J/ApJ/699/1742 LCID project. I. Cetus and Tucana variables (Bernard+, 2009)
The ACS LCID project.
I. Short-period variables in the isolated dwarf spheroidal galaxies Cetus and
Tucana.
Bernard E.J., Monelli M., Gallart C., Drozdovsky I., Stetson P.B.,
Aparicio A., Cassisi S., Mayer L., Cole A.A., Hidalgo S.L., Skillman E.D.,
Tolstoy E.
<Astrophys. J., 699, 1742-1764 (2009)>
=2009ApJ...699.1742B 2009ApJ...699.1742B
ADC_Keywords: Galaxies, nearby ; Photometry, HST ; Stars, variable
Keywords: galaxies: dwarf - galaxies: individual (Cetus, Tucana) - Local Group -
stars: horizontal-branch - stars: variables: other
Abstract:
We present the first study of the variable star populations in the
isolated dwarf spheroidal galaxies (dSphs) Cetus and Tucana. Based on
Hubble Space Telescope images obtained with the Advanced Camera for
Surveys in the F475W and F814W bands, we identified 180 and 371
variables in Cetus and Tucana, respectively. The vast majority are RR
Lyrae stars. In Cetus, we also found three anomalous Cepheids (ACs),
four candidate binaries and one candidate long-period variable (LPV),
while six ACs and seven LPV candidates were found in Tucana. Of the RR
Lyrae stars, 147 were identified as fundamental mode (RRab) and only
eight as first-overtone mode (RRc) in Cetus, with mean periods of
0.614 and 0.363 day, respectively. In Tucana, we found 216 RRab and 82
RRc giving mean periods of 0.604 and 0.353 day. These values place
both galaxies in the so-called Oosterhoff Gap, as is generally the
case for dSph. We found numerous RR Lyrae variables pulsating in both
modes simultaneously (RRd): 17 in Cetus and 60 in Tucana. We provide
the photometry and pulsation parameters for all the variables, and
compare the latter with values from the literature for well studied
dSph of the Local Group and Galactic globular clusters. The parallel
WFPC2 fields were also searched for variables, as they lie well within
the tidal radius of Cetus, and at its limit in the case of Tucana. No
variables were found in the latter, while 15 were discovered in the
outer field of Cetus (11 RRab, three RRc, and one RRd), even though
the lower signal-to-noise ratio of the observations did not allow us
to measure their periods accurately. We provide their coordinates and
approximate properties for completeness.
Description:
The present analysis is based on observations obtained with the ACS
onboard the HST. We required 25 and 32 HST orbits for Cetus and
Tucana, respectively. These were collected over about 2.5 and 5
consecutive days, between 2006 August 28 and 30 for Cetus and 2006
April 25 and 30 for Tucana. The observing sequence consisted of
alternating ∼1100s exposures in F475W and F814W for an optimal
sampling of the light curves.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 56 4500 Photometry of the variable stars in Cetus dSph
table4.dat 56 11872 Photometry of the variable stars in Tucana dSph
table5.dat 84 4500 BVI photometry of the variable stars in Cetus dSph
table6.dat 84 11872 BVI photometry of the variable stars in Tucana dSph
table7.dat 124 180 Pulsation properties of variable stars in Cetus
- ACS field
table8.dat 124 371 Pulsation properties of variable stars in Tucana
table9.dat 81 15 Pulsation properties of variable stars in Cetus
- WFPC2 field
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See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
J/AJ/133/715 : Dwarf galaxies of the Local Group (Whiting+, 2007)
J/AJ/120/1801 : C stars in Pegasus, DDO 210 and Tucana (Battinelli+, 2000)
J/A+A/310/715 : Tucana dwarf galaxy VI photometry (Castellani+, 1996)
J/A+A/315/40 : Photometry of the Tuc dwarf galaxy (Saviane, 1996)
http://www.iac.es/proyecto/LCID/ : Local Cosmology from Isolated Dwarfs
(LCID) project home page
Byte-by-byte Description of file: table[34].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 A1 --- --- [V]
2- 4 I03 --- ID Object identification (in Simbad:
<[BMG2009] Cetus ACS VNNN> for table 3 or
<[BMG2009] Tucana VNNN> for table 4)
6- 17 F12.6 d HJD(475) Truncated Heliocentric Julian Date for F475W (G1)
19- 24 F6.3 mag F475W ?=99.999 HST/ACS F475W magnitude
26- 30 F5.3 mag e_F475W ?=9.999 Error in F475W
32- 43 F12.6 d HJD(814) Truncated Heliocentric Julian Date for F814W (G1)
45- 50 F6.3 mag F814W ?=99.999 The HST/ACS F814W magnitude
