J/AJ/153/204 RR Lyrae stars from the PS1 3π survey (Sesar+, 2017)
Machine-learned identification of RR Lyrae stars from sparse, multi-band data:
the PS1 sample.
Sesar B., Hernitschek N., Mitrovic S., Ivezic Z., Rix H.-W., Cohen J.G.,
Bernard E.J., Grebel E.K., Martin N.F., Schlafly E.F., Burgett W.S.,
Draper P.W., Flewelling H., Kaiser N., Kudritzki R.P., Magnier E.A.,
Metcalfe N., Tonry J.L., Waters C.
<Astron. J., 153, 204-204 (2017)>
=2017AJ....153..204S 2017AJ....153..204S (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Photometry, ugriz ; Reddening ; Surveys
Keywords: catalogs; Galaxy: halo; methods: data analysis; methods: statistical;
stars: variables: RR Lyrae; surveys
Abstract:
RR Lyrae stars may be the best practical tracers of Galactic halo
(sub-)structure and kinematics. The PanSTARRS1 (PS1) 3π survey
offers multi-band, multi-epoch, precise photometry across much of the
sky, but a robust identification of RR Lyrae stars in this data set
poses a challenge, given PS1's sparse, asynchronous multi-band light
curves (≲12 epochs in each of five bands, taken over a 4.5yr period).
We present a novel template fitting technique that uses well-defined
and physically motivated multi-band light curves of RR Lyrae stars,
and demonstrate that we get accurate period estimates, precise to 2s
in >80% of cases. We augment these light-curve fits with other
features from photometric time-series and provide them to progressively
more detailed machine-learned classification models. From these
models, we are able to select the widest (three-fourths of the sky)
and deepest (reaching 120kpc) sample of RR Lyrae stars to date. The
PS1 sample of ∼45000 RRab stars is pure (90%) and complete (80% at
80kpc) at high galactic latitudes. It also provides distances that are
precise to 3%, measured with newly derived period-luminosity relations
for optical/near-infrared PS1 bands. With the addition of proper
motions from Gaia and radial velocity measurements from multi-object
spectroscopic surveys, we expect the PS1 sample of RR Lyrae stars to
become the premier source for studying the structure, kinematics, and
the gravitational potential of the Galactic halo. The techniques
presented in this study should translate well to other sparse,
multi-band data sets, such as those produced by the Dark Energy Survey
and the upcoming Large Synoptic Survey Telescope Galactic plane
sub-survey.
Description:
Building on the work by Hernitschek+ (2016, J/ApJ/817/73), in this
paper, we use the final PS1 data release (PV3) to significantly
increase the completeness and purity of the PS1 sample of RR Lyrae
stars.
Pan-STARRS1 (PS1; Kaiser+ 2010, see II/349) is a wide-field
optical/near-IR survey telescope system located at the Haleakala
Observatory on the island of Maui in Hawai'i. The largest survey
undertaken by the telescope, the PS1 3π survey (Chambers K.C. 2011,
BAAS, 43, 113.01), has observed the entire sky north of decl. -30°
in five filter bands, reaching 5σ single-epoch depths of about
22.0, 22.0, 21.9, 21.0, and 19.8mag in gP1, rP1, iP1, zP1, and
yP1 bands, respectively. The uncertainty in photometric calibration
of the survey is ≲0.01mag, and the astrometric precision of
single-epoch detections is 10mas.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 14 100 Expected RRab selection purity and completeness
at ∼80kpc ( ∼20mag)
table3.dat 14 100 Expected RRab selection purity and completeness
at ∼40kpc ( ∼18.5mag)
table4.dat 14 100 Expected RRc selection purity and completeness
at ∼40kpc ( ∼18.5mag)
table5.dat 166 239044 PS1 catalog of RR Lyrae stars
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See also:
B/gcvs : General Catalogue of Variable Stars (Samus+ 2007-2013)
VII/202 : Globular Clusters in the Milky Way (Harris, 1997)
II/349 : Pan-STARRS release 1 (PS1) Survey - DR1 (Chambers+, 2016)
I/343 : Gaia-PS1-SDSS (GPS1) proper motion catalog (Tian+, 2017)
J/AJ/127/1158 : QUEST RR Lyrae Survey first catalog (Vivas+, 2004)
J/AJ/127/861 : RR Lyrae in Draco dSph (Bonanos+, 2004)
J/AJ/132/714 : QUEST RR Lyrae survey. II. Halo overdensities (Vivas+, 2006)
J/MNRAS/371/1503 : Synthetic photometry of RR Lyr (Marconi+, 2006)
J/ApJ/678/851 : RR Lyrae survey in the Galactic Halo (Keller+, 2008)
J/AJ/136/1645 : Spectroscopy of bright QUEST RR Lyrae stars (Vivas+, 2008)
J/AJ/136/1921 : Variable stars of Draco dSph (Kinemuchi+, 2008)
J/ApJ/678/865 : LONEOS-I RR Lyrae stars (Miceli+, 2008)
J/ApJ/708/717 : Light curve templates of RR Lyrae stars (Sesar+, 2010)
J/AJ/142/187 : HST obs. of 7 Pop.II variable stars (Benedict+, 2011)
