J/ApJ/883/58 Cepheids from VVV in the southern Galactic midplane (Dekany+, 2019)
Into the darkness: classical and Type II Cepheids in the Zona Galactica
Incognita.
Dekany I., Hajdu G., Grebel E.K., Catelan M.
<Astrophys. J., 883, 58 (2019)>
=2019ApJ...883...58D 2019ApJ...883...58D
ADC_Keywords: Stars, variable; Photometry, infrared; Surveys; Galactic plane;
Extinction; Stars, distances
Keywords: Surveys ; Catalogs ; Milky Way disk ; Interstellar extinction ;
Delta Cepheid variable stars ; Population II Cepheid variable stars ;
Galactic bulge
Abstract:
The far side of the Milky Way's disk is one of the most concealed
parts of the known universe due to extremely high interstellar
extinction and point-source density toward low Galactic latitudes.
Large time-domain photometric surveys operating in the near-infrared
hold great potential for the exploration of these vast uncharted areas
of our Galaxy. We conducted a census of distant classical and type II
Cepheids along the southern Galactic midplane using near-infrared
photometry from the VISTA Variables in the Via Lactea survey. We
performed a machine-learned classification of the Cepheids based on
their infrared light curves using a convolutional neural network. We
have discovered 640 distant classical Cepheids with up to ∼40mag of
visual extinction and over 500 type II Cepheids, most of them located
in the inner bulge. Intrinsic color indices of individual Cepheids
were predicted from sparse photometric data using a neural network,
allowing their use as accurate reddening tracers. They revealed a
steep, spatially varying near-infrared extinction curve toward the
inner bulge. Type II Cepheids in the Galactic bulge were also employed
to measure robust mean selective-to-absolute extinction ratios. They
trace a centrally concentrated spatial distribution of the old bulge
population with a slight elongation, consistent with earlier results
from RR Lyrae stars. Likewise, the classical Cepheids were utilized to
trace the Galactic warp and various substructures of the Galactic disk
and uncover significant vertical and radial age gradients of the thin
disk population at the far side of the Milky Way.
Description:
Our study is based on photometric time series of low Galactic latitude
regions acquired by the the VISTA Variables in the Via Lactea (VVV;
Minniti+ 2010NewA...15..433M 2010NewA...15..433M) ESO Public survey in the near-IR JHKs
passbands of the VISTA system. Our target area is a combination of
those of our earlier studies (Dekany+ 2015ApJ...812L..29D 2015ApJ...812L..29D and
2018, J/ApJ/857/54), namely, the VVV's entire ∼4° wide disk
footprint along the Galactic equator and an ∼3° wide adjacent area
toward the inner bulge.
Each VVV field was observed at 50-100 epochs in the Ks band with a
nonuniform, space-varying cadence and a total baseline of ∼5yr and at
1-10 epochs in the J and H bands.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 56 544 Classifier training set of classical and
type II Cepheids
table4.dat 94 1294 Coordinates, classes, basic photometric properties,
and cross-identifications of the Cepheids
table5.dat 39 188340 Photometric time-series of the 1294 Cepheids
table7.dat 34 1294 Mean color indices of the Cepheids
table8.dat 77 1294 Heliocentric distances and Ks-band interstellar
extinctions of the Cepheids
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See also:
B/vsx : AAVSO International Variable Star Index VSX (Watson+, 2006-2014)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
II/337 : VISTA Variables in the Via Lactea Survey DR1 (Saito+, 2012)
I/349 : StarHorse, Gaia DR2 photo-astrometric distances (Anders+, 2019)
II/364 : VIRAC. The VVV Infrared Astrometric Catalogue (Smith+, 2019)
II/366 : ASAS-SN catalog of variable stars (Jayasinghe+, 2018-2020)
J/A+A/397/133 : Star-forming complexes in the Galaxy (Russeil+, 2003)
J/AJ/128/2239 : JHKs photometry of 92 LMC Cepheids (Persson+, 2004)
