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J/ApJ/837/54   Variable stars in the globular cluster DDO 216-A1   (Cole+, 2017)

DDO 216-A1: a central globular cluster in a low-luminosity transition-type galaxy. Cole A.A., Weisz D.R., Skillman E.D., Leaman R., Williams B.F., Dolphin A.E., Johnson L.C., McConnachie A.W., Boylan-Kolchin M., Dalcanton J., Governato F., Madau P., Shen S., Vogelsberger M. <Astrophys. J., 837, 54-54 (2017)> =2017ApJ...837...54C (SIMBAD/NED BibCode)
ADC_Keywords: Photometry, HST ; Stars, variable ; Clusters, globular Keywords: galaxies: dwarf; galaxies: individual: DDO 216; galaxies: star clusters: general; Local Group Abstract: We confirm that the object DDO 216-A1 is a substantial globular cluster at the center of Local Group galaxy DDO 216 (the Pegasus dwarf irregular), using Hubble Space Telescope ACS imaging. By fitting isochrones, we find the cluster metallicity [M/H]=-1.6±0.2, for reddening E(B-V)=0.16±0.02; the best-fit age is 12.3±0.8Gyr. There are ∼30 RR Lyrae variables in the cluster; the magnitude of the fundamental mode pulsators gives a distance modulus of 24.77±0.08 --identical to the host galaxy. The ratio of overtone to fundamental mode variables and their mean periods make DDO 216-A1 an Oosterhoff Type I cluster. We find a central surface brightness of 20.85±0.17 F814W mag/arcsec2, a half-light radius of 3.1" (13.4pc), and an absolute magnitude M814=-7.90±0.16 (M/M∼105). King models fit to the cluster give the core radius and concentration index, rc=2.1"±0.9" and c=1.24±0.39. The cluster is an "extended" cluster somewhat typical of some dwarf galaxies and the outer halo of the Milky Way. The cluster is projected ≲30pc south of the center of DDO 216, unusually central compared to most dwarf galaxy globular clusters. Analytical models of dynamical friction and tidal destruction suggest that it probably formed at a larger distance, up to ∼1kpc, and migrated inward. DDO 216 has an unexceptional specific cluster frequency, SN=10. DDO 216 is the lowest-luminosity Local Group galaxy to host a 105M globular cluster and the only transition-type (dSph/dIrr) galaxy in the Local Group with a globular cluster. Description: We observed the Pegasus dwarf irregular (PegDIG; DDO216) using the Advanced Camera for Surveys Wide Field Camera (ACS/WFC) as part of the Cycle 22 program GO-13768. The observations, which comprise 34.3 and 37.4ks in the F814W (Broad I band) and F475W (Sloan g band) filters, respectively, were made between 2015 July 23 and 26 using HST. Parallel observations at a distance of ∼6' were obtained simultaneously through the equivalent filters on the Wide Field Camera 3. Objects: ---------------------------------------------------------- RA (ICRS) DE Designation(s) ---------------------------------------------------------- 23 28 26.30 +14 44 25.2 DDO216-A1 = [HM82] A1 ---------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 118 36 Variable stars in DDO216-A1
See also: B/hst : HST Archived Exposures Catalog (STScI, 2007) VII/195 : Globular Clusters in the Milky Way (Harris, 1996) J/MNRAS/345/747 : RR Lyrae in 4 Fornax globular clusters (Mackey+, 2003) J/ApJS/161/304 : Star clusters in the MW and satellites (McLaughlin+, 2005) J/A+A/442/85 : GC candidates in Low SB Galaxies (Sharina+, 2005) J/ApJ/699/1742 : LCID project. I. Cetus and Tucana variables (Bernard+, 2009) J/ApJ/697/1993 : Spitzer study of AGB stars. III. (Boyer+, 2009) J/MNRAS/396/1075 : GC in nearby dwarf galaxies. II (Georgiev+, 2009) J/MNRAS/392/879 : Globular clusters in nearby dwarf galaxies (Georgiev+, 2009) J/MNRAS/406/329 : Variable stars in M54 (Sollima+, 2010) J/AJ/142/187 : HST obs. of 7 Pop.II variable stars (Benedict+, 2011) J/AJ/142/199 : Sizes and luminosities of stellar systems (Brodie+, 2011) J/MNRAS/411/1536 : Spectroscopy of of IC4499 red giants (Hankey+, 2011) J/AJ/144/4 : Dwarf galaxies in the Local Group (McConnachie+, 2012) J/ApJ/779/102 : Metallicities of RGB stars in dwarf galaxies (Kirby+, 2013) J/MNRAS/441/3570 : Nuclear star clusters in 228 spiral gal. (Georgiev+, 2014) J/MNRAS/439/1015 : Velocities of red giants in 7 LG dwarf gal. (Kirby+, 2014) J/ApJ/789/147 : Star formation histories of LG dwarf galaxies (Weisz+, 2014) J/ApJ/812/158 : Leo P RR Lyrae candidates & cumulative SFH (McQuinn+, 2015) J/ApJ/829/26 : Variable stars in Andromeda XXV field. III. (Cusano+, 2016) J/MNRAS/457/2122 : Nuclear star clusters photometric masses (Georgiev+, 2016) J/ApJ/827/33 : PHAT. XVI. Star cluster masses and ages (Johnson+, 2016) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 2 I2 h RAh [23] Hour of right ascension (J2000) 4- 5 I2 min RAm [28] Minute of right ascension (J2000) 7- 12 F6.3 s RAs [35.9/36.9] Second of right ascension (J2000) 17 A1 --- DE- [+] Sign of declination (J2000) 18- 19 I2 deg DEd [14] Degree of declination (J2000) 21- 22 I2 arcmin DEm [44] Arcminute of declination (J2000) 24- 28 F5.2 arcsec DEs [18.5/30.8] Arcsecond of declination (J2000) 33- 37 I5 --- ID [16415/40802] Index number (1) 41- 47 F7.2 pix Xpix X pixel coordinate 49- 55 F7.2 pix Ypix Y pixel coordinate 57- 62 F6.3 mag gmag [25.3/26.4] Mean HST/ACS F475W (g) band magnitude 65- 69 F5.3 mag e_gmag [0.02/0.1] Uncertainty in F475Wmag 73- 78 F6.3 mag Imag [24.4/25.3] Mean HST/ACS F814W (I) band magnitude 81- 85 F5.3 mag e_Imag [0.02/0.05] Uncertainty in F814Wmag 89- 93 F5.3 d Per [0.3/1] Period 97-101 F5.3 d e_Per [0.01/0.2]? Uncertainty in Per 105-118 A14 --- Type Variable type
Note (1): Variables within 8" of the cluster center.
History: From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 16-Oct-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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