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J/A+A/530/A58      AGB stars in Cen A dwarf galaxies     (Crnojevic+, 2011)

A close look at the Centaurus A group of galaxies. II. Intermediate-age populations in early-type dwarfs. Crnojevic D., Rejkuba, M., Grebel, E.K., da Costa, G., Jerjen, H. <Astron. Astrophys. 530, A58 (2011)> =2011A&A...530A..58C
ADC_Keywords: Galaxies, photometry ; Populations, stellar ; Photometry, infrared Keywords: galaxies: dwarfs - galaxies: photometry - galaxies: stellar content - galaxies: groups: individual: CenA group Abstract: We investigate the resolved stellar content of early-type dwarf galaxies in the Centaurus A group, to estimate their intermediate-age population fractions. We use near-infrared photometric data taken with the VLT/ISAAC instrument, together with previously analyzed archival HST/ACS data. The combination of the optical and infrared wavelength range permits us to firmly identify luminous asymptotic giant branch stars, which are indicative of an intermediate-age population in these galaxies. We consider one dwarf spheroidal (CenA-dE1) and two dwarf elliptical (SGC1319.1-4216 and ESO269-066) galaxies that are dominated by an old population. The most recent periods of star formation are estimated to have taken place between 2 and 5Gyr ago for SGC1319.1-4216 and ESO269-066, and approximately 9Gyr ago for CenA-dE1. For ESO269-066, we find that the intermediate-age populations are significantly more centrally concentrated than the predominantly old underlying stars. The intermediate-age population fraction is found to be small in the target galaxies, consistent with fractions of up to 15% of the total population. These values might be larger by a factor of two or three, if we considered the observational limitations and the recent discussion about the uncertainties in theoretical models. We suggest that there is a correlation between intermediate-age population fraction and proximity to the dominant group galaxy, with closer dwarfs having slightly smaller fractions, although our sample is too small to draw firm conclusions. Even when considering our results as lower limits, the intermediate-age population fractions for the studied dwarfs are clearly much smaller than those found in similar dwarfs around the Milky Way, but comparable to what is seen for the low-mass M31 companions. Our results confirm our previous work about early-type dwarfs in the Centaurus A group. Description: Position and photometry (optical and near-infrared) of candidate AGB stars in three dwarf galaxies companions to CenA. Variable candidates are denoted with an asterisk. Objects: ---------------------------------------------------------- RA (2000) DE Designation(s) ---------------------------------------------------------- 13 12 45.0 -41 49 55 CenA-dE1 = [KK98a] 189 13 22 01.8 -42 32 08 SGC 1319.1-4216 = [KK98a] 197 13 13 09.2 -44 53 23 ESO 269-66 = [KK98a] 190 ---------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table3.dat 99 228 AGB candidates list
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 14 A14 --- Gal Galaxy name 16- 20 I5 --- ID AGB candidate ID 21 A1 --- n_ID [*] * indicates variable 23- 24 I2 h RAh Right Ascension J2000 (hours) 26- 27 I2 min RAm Right Ascension J2000 (minutes) 29- 34 F6.3 s RAs Right Ascension J2000 (seconds) 36 A1 --- DE- Declination J2000 (sign) 37- 38 I2 deg DEd Declination J2000 (degrees) 40- 41 I2 arcmin DEm Declination J2000 (minutes) 43- 47 F5.2 arcsec DEs Declination J2000 (seconds) 49- 54 F6.3 mag J0mag Dereddened apparent J magnitude (1) 56- 60 F5.3 mag e_J0mag J magnitude error 62- 67 F6.3 mag K0mag Dereddened apparent K magnitude (1) 69- 73 F5.3 mag e_K0mag K magnitude error 75- 80 F6.3 mag V0mag Dereddened apparent V magnitude (1) 82- 86 F5.3 mag e_V0mag V magnitude error 88- 93 F6.3 mag I0mag Dereddened apparent I magnitude (1) 95- 99 F5.3 mag e_I0mag I magnitude error
Note (1): dereddened from the Galactic foreground reddening values from the NASA/IPAC Extragalactic Database (NED) (based on the Schlegel extinction maps).
Acknowledgements: Denija Crnojevic, denija(at) References: Crnojevic et al., Paper I 2010A&A...516A..85C
(End) D. Crnojevic [ARI/Univ. Heidelberg], P. Vannier [CDS] 17-May-2011
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