2008A&A...492....3G


Query : 2008A&A...492....3G

2008A&A...492....3G - Astronomy and Astrophysics, volume 492, 3-22 (2008/12-2)

Extremely massive young clusters in NGC1365.

GALLIANO E., ALLOIN D., PANTIN E., GRANATO G.L., DELVA P., SILVA L., LAGAGE P.O. and PANUZZO P.

Abstract (from CDS):

In a previous work, three bright mid-infrared/radio sources were discovered in the nuclear region of starburst/AGN galaxy NGC1365. The present study aims to confirm that these sources are indeed young and massive ``embedded'' clusters, and derive their physical parameters, such as extinction, age and mass. Using ISAAC and VISIR at the VLT we obtained maps and low resolution spectra in the near- and mid-infrared. The resulting datasets are first interpreted by comparing the observations with images and spectra of the close-by young cluster R136 in the Large Magellanic Cloud and then by using model predictions for both the nebular emission lines and the spectral energy distribution of the sources. We produce maps of the region containing the three sources in the R, J, Ks, L' bands and at 12.8µm and perform their accurate relative positioning. We also provide spectra in the ranges 1.8-2.4µm, 3.3-4.0µm, 8.1-9.3µm and 10.4-13.2µm. The spectral energy distribution of the three sources rises with wavelength. Emission lines from ionised hydrogen and molecular hydrogen are detected, as well as PAH emission. A conspicuous [NeII]12.8µm line is also observed, while neither the [ArIII]8.9µm nor the [SIV]10.4µm lines are detected. This provides a stringent constraint on the age of the sources: we argue that they are relatively evolved young clusters (6-8Myr). Owing to their ionising photon emission rates and ages, they must be extremely massive clusters (of the order of 107M). Their mid-infrared spectral energy distribution suggests the presence of two components: (1) an optically thin component, with a continuum comparable to that of R136; and (2) an optically thick component which might be related to subsequent or on-going episodes of star formation. We anticipate that these sources are good candidates for evolution according to a bi-modal hydrodynamical regime, in which matter is trapped at the centre of a compact and massive cluster and generates further star formation.

Abstract Copyright:

Journal keyword(s): ISM: dust, extinction - ISM: HII regions - galaxies: star clusters - galaxies: individual: NGC1365 - infrared: galaxies

Nomenclature: Figs 2,3, Table 1: [GAP2008] CN (Nos C1-C3).

Simbad objects: 19

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Number of rows : 19
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 3C 84 Sy2 03 19 48.1599902040 +41 30 42.108850836   13.10 12.48 11.09   ~ 3769 3
2 [GAP2005] NGC 1365 M4 Rad 03 33 36.377 -36 08 17.34           ~ 14 0
3 NGC 1365 Sy1 03 33 36.458 -36 08 26.37 10.48 10.08 9.63 8.79 9.7 ~ 1639 2
4 [GAP2005] NGC 1365 M5 Rad 03 33 36.55 -36 08 13.8           ~ 13 0
5 [GAP2005] NGC 1365 M6 Rad 03 33 36.750 -36 08 17.54           ~ 13 0
6 SBSG 0335-052 bCG 03 37 44.04 -05 02 38.5     16.65     ~ 448 1
7 NGC 1808 Sy2 05 07 42.343 -37 30 46.98 11.05 10.80 9.94 9.36 10.2 ~ 682 3
8 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 16002 1
9 RMC 136 Cl* 05 38 42.396 -69 06 03.36           ~ 1857 1
10 UGCA 116 H2G 05 55 42.645 +03 23 32.23 10.74 11.68 11.46   11.82 ~ 518 0
11 ESO 495-21 bCG 08 36 15.190 -26 24 33.66 12.04 11.93 11.45 11.09 12.3 ~ 529 3
12 M 82 IG 09 55 52.430 +69 40 46.93 9.61 9.30 8.41     ~ 5585 6
13 [SWG2006] A1 Cl* 09 55 53.5 +69 40 49           ~ 31 0
14 NGC 4038 GiP 12 01 53.002 -18 52 03.32   10.91   9.74 11.0 ~ 1296 1
15 NAME Antennae IG 12 01 53.170 -18 52 37.92           ~ 1619 0
16 NGC 4039 GiP 12 01 53.8 -18 53 06   11.08   9.77   ~ 1145 1
17 NGC 5253 AGN 13 39 55.990 -31 38 24.11 11.48 10.94 10.49 10.33   ~ 1311 4
18 NGC 7582 GiP 23 18 23.621 -42 22 14.06 11.62 10.92 10.62     ~ 855 2
19 NAME Local Group GrG ~ ~           ~ 7641 0

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2022.05.27-06:10:33

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