J/MNRAS/414/2602 : Automated classification of HIP variables (Dubath+, 2011)
J/ApJ/733/46 : Velocity measurements in Segue 1 (Simon+, 2011)
J/AJ/144/114 : Radial velocities of 6 field RR Lyrae (Sesar+, 2012)
J/MNRAS/424/2528 : RR Lyrae in SDSS Stripe 82 (Suveges+, 2012)
J/ApJ/750/99 : The Pan-STARRS1 photometric system (Tonry+, 2012)
J/ApJ/763/32 : Galactic halo RRab stars from CSS (Drake+, 2013)
J/ApJ/776/26 : RRab stars in the Orphan stream distances (Sesar+, 2013)
J/ApJ/781/22 : La Silla QUEST RR Lyrae star survey (Zinn+, 2014)
J/ApJ/793/135 : Positions and distances of RR Lyrae stars (Sesar+, 2014)
J/ApJ/809/59 : Ophiuchus stellar stream with PS1 data (Sesar+, 2015)
J/ApJ/811/30 : Machine learning metallicity predictions (Miller, 2015)
J/ApJ/817/73 : QSOs & RR Lyrae in PS1 3π data (Hernitschek+ 2016)
J/ApJ/844/L4 : PS1 RRab stars for tracing outer VOD (Sesar+, 2017)
Byte-by-byte Description of file: table[234].dat
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Bytes Format Units Label Explanations
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1- 4 F4.2 --- Thrsh [0/1] Threshold on Score3 (ab or c)
6- 9 F4.2 --- Pur [0.3/1] Purity
11- 14 F4.2 --- Comp [0.04/1] Completeness
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension in decimal degrees (J2000)
11- 19 F9.5 deg DEdeg Declination in decimal degrees (J2000)
21- 24 F4.2 --- S3ab [0/1] Final RRab classification score
26- 29 F4.2 --- S3c [0/1] Final RRc classification score
31- 37 F7.2 mag DM [-206.3/21.2] Distance modulus (1)
39- 50 F12.10 d Per [0.19/0.9] Period
52- 59 F8.5 --- phi0 [-0.5/0.5] Phase offset φ0 (2)
61- 64 F4.2 mag gAmp [0.1/2] Best-fit g band amplitude (3)
66- 69 F4.2 mag rAmp [0.1/1.6] Best-fit r band amplitude (3)
71- 74 F4.2 mag iAmp [0.08/1.3] Best-fit i band amplitude (3)
76- 79 F4.2 mag zAmp [0.08/1.1] Best-fit z band amplitude (3)
81- 87 F7.2 mag gmag [-207.3/21.1] Best-fit g band magnitude
at φ=0 (4)
89- 95 F7.2 mag rmag [-207/21] Best-fit r band magnitude
at φ=0 (4)
97-103 F7.2 mag imag [-206.8/21.1] Best-fit i band magnitude
at φ=0 (4)
105-111 F7.2 mag zmag [-206.7/21.1] Best-fit z band magnitude
at φ=0 (4)
113-115 I3 --- Tg [0/120]? Best-fit g band template ID number (5)
117-119 I3 --- Tr [0/119]? Best-fit r band template ID number (5)
121-123 I3 --- Ti [0/119]? Best-fit i band template ID number (5)
125-127 I3 --- Tz [0/117]? Best-fit z band template ID number (5)
129-135 F7.2 mag [-205.7/21.7] Flux-averaged g band magnitude (4)
137-143 F7.2 mag [-206/21.5] Flux-averaged r band magnitude (4)
145-151 F7.2 mag [-206/21.4] Flux-averaged i band magnitude (4)
153-159 F7.2 mag [-206/21.4] Flux-averaged z band magnitude (4)
161-166 F6.3 mag E(B-V) [0/99.8] Adopted reddening (6)
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Note (1): Calculated using the flux-averaged iP1-band magnitude and
Equation 5. The uncertainty in distance modulus is
0.06(rnd)±0.03(sys) mag for RRab stars. This distance modulus
may be biased and more uncertain for RRc stars.
Note (2): Assuming a period of P days and a phase offset φ0, we calculate
the phase of each PS1 observation epoch as Equation (2):
φ(t|P,φ0)=(t-2400000)moduloP/P+φ0
where the time of observation t is in units of heliocentric Julian
days, and -0.5≤φ0<0.5. The purpose of the phase offset φ0
is to make sure the maximum light of the best-fit multi-band template
occurs at φ=0. See section 3.2.
Note (3): See Equation 1:
g(φ)=FAgTg(φ)+g0-r0+r'
r(φ)=FArTr(φ)+r'
i(φ)=FAiTi(φ)+i0-r0+r'
z(φ)=FAzTz(φ)+z0-r0+r'
where Tm(φ) is the best-fit template light curve, Am is the
(known and fixed) amplitude of this template, and m0 is the (known
and fixed) best-fit magnitude at peak brightness (i.e., at φ=0) in
the m=g,r,i,z band of the kth RR Lyrae star in SDSS Stripe 82 (see
Table 2 of Sesar+ 2010, J/ApJ/708/717 for values of Am and m0).
The free parameter F allows the amplitudes of model griz light curves
to vary by up to 20% from their original values (which are listed in
Table 2 of Sesar+ 2010, J/ApJ/708/717).
See section 3.2 for further explanations.
Note (4): Corrected for dust extinction using extinction coefficients of
Schlafly & Finkbeiner (2011ApJ...737..103S 2011ApJ...737..103S) and the dust map
of Schlafly+ (2014ApJ...789...15S 2014ApJ...789...15S)
(e.g., g'=g0-r0+r'); see Equation 1).
Note (5): See Section 3.1 and Table 2 of Sesar+ 2010, J/ApJ/708/717
Note (6): From the Schlafly+ (2014ApJ...789...15S 2014ApJ...789...15S) dust map.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 16-Apr-2018