Indications of M-dwarf deficits in the halo and thick disk of the Galaxy

Mihoko Konishi, Hiroshi Shibai, Takahiro Sumi, Misato Fukagawa, Taro Matsuo, Matthias S. Samland, Kodai Yamamoto, Jun Sudo, Yoichi Itoh, Nobuo Arimoto, Masaru Jisawa, Lyu Abe, Wolfgang Brandner, Timothy D. Brandt, Joseph Carson, Thayne Currie, Sebastian E. Egner, Markus Feldt, Miwa Goto, Carol A. GradyOlivier Guyon, Jun Hashimoto, Yutaka Hayano, Masahiko Hayashi, Saeko S. Hayashi, Thomas Henning, Klaus W. Hodapp, Miki Ishii, Masanori Iye, Markus Janson, Ryo Kandori, Gillian R. Knapp, Tomoyuki Kudo, Nobuhiko Kusakabe, Masayuki Kuzuhara, Jungmi Kwon, Michael W. McElwain, Shoken Miyama, Jun Ichi Morino, Amaya Moro-Martín, Tetsuo Nishimura, Tae Soo Pyo, Eugene Serabyn, Takuya Suenaga, Hiroshi Suto, Ryuji Suzuki, Yasuhiro H. Takahashi, Hideki Takami, Naruhisa Takato, Hiroshi Terada, Christian Thalmann, Daigo Tomono, Edwin L. Turner, Tomonori Usuda, Makoto Watanabe, John P. Wisniewski, Toru Yamada, Motohide Tamura

Research output: Contribution to journalArticle

1 Scopus citations

Abstract

We compared the number of faint stars detected in deep survey fields with the current stellar distribution model of the Galaxy and found that the detected number in the H band is significantly smaller than the predicted number. This indicates that M-dwarfs, the major component, are fewer in the halo and the thick disk. We used archived data of several surveys in both the north and south field of GOODS (Great Observatories Origins Deep Survey), MODS (MOIRCS Deep Survey) in GOODS-N, and ERS (Early Release Science) and CANDELS (Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey) in GOODS-S. The number density of M-dwarfs in the halo has to be 20%±13% relative to that in the solar vicinity, in order for the detected number of stars fainter than 20.5 mag in the H band to match with the predicted value from the model. In the thick disk, the number density of M-dwarfs must be reduced (52%±13%) or the scale height must be decreased (∼600 pc). Alternatively, overall fractions of the halo and thick disks can be significantly reduced to achieve the same effect, because our sample mainly consists of faint M-dwarfs. Our results imply that the M-dwarf population in regions distant from the Galactic plane is significantly smaller than previously thought. We then discussed the implications this has on the suitability of the model predictions for the prediction of non-companion faint stars in direct imaging extrasolar planet surveys by using the best-fitting number densities.

Original languageEnglish (US)
JournalPublications of the Astronomical Society of Japan
Volume67
Issue number1
DOIs
StatePublished - Jan 1 2015
Externally publishedYes

Keywords

  • Galaxy: disk
  • Galaxy: halo
  • Stars: imaging
  • Stars: low-mass

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Konishi, M., Shibai, H., Sumi, T., Fukagawa, M., Matsuo, T., Samland, M. S., Yamamoto, K., Sudo, J., Itoh, Y., Arimoto, N., Jisawa, M., Abe, L., Brandner, W., Brandt, T. D., Carson, J., Currie, T., Egner, S. E., Feldt, M., Goto, M., ... Tamura, M. (2015). Indications of M-dwarf deficits in the halo and thick disk of the Galaxy. Publications of the Astronomical Society of Japan, 67(1). https://doi.org/10.1093/pasj/psu125