J/MNRAS/510/3575 RR Lyrae study with ZTF DR3 light curves (Huang+, 2022)
Identifying RR Lyrae in the ZTF DR3 data set.
Huang K.-W., Koposov S.E.
<Mon. Not. R. Astron. Soc., 510, 3575-3588 (2022)>
=2022MNRAS.510.3575H 2022MNRAS.510.3575H (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Stars, standard ; Positional data ;
Extinction ; Stars, distances ; Optical ; Infrared ; Photometry
Keywords: catalogues - stars: variables - RR Lyrae - Galaxy: structure
Abstract:
We present an RR Lyrae (RRL) catalogue based on the combination of the
third data release of the Zwicky Transient Facility (ZTF DR3) and Gaia
EDR3. We use a multistep classification pipeline relying on the
Fourier decomposition fitting to the multiband ZTF light curves and
random forest classification. The resulting catalogue contains 71755
RRLs with period and light-curve parameter measurements and has a
completeness of 0.92 and a purity of 0.92 with respect to the Specific
Objects Study Gaia DR2 RRLs. The catalogue covers the Northern sky
with declination => -28°, its completeness is ~> 0.8 for
heliocentric distance ≤ 80 kpc, and the most distant RRL is at 132 kpc.
Compared with several other RRL catalogues covering the Northern sky,
our catalogue has more RRLs around the Galactic halo and is more
complete at low-Galactic latitude areas. Analysing the spatial
distribution of RRL in the catalogue reveals the previously known
major overdensities of the Galactic halo, such as the Virgo
overdensity and the Hercules-Aquila Cloud, with some evidence of an
association between the two. We also analyse the Oosterhoff fraction
differences throughout the halo, comparing it with the density
distribution, finding increasing Oosterhoff I fraction at the
elliptical radii between 16 and 32 kpc and some evidence of different
Oosterhoff fractions across various halo substructures.
Description:
RR Lyrae (RRL) stars are pulsating variables with periodic light
curves of a period ranging from 0.2 to 0.9 d, found primarily in the
horizontal branches of old stellar systems (age >10 Gyr). These old,
metal-poor, bright variable stars follow a well-understood per
luminosity metallicity relation. This relation makes RRLs excellent
distance indicators for old, low-metallicity stellar populations in
the outer halo of the Milky Way. Being beneficial to many Galactic
studies, there have been several RRL catalogues classified from
existing surveys over the years, e.g. SDSS Stripe 82 (Sesar et al.
2010ApJ...708..717S 2010ApJ...708..717S, Cat. J/ApJ/708/717), CRTS (Drake et al.
2014ApJS..213....9D 2014ApJS..213....9D, Cat. J/ApJS/213/9), PS1 (Sesar et al.
2017AJ....153..204S 2017AJ....153..204S, Cat. J/AJ/153/204), nTransits:2 + Gaiadata
release 2 (DR2; Holl et al. 2018A&A...618A..30H 2018A&A...618A..30H), Specific Objects
Study (SOS) Gaia DR2 (Clementini et al. 2019A&A...622A..60C 2019A&A...622A..60C,
Cat. J/A+A/622/A60), ZTF DR2 (Chen et al. 2020ApJS..249...18C 2020ApJS..249...18C,
Cat. J/ApJS/249/18), and DES Y6 (Stringer et al. 2021ApJ...911..109S 2021ApJ...911..109S,
Cat. J/ApJ/911/109). The quality of the catalogues has progressed from
being either deep with limited sky coverage.
In this paper, we utilize the joint set of the Gaia early third DR
(Gaia EDR3; Gaia Collaboration 2021A&A...649A...1G 2021A&A...649A...1G, Cat. I/350) and
the third DR of the Zwicky Transient Facility (ZTF DR3; Masci et al.
2019PASP..131a8003M 2019PASP..131a8003M) to classify RRL stars in the Northern sky. Thanks
to the high angular resolution of Gaia and the fast cadence of ZTF
observations, the sources in the joint set thus have high spatial
resolution and multiband light curves with large observation epochs.
Assisted with the SOS GaiaDR2 RRL catalogue (Clementini et al.
2019A&A...622A..60C 2019A&A...622A..60C, Cat. J/A+A/622/A60) as the label (serves as the
label for training models), we process the data set following the
pipeline we come up with, which includes data labelling, feature
building, and classifier training, to obtain the predicted RRL
catalogue.
