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 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:
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RA (2000) DE Designation(s)
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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
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 99 228 AGB candidates list
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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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
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Note (1): dereddened from the Galactic foreground reddening values from
the NASA/IPAC Extragalactic Database (NED) (based on the Schlegel
extinction maps).
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Acknowledgements:
Denija Crnojevic, denija(at)ari.uni-heidelberg.de
References:
Crnojevic et al., Paper I 2010A&A...516A..85C 2010A&A...516A..85C
(End) D. Crnojevic [ARI/Univ. Heidelberg], P. Vannier [CDS] 17-May-2011