Browsing by Author "Palma, Tali"

Now showing 1 - 6 of 6
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    Characterization of the VVV Survey RR Lyrae Population across the Southern Galactic Plane
    (2017) Minniti, D.; Dekany, Istvan; Majaess, Daniel; Palma, Tali; Pullen, Joyce; Rejkuba, Marina; Alonso-García, Javier; Catelan, Márcio; Hempel, Maren; Zoccali, Manuela; Contreras Ramos, Rodrigo Andrés; Gonzalez, Oscar A.; Irwin, Mike; Lucas, Philip W.; Saito, Roberto K.; Tissera, Patricia; Valenti, Elena
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    Confirmation of a New Metal-poor Globular Cluster in the Galactic Bulge
    (2018) Minniti, D.; Schlafly, E. F.; Palma, Tali; Claria, Juan J.; Hempel, Maren; Alonso-Garcia, Javier; Bica, Eduardo; Bonatto, Charles; Braga, Vittorio F.; Clementini, Gisella; Garofalo, Alessia; Gomez, Matias; Ivanov, Valentin D.; Lucas, Phill
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    Determination of Reddening and Age for Ten Large Magellanic Cloud Star Clusters from Integrated Spectroscopy
    (2016) Ahumada, Andrea V.; Vega, Luis R.; Claria, Juan J.; Oddone, Monica A.; Palma, Tali
    We present flux-calibrated integrated spectra in the optical range (3700-6800 angstrom) obtained at Complejo Astronomico El Leoncito (CASLEO, Argentina) for a sample of 10 concentrated star clusters belonging to the Large Magellanic Cloud (LMC). No previous data exist for two of these objects (SL 142 and SL 624), while most of the remaining clusters have been only poorly studied. We derive simultaneously foreground E(B - V) reddening values and ages for the cluster sample by comparing their integrated spectra with template LMC cluster spectra and with two different sets of simple stellar population models. Cluster reddening values and ages are also derived from both available interstellar extinction maps and by using diagnostic diagrams involving the sum of equivalent widths of some selected spectral features and their calibrations with age, respectively. For the studied sample, we derive ages between 1 Myr and 240 Myr. In an effort to create a spectral library at the LMC metallicity level with several clusters per age range, the cluster sample presented here stands out as a useful complement to previous ones.
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    FORMATION OF RAMAN SCATTERING WINGS AROUND Hα, Hβ, AND PAα IN ACTIVE GALACTIC NUCLEI
    (2015) Chang, Seok-Jun; Heo, Jeong-Eun; Di Mille, Francesco; Angeloni, Rodolfo; Palma, Tali; Lee, Hee-Won
    Powered by a supermassive black hole with an accretion disk, the spectra of active galactic nuclei (AGNs) are characterized by prominent emission lines including Balmer lines. The unification schemes of AGNs require the existence of a thick molecular torus that may hide the broad emission line region from the view of observers near the equatorial direction. In this configuration, one may expect that the far-UV radiation from the central engine can be Raman scattered by neutral hydrogen to reappear around Balmer and Paschen emission lines, which can be identified with broad wings. We produce H alpha, H beta, and Pa alpha wings using a Monte Carlo technique to investigate their properties. The neutral scattering region is assumed to be a cylindrical torus specified by the inner and outer radii and the height. While the covering factor of the scattering region affects the overall strengths of the wings, the wing widths are primarily dependent on the neutral hydrogen column density N-H (I) being roughly proportional to N-H I(1/2). In particular, with N-H (I) = 10(23) cm(-2) the H alpha wings typically show a width similar to 2 x 10(4) kms(-1). We also find that H alpha and Paa wing profiles are asymmetric with the red part stronger than the blue part and an opposite behavior is seen for H beta wings.
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    Milky Way demographics with the VVV survey IV. PSF photometry from almost one billion stars in the Galactic bulge and adjacent southern disk
    (2018) Alonso-Garcia, Javier; Saito, Roberto K.; Hempel, Maren; Minniti, D.; Pullen, Joyce; Catelan, Márcio; Contreras Ramos, Rodrigo Andrés; Cross, Nicholas J.G.; Gonzalez, Oscar A.; Zoccali, Manuela; Lucas, Philip W.; Palma, Tali; Valenti, Elena
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    Variable stars in the VVV globular clusters. II. NGC 6441, NGC 6569, NGC 6626 (M 28), NGC 6656 (M 22), 2MASS-GC 02, and Terzan 10
    (2021) Alonso-García, Javier; Smith, Leigh C.; Catelan, Márcio; Minniti, Dante; Navarrete, Camila; Borissova, Jura; Carballo-Bello, Julio A.; Contreras Ramos, Rodrigo; Fernández-Trincado, José G.; Ferreira Lopes, Carlos E.; Gran, Felipe; Garro, Elisa R.; Geisler, Doug; Guo, Zhen; Hempel, Maren; Kerins, Eamonn; Lucas, Philip W.; Palma, Tali; Peña Ramírez, Karla; Ramírez Alegría, Sebastián; Saito, Roberto K.
    Context. The Galactic globular clusters (GGCs) located in the inner regions of the Milky Way suffer from high extinction that makes their observation challenging. High densities of field stars in their surroundings complicate their study even more. The VISTA Variables in the Via Lactea (VVV) survey provides a way to explore these GGCs in the near-infrared where extinction effects are highly diminished. Aims: We conduct a search for variable stars in several inner GGCs, taking advantage of the unique multi-epoch, wide-field, near-infrared photometry provided by the VVV survey. We are especially interested in detecting classical pulsators that will help us constrain the physical parameters of these GGCs. In this paper, the second of a series, we focus on NGC 6656 (M 22), NGC 6626 (M 28), NGC 6569, and NGC 6441; these four massive GGCs have known variable sources, but quite different metallicities. We also revisit 2MASS-GC 02 and Terzan 10, the two GGCs studied in the first paper of this series. Methods: We present an improved method and a new parameter that efficiently identify variable candidates in the GGCs. We also use the proper motions of those detected variable candidates and their positions in the sky and in the color-magnitude diagrams to assign membership to the GGCs. Results: We identify and parametrize in the near-infrared numerous variable sources in the studied GGCs, cataloging tens of previously undetected variable stars. We recover many known classical pulsators in these clusters, including the vast majority of their fundamental mode RR Lyrae. We use these pulsators to obtain distances and extinctions toward these objects. Recalibrated period-luminosity-metallicity relations for the RR Lyrae bring the distances to these GGCs to a closer agreement with those reported by Gaia, except for NGC 6441, which is an uncommon Oosterhoff III GGC. Recovered proper motions for these GGCs also agree with those reported by Gaia, except for 2MASS-GC 02, the most reddened GGC in our sample, where the VVV near-infrared measurements provide a more accurate determination of its proper motions. Lightcurves and full Tables 2, 5, 6, 7, 8, and 9 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/651/A47...