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Probing the dust properties of galaxies up to submillimetre wavelengths. I. The spectral energy distribution of dwarf galaxies using LABOCA

Galametz, M. and Madden, S. and Galliano, F. and Hony, S. and Schuller, F. and Beelen, A. and Bendo, G. and Sauvage, M. and Lundgren, A. and Billot, N. (2009) Probing the dust properties of galaxies up to submillimetre wavelengths. I. The spectral energy distribution of dwarf galaxies using LABOCA. Astronomy and Astrophysics, 508 (2). pp. 645-664. ISSN 0004-6361.

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Aims. We study the dust properties of four low metallicity galaxies by modelling their spectral energy distributions. This modelling enables us to constrain the dust properties such as the mass, the temperature or the composition to characterise the global ISM properties in dwarf galaxies. Methods. We present 870 μm images of four low metallicity galaxies (NGC 1705, Haro 11, Mrk 1089 and UM311) observed with the Large APEX BOlometer CAmera (LABOCA) on the Atacama Pathfinder EXperiment (APEX) telescope. We modeled their spectral energy distributions combining the submm observations of LABOCA, 2MASS, IRAS, Spitzer photometric data, and the IRS data for Haro 11. Results. We found that the PAH mass abundance is very low in these galaxies, 5 to 50 times lower than the PAH mass fraction of our Galaxy. We also found that a significant mass of dust is revealed when using submm constraints compared to that measured with only mid-IR to far-IR observations extending only to 160 μm. For NGC 1705 and Haro 11, an excess in submillimeter wavelengths was detected when we used our standard dust SED model. We rerun our SED procedure adding a cold dust component (10 K) to better describe the high 870 μm flux derived from LABOCA observations, which significantly improves the fit. We found that at least 70% of the dust mass of these two galaxies can reside in a cold dust component. We also showed that the subsequent dust-to-gas mass ratios, considering HI and CO observations, can be strikingly high for Haro 11 in comparison with what is usually expected for these low-metallicity environments. Furthermore, we derived the star formation rate of our galaxies and compared them to the Schmidt law. Haro 11 falls anomalously far from the Schmidt relation. These results may suggest that a reservoir of hidden gas could be present in molecular form not traced by the current CO observations. While there can be a significant cold dust mass found in Haro 11, the SED peaks at exceptionally short wavelengths (36 μm), also highlighting the importance of the much warmer dust component heated by the massive star clusters in Haro 11. We also derived the total IR luminosities derived from our models and compared them with relations that derive this luminosity from Spitzer bands. We found that the Draine & Li (2007) formula compares well to our direct IR determinations.

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Galametz, M.0000-0002-0283-8689
Additional Information:© ESO 2009. Received 23 July 2009. Accepted 28 September 2009. We first thank the referee for his/her detail suggestions and comments that help to improve the understanding of the paper. We thank Xander Tielens, Ant Jones and Eli Dwek for very stimulating discussion which improved the content of this paper. We would also like to thank Gerhardt R. Meurer for his high quality HI map of NGC 1705. This publication is based on data acquired with the Atacama Pathfinder Experiment (APEX). APEX is a collaboration between the Max-Planck-Institut fur Radioastronomie, the European Southern Observatory, and the Onsala Space Observatory.
Subject Keywords:galaxies: ISM; galaxies: dwarf; infrared: ISM; dust, extinction
Issue or Number:2
Record Number:CaltechAUTHORS:20100127-105901483
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Official Citation: Probing the dust properties of galaxies up to submillimetre wavelengths - I. The spectral energy distribution of dwarf galaxies using LABOCA M. Galametz, S. Madden, F. Galliano, S. Hony, F. Schuller, A. Beelen, G. Bendo, M. Sauvage, A. Lundgren and N. Billot A&A 508 (2) 645-664 (2009) DOI: 10.1051/0004-6361/200912963
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:17318
Deposited By: Tony Diaz
Deposited On:28 Jan 2010 19:31
Last Modified:03 Oct 2019 01:26

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