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

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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 (US)
Article number	21
Journal	Astrophysical Journal
Volume	832
Issue number	1
DOIs	https://doi.org/10.3847/0004-637X/832/1/21
State	Published - Nov 20 2016

All Science Journal Classification (ASJC) codes

Astronomy and Astrophysics
Space and Planetary Science

Keywords

Local Group
galaxies: dwarf
galaxies: individual (Virgo)

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

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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), Article 21. https://doi.org/10.3847/0004-637X/832/1/21

@article{c55efb2a34134a6a966e375a6ebac6bb,

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.",

keywords = "Local Group, galaxies: dwarf, galaxies: individual (Virgo)",

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}",

year = "2016",

month = nov,

day = "20",

doi = "10.3847/0004-637X/832/1/21",

language = "English (US)",

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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

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

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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SN - 0004-637X

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JO - Astrophysical Journal

JF - Astrophysical Journal

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M1 - 21

ER -

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

Abstract

All Science Journal Classification (ASJC) codes

Keywords

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