J/MNRAS/370/1979 : JHKs phot. of T2Cs in globular clusters (Matsunaga+, 2006)
J/A+A/475/1159 : Supervised classif. of variable stars (Debosscher+, 2007)
J/ApJS/193/12 : JHK photometry of Northern Galactic Cepheids (Monson+, 2011)
J/ApJS/203/32 : Machine-learned ASAS Classif. Cat. (MACC) (Richards+, 2012)
J/MNRAS/434/2238 : Cepheids in open clusters (Anderson+, 2013)
J/MNRAS/432/3349 : Galactic star clusters structural param. (Camargo+, 2013)
J/MNRAS/429/385 : Short-period variables near the GC (Matsunaga+, 2013)
J/A+A/566/A37 : Iron abundances for 42 Galactic Cepheids (Genovali+, 2014)
J/A+A/569/A125 : Spiral structure of the Milky Way (Hou+, 2014)
J/A+A/584/A2 : KMOS view of the Gal. centre. I. (Feldmeier-Krause+, 2015)
J/A+A/576/A30 : NIR LC templates for classical Cepheids (Inno+, 2015)
J/AJ/149/117 : LMC infrared survey. I. Phot. of Cepheids (Macri+, 2015)
J/AcA/65/297 : OGLE4 LMC and SMC Cepheids (Soszynski+, 2015)
J/AJ/153/154 : LMC NIR survey. IV. Type II Cepheids (Bhardwaj+, 2017)
J/A+A/605/A100 : VVV survey Galactic Bulge Pop. II Cepheids (Bhardwaj+, 2017)
J/AcA/67/297 : OGLE Galactic center Cepheids & RR Lyrae (Soszynski+, 2017)
J/A+A/619/A51 : Type II Cepheids in the Galactic bulge (Braga+, 2018)
J/ApJS/237/28 : WISE catalog of periodic variable stars (Chen+, 2018)
J/ApJ/857/54 : JHKs photometry of VVV RR Lyrae stars (Dekany+, 2018)
J/AJ/156/171 : Cepheid abund.: multiphase results & gradients (Luck, 2018)
J/AcA/68/315 : OGLE Galactic Cepheids (Udalski+, 2018)
J/A+A/616/L15 : Parallaxes and Proper Motions of OB stars (Xu+, 2018)
J/A+A/625/A14 : Reclassification of Cepheids in the Gaia DR2 (Ripepi+, 2019)
J/other/Sci/365.478 : Milky Way classical Cepheids sample (Skowron+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- Name Object identifier
21- 28 F8.5 d Period [3.82/39.3] Pulsation period
30- 34 F5.3 mag TotAmp [0.08/1.7] Total (peak-to-valley) amplitude
of light curve
36- 40 A5 --- Type Cepheid type (1)
42- 48 A7 --- RefPer Reference code for the period (2)
50- 56 A7 --- RefLC Reference code for the light curve (2)
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Note (1): Type as follows:
DCEP = classical Cepheid (188 occurrences)
T2CEP = type II Cepheid (356 occurrences)
Note (2): Reference code as follows:
MP11 = Monson & Pierce, 2011, J/ApJS/193/12
P04 = Persson et al., 2004, J/AJ/128/2239
OGLE-IV = Soszynski et al., 2017, J/AcA/67/297
I18 = Ita et al. 2018MNRAS.481.4206I 2018MNRAS.481.4206I
LS92 = Laney & Stobie 1992A&AS...93...93L 1992A&AS...93...93L
W84 = Welch et al. 1984ApJS...54..547W 1984ApJS...54..547W
B97 = Barnes et al. 1997PASP..109..645B 1997PASP..109..645B
VVV = this study;
opt = period computed from a compilation of optical data.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Seq [1/1294] Object identifier
6- 7 I2 h RAh [11/18] Hour of Right ascension (ICRS)
9- 10 I2 min RAm Minute of Right ascension (ICRS)
12- 16 F5.2 s RAs Second of Right ascension (ICRS)
18 A1 --- DE- [-] Sign of the Declination (ICRS)
19- 20 I2 deg DEd [19/64] Degree of Declination (ICRS)
22- 23 I2 arcmin DEm Arcminute of Declination (ICRS)
25- 28 F4.1 arcsec DEs Arcsecond of Declination (ICRS)
30 I1 --- Class [1/2] Classification (G1)
32- 39 F8.5 d Period [3.8/40] Pulsation period
41- 46 F6.3 mag Ksmag [10.5/16.1] Magnitude of intensity mean in
VISTA Ks-band
48 I1 --- Ap [1/5] Optimal photometric aperture;
see Sect. 3.2
50- 54 F5.1 --- SNR [60.2/720] Signal-to-noise ratio in Ks-band
light curve
56- 60 F5.3 mag TotAmp [0.095/1.61] Total (peak-to-valley) amplitude
of Ks-band light curve
62- 94 A33 --- OID Cross-references (1)
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Note (1): The references "D15-X" and "M16-X" indicated source "X" in the
articles D15 (Dekany+ 2015ApJ...812L..29D 2015ApJ...812L..29D ; <[DMM2015] NN> in Simbad)
and M16 (Matsunaga+ 2016MNRAS.462..414M 2016MNRAS.462..414M ; <[MFB2016] NN> in Simbad),
respectively.
