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The HST Large Programme on NGC 6752. I. Serendipitous discovery of a dwarf Galaxy in background

Bedin, LR, Salaris, M, Rich, RM, Richer, H, Anderson, J, Bettoni, D, Nardiello, D, Milone, AP, Marino, AF, Libralato, M, Bellini, A, Dieball, A, Bergeron, P, Burgasser, AJ and Apai, D (2019) The HST Large Programme on NGC 6752. I. Serendipitous discovery of a dwarf Galaxy in background. Monthly Notices of the Royal Astronomical Society Letters, 484 (1). L54-L58. ISSN 1745-3933

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Open Access URL: https://dx.doi.org/10.1093/mnrasl/slz004 (Published version)

Abstract

© 2019 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. 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.

Item Type: Article
Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society Letters ©: 2019 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Uncontrolled Keywords: 0201 Astronomical and Space Sciences
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: Oxford University Press
Date Deposited: 11 Mar 2019 09:39
Last Modified: 11 Mar 2019 09:40
DOI or Identification number: 10.1093/mnrasl/slz004
URI: http://researchonline.ljmu.ac.uk/id/eprint/10281

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