52- 56 F5.3 mag e_F814W ?=9.999 Error in F814W
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Byte-by-byte Description of file: table[56].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 A1 --- --- [V]
2- 4 I03 --- ID Object identification (in Simbad:
<[BMG2009] Cetus ACS VNNN> for table 5 or
<[BMG2009] Tucana VNNN> for table 6)
6- 17 F12.6 d HJD(B) Truncated Heliocentric Julian Date for B (G1)
19- 24 F6.3 mag Bmag ?=99.999 The Johnson B magnitude
26- 30 F5.3 mag e_Bmag ?=9.999 Error in Bmag
32- 44 F13.6 d HJD(V) Truncated Heliocentric Julian Date for V (G1)
46- 51 F6.3 mag Vmag ?=99.999 The Johnson V magnitude
53- 57 F5.3 mag e_Vmag ?=9.999 Error in Vmag
59- 71 F13.6 d HJD(I) Truncated Heliocentric Julian Date for I (G1)
73- 78 F6.3 mag Imag ?=99.999 The Johnson I magnitude
80- 84 F5.3 mag e_Imag ?=9.999 Error in Imag
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Byte-by-byte Description of file: table[78].dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 A1 --- --- [V]
2- 4 I03 --- ID Object identification (in Simbad:
<[BMG2009] Cetus ACS VNNN> for table 7 or
<[BMG2009] Tucana VNNN> for table 8 )
6- 8 A3 --- Type Variable classification (G2)
10- 11 I2 h RAh Hour of right Ascension (J2000)
13- 14 I2 min RAm Minute of right Ascension (J2000)
16- 20 F5.2 s RAs Second of right Ascension (J2000)
22 A1 --- DE- Sign of Declination (J2000)
23- 24 I2 deg DEd Degree of Declination (J2000)
26- 27 I2 arcmin DEm Arcminute of Declination (J2000)
29- 32 F4.1 arcsec DEs Arcsecond of Declination (J2000)
34 A1 --- u_Per [u] Indicates an uncertainty in period,
magnitudes, or amplitudes
36- 40 F5.3 d Per ? Period
42- 47 F6.3 [d] logP ? Logarithm of the Period
49- 55 F7.3 mag F475W Intensity-averaged HST/ACS F475W magnitude
57- 61 F5.3 mag A475 ? The F475W amplitude
63- 69 F7.3 mag F814W Intensity-averaged HST/ACS F814W magnitude
71- 75 F5.3 mag A814 ? The F814W amplitude
77- 82 F6.3 mag F475-814 Intensity-averaged F475W-F814W color index
84- 90 F7.3 mag Bmag Intensity-averaged Johnson B magnitude
92- 96 F5.3 mag Bamp ? The B amplitude
98-104 F7.3 mag Vmag Intensity-averaged Johnson V magnitude
106-110 F5.3 mag Vamp ? The V amplitude
112-118 F7.3 mag Imag Intensity-averaged Johnson I magnitude
120-124 F5.3 mag Iamp ? The I amplitude
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Byte-by-byte Description of file: table9.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 A1 --- --- [V]
2- 4 I03 --- ID Object identification (in Simbad:
<[BMG2009] Cetus WFPC2 VNNN>)
6- 8 A3 --- Type Variable classification (G2)
10- 11 I2 h RAh Hour of right Ascension (J2000)
13- 14 I2 min RAm Minute of right Ascension (J2000)
16- 20 F5.2 s RAs Second of right Ascension (J2000)
22 A1 --- DE- Sign of Declination (J2000)
23- 24 I2 deg DEd Degree of Declination (J2000)
26- 27 I2 arcmin DEm Arcminute of Declination (J2000)
29- 32 F4.1 arcsec DEs Arcsecond of Declination (J2000)
34 A1 --- u_Per [u] Indicates an uncertainty in period,
magnitudes, or amplitudes
36- 40 F5.3 d Per Period
42- 47 F6.3 [d] logP Logarithm of the Period
49- 55 F7.3 mag F450W Intensity-averaged F450W magnitude
57- 62 F6.3 mag F814W Intensity-averaged F814W magnitude
64- 68 F5.3 mag F450-814 Intensity-averaged F450W-F814W color index
70- 75 F6.3 mag A450 The F450W amplitude
77- 81 F5.3 mag A814 The F814W amplitude
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Global Notes:
Note (G1): Heliocentric Julian Date minus 2400000.0 (HJD-2400000.0)
at mid-exposure
Note (G2): Variability type as follows:
ab = Fundamental mode RR Lyrae;
c = First-overtone mode RR Lyrae;
d = Double mode RR Lyrae;
AC = Anomalous Cepheid;
EB = Candidate eclipsing binary;
LPV = Candidate long-period variable.
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History:
From electronic version of the journal
References:
Bernard E.J. et al. Introduction 2008ApJ...678L..21B 2008ApJ...678L..21B
Bernard E.J. et al. Paper II. 2010ApJ...712.1259B 2010ApJ...712.1259B
Monelli M. et al. Paper III. 2010ApJ...720.1225M 2010ApJ...720.1225M
Monelli M. et al. Paper IV. 2010ApJ...718..707M 2010ApJ...718..707M
Hidalgo S.L. et al. Paper V. 2011ApJ...730...14H 2011ApJ...730...14H
Monelli M. et al. Paper VI. 2010ApJ...722.1864M 2010ApJ...722.1864M
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 11-Jul-2011