Browsing by Author "Lucas, P."

Now showing 1 - 10 of 10
  • Thumbnail Image
    Item
    A colour-excess extinction map of the southern Galactic disc from the VVV and GLIMPSE surveys
    (2019) Soto, M.; Barba, R.; Minniti, D.; Kunder, A.; Majaess, D.; Nilo Castellon, J. L.; Alonso García, J.; Leone, G.; Contreras Ramos, Rodrigo Andrés; Hempel, Maren; Morelli, Lorenzo; Haikala, L.; Firpo, V.; Lucas, P.; Emerson, J. P.; Bidin, C. M.; Geisler, D.; Saito, R. K.; Gurovich, S.; Rejkuba, M.; Barbieri, M.; Román Lopes, A.; Alonso, M. V.; Baravalle, L. D.; Borissova, J.; Kurtev, R.; Milla, F
  • Thumbnail Image
    Item
    Discovery of a brown dwarf companion to the A3V star beta Circini
    (2015) Smith, L.; Lucas, P.; Pena, C.; Kurtev, R.; Marocco, F.; Jones, H.; Beamin Muhlenbrock, Juan Carlos; Napiwotzki, R.; Borissova, J.; Burningham, B.; Faherty, J.; Pinfield, D.; Gromadzki, M.; Ivanov, V.; Minniti, D.; Stimson, W.; Villanueva, V.
  • Thumbnail Image
    Item
    Milky Way demographics with the VVV survey: III. Evidence for a great dark lane in the 157 million star bulge color-magnitude diagram
    (2014) Minniti, D.; Saito, R.; Gonzalez, O.; Zoccali, Manuela; Rejkuba, M.; Alonso-Garcia, J.; Benjamin, R.; Catelan, Márcio; Dekany, Istvan; Emerson, J.; Hempel, M.; Lucas, P.; Schultheis, M.
  • Thumbnail Image
    Item
    The Mass of the Most Massive Star in Stellar Clusters Determined from 25 Million MASSCLEAN Monte Carlo Simulations
    (2013) Popescu, Bogdan; Hanson, M. M.; Borissova, J.; Kurtev, R.; Ivanov, V.; Larsen, S. S.; Catelan, Marcio; Minniti, D.; Lucas, P.
    Is there a maximum universal stellar mass, or might the maximum stellar mass in a cluster be tied to the mass of the associated cluster? Direct measurements of the maximum stellar mass of hundreds of young stellar clusters would help us to answer this fundamental question. However, such information does not presently exist. We are mindful that the most massive star in a stellar cluster can have a strong influence on the integrated magnitudes and colors of their host stellar cluster, especially clusters in the low-mass range. Thinking strategically, this color variation provides us with a mechanism for divulging the properties of that most massive star. We performed 25 million MASSCLEAN Monte Carlo simulations of stellar clusters in the 200-1000 M_Sun range in the U, B, and V bands. These simulations were then used to estimate the mass of the most massive star for 40 young, low-mass LMC clusters. In a similar way, the integrated colors and magnitudes in VISTA's Z, Y, J, H, and Ks bands can also be used to estimate the mass of the most massive star in VISTA-identified stellar clusters. Is the IMF for one hundred young 1000 solar mass clusters the same at the high end as ten young 10,000 solar mass clusters? Using the VISTA's clusters, we intend to answer the question, "Does the lower mass of a stellar cluster artificially steepen the high-mass IMF?"....
  • Thumbnail Image
    Item
    The Wide View of the Galactic Bulge as seen by the VVV ESO Public Survey
    (2013) Gonzalez, O. A.; Minniti, D.; Lucas, P.; Rejkuba, M.; Zoccali, M.; Valenti, E.; Saito, R.; Emerson, J.; Catelan, Marcio; Toledo, I.; Hempel, M.; Tobar, R.
    The first year of observations of the Galactic Bulge in the Vista Variables in the Via Lactea (VVV), one of ESO's public surveys with the VISTA telescope, have yielded a deep, near-infrared, multi-colour (Z,Y,J,H,Ks) photometric coverage of over 320 square degrees. Results based on this impressive dataset are presented, showing the global properties of the Bulge. Extinction has been mapped using the magnitude and colour of the red clump, revealing a large amount of small-scale structure. This extinction map has been used to de-redden the VVV stellar photometry to study the Bulge morphology from the absolute magnitude of the red clump and to derive photometric metallicities from the colour of red giant branch stars. The VVV survey continues to obtain multi-epoch data to investigate the variable stars in the Bulge.
