIME-CAM SURVEY. In: Astrophysical Journal. 2016 ; Vol. 832, No. 1.

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title = "A NEW MILKY WAY SATELLITE DISCOVERED in the SUBARU/HYPER SUPRIME-CAM SURVEY",

abstract = "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.",

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author = "Daisuke Homma and Masashi Chiba and Sakurako Okamoto and Yutaka Komiyama and Masayuki Tanaka and Mikito Tanaka and Ishigaki, {Miho N.} and Masayuki Akiyama and Nobuo Arimoto and Garmilla, {Jos{\'e} A.} and Lupton, {Robert H.} and Strauss, {Michael A.} and Hisanori Furusawa and Satoshi Miyazaki and Hitoshi Murayama and Nishizawa, {Atsushi J.} and Masahiro Takada and Tomonori Usuda and Wang, {Shiang Yu}",

note = "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).",

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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).

PY - 2016/11/20

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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.

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KW - galaxies: individual (Virgo)

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