FSR 1716: a new Milky Way globular cluster confirmed using VVV RR Lyrae stars
- Departamento de Física, Facultad de Ciencias Exactas, Universidad Andrés Bello, Av. Fernandez Concha 700, Las Condes, Santiago (Chile)
- Instituto Milenio de Astrofísica, Santiago (Chile)
- Astronomisches Rechen-Institut, Zentrum fuer Astronomie der Universitaet Heidelberg, Moenchhofstr. 12-14, D-69120 Heidelberg (Germany)
- Pontificia Universidad Católica de Chile, Instituto de Astrofísica, Av. Vicuña Mackenna 4860, Santiago (Chile)
- European Southern Observatory, Karl-Schwarszchild-Str. 2, D-85748 Garching bei Muenchen (Germany)
- Unidad de Astronomia, Facultad Cs. Básicas, Universidad de Antofagasta, Avda. U. de Antofagasta 02800, Antofagasta (Chile)
- Departamento de Física y Astronomía, Universidad de la Serena, Av. Juan Cisternas 1200 Norte, La Serena (Chile)
- Dept. of Astronomy, University of Sao Paulo, Sao Paulo (Brazil)
- Universidade Federal do Rio Grande do Sul (Brazil)
- Instituto de Física y Astronomía, Universidad de Valparaíso, Av. Gran Bretaña 1111, Playa Ancha, Casilla 5030, Valparaíso (Chile)
- Gemini Observatory, Northern Operations Center, 670 North A’ohoku Place, Hilo, HI 96720 (United States)
We use deep multi-epoch near-IR images of the VISTA Variables in the Vía Láctea (VVV) Survey to search for RR Lyrae stars toward the Southern Galactic plane. Here, we report the discovery of a group of RR Lyrae stars close together in VVV tile d025. Inspection of the VVV images and PSF photometry reveals that most of these stars are likely to belong to a globular cluster that matches the position of the previously known star cluster FSR 1716. The stellar density map of the field yields a >100σ detection for this candidate globular cluster that is centered at equatorial coordinates R.A.{sub J2000} = 16:10:30.0, decl.{sub J2000} = −53:44:56 and galactic coordinates l = 329.77812, b = −1.59227. The color–magnitude diagram of this object reveals a well-populated red giant branch, with a prominent red clump at K {sub s} = 13.35 ± 0.05, and J − K {sub s} = 1.30 ± 0.05. We present the cluster RR Lyrae positions, magnitudes, colors, periods, and amplitudes. The presence of RR Lyrae indicates an old globular cluster, with an age >10 Gyr. We classify this object as an Oosterhoff type I globular cluster, based on the mean period of its RR Lyrae type ab, 〈P〉=0.540 days, and argue that this is a relatively metal-poor cluster with [Fe/H] = −1.5 ± 0.4 dex. The mean extinction and reddening for this cluster are A{sub K{sub s}}=0.38±0.02 and E(J − K {sub s}) = 0.72 ± 0.02 mag, respectively, as measured from the RR Lyrae colors and the near-IR color–magnitude diagram. We also measure the cluster distance using the RR Lyrae type ab stars. The cluster mean distance modulus is (m − M){sub 0} = 14.38 ± 0.03 mag, implying a distance D = 7.5 ± 0.2 kpc and a Galactocentric distance R {sub G} = 4.3 kpc.
- OSTI ID:
- 22869172
- Journal Information:
- Astrophysical Journal Letters, Vol. 838, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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