TY - JOUR
T1 - The HST Large Programme on NGC 6752. I. Serendipitous discovery of a dwarf Galaxy in background
AU - Bedin, L. R.
AU - Salaris, M.
AU - Rich, R. M.
AU - Richer, H.
AU - Anderson, J.
AU - Bettoni, D.
AU - Nardiello, D.
AU - Milone, A. P.
AU - Marino, A. F.
AU - Libralato, M.
AU - Bellini, A.
AU - Dieball, A.
AU - Bergeron, P.
AU - Burgasser, A. J.
AU - Apai, D.
N1 - Funding Information:
We are grateful to an anonymous referee for his/her prompt review of our work. This work is based on observations with the NASA/ESA HST, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555. JA, RMR, AB, and ML acknowledge support from HST-GO-15096. APM acknowledges funding from the European Research Council (ERC) under the European Union's Horizon 2020 research innovation programme (Grant Agreement ERC-StG 2016, No 716082 'GALFOR'. APM acknowledges support from MIUR through the the FARE project R164RM93XW 'SEMPLICE'. AFM has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie Grant Agreement No. [797100]. This work is based on observations with the NASA/ESA Hubble Space Telescope , obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555.
Publisher Copyright:
© 2019 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.
PY - 2019/3/21
Y1 - 2019/3/21
N2 - As part of a large Hubble Space Telescope investigation aiming at reaching the faintest stars in the Galactic globular cluster NGC6752, an Advanced Camera for Surveys/Wide Field Channel field was the subject of deep optical observations reaching magnitudes as faint as V ∼ 30. In this field, we report the discovery of Bedin I, a dwarf spheroidal galaxy too faint and too close to the core of NGC6752 for detection in earlier surveys. As it is of broad interest to complete the census of galaxies in the local Universe, in this letter we provide the position of this new object along with preliminary assessments of its main parameters. Assuming the same reddening as for NGC6752, we estimate a distance modulus of (m-M) 0 =29.70±0.13 from the observed red giant branch, i.e. 8.7 -0.7 +0.5 Mpc, and size of ∼840 × 340 pc, about one-fifth the size of the Large Magellanic Cloud. A comparison of the observed colour-magnitude diagram with synthetic counterparts, which account for the galaxy distance modulus, reddening, and photometric errors, suggests the presence of an old (∼13 Gyr) and metal-poor ([Fe/H]∼-1.3) population. This object is most likely a relatively isolated satellite dwarf spheroidal galaxy of the nearby great spiral NGC6744, or potentially the most distant isolated dwarf spheroidal known with a secure distance.
AB - As part of a large Hubble Space Telescope investigation aiming at reaching the faintest stars in the Galactic globular cluster NGC6752, an Advanced Camera for Surveys/Wide Field Channel field was the subject of deep optical observations reaching magnitudes as faint as V ∼ 30. In this field, we report the discovery of Bedin I, a dwarf spheroidal galaxy too faint and too close to the core of NGC6752 for detection in earlier surveys. As it is of broad interest to complete the census of galaxies in the local Universe, in this letter we provide the position of this new object along with preliminary assessments of its main parameters. Assuming the same reddening as for NGC6752, we estimate a distance modulus of (m-M) 0 =29.70±0.13 from the observed red giant branch, i.e. 8.7 -0.7 +0.5 Mpc, and size of ∼840 × 340 pc, about one-fifth the size of the Large Magellanic Cloud. A comparison of the observed colour-magnitude diagram with synthetic counterparts, which account for the galaxy distance modulus, reddening, and photometric errors, suggests the presence of an old (∼13 Gyr) and metal-poor ([Fe/H]∼-1.3) population. This object is most likely a relatively isolated satellite dwarf spheroidal galaxy of the nearby great spiral NGC6744, or potentially the most distant isolated dwarf spheroidal known with a secure distance.
KW - galaxies: dwarf
KW - galaxies: individual: Bedin I
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U2 - 10.1093/mnrasl/slz004
DO - 10.1093/mnrasl/slz004
M3 - Article
AN - SCOPUS:85062188461
VL - 484
SP - L54-L58
JO - Monthly Notices of the Royal Astronomical Society: Letters
JF - Monthly Notices of the Royal Astronomical Society: Letters
SN - 1745-3933
IS - 1
ER -