FSR 1716: A New Milky Way Globular Cluster Confirmed Using VVV RR Lyrae Stars

Dante Minniti, Tali Palma, Istvan Dékány, Maren Hempel, Marina Rejkuba, Joyce Pullen, Javier Alonso-García, Rodolfo Barbá, Beatriz Barbuy, Eduardo Bica, Charles Bonatto, Jura Borissova, Marcio Catelan, Julio A. Carballo-Bello, Andre Nicolas Chene, Juan José Clariá, Roger E. Cohen, Rodrigo Contreras Ramos, Bruno Dias, Jim EmersonDirk Froebrich, Anne S.M. Buckner, Douglas Geisler, Oscar A. Gonzalez, Felipe Gran, Gergely Hagdu, Mike Irwin, Valentin D. Ivanov, Radostin Kurtev, Philip W. Lucas, Daniel Majaess, Francesco Mauro, Christian Moni-Bidin, Camila Navarrete, Sebastian Ramírez Alegría, Roberto K. Saito, Elena Valenti, Manuela Zoccali

Research output: Contribution to journalArticlepeer-review

25 Citations (Scopus)

Abstract

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.J2000 = 16:10:30.0, decl.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 s = 13.35 ±0.05, and J - K 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, 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 and E(J - K 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)0 = 14.38 ±0.03 mag, implying a distance D = 7.5 ±0.2 kpc and a Galactocentric distance R G = 4.3 kpc.

Original languageEnglish
Article numberL14
JournalAstrophysical Journal Letters
Volume838
Issue number1
DOIs
Publication statusPublished - 20 Mar 2017

Keywords

  • galaxies: photometry
  • globular clusters: general
  • stars: variables: RR Lyrae

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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