J/A+A/689/A240 VVV catalog and light curves of bulge RRab Lyrae (Zoccali+, 2024)
VVV catalog of ab-type RR Lyrae in the inner Galactic bulge
Zoccali M., Quezada C., Contreras Ramos R., Valenti E.,
Valenzuela-Navarro A., Olivares Carvajal J., Rojas Arriagada A.,
Minniti J.H., Gran F., De Leo M.
<Astron. Astrophys. 689, A240 (2024)>
=2024A&A...689A.240Z 2024A&A...689A.240Z (SIMBAD/NED BibCode)
ADC_Keywords: Stars, horizontal branch ; Stars, variable ;
Photometry, infrared ; Photometry, classification
Keywords: stars: variables: RR Lyrae - Galaxy: bulge - Galaxy: formation -
Galaxy: structure
Abstract:
Observational evidence has accumulated in recent years, showing that
the Galactic bulge includes two populations, a metal-poor one and a
metal-rich one, which in addition to having different metallicities
show different alpha over iron abundances, spatial distribution, and
kinematics. While the metal-rich, barred component has been fairly
well characterized, the metal-poor, spheroidal component has been more
elusive and harder to describe. RR Lyrae variables are clean tracers
of the old bulge component, and they are, on average, more metal-poor
than red clump stars.
In the present paper, we provide a new catalog of 16488 ab-type RR
Lyrae variables in the bulge region within |l|<10 and |b|<2.8,
extracted from multi-epoch Point Spread Function photometry performed
on VISTA Variable in the Via Lactea survey data. We used the catalog
to constrain the shape of the old, metal-poor, bulge stellar
population.
The identification of ab-type RR Lyrae among a large sample of
candidate variables of different types has been performed via a
combination of a Random Forest classifier and visual inspection. We
optimized this process in such a way to extract a clean catalog with
high purity, although for this reason its completeness, close to the
midplane, is lower compared to a few other near-infrared catalogs
covering the same region of the sky.
We used the present catalog to derive the shape of their distribution
around the Galactic center, resulting in an elongated spheroid with
projected axis ratio of b/a∼0.7 and an inclination angle of φ∼20
degrees. We discuss how observational biases, such as errors on the
distances and a nonuniform sampling in longitude, affect both the
present measurements and previous ones, especially those based on red
clump stars. Because the latter have not been taken into account
before, we refrain from a quantitative comparison between these shape
parameters and those derived for the main Galactic bar. Nonetheless,
qualitatively, taking into account observational biases would lower
the estimated ellipticity of the bar derived from red clump stars, and
hence reduce the difference with the present results.
We publish a high-purity RRab sample for future studies of the oldest
Galactic bulge population, close to the midplane. We explore different
choices for the period-luminosity-metallicity relation, highlighting
how some of them introduce spurious trends of distance with either the
period or the metallicity, or both. We provide evidence that they
trace a structure that is less elongated than the main bar, though we
also highlight some biases of these kind of studies not discussed
before.
Description:
The catalog of RRL presented here is based on PSF-fitting photometry
performed on multi-epoch near-IR data from the VVV ESO Public Survey.
Coordinates, mean magnitudes, E(J-K) reddening, photometric
metallicities, distances and Ks-band light curves for a sample of
12965 ab-type RR Lyrae in the inner Galactic bulge. The catalog
includes another 3523 from the OGLE-IV survey, for which we provide
parameters but not light curves.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 191 16488 Catalog of ab-type RR Lyrae within
|l|<10 and |b|<2.8 (catalog))
features.dat 359 12965 Features used by the Random Forest classifier
postfeat.dat 107 12965 Post-Random-Forest classification features
lc/* . 12965 Individual light curves
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See also:
II/376 : VISTA Variable in the Via Lactea Survey (VVV) DR4.2
(Minniti+, 2023)
J/AcA/69/321 : OGLE RR Lyrae stars in Galactic bulge & disk (Soszynski+, 2019)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- ID Star ID (bNNNNNNNNNNN)
17- 25 F9.5 deg GLON [] Galactic longitude
27- 34 F8.5 deg GLAT Galactic latitude
36- 42 F7.3 mag Kmag K band magnitude
44- 49 F6.3 mag e_Kmag Error in K band magnitude
51- 57 F7.3 mag Jmag ?=- J band magnitude
59- 64 F6.3 mag e_Jmag ?=- Error in J band magnitude
66- 73 F8.4 [-] [Fe/H] Metallicity in dex
76- 81 F6.4 [-] e_[Fe/H] Error in metallicity
83- 89 F7.3 mag E(J-K) ?=- Reddening measured from intrinsic color
91- 97 F7.3 mag e_E(J-K) ?=- Error in reddening
99-106 F8.5 mag Amp Amplitude in magnitude
