J/ApJ/857/54 JHKs photometry of VVV RR Lyrae stars (Dekany+, 2018)
A near-infrared RR Lyrae census along the southern Galactic plane:
the Milky Way's stellar fossil brought to light.
Dekany I., Hajdu G., Grebel E.K., Catelan M., Elorrieta F., Eyheramendy S.,
Majaess D., Jordan A.
<Astrophys. J., 857, 54-54 (2018)>
=2018ApJ...857...54D 2018ApJ...857...54D (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable; Photometry, infrared; Stars, distances; Surveys;
Galactic plane
Keywords: catalogs; Galaxy: abundances; Galaxy: disk; stars: variables: RR Lyrae
surveys
Abstract:
RR Lyrae stars (RRLs) are tracers of the Milky Way's fossil record,
holding valuable information on its formation and early evolution.
Owing to the high interstellar extinction endemic to the Galactic
plane, distant RRLs lying at low Galactic latitudes have been elusive.
We attained a census of 1892 high-confidence RRLs by exploiting the
near-infrared photometric database of the VVV survey's disk footprint
spanning ∼70° of Galactic longitude, using a machine-learned
classifier. Novel data-driven methods were employed to accurately
characterize their spatial distribution using sparsely sampled
multi-band photometry. The RRL metallicity distribution function (MDF)
was derived from their Ks-band light-curve parameters using
machine-learning methods. The MDF shows remarkable structural
similarities to both the spectroscopic MDF of red clump giants and the
MDF of bulge RRLs. We model the MDF with a multi-component density
distribution and find that the number density of stars associated with
the different model components systematically changes with both the
Galactocentric radius and vertical distance from the Galactic plane,
equivalent to weak metallicity gradients. Based on the consistency
with results from the ARGOS survey, three MDF modes are attributed to
the old disk populations, while the most metal-poor RRLs are probably
halo interlopers. We propose that the dominant [Fe/H] component with a
mean of -1dex might correspond to the outskirts of an ancient Galactic
spheroid or classical bulge component residing in the central Milky
Way. The physical origins of the RRLs in this study need to be
verified by kinematical information.
Description:
Our study is entirely based on near-IR time-series photometric data
from the VISTA Variables in the Via Lactea survey (VVV, Minniti+
2010NewA...15..433M 2010NewA...15..433M ; see Cat. II/348). We analyzed observational data
from the VVV's disk footprint (fields d001-d151), an approximately
4°x57° elongated area running parallel with and nearly
symmetrically to the Galactic equator, covering the mid-plane toward
the 4th Galactic quadrant. The data were acquired between 2010 January
30 and 2015 August 14. Images were taken in the ZY JHKs broadband
filter set of the VISTA photometric system.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 129 1892 Parameters of the RR Lyrae stars in our
fiducial sample
table2.dat 39 203035 JHKs photometric time-series of the candidate
RR Lyrae stars with score >0.6
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See also:
II/348 : VISTA Variable in the Via Lactea Survey DR2 (Minniti+, 2017)
J/AJ/155/171 : RR Lyrae stars in and around NGC 6441 (Kunder+, 2018)
J/other/ApSS/363.127 : Bulge RR Lyrae VVVDR4 photometry (Majaess+, 2018)
J/A+A/604/A120 : omega Cen RR Lyrae and SX Phoenicis stars (Navarrete+, 2017)
J/AJ/153/179 : VVV Survey RR Lyr in Southern Galactic plane (Minniti+, 2017)
J/AJ/153/96 : Standard Galactic field RR Lyrae. I. Phot. (Monson+, 2017)
J/AJ/152/170 : RRLs in globulars. IV. UBVRI phot. in Omega Cen (Braga+, 2016)
J/ApJ/821/L25 : Bulge RR Lyrae RV Assay (BRAVA-RR) (Kunder+, 2016)
J/ApJ/807/127 : 70 RR Lyrae stars data in the LMC bar (Muraveva+, 2015)
J/AcA/64/177 : VI light curves of Galactic Bulge RR Lyrae (Soszynski+, 2014)
J/AJ/146/21 : LINEAR. II. Catalog of RR Lyrae stars (Sesar+, 2013)
J/MNRAS/428/3660 : ARGOS line list λ8395-8830Å (Freeman+, 2013)
J/ApJ/763/32 : Galactic halo RRab stars from CSS (Drake+, 2013)
J/ApJ/678/851 : RR Lyrae survey in the Galactic Halo (Keller+, 2008)
J/AJ/129/2714 : JHK photometry of M92 variable stars (Del Principe+, 2005)
J/A+A/312/111 : [Fe/H] from RR Lyrae light curves (Jurcsik+, 1996)
J/AJ/108/1016 : Kinematics of local RR lyrae stars. I. (Layden, 1994)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Seq [1/1892] Running sequence number
6- 7 I2 h RAh [11/17] Hour of Right Ascension (J2000)
9- 10 I2 min RAm Minute of Right Ascension (J2000)
12- 16 F5.2 s RAs Second of Right Ascension (J2000)
18 A1 --- DE- [-] Sign of the Declination (J2000)
19- 20 I2 deg DEd [35/65] Degree of Declination (J2000)
22- 23 I2 arcmin DEm Arcminute of Declination (J2000)
25- 28 F4.1 arcsec DEs Arcsecond of Declination (J2000)
30- 34 F5.3 --- Score [0.6/0.9] Classification score
36- 43 F8.6 d Per [0.3/0.9] Pulsation period
45 I1 --- Ap [1/5] Optimal aperture
47- 52 F6.3 mag KsmagAvg [11/16.4] Magnitude of Ks intensity mean
54- 58 F5.3 mag sigma [0.006/0.2] Standard deviation of
the Ks residual
60- 64 F5.1 --- S/N [27/315] Signal-to-noise ratio of
the Ks light-curve
66- 70 F5.3 mag AmpKs [0.07/0.6] Total amplitude in the Ks band
72- 77 F6.3 mag JmagAvg [11.3/19.5] Magnitude of J intensity mean
79- 84 F6.3 mag HmagAvg [11.2/17]? Magnitude of H intensity mean
86- 90 F5.3 mag U1 [0.3/1.2] Amplitude of first Ks principal
component
92- 97 F6.3 mag U2 [-0.5/0.7] Amplitude of second Ks principal
component
99-104 F6.3 mag U3 [-0.2/0.2] Amplitude of third Ks principal
component
106-111 F6.3 mag U4 [-0.1/0.2] Amplitude of fourth Ks principal
component
113-117 F5.2 --- [Fe/H]Ks [-3.4/-0.01] Metallicity predicted
from Ks light-curve
119-123 F5.3 mag E(J-Ks) [0/6.3] J-Ks color excess
125-129 F5.2 kpc Dist [0.7/18.6] Heliocentric distance
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Seq [1/1892] Identifier
6- 7 A2 --- Filt Filter of the VISTA photometric system
9- 20 F12.6 d JD [55226.7/57248.6] Heliocentric Julian Date;
JD-2455000
22- 27 F6.3 mag mag [10.6/19.5] Apparent magnitude in Filt
29- 33 F5.3 mag e_mag [0.01/1] Error in mag (1)
35- 39 F5.3 mag ZPErr [0.01/1] Magnitude zero-point error
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Note (1): Includes photometric and zero-point errors.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 19-Feb-2019