Issue |
A&A
Volume 434, Number 3, May II 2005
|
|
---|---|---|
Page(s) | 867 - 885 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20042369 | |
Published online | 18 April 2005 |
ISM properties in low-metallicity environments
III. The dust spectral energy distributions of II Zw 40, He 2-10 and NGC 1140
1
Service d'Astrophysique, CEA/Saclay, L'Orme des Merisiers, 91191 Gif-sur-Yvette, France e-mail: galliano@avak.gsfc.nasa.gov
2
Institut d'Astrophysique Spatiale (IAS), Université de Paris XI, 91405 Orsay Cedex, France
3
Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1, Canada
4
Centre d'Étude Spatiale des Rayonnements (CESR), 31028 Toulouse, France
Received:
16
November
2004
Accepted:
28
January
2005
We present new 450 and 850 SCUBA data and 1.3 mm MAMBO data
of the dwarf galaxies II Zw 40, He 2-10 and NGC 1140.
Additional ISOCAM, IRAS as well as ground based data are used to construct
the observed mid-infrared to millimeter spectral energy distribution of these
galaxies.
These spectral energy distributions are modeled in a self-consistent way, as
was achieved with NGC 1569 (Galliano et al. 2003, A&A, 407, 159), synthesizing both
the global stellar radiation field and the dust emission, with further
constraints provided by the photoionisation of the gas.
Our study shows that low-metallicity galaxies have very different dust
properties compared to the Galaxy.
Our main results are:
(i) a paucity of PAHs which are likely destroyed by the
hard penetrating radiation field;
(ii) a very small (~
) average size of grains,
consistent with the fragmentation and erosion of dust particles by the
numerous shocks;
(iii) a significant millimetre excess in the dust spectral energy
distribution which can be
explained by the presence of ubiquitous very cold dust
(
K) accounting for 40 to 80% of the total dust
mass, probably distributed in small clumps.
We derive a range of gas-to-dust mass ratios between 300 and 2000,
larger than the Galactic values and dust-to-metals ratios of
to
.
The modeled dust size distributions are used to synthesize an
extinction curve for each galaxy.
The UV slopes of the extinction curves resemble that observed in some regions
in the Large Magellanic Cloud.
The 2175 Å bumps of the modeled extinction curves are weaker than that
of the Galaxy, except in the case of II Zw 40 where we are unable to accurately
constrain the 2175 Å bump carrier.
Key words: ISM: dust, extinction / galaxies: dwarf / galaxies: starburst / infrared: galaxies / submillimeter
© ESO, 2005
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.