A close look at the Centaurus A group of galaxies II. Intermediate-age populations in early-type dwarfs

Abstract

We investigate the resolved stellar content of early-type dwarf galaxies in the CenA group, in order to estimate the fraction of their intermediate-age populations. 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 ~5 Gyr ago for SGC1319.1-4216 and ESO269-066, and approximately 9 Gyr 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 low in the target galaxies (up to ~15% of the total population). These values could be higher by a factor of two or three, if we consider 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 such 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 lower 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 the work by Rejkuba et al. (2006) about early-type dwarfs in the CenA group.

15 pages, 12 figures; accepted for publication in A&A

References in corpus (13)

• The Dartmouth Stellar Evolution Database
• The ACS Nearby Galaxy Survey Treasury IX. Constraining asymptotic giant branch evolution with old metal-poor galaxies
• The Distance to NGC 5128 (Centaurus A)
• The Hubble flow around the CenA / M83 galaxy complex
• The ACS LCID project. III. The star formation history of the Cetus dSph galaxy: a post-reionization fossil
• AGB Stars in the Fornax Dwarf Spheroidal Galaxy
• Old globular clusters in magellanic-type dwarf irregular galaxies
• The evolved stars of Leo II dSph galaxy from near-infrared UKIRT/WFCAM observations
• A close look at the Centaurus A group of galaxies: I. Metallicity distribution functions and population gradients in early-type dwarfs
• The Environmental Influence on the Evolution of Local Galaxies
• Interstellar medium disruption in the Centaurus A group
• Dwarf spheroidals in the M81 Group - Metallicity distribution functions and population gradients
• The Asymptotic Giant Branch and the Tip of the Red Giant Branch as Probes of Star Formation History: The Nearby Dwarf Irregular Galaxy KKH 98

Cited by in corpus (12)

• The faint end of the Centaurus A satellite luminosity function
• The dwarf galaxy satellite system of Centaurus A
• New low surface brightness dwarf galaxies in the Centaurus group
• Tip of the red giant branch distances to the dwarf galaxies dw1335-29 and dw1340-30 in the Centaurus group
• Spectroscopic versus Photometric Metallicities: Milky Way Dwarf Spheroidal Companions as a Test Case
• The properties of dwarf spheroidal galaxies in the Cen A group: Stellar populations, internal dynamics, and a heart-shaped Halpha ring
• A close look at the Centaurus A group of galaxies III. Recent star formation histories of late-type dwarfs around M83
• Theory of Stellar Population Synthesis with an application to N-Body simulations
• A close look at the Centaurus A group of galaxies IV. Recent star formation histories of late-type dwarfs around CenA
• Nuclei of dwarf spheroidal galaxies KKs3 and ESO269-66 and their counterparts in our Galaxy
• Dissipative phenomena in extended-bodies interactions I: Methods Dwarf galaxies of the Local Group and their synthetic CMDs
• Population gradients and photometric metallicities in early- and transition-type dwarf galaxies: Clues from the Sculptor group