J/ApJ/863/79 RR Lyrae cand. in the Galactic Center (Contreras Ramos+, 2018)
The VVV survey RR Lyrae population in the Galactic Center region.
Contreras Ramos R., Minniti D., Gran F., Zoccali M., Alonso-Garcia J.,
Huijse P., Navarro M.G., Rojas-Arriagada A., Valenti E.
<Astrophys. J., 863, 79 (2018)>
=2018ApJ...863...79C 2018ApJ...863...79C
ADC_Keywords: Stars, variable; Photometry, infrared; Proper motions;
Abundances, [Fe/H]; Stars, distances; Extinction; Galactic center
Keywords: catalogs ; Galaxy: bulge ; proper motions ;
stars: variables: RR Lyrae ; surveys
Abstract:
Deep near-IR images from the VISTA Variables in the Via Lactea (VVV)
Survey were used to search for RR Lyrae stars within 100 arcmin from
the Galactic Center. A large sample of 960 RR Lyrae of type ab (RRab)
stars were discovered. A catalog is presented featuring the positions,
magnitudes, colors, periods, and amplitudes for the sample, in
addition to estimated reddenings, distances, and metallicities, and
measured individual relative proper motions. We use the
reddening-corrected Wesenheit magnitudes, defined as
WKs=Ks-0.428x(J-Ks), in order to isolate bona fide RRL belonging to
the Galaxy Center, finding that 30 RRab are foreground/background
objects. We measure a range of extinctions from AKs=0.19 to 1.75mag
for the RRab in this region, finding that large extinction is the main
cause of the sample incompleteness. The mean period is
P=0.5446±0.0025d, yielding a mean metallicity of [Fe/H]=-1.30±0.01
(σ=0.33)dex for the RRab sample in the Galactic Center region.
The median distance for the sample is D=8.05±0.02kpc. We measure the
RRab surface density using the less reddened region sampled here,
finding a density of 1000 RRab/sq deg at a projected Galactocentric
distance RG=1.6deg. Under simple assumptions, this implies a large
total mass (M>109M☉) for the old and metal-poor population
contained inside RG. We also measure accurate relative proper motions,
from which we derive tangential velocity dispersions of
σVl=125.0 and σVb=124.1km/s along the Galactic
longitude and latitude coordinates, respectively. The fact that these
quantities are similar indicate that the bulk rotation of the RRab
population is negligible, and implies that this population is
supported by velocity dispersion. In summary, there are two main
conclusions of this study. First, the population as a whole is no
different from the outer bulge RRab, predominantly a metal-poor
component that is shifted with respect to the Oosterhoff type I
population defined by the globular clusters in the halo. Second, the
RRab sample, as representative of the old and metal-poor stellar
population in the region, has high velocity dispersions and zero
rotation, suggesting a formation via dissipational collapse.
Description:
The VISTA Variables in the Via Lactea (VVV) survey has been acquiring
data since early 2010 using the VISTA InfraRed Camera (VIRCAM) mounted
on the VISTA telescope in Cerro Paranal Observatory, Chile. The entire
VVV observations comprise 348 tiles, 194 tiles in the bulge and 152 in
the disk area, each covering a field of view (FoV) of ∼1.6deg2.
In this work we focus on the innermost region of the Galaxy, where the
crowding is so severe that PSF modeling is mandatory.
