J/ApJ/926/78 Variable stars in the Ant 2 satellite galaxy (Vivas+, 2022)
Variable stars in the giant satellite galaxy Antlia 2.
Vivas A.K., Martinez-Vazquez C.E., Walker A.R., Belokurov V., Li T.S.,
Erkal D.
<Astrophys. J., 926, 78 (2022)>
=2022ApJ...926...78V 2022ApJ...926...78V
ADC_Keywords: Stars, variable; Photometry, VRI; Stars, distances
Keywords: RR Lyrae variable stars ; Dwarf galaxies ; Local Group ;
Anomalous Cepheid variable stars
Abstract:
We report 350 pulsating variable stars found in four DECam fields
(∼12deg2) covering the Antlia 2 satellite galaxy. The sample of
variables includes 318 RR Lyrae stars and eight anomalous Cepheids in
the galaxy. Reclassification of several objects designated previously
to be RR Lyrae as anomalous Cepheids get rid of the satellite's stars
intervening along the line of sight. This in turn removes the need for
prolific tidal disruption of the dwarf, in agreement with the recently
updated proper motion and pericenter measurements based on Gaia EDR3.
There are also several bright foreground RR Lyrae stars in the field,
and two distant background variables located ∼45kpc behind Antlia 2.
We found RR Lyrae stars over the full search area, suggesting that the
galaxy is very large and likely extends beyond our observed area. The
mean period of the RRab in Antlia 2 is 0.599 days, while the RRc have
a mean period of 0.368 days, indicating the galaxy is an
Oosterhoff-intermediate system. The distance to Antlia 2 based on the
RR Lyrae stars is 124.1kpc (µ0=20.47) with a dispersion of
5.4kpc. We measured a clear distance gradient along the semimajor axis
of the galaxy, with the southeast side of Antlia 2 being ∼13kpc
farther away from the northwest side. This elongation along the line
of sight is likely due to the ongoing tidal disruption of Ant 2.
Description:
The Ant 2 observations presented here were collected using DECam on
the Victor M. Blanco 4m telescope at the Cerro Tololo Inter-American
Observatory, Chile, on two part nights in 2018 November and December,
and two full nights in 2019 January.
We decided to observe in the r and i filters, with exposures of
180 and 240s, respectively.
We used four pointings, almost nonoverlapping, to cover the galaxy
(see Figure 2).
Objects:
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RA (ICRS) DE Designation(s)
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09 35 32.83 -36 46 02.2 Antlia 2 = NAME Ant 2 dSph
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 79 350 Periodic variable stars in the field of Ant 2
table6.dat 34 22615 Time series photometry of variable stars in the
field of view of Ant 2
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See also:
J/AJ/110/2166 : Variables in Sextans dSph galaxy (Mateo+ 1995)
J/AJ/136/1921 : Variable stars of Draco dSph (Kinemuchi+, 2008)
J/AJ/139/2014 : BV light curves of 11 RR Lyrae (Kinman+, 2010)
J/ApJ/708/717 : Light curve templates of RR Lyrae stars (Sesar+, 2010)
J/ApJ/756/108 : HST VI phot. of variable stars in Leo T (Clementini+, 2012)
J/AJ/144/4 : Dwarf galaxies in the Local Group (McConnachie+, 2012)
J/AJ/146/141 : BV photometry of dwarf Cepheids in Carina (Vivas+, 2013)
J/ApJS/213/9 : Catalina Surveys periodic variable stars (Drake+, 2014)
J/ApJ/814/71 : Carina project IX: UBVI data of Carina var. (Coppola+, 2015)
J/ApJ/833/167 : PAndAS view of Andromeda satellites. II. (Martin+, 2016)
J/MNRAS/462/4349 : Variable stars in Sculptor dSph (Martinez-Vazquez+, 2016)
J/ApJ/850/137 : ISLAndS project. III. Var. stars (Martinez-Vazquez+, 2017)
J/AJ/154/199 : SMASH: the MAgellanic Stellar History (Nidever+, 2017)
J/ApJ/855/43 : Distant RR Lyrae stars discovered with HiTS (Medina+, 2018)
J/A+A/622/A60 : Gaia DR2 misclassified RR Lyrae list (Clementini+, 2019)
J/MNRAS/488/2743 : Giant Gal. dwarf satellite in Gaia DR2 (Torrealba+, 2019)
J/AJ/157/35 : Pulsating variable stars in Sextans (Vivas+, 2019)
J/ApJ/893/47 : MW satellite census. I. DES & PS1 (Drlica-Wagner+, 2020)
J/MNRAS/492/1061 : A DECam view of Crater II - Variable stars (Vivas+, 2020)
J/ApJ/921/32 : Kinematics of Ant2 & Cra2 with S5 & Gaia (Ji+, 2021)
J/ApJ/911/149 : Spectroscopic obs. in ATLAS & Aliqa Uma streams (Li+, 2021)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- ID Identification number (VNNN)
6- 14 F9.5 deg RAdeg [141.7/145.7] Right Ascension (J2000)
16- 24 F9.5 deg DEdeg [-39.2/-34.3] Declination (J2000)
26- 32 F7.5 d Per [0.2/2.8] Period
34- 35 I2 --- o_rmag [12/68] Number of rmag observations
37- 40 F4.2 mag ramp [0.19/1.3] The r-band amplitude
42- 46 F5.2 mag rmag [17/22.1] Mean CTIO/DECam magnitude in r band
48- 49 I2 --- o_imag [12/67] Number of imag observations
51- 54 F4.2 mag iamp [0.14/0.92] The i-band amplitude
56- 60 F5.2 mag imag [16.9/22] Mean CTIO/DECam magnitude in i band
62- 65 F4.2 mag Ai [0.2/0.7] Extinction in the i band
67- 71 F5.1 kpc Dist [16.4/173]? Distance
73- 75 F3.1 kpc e_Dist [0.3/4]? Error in Dist
77- 79 A3 --- Type Variable type (1)
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Note (1): Variable type as follows:
ab = type ab RRL stars (195 occurrences)
c = type c RRL stars (104 occurrences)
AC = anomalous Cepheids (8 occurrences)
Fab = type ab field RRL stars (12 occurrences)
Fc = type c field RRL stars (10 occurrences)
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- ID Identification number
6- 6 A1 --- Filt [ir] Filter
8- 21 F14.6 d MJD Modified Julian date
23- 28 F6.3 mag mag [16.76/22.55] Apparent magnitude in Filter
30- 34 F5.3 mag e_mag [0.002/0.3] Error in mag
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 03-Oct-2023