108-115 F8.3 --- SNR Signal-to-noise ratio
117-125 F9.6 d Per Period
127-130 A4 --- Flag Star origin catalog (OGLE or VVV)
132-138 F7.3 kpc Dist ?=- Distance
140-145 F6.3 kpc e_Dist ?=- Error in distance
147-153 F7.3 kpc X ?=- X coordinate in Cartesian system
155-161 F7.3 kpc Y ?=- Y coordinate in Cartesian system
163-169 F7.3 kpc Z ?=- Z coordinate in Cartesian system
171-181 F11.5 deg RAdeg Right Ascension (J2000)
183-191 F9.5 deg DEdeg Declination (J2000)
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Byte-by-byte Description of file: features.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- ID Star ID (bNNNNNNNNNNN)
17- 19 A3 --- Flag Star origin catalog (VVV)
21- 28 F8.6 d Per2 Second period
30- 35 F6.4 --- A1/A2 Ratio of two amplitudes
37- 42 F6.4 --- ACstd Standard deviation of the light curve's
auto-convolution
44- 50 F7.4 --- AD Anderson-Darling test result
52- 57 F6.4 --- Beyond1Std Percentage of points beyond one standard
deviation from the weighted mean
59- 64 F6.4 --- GPDownRatio Time of descent in phase (Gaussian process)
66- 71 F6.4 --- GPRDRatio Rise to descent ratio
73- 78 F6.4 --- GPRiseRatio Rising time ratio
80- 85 F6.4 --- GPSkew Skewness of the light curve
(Gaussian process)
87- 93 F7.4 --- Rcs Ratio between MAD and Sigma
95-100 F6.4 --- Tm Ratio between minimum-mean difference and
total amplitude
102-108 F7.4 --- A0 Amplitude of the Fourier harmonic 0
110-115 F6.4 --- A1 Amplitude of the Fourier harmonic 1
117-122 F6.4 --- A2 Amplitude of the Fourier harmonic 2
124-129 F6.4 --- A3 Amplitude of the Fourier harmonic 3
131-136 F6.4 --- A4 Amplitude of the Fourier harmonic 4
138-143 F6.4 --- A5 Amplitude of the Fourier harmonic 5
145-150 F6.4 --- A6 Amplitude of the Fourier harmonic 6
152-157 F6.4 --- A7 Amplitude of the Fourier harmonic 7
159-164 F6.4 mag Amp Amplitude of the light curve
166-172 F7.4 --- kurtosis Kurtosis of the magnitude distribution
174-179 F6.4 --- mad Mean absolute deviation
181-187 F7.4 --- mediana Median value of the light curve
189-194 F6.4 --- mpr20 Ratio between magnitude at 60th and 40th
percentile
196-201 F6.4 --- mpr35 Ratio between magnitude at 67th and 32nd
percentile
203-208 F6.4 --- mpr50 Ratio between magnitude at 75th and 25th
percentile
210-215 F6.4 --- mpr65 Ratio between magnitude at 82nd and 17th
percentile
217-222 F6.4 --- mpr80 Ratio between magnitude at 90th and 10th
percentile
224-229 F6.4 --- mv Ratio between Sigma and median magnitude
231-238 F8.4 --- phi1 Phase shift of Fourier harmonic 1
240-247 F8.4 --- phi2 Phase shift of Fourier harmonic 2
249-256 F8.4 --- phi3 Phase shift of Fourier harmonic 3
258-266 F9.4 --- phi4 Phase shift of Fourier harmonic 4
268-276 F9.4 --- phi5 Phase shift of Fourier harmonic 5
278-285 F8.4 --- phi6 Phase shift of Fourier harmonic 6
287-294 F8.4 --- phi7 Phase shift of Fourier harmonic 7
296-301 F6.4 --- sigma Standard deviation of magnitudes
303-309 F7.4 --- skewness Skewness of magnitude distribution
311-317 F7.4 --- slope Slope of linear fit to light curve
319-324 F6.4 --- A21 Amplitude ratio (A2/A1)
326-331 F6.4 --- A31 Amplitude ratio (A3/A1)
333-338 F6.4 --- A41 Amplitude ratio (A4/A1)
340-345 F6.4 --- P21 Phase shift ratio (phi2/phi1)
347-352 F6.4 --- P31 Phase shift ratio (phi3/phi1)
354-359 F6.4 --- P41 Phase shift ratio (phi4/phi1)
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Byte-by-byte Description of file: postfeat.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- ID Star ID (bNNNNNNNNNNN)
17- 19 A3 --- Flag Star origin catalog (VVV)
21- 28 F8.6 d Per2 Second period
30- 35 F6.4 --- postmseRRab Mean square error of the RRab template fit
37- 42 F6.4 --- postmseRRc Mean square error of the RRc template fit
44- 49 F6.4 --- postGPmse Mean square error of the Gaussian Process
51- 56 F6.4 --- postsigma Standard deviation
58- 63 F6.4 --- postrho Correlation coefficient
65- 70 F6.4 --- postGPRiseRatio Ratio of rise time in phase
72- 77 F6.4 --- postGPDownRatio Ratio of descent time in phase
79- 84 F6.4 --- postGPRDRatio Ratio of rise over descent time in phase
86- 91 F6.4 --- postGPSkew Skewness
93- 99 F7.3 --- postSNratio Signal-to-noise ratio
101 I1 --- postNpeaks Number of peaks
103 I1 --- postaliasscore Alias score
105-107 I3 --- postNpoints Number of epochs
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Byte-by-byte Description of file: lc/*
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Bytes Format Units Label Explanations
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1- 12 F12.6 d Date Mean Julian Day (JD-2400000)
17- 25 F9.6 mag Ksmag Ks magnitude
33- 40 F8.6 mag e_Ksmag Ks magnitude error
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Acknowledgements:
Carlos Quezada, ciquezada(at)uc.cl
Manuela Zoccali, mzoccali(at)uc.cl
(End) Patricia Vannier [CDS] 07-Aug-2024