Stroemgren - near-infrared photometry of the Baade's Window. I. The bulge globular cluster NGC6528 and the surrounding field

We present Stroemgren-NIR photometry of NGC6528 and its surroundings in the Baade's Window. uvby images were collected with EFOSC2@NTT, while NIR catalogs are based on VIRCAM@VISTA and SOFI@NTT data. The matching with HST photometry allowed us to obtain proper-motion-cleaned samples of cluster and bulge stars. The huge color sensitivity of Stroemgren-NIR CMDs helped us in disentangling age and metallicity effects. The RGB of NGC6528 is reproduced by scaled-solar isochrones with solar abundance or alpha-enhanced isochrones with the same iron content, and an age of t = 11+/-1 Gyr. These findings support literature age estimates for NGC6528. We also performed a theoretical metallicity calibration based on the Stroemgren index m1 and on visual-NIR colors for RGs, by adopting scaled-solar and alpha-enhanced models. We applied the calibration to estimate the metallicity of NGC6528, finding [Fe/H] = -0.04+/-0.02, with an intrinsic dispersion of 0.27 dex (by averaging abundances based on the scaled-solar [m], y - J and [m], y - K Metallicity-Index-Color relations), and of -0.11+/-0.01 (sig = 0.27 dex), by using the m1, y - J and m1, y - K relations. These findings support the results of Zoccali et al. (2004) which give [Fe/H] = -0.10+/-0.2, and a low alpha-enhancement, [alpha/Fe] = 0.1, and of Carretta et al. (2001), that find [Fe/H] = 0.07+/-0.01, with [alpha/Fe] = 0.2. By applying the scaled-solar MIC relations to Baade's window RGs, we find a metallicity distribution extending from [Fe/H] ~ -1.0 to ~ 1 dex, with peaks at [Fe/H] ~ -0.2 and +0.55 ([m], y - J and [m], y - K relations), and [Fe/H] ~ -0.25 and +0.4 (m1, y - J and m1, y - K relations). These findings are in good agreement with the spectroscopic studies of Hill et al. (2011) for the Baade's window, of Uttenthaler et al. (2012) for a region centered at (l,b) = (0, -10), and with the results of the ARGOS survey (Ness et al. 2013a).Comment: 19 pages, 13 figures, 3 tables, accepted for publication on Astronomy & Astrophysic

VISTA Variables in the <i>Vía Láctea</i> (VVV): Halfway Status and Results

The VISTA Variables in the Vía Láctea (VVV) survey is one of six near-infrared ESO public surveys, and is now in its fourth year of observing. Although far from being complete, the VVV survey has already delivered many results, some directly connected to the intended science goals (detection of variable stars, microlensing events, new star clusters), others concerning more exotic objects, e.g., novae. Now, at the end of the fourth observing period, and comprising roughly 50% of the proposed observations, the status of the survey, as well some of results based on the VVV data, are presented.Facultad de Ciencias Astronómicas y Geofísica

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

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 >100? 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, $\langle P\rangle =0.540$ 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 ${A}_{{K}_{s}}=0.38\pm 0.02$ 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

