FSR 1716 : a new Milky Way globular cluster confirmed using VVV RR Lyrae stars

• Autor(a) principal: Minniti, Dante
• Data de Publicação: 2017
• Outros Autores: Palma, Tali, Dékány, István, Hempel, Maren, Rejkuba, Marina, Pullen, Joyce, Alonso Garcia, Javier, Barbá, Rodolfo H., Barbuy, Beatriz, Bica, Eduardo Luiz Damiani, Bonatto, Charles Jose, Borissova, Jura, Catelan, Márcio, Carballo-Bello, Julio A., Chené, André-Nicolas, Claria Olmedo, Juan Jose, Cohen, Roger, Contreras Ramos, Rodrigo, Dias, Bruno Moreira de Souza, Emerson, Jim P., Froebrich, Dirk, Buckner, Anne S. M., Geisler, Doug, Gonzalez, Oscar A., Gran, Felipe, Hajdu, Gergely, Irwin, Michael John, Ivanov, Valentin D., Kurtev, Radostin Georgiev, Lucas, Philip W., Majaess, Daniel J., Mauro, Francesco, Moni Bidin, Christian, Navarrete, Camila, Ramírez Alegría, Sebastián, Saito, Roberto K., Valenti, Elena, Zoccali, Manuela
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional da UFRGS
• Texto Completo: http://hdl.handle.net/10183/169045
• topic: Aglomerados globulares; Fotometria estelar; Galáxias; Globular clusters: general; Galaxies: photometry; Stars: variables: RR Lyrae

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 Ks = 13.35±0.05, and J−Ks = 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, áPñ = 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 AKs = 0.38 0.02 and E( J−Ks) = 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 RG = 4.3 kpc.