  • No Thumbnail Available
    Item
    Using MASSCLEAN to Describe Stellar Clusters Found in the Vista Variables in the Via Lactea (VVV) Survey
    (2014) Popescu, B.; Hanson, M. M.; Borissova, J.; Kurtev, R.; Ivanov, V. D.; Catelan, Marcio; Larsen, S. S.; Minniti, D.; Lucas, P.
    The important parameters: age, mass and distance of resolved or partially resolved stellar clusters are better accurately determined by using color-magnitude diagrams (CMD). However, when the main sequence turnoff is not available or clearly identifiable, large errors in all parameters result when using simple isochrone fitting, particularly when observations are limited to near-infrared bands. We used the MASSCLEAN package to perform 5 million Monte Carlo simulations of stochastically sampled stellar clusters in order to generate CMD templates for a variety of cluster masses and ages and which mimic the observational photometric errors. This results in the creation of tens of thousands of n-dimensional stellar density maps (templates) in numerous color planes as a function of age and mass. We use these MASSCLEAN CMD templates to refine and sharpen traditional isochrone fitting to analyze the newly discovered stellar clusters/cluster candidates from the Vista Variables in the Via Lactea (VVV) Survey. Our MASSCLEAN templates are also being used to design and optimize search algorithms for stellar clusters in broad-band surveys....
  • Thumbnail Image
    Item
    VISTA Milky Way Public Survey
    (2009) Minniti, D.; Lucas, P.; Ahumada, A. V.; Zoccali, M.; Catelan, Marcio; Morelli, L.; Tappert, C.; Pignata, G.; Toledo, I.; Ruiz, M. T.; Carraro, G.; Casassus, S.; Bronfman, L.; Barbá, R. H.; Gamen, R.; Gieren, W.; Geisler, D.; Pietrzynski, G.; Mennickent, R. E.; Kurtev, R.; Borissova, J.; Mirabel, F.; Ivanov, V. D.; Saviane, I.; Vanzi, L.; Monaco, L.; Rejkuba, M.; Messineo, M.; Bedin, L.; Stephens, A.; Barbuy, B.; Bica, E.; Clariá, J. J.; CASU (VDFS) Team; WFAU (VDFS) Team; Emerson, J.; Drew, J.; López-Correidora, M.; Martin, E.; Goldman, B.; Gianinni, T.; Eisloeffel, J.; Groot, P.; Fabregat, J.; Hambly, N.; Longmore, A.; Walton, N.; de Grijs, R.; Hoare, M.; Schroeder, A.; Naylor, T.; Barlow, M.; Zijlstra, A.; White, G.; Gosling, A.; McGowan, K.; Adamson, A.; Bandyopadhyay, R.; Thompson, M.; Cropper, M.; Lucey, J.; Kerins, E.; Hodgkin, S.; Pinfield, D.
    We propose a public IR variability survey, named ``Vista Variables in the Vía Láctea'' (VVV), of the Milky Way bulge and an adjacent section of the mid-plane where star formation activity is high. This would take 1920 hours, covering ∼ 10^9 point sources within an area of 520 sq deg, including 33 known globular clusters and ∼ 350 open clusters. The final products will be a deep IR atlas in 5 passbands and a catalogue of ∼ 10^6 variable point sources. These will produce a 3-D map of the surveyed region (unlike single-epoch surveys that only give 2-D maps) using well-understood primary distance indicators such as RR Lyrae stars. It will yield important information on the ages of the populations. The observations will be combined with data from MACHO, OGLE, EROS, VST, SPITZER, HST, CHANDRA, INTEGRAL, and ALMA for a complete understanding of the variable sources in the inner Milky Way. Several important implications for the history of the Milky Way, for globular cluster evolution, for the population census of the bulge and center, and for pulsation theory would follow from this survey....