VISTA Variables in the Vía Láctea (VVV): Halfway Status and Results

The VISTA Variables in the Vía Láctea (VVV) survey is one of six near-infrared ESO public surveys, and is now in its fourth year of observing. Although far from being complete, the VVV survey has already delivered many results, some directly connected to the intended science goals (detection of variable stars, microlensing events, new star clusters), others concerning more exotic objects, e.g., novae. Now, at the end of the fourth observing period, and comprising roughly 50% of the proposed observations, the status of the survey, as well some of results based on the VVV data, are presented.Fil: Hempel, Maren. Pontificia Universidad Católica de Chile; Chile. The Milky Way Millennium Nucleus; ChileFil: Minniti, Dante. Pontificia Universidad Católica de Chile; Chile. Vatican Observatory; ItaliaFil: Dékány, István. Pontificia Universidad Católica de Chile; ChileFil: Saito, Roberto K.. Pontificia Universidad Católica de Chile; Chile. Universidade Federal de Sergipe; BrasilFil: Lucas, Philip W.. University Of Hertfordshire; Reino UnidoFil: Emerson, Jim P.. Queen Mary University of London; Reino UnidoFil: Ahumada, Andrea Veronica. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Aigrain, Suzanne. University of Exeter; Reino UnidoFil: Alonso, Maria Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; ArgentinaFil: Alonso García, Javier. Pontificia Universidad Católica de Chile; ChileFil: Amôres, Eduardo B.. Universidade de Lisboa; PortugalFil: Angeloni, Rodolfo. Pontificia Universidad Católica de Chile; ChileFil: Arias, Julia. Universidad de La Serena; ChileFil: Bandyopadhyay, Reba. University of Florida; Estados UnidosFil: Barba, Rodolfo Hector. Universidad de La Serena; Chile. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Barbuy, Beatriz. Universidade de São Paulo; BrasilFil: Baume, Gustavo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Beamin, Juan Carlos. Pontificia Universidad Católica de Chile; ChileFil: Bedin, Luigi. Space Telescope Science Institute; Estados UnidosFil: Bica, Eduardo. Universidade Federal do Rio Grande do Sul; BrasilFil: Borissova, Jordanka. Universidad de Chile; ChileFil: Bronfman, Leonardo. Universidad de Chile; ChileFil: Carraro, Giovanni. European Southern Observatory; ChileFil: Catelan, Márcio. Pontificia Universidad Católica de Chile; ChileFil: Claria Olmedo, Juan Jose. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Contreras, Carlos. Pontificia Universidad Católica de Chile; ChileFil: Cross, Nicholas. University of Edinburgh; Reino UnidoFil: Davis, Christopher. Joint Astronomy Centre; Estados UnidosFil: de Grijs, Richard. Peking University; ChinaFil: Drew, Janet E.. University Of Hertfordshire; Reino UnidoFil: Fariña, Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Feinstein Baigorri, Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Fernandez Lajus, Eduardo Eusebio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Folkes, Stuart. University Of Hertfordshire; Reino UnidoFil: Gamen, Roberto Claudio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Geisler, Douglas. Universidad de Concepción; ChileFil: Gieren, Wolfgang. Universidad de Concepción; ChileFil: Goldman, Bertrand. Max Planck Institute for Astronomy; AlemaniaFil: González, Oscar. European Southern Observatory; ChileFil: Gosling, Andrew. University of Oxford; Reino UnidoFil: Gunthardt, Guillermo Ivan. Universidad de La Serena; ChileFil: Gurovich, Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Hambly, Nigel C.. University of Edinburgh; Reino UnidoFil: Hanson, Margaret. University of Cincinnati; Estados UnidosFil: Hoare, Melvin. University of Leeds; Reino UnidoFil: Irwin, Mike J.. University of Cambridge; Reino UnidoFil: Ivanov, Valentin D.. European Southern Observatory; ChileFil: Jordán, Andrés. Pontificia Universidad Católica de Chile; ChileFil: Kerins, Eamonn. University of Manchester; Reino UnidoFil: Kinemuchi, Karen. National Aeronautics and Space Administration; Estados UnidosFil: Kurtev, Radostin. Universidad de Valparaíso; ChileFil: Longmore, Andy. University of Edinburgh; Reino UnidoFil: López Corredoira, Martin. Instituto de Astrofísica de Canarias; EspañaFil: Maccarone, Tom. Texas Tech University; Estados UnidosFil: Martín, Eduardo. Instituto de Astrofísica de Canarias; EspañaFil: Masetti, Nicola. Instituto di Astrofisica Spaziale e Fisica Cosmica de Bologna; ItaliaFil: Mennickent, Ronald E.. Universidad de Concepción; ChileFil: Merlo, David. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; ArgentinaFil: Messineo, Maria. Rochester Institute of Technology; Estados UnidosFil: Mirabel Miquele, Igor Felix. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Monaco, Lorenzo. European Southern Observatory; ChileFil: Moni Bidin, Christian. Universidad Católica del Norte; ChileFil: Morelli, Lorenzo. Università di Padova; ItaliaFil: Padilla, Nelson. Pontificia Universidad Católica de Chile; ChileFil: Palma, Tali. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Parisi, Maria Celeste. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Parker, Quentin. Macquarie University; AustraliaFil: Pavani, Daniela. Universidade Federal do Rio Grande do Sul; BrasilFil: Pietrukowicz, Pawel. Nicolaus Copernicus Astronomical Center; PoloniaFil: Pietrzynski, Grzegorz. Imperial College London; Reino UnidoFil: Pignata, Giuliano. Universidad Andrés Bello; ChileFil: Rejkuba, Marina. European Southern Observatory; ChileFil: Rojas, Alejandra. Pontificia Universidad Católica de Chile; ChileFil: Roman Lopes, Alexandre. Universidad de La Serena; ChileFil: Ruiz, María Teresa. Universidad de Chile; ChileFil: Sale, Stuart E.. Pontificia Universidad Católica de Chile; ChileFil: Saviane, Ivo. European Southern Observatory; ChileFil: Schreiber, Matthias R.. Universidad de Valparaíso; ChileFil: Schröder, Anja C.. Hartebeesthoek Radio Astronomy Observatory; SudáfricaFil: Sharma, Saurabh. Universidad de Valparaíso; ChileFil: Smith, Michael. University Of Kent; Reino UnidoFil: Sodré Jr., Laerte. Universidade de Sao Paulo; BrasilFil: Soto, Mario. Universidad de La Serena; ChileFil: Stephens, Andrew W.. National Astronomical Observatory of Japan; JapónFil: Tamura, Motohide. Gemini Observatory; Estados UnidosFil: Tappert, Claus. Universidad de Valparaíso; ChileFil: Thompson, Mark A.. University Of Hertfordshire; Reino UnidoFil: Toledo, Ignacio. ALMA Observatory; ChileFil: Valenti, Elena. European Southern Observatory; ChileFil: Vanzi, Leonardo. Pontificia Universidad Católica de Chile; ChileFil: Weidmann, Walter Alfredo. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Zoccali, Manuela. Pontificia Universidad Católica de Chile; Chil