2001A&A...370..176M


C.D.S. - SIMBAD4 rel 1.7 - 2021.01.19CET17:23:20

2001A&A...370..176M - Astronomy and Astrophysics, volume 370, 176-193 (2001/4-4)

The AGB phase-transition outside the local group: K-band observations of young star clusters in NGC 7252.

MARASTON C., KISSLER-PATIG M., BRODIE J.P., BARMBY P. and HUCHRA J.P.

Abstract (from CDS):

We have extended the study of the young star clusters observed in the merger remnant galaxy NGC 7252 by obtaining K band photometry for these clusters. Our K band data significantly complement the optical photometry and spectroscopy in the literature: K band data are fundamental to study the Asymptotic Giant Branch (AGB) population of these clusters, since the AGB phase transition (occuring between the age of ∼200Myr and ∼1Gyr) causes abrupt changes in the near-infrared luminosity of the clusters while producing only small changes in the optical. Therefore, the e.g. V-K colour is ideal to study this evolutionary phase of stellar populations. For the present analysis we present models for Simple Stellar Populations which include the contribution of the AGB stellar phase, calibrated with the young and intermediate age star clusters of the Magellanic Clouds. The comparison with the colour distribution of the NGC 7252 star clusters shows that they are indeed intermediate age clusters undergoing the AGB phase transition. The AGB phase transition is observed for the first time outside the Local Group. Most of the studied clusters span the very narrow age range 300-500Myr, and likely have metallicities 0.5-1Z. A very important exception is the cluster W32, which has already completed its AGB epoch, its colours being consistent with an age of ∼1-2Gyr. This impacts on the duration of the merger-induced starburst. The strengths of the magnesium and iron lines in the spectrum of the best observed cluster W3, and in the spectrum of the diffuse central light of NGC 7252, do not show an overabundance in α-elements, in contrast to the bulk stellar population of elliptical galaxies.

Abstract Copyright:

Journal keyword(s): galaxies: star clusters: stellar content: interactions - stars: AGB and post-AGB - stars: evolution

Simbad objects: 20

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Number of rows : 20

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 5823 1
2 NGC 6618 OpC 18 20 47 -16 10.3           ~ 1499 0
3 [SS98b] S101 Cl* 22 20 41.26 -24 40 44.9           ~ 4 0
4 [SS98b] S105 Cl* 22 20 42.35 -24 40 35.8           ~ 4 0
5 [WSL93] 3 GlC 22 20 43.878 -24 40 37.87     17.86     ~ 50 0
6 [WSL93] 6 GlC 22 20 44.135 -24 40 27.60     19.43     ~ 8 0
7 NGC 7252 IG 22 20 44.7751096408 -24 40 41.905677809 12.26 12.46 12.06 11.57   ~ 667 1
8 [WSL93] 19 Gl? 22 20 44.928 -24 40 47.59     21.99     ~ 3 0
9 [WSL93] 22 Gl? 22 20 45.089 -24 40 55.52     21.58     ~ 3 0
10 [WSL93] 24 Gl? 22 20 45.140 -24 40 49.38     22.58     ~ 3 0
11 [WSL93] 25 Gl? 22 20 45.162 -24 40 56.89     22.25     ~ 2 0
12 [WSL93] 26 GlC 22 20 45.272 -24 40 32.30     20.30     ~ 8 0
13 [WSL93] 27 Gl? 22 20 45.448 -24 40 52.85     21.97     ~ 2 0
14 [WSL93] 30 GlC 22 20 45.493 -24 40 49.36     19.39     ~ 16 0
15 [WSL93] 31 GlC 22 20 45.602 -24 40 47.96     20.91     ~ 5 0
16 [WSL93] 32 Gl? 22 20 45.632 -24 40 37.87     21.33     ~ 4 0
17 [MWS97] 42 Cl* 22 20 46.33 -24 41 00.5   21.65 21.23     ~ 5 0
18 NGC 7284 IG 22 28 35.925 -24 50 38.57   12.96   11.59   ~ 41 0
19 NGC 7285 IG 22 28 37.03 -24 50 25.9   12.82   11.54   ~ 35 0
20 NAME Local Group GrG ~ ~           ~ 7138 0

    Equat.    Gal    SGal    Ecl

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