  • No Thumbnail Available
    Item
    VISTA Variables in the Via Lactea (VVV): Current Status and First Results
    (2010) Saito, R.; Hempel, M.; Alonso-García, J.; Toledo, I.; Borissova, J.; González, O.; Beamin, J. C.; Minniti, D.; Lucas, P.; Emerson, J.; Ahumada, A.; Aigrain, S.; Alonso, M. V.; Amôres, E.; Angeloni, R.; Arias, J.; Bandyopadhyay, R.; Barbá, R.; Barbuy, B.; Baume, G.; Bedin, L.; Bica, E.; Bronfman, L.; Carraro, G.; Catelan, Marcio; Clariá, J.; Contreras, C.; Cross, N.; Davis, C.; de Grijs, R.; Dékány, I.; Janet Drew, J. D.; Fariña, C.; Feinstein, C.; Fernández Lajús, E.; Folkes, S.; Gamen, R.; Geisler, D.; Gieren, W.; Goldman, B.; Gosling, A.; Gunthardt, G.; Gurovich, S.; Hambly, N.; Hanson, M.; Hoare, M.; Irwin, M.; Ivanov, V.; Jordán, A.; Kerins, E.; Kinemuchi, K.; Kurtev, R.; Longmore, A.; López-Corredoira, M.; Maccarone, T.; Martín, E.; Masetti, N.; Mennickent, R.; Merlo, D.; Messineo, M.; Mirabel, F.; Monaco, L.; Moni Bidin, C.; Morelli, L.; Padilla, N.; Palma, T.; Parisi, M. C.; Parker, Q.; Pavani, D.; Pietrukowicz, P.; Pietrzynski, G.; Pignata, G.; Rejkuba, M.; Rojas, A.; Roman Lopes, A.; Ruiz, M. T.; Sale, S.; Saviane, I.; Schreiber, M.; Schröder, A.; Sharma, S.; Smith, M.; Sodré, L., Jr.; Soto, M.; Stephens, A.; Tamura, M.; Tappert, C.; Thompson, M.; Valenti, E.; Vanzi, L.; Weidmann, W.; Zoccali, M.
    VISTA Variables in the Vía Láctea (VVV) is a public ESO near-IR variability survey aimed at scanning the Milky Way Bulge and an adjacent section of the mid-plane. VVV observations started in October 2009 during ESO science verification. Regular observations for the first year of the survey have been conducted since February 2010 and will cover a total area of 520 square degrees in five passbands and five epochs. Here we address the first results obtained from the VVV Survey as well as the current status of the observations....
  • No Thumbnail Available
    Item
    VVV IR high proper motion stars
    (UNIVERSIDAD NACIONAL AUTONOMA MEXICO INSTITUTO ASTRONOMIA, 2015) Kurtev, R.; Gromadzki, M.; Beamin Muhlenbrock, Juan Carlos; Pena, K.; Folkes, S.; Ivanov, V. D.; Borissova, J.; Kuhn, M.; Villanueva, V.; Minniti, D.; Mendez, R.; Lucas, P.; Smith, L.; Pinfield, D.; Antonova, A.; Vieira, K; VanAltena, W; Mendez, RA
    We used the VISTA Variables en Via Lactea (VVV) survey to search for large proper motion (PM) objects in the zone of avoidance in the Milky Way bulge and southern Galactic disk. This survey is multi-epoch and already spans a period of more than four years, giving us an excellent opportunity for proper motion and parallax studies. We found around 1700 PM objects with PM>30 mas yr(-1). The majority of them are early and mid M-dwarfs. There are also few later spectral type objects, as well as numerous new K- and G-dwarfs. 75 of the stars have PM>300 mas(-1) and 189 stars have PM>200 mas(-1). There are only 42 previously known stars in the VVV area with proper motion PM>200 mas(-1). We also found three dM+WD binaries and new members of the immediate solar vicinity of 25 pc. We generated a catalog which will be a complementary to the existing catalogs outside this zone.
  • No Thumbnail Available
    Item
    Young Stellar Clusters in the VVV Survey
    (2012) Chené, A. -N.; Borissova, J.; Clarke, J. R. A.; Sale, S. E.; Moni-Bidin, C.; Mauro, F.; Bonatto, C.; Kurtev, R.; Baume, G.; Feinstein, C.; Ivanov, V. D.; Geisler, D.; Catelan, Marcio; Minniti, D.; Lucas, P.; VVV Team
    The large survey “VISTA Variables in the Vía Láctea” (VVV) performs wide field-of-view, unprecedented deep infrared observations of the Galaxy's bulge and an adjacent section of the mid-plane. Our group is currently using this unique database, combined with spectroscopic follow-up, to achieve a homogeneous, statistically significant sample of clusters of different ages, distances and masses, including many candidates newly discovered by us....