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Title: Characterization of the VVV Survey RR Lyrae Population across the Southern Galactic Plane

Abstract

Deep near-IR images from the VISTA Variables in the Vía Láctea (VVV) Survey were used to search for RR Lyrae stars in the Southern Galactic plane. A sizable sample of 404 RR Lyrae of type ab stars was identified across a thin slice of the fourth Galactic quadrant (295° < ℓ < 350°, −2.°24 < b < −1.°05). The sample’s distance distribution exhibits a maximum density that occurs at the bulge tangent point, which implies that this primarily Oosterhoff type I population of RRab stars does not trace the bar delineated by their red clump counterparts. The bulge RR Lyrae population does not extend beyond ℓ  ∼ 340°, and the sample’s spatial distribution presents evidence of density enhancements and substructure that warrants further investigation. Indeed, the sample may be employed to evaluate Galactic evolution models, and is particularly lucrative since half of the discovered RR Lyrae are within reach of Gaia astrometric observations.

Authors:
; ; ;  [1];  [2];  [3]; ;  [4]; ; ; ;  [5];  [6];  [7];  [8];  [9];  [10]
  1. Departamento de Ciencias Físicas, Facultad de Ciencias Exactas, Universidad Andrés Bello, Av. Fernández Concha 700, Las Condes, Santiago (Chile)
  2. Astronomisches Rechen-Institut, Zentrum fuer Astronomie der Universitaet Heidelberg, Moenchhofstr. 12-14, D-69120 Heidelberg (Germany)
  3. Mount Saint Vincent University, Halifax, Nova Scotia (Canada)
  4. European Southern Observatory, Karl-Schwarszchild-Str. 2, D-85748 Garching bei Muenchen (Germany)
  5. Instituto Milenio de Astrofísica, Santiago (Chile)
  6. Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ (United Kingdom)
  7. Pontificia Universidad Católica de Chile, Instituto de Astrofisica, Av. Vicuna Mackenna 4860, Santiago (Chile)
  8. Institute of Astronomy, Cambridge University, Cambridge, CB3 0HA (United Kingdom)
  9. Department of Astronomy, University of Hertfordshire, Hertfordshire (United Kingdom)
  10. Departamento de Física, Universidade Federal de Santa Catarina, Trindade 88040-900, Florianópolis, SC (Brazil)
Publication Date:
OSTI Identifier:
22663725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astronomical Journal (Online); Journal Volume: 153; Journal Issue: 4; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; DENSITY; DISTANCE; GALACTIC EVOLUTION; IMAGES; MILKY WAY; NEAR INFRARED RADIATION; SPATIAL DISTRIBUTION; VARIABLE STARS

