期刊
ASTROPHYSICAL JOURNAL LETTERS
卷 870, 期 2, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.3847/2041-8213/aaf811
关键词
Galaxy: bulge; Galaxy: stellar content; globular clusters: individual (FSR 1758); stars: kinematics and dynamics
资金
- ESO Public Survey program [179]
- DIDULS project [PR18143, PR16142]
- Big Data and Cosmography: the skyscape of large astrophysical surveys project
- BASAL Center for Astrophysics and Associated Technologies (CATA) [AFB-170002]
- Direccion de Investigacion y Desarrollo de la Universidad de La Serena through the Programa de Incentivo a la Investigacion de Academicos (PIA-DIDULS)
- Ministry for the Economy, Development and Tourism, Programa Iniciativa Cientifica Milenio grant [IC120009]
- FONDECYT [1170121, 1181797, 1181264]
- FONDECYT Iniciation grant [11150916]
- Ministry of Education [ANT-1656]
- Max Planck Society through a Partner Group grant
We present the physical characterization of FSR 1758, a new large, massive object very recently discovered in the Galactic Bulge. The combination of optical data from the 2nd Gaia Data Release and the DECam Plane Survey and near-IR data from the VISTA Variables in the Via Lactea Extended Survey led to a clean sample of likely members. Based on this integrated data set, position, distance, reddening, size, metallicity, absolute magnitude, and proper motion (PM) of this object are measured. We estimate the following parameters: alpha -17: 31: 12, delta = 39: 48: 30 (J2000), D = 11.5 +/- 1.0 kpc, E(J - Ks) = 0.20 +/- 0.03mag, R-c =. 10 pc, R-t = 150 pc, [Fe/H] = -1.5 +/- 0.3 dex, M-i -8.6 +/- 1.0, mu(alpha). =. -2.85 mas yr(-1), and mu(delta) =. 2.55 mas yr(-1). The nature of this object is discussed. If FRS 1758 is a genuine globular cluster (GC), it is one of the largest in the Milky Way, with a size comparable or even larger than that of omega Cen, being also an extreme outlier in the size versus Galactocentric distance diagram. The presence of a concentration of long-period RR Lyrae variable stars and blue horizontal branch stars suggests that it is a typical metal-poor GC of Oosterhoff type II. Further exploration of a larger surrounding field reveals common PM stars, suggesting either tidal debris or that FRS 1758 is actually the central part of a larger extended structure such as a new dwarf galaxy, tentatively named Scorpius. In either case, this object is remarkable, and its discovery graphically illustrates the possibility of finding other large objects hidden in the Galactic Bulge using future surveys.
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