J/A+A/591/A145 VVV Survey outer bulge RRab stars (Gran+, 2016)
Mapping the outer bulge with RRab stars from the VVV Survey.
Gran F., Minniti D., Saito R.K., Zoccali M., Gonzalez O.A., Navarrete C.,
Catelan M., Contreras Ramos R., Elorrieta F., Eyheramendy S., Jordan A.
<Astron. Astrophys., 591, A145 (2016)>
=2016A&A...591A.145G 2016A&A...591A.145G (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Stars, variable ; Infrared sources
Keywords: Galaxy: bulge - Galaxy: stellar content - Galaxy: structure -
infrared: stars - surveys - stars: variables: RR Lyrae
Abstract:
The VISTA Variables in the Via Lactea (VVV) is a near-IR time-domain
survey of the Galactic bulge and southern plane. One of the main goals
of this survey is to reveal the 3D structure of the Milky Way through
their variable stars. In particular, enormous numbers of RR Lyrae
stars have been discovered in the inner regions of the bulge
(-8°≲b≲-1°) by optical surveys such as OGLE and MACHO, but
leaving an unexplored window of more than ∼47 sq deg
(-10.0°≲l≲+10.7° and -10.3°≲b≲-8.0°) observed by
the VVV Survey.
Our goal is to characterize the RR Lyrae stars in the outer bulge in
terms of their periods, amplitudes, Fourier coefficients, and
distances in order to evaluate the 3D structure of the bulge in this
area. The distance distribution of RR Lyrae stars will be compared to
that of red clump stars, which is known to trace a X-shaped structure,
in order to determine whether these two different stellar populations
share the same Galactic distribution.
A search for RR Lyrae stars was performed in more than ∼47 sq deg at
low Galactic latitudes (-10.3°≲b≲-8.0°). In the procedure
the χ2 value and analysis of variance (AoV) statistic methods
were used to determine the variability and periodic features of the
light curves, respectively. To prevent misclassifications, the
analysis was performed only on the fundamental mode RR Lyrae stars
(RRab) owing to similarities found in the near-IR light curve shapes
of contact eclipsing binaries (W UMa) and first overtone RR Lyrae
stars (RRc). On the other hand, the red clump stars of the same
analyzed tiles were selected, and cuts in the color-magnitude diagram
were applied and the maximum distance restricted to ∼20kpc in order to
construct a similar catalog in terms of distances and covered area
compared to the RR Lyrae stars.
We report the detection of more than 1000 RR Lyrae ab-type stars in
the VVV Survey located in the outskirts of the Galactic bulge. A few
of them are possibly associated with the Sagittarius Dwarf Spheroidal
Galaxy. We calculated colours, reddening, extinction, and distances of
the detected RR Lyrae stars in order to determine the outer bulge 3D
structure. Our main result is that, at the low galactic latitudes
mapped here, the RR Lyrae stars trace a centrally concentrated
spheroidal distribution. This is a noticeably different spatial
distribution to the one traced by red clump stars known to follow a
bar and X-shaped structure. We estimate the completeness of our sample
at 80% for Ks≤15mag.
Description:
The VVV Survey is a public ESO near-IR survey that is mapping the
inner Milky Way, including the inner halo, the bulge and an adjacent
section of the disk with the VISTA 4m telescope at the ESO Paranal
Observatory (Minniti et al., 2010NewA...15..433M 2010NewA...15..433M).
In this analysis we used data covering more than ∼47 sq deg in the
outer bulge (-10.0°≲l≲+10.7° and -10.3°≲b≲-8.0°).
This area corresponds to the VVV tiles b201 through b228, obtained
between April 2010 and August 2014 with 60-62 epochs in all the
selected tiles. We use aperture photometry applied to the stacked
images known as tiles, provided by the Cambridge Astronomical Survey
Unit (CASU) and setting the minimum number of epochs per star
analyzed to 30 in order to achieve a better frequency analysis and
avoid gaps in the light curves.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 86 1019 VVV RRab variables
tablea2.dat 71 210 207 VVV RRab matching a variable in the General
Cataloge of Variable Stars (GCVS) and 3 VVV
RRab previously discovered by OGLE-IV
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See also:
B/gcvs : General Catalogue of Variable Stars (Samus+ 2007-2013)
II/337 : VISTA Variables in the Via Lactea Survey DR1 (Minniti+, 2014)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- VVV VVV designation (JHHMMSS.ss+DDMMSS.s)
20- 21 A2 --- n_VVV [* ] indicates stars matched in GCVS (*)
or OGLE-IV (**) in tablea2
23- 24 I2 h RAh Right ascension (J2000.0)
26- 27 I2 min RAm Right ascension (J2000.0)
29- 33 F5.2 s RAs Right ascension (J2000.0)
35 A1 --- DE- Declination sign (J2000.0)
36- 37 I2 deg DEd Declination (J2000.0)
39- 40 I2 arcmin DEm Declination (J2000.0)
42- 45 F4.1 arcsec DEs Declination (J2000.0)
47- 52 F6.3 deg GLON [] Galactic longitude
54- 60 F7.3 deg GLAT Galactic latitude
62- 67 F6.3 mag Ksmag Ks magnitude
69- 76 F8.6 d Per Period
78- 81 F4.2 mag Amp Amplitude of variation
83- 86 F4.1 kpc Dist Distance
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- VVV Correct VVV designation (JHHMMSS.ss+DDMMSS.s)
(added by CDS)
21- 29 A9 --- GCVS GCVS name
31- 50 A20 --- OGLE OGLE-IV designation (OGLE-BLG-RRLYR-NNNN)
52- 71 A20 --- vvv Erroneous VVV name, as in original table2
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 12-Sep-2016