Citation Formats

Minniti, Dante, Palma, Tali, Pullen, Joyce, Tissera, Patricia, Dékány, Istvan, Majaess, Daniel, Rejkuba, Marina, Valenti, Elena, Alonso-García, Javier, Catelan, Marcio, Contreras Ramos, Rodrigo, Zoccali, Manuela, Gonzalez, Oscar A., Hempel, Maren, Irwin, Mike, Lucas, Philip W., and Saito, Roberto K. Characterization of the VVV Survey RR Lyrae Population across the Southern Galactic Plane. United States: N. p., 2017. Web. doi:10.3847/1538-3881/AA5BE4.
Minniti, Dante, Palma, Tali, Pullen, Joyce, Tissera, Patricia, Dékány, Istvan, Majaess, Daniel, Rejkuba, Marina, Valenti, Elena, Alonso-García, Javier, Catelan, Marcio, Contreras Ramos, Rodrigo, Zoccali, Manuela, Gonzalez, Oscar A., Hempel, Maren, Irwin, Mike, Lucas, Philip W., & Saito, Roberto K. Characterization of the VVV Survey RR Lyrae Population across the Southern Galactic Plane. United States. doi:10.3847/1538-3881/AA5BE4.
Minniti, Dante, Palma, Tali, Pullen, Joyce, Tissera, Patricia, Dékány, Istvan, Majaess, Daniel, Rejkuba, Marina, Valenti, Elena, Alonso-García, Javier, Catelan, Marcio, Contreras Ramos, Rodrigo, Zoccali, Manuela, Gonzalez, Oscar A., Hempel, Maren, Irwin, Mike, Lucas, Philip W., and Saito, Roberto K. Sat . "Characterization of the VVV Survey RR Lyrae Population across the Southern Galactic Plane". United States. doi:10.3847/1538-3881/AA5BE4.
@article{osti_22663725,
title = {Characterization of the VVV Survey RR Lyrae Population across the Southern Galactic Plane},
author = {Minniti, Dante and Palma, Tali and Pullen, Joyce and Tissera, Patricia and Dékány, Istvan and Majaess, Daniel and Rejkuba, Marina and Valenti, Elena and Alonso-García, Javier and Catelan, Marcio and Contreras Ramos, Rodrigo and Zoccali, Manuela and Gonzalez, Oscar A. and Hempel, Maren and Irwin, Mike and Lucas, Philip W. and Saito, Roberto K.},
abstractNote = {Deep near-IR images from the VISTA Variables in the Vía Láctea (VVV) Survey were used to search for RR Lyrae stars in the Southern Galactic plane. A sizable sample of 404 RR Lyrae of type ab stars was identified across a thin slice of the fourth Galactic quadrant (295° < ℓ < 350°, −2.°24 < b < −1.°05). The sample’s distance distribution exhibits a maximum density that occurs at the bulge tangent point, which implies that this primarily Oosterhoff type I population of RRab stars does not trace the bar delineated by their red clump counterparts. The bulge RR Lyrae population does not extend beyond ℓ  ∼ 340°, and the sample’s spatial distribution presents evidence of density enhancements and substructure that warrants further investigation. Indeed, the sample may be employed to evaluate Galactic evolution models, and is particularly lucrative since half of the discovered RR Lyrae are within reach of Gaia astrometric observations.},
doi = {10.3847/1538-3881/AA5BE4},
journal = {Astronomical Journal (Online)},
number = 4,
volume = 153,
place = {United States},
year = {Sat Apr 01 00:00:00 EDT 2017},
month = {Sat Apr 01 00:00:00 EDT 2017}
}
  • We have combined optical and near-infrared data of known RR Lyrae (RRL) stars in the bulge in order to study the spatial distribution of its metal-poor component by measuring precise reddening values and distances of 7663 fundamental-mode RRL stars with high-quality photometry. We obtain a distance to the Galactic center of R {sub 0} = 8.33 ± 0.05 ± 0.14 kpc. We find that the spatial distribution of the RRL stars differs from the structures traced by the predominantly metal-rich red clump (RC) stars. Unlike the RC stars, the RRL stars do not trace a strong bar, but have amore » more spheroidal, centrally concentrated distribution, showing only a slight elongation in its very center. We find a hint of bimodality in the density distribution at high southern latitudes (b < –5°), which needs to be confirmed by extending the areal coverage of the current census. The different spatial distributions of the metal-rich and metal-poor stellar populations suggest that the Milky Way has a composite bulge.« less
  • VISTA Variables in the Via Lactea (VVV) is an ESO variability survey that is performing observations in near-infrared bands (ZY JHK{sub s}) toward the Galactic bulge and part of the disk with the completeness limits at least 3 mag deeper than Two Micron All Sky Survey. In the present work, we searched in the VVV survey data for background galaxies near the Galactic plane using ZY JHK{sub s} photometry that covers 1.636 deg{sup 2}. We identified 204 new galaxy candidates by analyzing colors, sizes, and visual inspection of multi-band (ZY JHK{sub s}) images. The galaxy candidate colors were also comparedmore » with the predicted ones by star count models considering a more realistic extinction model at the same completeness limits observed by VVV. A comparison of the galaxy candidates with the expected one by Millennium simulations is also presented. Our results increase the number density of known galaxies behind the Milky Way by more than one order of magnitude. A catalog with galaxy properties including ellipticity, Petrosian radii, and ZY JHK{sub s} magnitudes is provided, as well as comparisons of the results with other surveys of galaxies toward the Galactic plane.« less
  • Mean colors and magnitudes of RR Lyrae stars in 24 fields toward the Galactic bulge from the MACHO database are presented. Accurate mean reddenings are computed for these fields on the basis of the mean colors. The distribution along the line of sight of the RR Lyrae population is examined on the basis of the mean magnitudes, and it is shown that the bulk of the RR Lyrae population is not barred. Only the RR Lyrae stars in the inner fields closer to the Galactic center (l{lt}4{degree}, b{gt}{minus}4{degree}) show evidence for a bar. The red giant clump stars in themore » MACHO fields, however, clearly show a barred distribution, confirming the results of previous studies. Given the different spatial distribution, the RR Lyrae stars and the clump giants trace two different populations. The RR Lyrae variables would represent the inner extension of the Galactic halo in these fields. {copyright} {ital 1998} {ital The American Astronomical Society}« less
  • We present 838 ab-type RR Lyrae stars from the Lowell Observatory Near Earth Objects Survey Phase I (LONEOS-I). These objects cover 1430 deg{sup 2} and span distances ranging from 3-30kpc from the Galactic Center. Object selection is based on phased, photometric data with 28-50 epochs. We use this large sample to explore the bulk properties of the stellar halo, including the spatial distribution. The period-amplitude distribution of this sample shows that the majority of these RR Lyrae stars resemble Oosterhoff type I, but there is a significant fraction (26%) which have longer periods and appear to be Oosterhoff type II.more » We find that the radial distributions of these two populations have significantly different profiles ({rho}{sub OoI} {approx} R{sup -2.26{+-}0.07} and {rho}{sub OoII} {approx} R{sup -2.88{+-}0.11}). This suggests that the stellar halo was formed by at least two distinct accretion processes and supports dual-halo models.« less