The final catalog presented here includes 960 RRab candidate variable
stars within 100 arcmin of the Galactic Center, some of which have
been previously discovered (Soszynski+ 2014, J/AcA/64/177 ;
Minniti+ 2016ApJ...830L..14M 2016ApJ...830L..14M).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 95 960 RR Lyrae sample photometric observations and
relative proper motions
table2.dat 63 960 Measured stellar parameters
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See also:
II/337 : VISTA Variables in the Via Lactea Survey DR1 (Saito+, 2012)
II/348 : VISTA Variable in the Via Lactea Survey DR2 (Minniti+, 2017)
J/AJ/108/1016 : Kinematics of local RR lyrae stars. I. (Layden, 1994)
J/A+A/486/177 : Bulge field stars from FLAMES-GIRAFFE spectra (Zoccali+, 2008)
J/MNRAS/399/1709 : Near-infrared survey of Miras (Matsunaga+, 2009)
J/ApJ/724/799 : RR Lyrae variables in M33. II. (Yang+, 2010)
J/AJ/139/357 : Variable stars in NGC 5286 (Zorotovic+, 2010)
J/AcA/61/1 : VI LCs of Galactic Bulge RR Lyrae (Soszynski+, 2011)
J/MNRAS/441/1230 : RRLyr stars in the Catalins Sky Survey (CS2) (Abbas+, 2014)
J/AcA/64/177 : VI LCs of Galactic Bulge RR Lyrae (Soszynski+, 2014)
J/AJ/149/99 : VVV globulars I. 2MASS-GC 02, Terzan 10 (Alonso-Garcia+, 2015)
J/ApJ/807/127 : 70 RR Lyrae stars in the LMC bar (Muraveva+, 2015)
J/MNRAS/446/2251 : Southern Catalina Survey type-ab RR Lyrae (Torrealba+, 2015)
J/A+A/591/A145 : VVV Survey outer bulge RRab stars (Gran+, 2016)
J/ApJ/821/L25 : Bulge RR Lyrae RVel Assay (BRAVA-RR) (Kunder+, 2016)
J/AJ/153/179 : VVV Survey RR Lyrae in Southern Gal. plane (Minniti+, 2017)
J/A+A/604/A120 : omega Cen RR Lyrae and SX Phoenicis stars (Navarrete+, 2017)
J/A+A/599/A12 : [Fe/H] & kinematics of Galactic bulge fields (Zoccali+, 2017)
J/ApJ/857/54 : JHKs photometry of VVV RR Lyrae stars (Dekany+, 2018)
J/other/ApSS/363.127 : Bulge RR Lyrae VVVDR4 photometry (Majaess+, 2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- ID RR Lyrae identifier
17- 24 F8.4 deg GLON Galactic longitude
26- 32 F7.4 deg GLAT Galactic latitude
34- 39 F6.3 mag Ksmag [12.6/16.1] VISTA Ks band magnitude
41- 46 F6.3 mag Hmag [13.2/17.8]?=99.999 VISTA H band magnitude
48- 53 F6.3 mag Jmag [14/20.4]?=99.999 VISTA J band magnitude
55- 60 F6.3 mag Ymag [14.6/21.1]?=99.999 VISTA Y band magnitude
62- 67 F6.3 mag Zmag [15/21.7]?=99.999 VISTA Z band magnitude
69- 75 F7.3 mas/yr pmGLON [-11/11.1]?=99.999 Relative proper motion
along GLON *cos(GLAT)
77- 81 F5.2 mas/yr e_pmGLON [0.4/5]?=99.99 Uncertainty in pmGLON
83- 89 F7.3 mas/yr pmGLAT [-14.6/]?=99.999 Relative proper motion
along GLAT
91- 95 F5.2 mas/yr e_pmGLAT [0.3/5.3]?=99.99 Uncertainty in pmGLAT
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- ID RR Lyrae identifier
17- 22 F6.3 mag E(J-Ks) [0.4/4.2]?=99.999 The J-Ks color index
24- 29 F6.3 mag AKs [0.1/1.8]?=99.999 The Ks band extinction
31- 36 F6.3 mag DM [12.6/15.5]?=99.999 Intrinsic distance modulus
38- 43 F6.3 kpc Dist [3.3/12.5]?=99.999 Distance from the Sun
45- 51 F7.5 d Per [0.3/1] Period
53- 57 F5.3 mag KsAmp [0.1/0.6] The Ks band amplitude
59- 63 F5.2 [Sun] [Fe/H] [-2.6/-0.1] Metallicity
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Nomenclature note:
The RR Lyrae candidates are named <[CMG2018] bNNN NNN NNNNNN> in Simbad.
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 02-Aug-2019