2005A&A...443..413L


C.D.S. - SIMBAD4 rel 1.7 - 2021.02.26CET02:33:41

2005A&A...443..413L - Astronomy and Astrophysics, volume 443, 413-433 (2005/11-4)

Globular clusters in NGC 4365: new K-band imaging and a reassessment of the case for intermediate-age clusters.

LARSEN S.S., BRODIE J.P. and STRADER J.

Abstract (from CDS):

We study the globular cluster (GC) system of the Virgo giant elliptical galaxy NGC 4365, using new wide-field K-band imaging from the ESO 3.5m New Technology Telescope, archive V and I imaging from FORS1 on the ESO VLT and HST/WFPC2+ACS data. As in most other large ellipticals, the GC colour distribution has (at least) two peaks, but the colours of the red GCs appear more strongly weighted towards intermediate colours compared to most other large ellipticals and the integrated galaxy light. The intermediate-color/red peak may itself be composed of two sub-populations, with clusters of intermediate colours more concentrated towards the centre of the galaxy than both the blue and red GCs. Nearly all GCs in our sample fall along a well-defined narrow sequence in the (V-K, V-I) two-colour diagram, with an offset towards red V-K and/or blue V-I colours compared to simple stellar population models for old ages. This has in the past been interpreted as evidence for an intermediate-age population of GCs. The offset is however seen for nearly all metal-rich clusters within the 5'x5' SOFI field, not just those of intermediate colours. We combine our VIK data with previously published spectroscopy resulting in a sample of 25 GCs with both spectroscopy and photometry. The differences between observed and model colour-metallicity relations are consistent with the offsets observed in the two-colour diagram, with the metal-rich GCs being too red (by ≃0.2mag) in V-K and too blue (by ≃0.05mag) in V-I compared to the models at a given metallicity. These offsets cannot easily be explained as an effect of younger ages. We further compare the colour-metallicity relation for GCs in NGC 4365 with previously published data for NGC 3115 and the Sombrero galaxy, both of which are believed from spectroscopic studies to host exclusively old GC populations, and find the colour-metallicity relations for all three galaxies to be very similar. We review the available evidence for intermediate-age GCs in NGC 4365 and conclude that, while this cannot be definitively ruled out, an alternative scenario is more likely whereby all the GCs are old but the relative number of intermediate-metallicity GCs is greater than typical for giant ellipticals. The main obstacle to reaching a definitive conclusion is the lack of robust calibrations of integrated spectral and photometric properties for stellar populations with near-solar metallicity. In any case, it is puzzling that the significant intermediate-colour GC population in NGC 4365 is not accompanied by a corresponding shift of the integrated galaxy light towards bluer colours.

Abstract Copyright:

Journal keyword(s): galaxies: elliptical and lenticular, cD - galaxies: evolution - galaxies: star clusters - galaxies: individual: NGC 4365

VizieR on-line data: <Available at CDS (J/A+A/443/413): table3.dat>

Nomenclature: Table 3: [LBS2005] NNNN N=1908 among (Nos 1-1911).

Status at CDS : All or part of tables of objects could be ingested in SIMBAD with priority 2.

CDS comments: In ref. list 2002AJ....124..828L instead of 2003ApJ.124.8232L

Simbad objects: 21

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Number of rows : 21

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 M 31 G 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 11201 1
2 NGC 1399 BiC 03 38 29.083 -35 27 02.67 11.05 9.74 9.59 8.12   ~ 1473 1
3 NGC 3115 GiG 10 05 13.978 -07 43 06.89   11   9.37   ~ 942 2
4 NAME Virgo W GrG 12 20.0 +05 48   6.3       ~ 77 0
5 FS 132 * 12 21 39.2798102356 -00 07 12.150160494   13.88 13.33     G1 18 0
6 NGC 4365 GiG 12 24 28.228 +07 19 03.07   11.5       ~ 805 0
7 M 86 GiG 12 26 11.814 +12 56 45.49 10.32 9.83 8.90   7.50 ~ 1022 1
8 NAME Vir I ClG 12 26 32.1 +12 43 24   10.00 8.49     ~ 5979 0
9 M 49 Sy2 12 29 46.798 +08 00 01.48   13.21 12.17     ~ 1984 2
10 NGC 4478 GiP 12 30 17.439 +12 19 42.88 12.82 12.36 11.45   10.17 ~ 474 1
11 M 87 BiC 12 30 49.42338230 +12 23 28.0438581 10.16 9.59 8.63   7.49 ~ 6348 3
12 M 104 LIN 12 39 59.43185 -11 37 22.9954 9.51 9.55 8.00 8.05   ~ 1295 3
13 NGC 4636 LIN 12 42 49.867 +02 41 16.01   12.62 11.84     ~ 1048 1
14 M 60 GiP 12 43 40.008 +11 33 09.40   10.3       ~ 1265 0
15 GSPC S791-C * 13 17 29.6 -05 32 37           ~ 14 0
16 NAME Centaurus A Sy2 13 25 27.61509104 -43 01 08.8056025   8.18 6.84 6.66   ~ 4075 3
17 GSPC S273-E * 14 56 52.0 -44 49 15           ~ 15 0
18 NGC 5846 BiC 15 06 29.253 +01 36 20.29   11.9   9.74   ~ 786 1
19 GSPC S870-T * 15 39 03.6 +00 14 54           ~ 5 0
20 Cl Westerlund 1 OpC 16 47 04.00 -45 51 04.9           ~ 485 0
21 NGC 7192 GiG 22 06 50.178 -64 18 58.38   12.21 11.21 10.77   ~ 135 0

    Equat.    Gal    SGal    Ecl

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