A Sequoia in the Garden: FSR 1758 - Dwarf Galaxy or Giant Globular Cluster?
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Archivos
Fecha
2019-01
Profesor/a Guía
Facultad/escuela
Idioma
en
Título de la revista
ISSN de la revista
Título del volumen
Editor
Institute of Physics Publishing
Nombre de Curso
Licencia CC
Licencia CC
Resumen
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 Vía Láctea 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: α = 17:31:12, δ = -39:48:30 (J2000), D = 11.5 ±1.0 kpc, mag, R c = 10 pc, R t = 150 pc, dex, Mi < -8.6 ±1.0, μ α = -2.85 mas yr-1, and μ δ = 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 ω 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. © 2019. The American Astronomical Society. All rights reserved..
Notas
Palabras clave
Galaxy: bulge; Galaxy: stellar content; globular clusters: individual (FSR 1758); stars: kinematics and dynamics
Citación
Astrophysical Journal Letters Open AccessVolume 870, Issue 210 January 2019 Article number L24