J/ApJ/786/147 RR Lyrae population in the Phoenix dwarf galaxy (Ordonez+, 2014)
The RR Lyrae variable population in the Phoenix dwarf galaxy.
Ordonez A.J., Yang S.-C., Sarajedini A.
<Astrophys. J., 786, 147 (2014)>
=2014ApJ...786..147O 2014ApJ...786..147O (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Stars, variable ; Photometry, VRI
Keywords: dust, extinction - galaxies: dwarf - galaxies: evolution -
galaxies: individual: Phoenix - stars: abundances -
stars: variables: RR Lyrae
Abstract:
We present the first detailed study of the RR Lyrae variable
population in the Local Group dSph/dIrr transition galaxy, Phoenix,
using previously obtained HST/WFPC2 observations of the galaxy. We
utilize template light curve fitting routines to obtain best fit light
curves for RR Lyrae variables in Phoenix. Our technique has identified
78 highly probable RR Lyrae stars (54 ab-type; 24 c-type) with about
40 additional candidates. We find mean periods for the two populations
of <Pab≥0.60±0.03 days and <Pc≥0.353±0.002 days. We use the
properties of these light curves to extract, among other things, a
metallicity distribution function for ab-type RR Lyrae. Our analysis
yields a mean metallicity of <[Fe/H]≥-1.68±0.06 dex for the RRab stars.
From the mean period and metallicity calculated from the ab-type RR Lyrae,
we conclude that Phoenix is more likely of intermediate Oosterhoff type;
however the morphology of the Bailey diagram for Phoenix RR Lyraes
appears similar to that of an Oosterhoff type I system. Using the RRab
stars, we also study the chemical enrichment law for Phoenix. We find
that our metallicity distribution is reasonably well fitted by a
closed-box model. The parameters of this model are compatible with the
findings of Hidalgo et al. (2009ApJ...705..704H 2009ApJ...705..704H; 2013ApJ...778..103H 2013ApJ...778..103H),
further supporting the idea that Phoenix appears to have been
chemically enriched as a closed-box-like system during the early stage
of its formation and evolution.
Description:
The HST/WFPC2 images of the two target fields around Phoenix used in
this study were retrieved from the Mikulski Archive for Space
Telescopes. The original observing campaign (PI: A. Aparicio; GO-8706)
was intended to study the spatial structure and the stellar age and
metallicity distribution of this dwarf galaxy. Therefore, it provides
deep time-series photometry with fairly good quality for detecting
legitimate RR Lyrae variable candidates. Images were taken in both the
F555W and F814W filters. A total of two fields were observed: one
centered on Phoenix itself, and the other on the outskirts of the
galaxy 2.7' from the centered field. The total observed field of
view with these observations is equal to 11.4 arcmin2 on the sky.
Objects:
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RA (ICRS) DE Designation(s)
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01 51 06.3 -44 26 41 NAME Phoenix Galaxy
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 68 78 IDs, Positions, and Light Curve Parameters for
the Probable RR Lyrae Stars within Phoenix
table4.dat 68 43 IDs, Positions, and Light Curve Parameters for
the Remaining RR Lyrae Candidates
table2.dat 42 2045 Time-series photometry
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See also:
J/MNRAS/424/1113 : VI photometry in Phoenix dwarf galaxy (Battaglia+, 2012)
Byte-by-byte Description of file: table3.dat table4.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Name RR Lyrae star candidate identifier (VNNNNN)
8 I1 h RAh Hour of Right Ascension (J2000)
10- 11 I2 min RAm Minute of Right Ascension (J2000)
13- 19 F7.4 s RAs Second of Right Ascension (J2000)
21 A1 --- DE- Sign of the Declination (J2000)
22- 23 I2 deg DEd Degree of Declination (J2000)
25- 26 I2 arcmin DEm Arcminute of Declination (J2000)
28- 33 F6.3 arcsec DEs Arcsecond of Declination (J2000)
35- 36 A2 --- Type [ab c] RR Lyrae type (1)
38- 42 F5.3 d Period Period
44- 48 F5.3 mag Vamp V band amplitude
50- 54 F5.3 mag Iamp I band amplitude
56- 61 F6.3 mag Vmag Mean V band magnitude
63- 68 F6.3 mag Imag Mean I band magnitude
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Note (1): Type as follows:
ab = Pulsate in the fundamental mode (RRab);
c = Pulsate in the first overtone (RRc).
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Loc Location (Inner, Outer)
7- 12 A6 --- Name RR Lyrae star candidate identifier (VNNNNN)
14- 18 A5 --- Filter Filter used (F555W, F814W)
20- 29 F10.5 d HJD Heliocentric Julian Date; HJD-2451900
31- 36 F6.3 mag mag Observed magnitude in Filter
38- 42 F5.3 mag e_mag Error in mag
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 22-Jun-2017