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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 (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; 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: ---------------------------------------------------------- RA (ICRS) DE Designation(s) ---------------------------------------------------------- 01 51 06.3 -44 26 41 NAME Phoenix Galaxy ---------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
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
See also: J/MNRAS/424/1113 : VI photometry in Phoenix dwarf galaxy (Battaglia+, 2012) Byte-by-byte Description of file: table3.dat table4.dat
Bytes Format Units Label Explanations
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
Note (1): Type as follows: ab = Pulsate in the fundamental mode (RRab); c = Pulsate in the first overtone (RRc).
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
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
History: From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 22-Jun-2017
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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