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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- 4 I4 --- Seq [1/1294] Object identifier
6- 7 A2 --- Filt VISTA photometric passband
9- 20 F12.6 d HJD [55244.8/57637.6] Observation day; HJD-2400000.0
22- 27 F6.3 mag mag [10.17/19.8] Apparent magnitude in Filt
29- 33 F5.3 mag e_mag [0.001/0.8] Statistical error in mag
35- 39 F5.3 mag ZP [0.01/0.8] Zero point error in apparent magnitude
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Byte-by-byte Description of file: table7.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Seq [1/1294] Object identifier
6- 6 I1 --- Class [1/2] Classification (G1)
8- 12 F5.3 mag J-Ks [0.018/7.514]? Mean VISTA J-Ks color index
14- 18 F5.3 mag e_J-Ks [0.013/5.724]? Total error in <J-Ks>
20- 20 I1 --- nJep [0/6] Number of J epochs used
22- 26 F5.3 mag H-Ks [0.15/3.915]? Mean VISTA H-Ks color index
28- 32 F5.3 mag e_H-Ks [0.01/0.678]? Total error in <H-Ks>
34- 34 I1 --- nHep [0/5] Number of H epochs used
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Byte-by-byte Description of file: table8.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Seq [1/1294] Object identifier
6 I1 --- Class [1/2] Classification (G1)
8- 13 F6.2 kpc d(JK) [1.79/166]? Heliocentric distance based on
J,Ks photometry
15- 18 F4.2 kpc e_d(JK) [0/3.8]? Statistical error in d (JK)
20- 23 F4.2 kpc s_d(JK) [0.1/4.3]? Systematic error in d (JK)
25- 29 F5.3 mag AK(JK) [0.16/3.8]? Absolute Ks-band extinction based
on J,Ks photometry
31- 35 F5.3 mag e_AK(JK) [0.007/0.5]? Statistical error in AK (JK)
37- 41 F5.3 mag s_AK(JK) [0.006/0.2]? Systematic error in AK (JK)
43- 48 F6.2 kpc d(HK) [1.94/180]? Heliocentric distance based on
H,Ks photometry
50- 54 F5.2 kpc e_d(HK) [0.04/32]? Statistical error in d (HK)
56- 59 F4.2 kpc s_d(HK) [0/8]? Systematic error in d (HK)
61- 65 F5.3 mag AK(HK) [0.09/5.8]? Absolute Ks-band extinction based
on H,Ks photometry
67- 71 F5.3 mag e_AK(HK) [0.015/1]? Statistical error in AK (HK)
73- 77 F5.3 mag s_AK(HK) [0.011/0.3]? Systematic error in AK (HK)
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Global notes:
Note (G1): Classification code as follows:
1 = classical Cepheid (689 occurrences);
2 = type II Cepheid (605 occurrences).
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 03-Mar-2021