As indicated in the section 2 Data sets, besides Gaia EDR3 and ZTF
DR3, we use the SOS Gaia DR2 RRLs as the label for the binary
classification task; we label each source in the joint data set as
true if it is classified as an RRL in the SOS Gaia DR2 RRL catalogue
and as false otherwise. Among the 140784 RRLs in the SOS Gaia DR2 RRL
catalogue, 48365 RRLs have ZTF light curves when cross-matched by the
closest separation within 1 arcsec. With the data set of 600 million
sources in the joint set of Gaia EDR3 and ZTF DR3 and the label of the
SOS Gaia DR2 RRLs, we then proceed to the supervised classification of
RRL candidates through the multistep process summarized and described
in the section 3 The classification pipeline. Thus, section 3.3 the
final classification of RRLs, we build features for the data set of 3
million sources using the parameters obtained by fitting truncated
Fourier Series to each light curve in multiple bands. Then, we train
another random forest classifier to predict the probability of a
source being an RRL and generate a catalogue of 71755 RRLs. Results of
forest classifier and fourier Series fitting are provided in the
table4.dat.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 443 71755 RR Lyrae ZTF/Gaia catalogue
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See also:
J/ApJ/708/717 : Light curve templates of RR Lyrae stars (Sesar+, 2010)
J/ApJS/213/9 : Catalina Surveys periodic variable stars (Drake+, 2014)
J/AJ/153/204 : RR Lyrae stars from the PS1 3π survey (Sesar+, 2017)
J/A+A/622/A60 : Gaia DR2 misclassified RR Lyrae list (Clementini+, 2019)
J/ApJS/249/18 : The ZTF catalog of periodic variable stars (Chen+, 2020)
J/ApJ/911/109 : RR Lyrae variable stars in DES Y6 (Stringer+, 2021)
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
J/A+A/622/A60 : Gaia DR2 misclassified RR Lyrae list (Clementini+, 2019)
Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 16 I16 --- ZTFDR3 Object identifier number for ZTF DR3 (objid)
18- 36 I19 --- GaiaEDR3 Unique source identifier number from GaiaEDR3
(source_id)
38- 57 F20.16 deg RAdeg Right ascension (J2000) (ra)
59- 80 F22.18 deg DEdeg Declination (J2000) (dec)
82- 85 F4.2 --- ProbRRL Predicted probability for being an RRL as
explained in the section 3.3 The final RRL
classification step (prob_rrl)
87- 94 F8.6 d Pbest Best-fitting period P as 2π/ω
(best_period)
96-106 F11.8 mag E(B-V) Extinction E(B-V) (ebv)
108-120 E13.11 pc D* Heliocentric distance (distance)
122-131 F10.7 mag gmag ? Mean ZTF-g DR3 magnitude (mean_g)
133-142 F10.7 mag rmag ? Mean ZTF-r DR3 magnitude (mean_r)
144-153 F10.7 mag imag ? Mean ZTF-i DR3 magnitude (mean_i)
155-162 F8.5 mag Gmag ? Gaia EDR3 mean G magnitude (photgmean_mag)
164-176 F13.11 mag A1r ? First Fourier amplitude in ZTF-r light curve
(amp1r) (1)
178-192 F15.12 rad Phi1r ? First Fourier phase in ZTF-r light curve
(phi1r) (1)
194-206 F13.11 mag A1g ? First Fourier amplitude in ZTF-g light curve
(amp1g) (1)
208-221 F14.11 rad Phig ? First Fourier phase in ZTF-g light curve
(phi1g) (1)
223-234 F12.10 mag A1i ? First Fourier amplitude in ZTF-i light curve
(amp1i) (1)
236-249 F14.11 rad Phi1i ? First Fourier phase in ZTF-i light curve
(phi1i) (1)
251-263 F13.11 mag A2r ? Second Fourier amplitude in ZTF-r light
curve (amp2r) (1)
265-279 F15.12 rad Phi2r ? Second Fourier phase in ZTF-r light curve
(phi2r) (1)
281-293 F13.11 mag A2g ? Second Fourier amplitude in ZTF-g light
curve (amp2g) (1)
295-309 F15.12 rad Phi2g ? Second Fourier phase in ZTF-g light curve
(phi2g) (1)
311-323 F13.11 mag A2i ? Second Fourier amplitude in ZTF-i light
curve (amp2i) (1)
325-338 F14.11 rad Phi2i ? Second Fourier phase in ZTF-i light curve
(phi2i) (1)
340-353 F14.12 mag A3r ? Third Fourier amplitude in ZTF-r light curve
(amp3r) (1)
355-370 F16.13 rad Phi3r ? Third Fourier phase in ZTF-r light curve
(phi3r) (1)
372-384 F13.11 mag A3g ? Third Fourier amplitude in ZTF-g light curve
(amp3g) (1)
386-400 F15.12 rad Phi3g ? Third Fourier phase in ZTF-g light curve
(phi3g) (1)
402-414 F13.11 mag A3i ? Third Fourier amplitude in ZTF-i light curve
(amp3i) (1)
416-430 F15.12 rad Phi3i ? Third Fourier phase in ZTF-i light curve
(phi3i) (1)
432-435 I4 --- Ng Number of ZTF detection epoch ideal to fit the
light curve in ZTF-g (ngooddet_g)
437-440 I4 --- Nr Number of ZTF detection epoch ideal to fit the
light curve in ZTF-r (ngooddet_r)
442-443 I2 --- Ni Number of ZTF detection epoch ideal to fit the
light curve in ZTF-i (ngooddet_i)
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Note (1): As detailed in the dedicated section 3.3.1 Fourier Series fitting.
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History:
From electronic version of the journal
(End) Luc Trabelsi [CDS] 03-Dec-2024