Issue |
A&A
Volume 465, Number 3, April III 2007
|
|
---|---|---|
Page(s) | 839 - 854 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20065835 | |
Published online | 22 January 2007 |
A broadband study of galactic dust emission
1
Centre d'Étude Spatiale des Rayonnements, 9 avenue du Colonel Roche, BP 4346, 31028 Toulouse, France
2
Spitzer Science Infrared Center, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125, USA e-mail: paladini@ipac.caltech.edu
3
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 72, Cambridge, MA 02138, USA
4
Department of Astrophysics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
5
Laboratoire de Physique Subatomique et de Cosmologie, 53 avenue des Martyrs, 38026 Grenoble Cedex, France
Received:
15
June
2006
Accepted:
16
November
2006
We have combined infrared data with H, H
, and H
surveys to spatially decompose the observed dust emission into components associated
with different phases of the gas. An inversion technique is applied. For the decomposition, we use the IRAS 60 and 100 μm bands, the DIRBE 140
and 240 μm bands, as well as Archeops 850 and 2096 μm wavelengths. In addition, we
apply the decomposition to all five WMAP bands. We obtain longitude and
latitude profiles for each wavelength and for each gas component in carefully selected Galactic radius bins. We also derive emissivity coefficients for dust in atomic, molecular, and ionized gas in each of the bins.
The H
emissivity appears to decrease with increasing Galactic radius indicating that dust associated with atomic
gas is heated by the ambient interstellar radiation field (ISRF). By contrast, we find evidence
that dust mixed with molecular clouds is significantly heated by O/B stars still embedded in their
progenitor clouds.
By assuming a modified blackbody with emissivity law
, we also derive the
radial distribution of temperature for each phase of the gas. All of the WMAP bands except W appear to be dominated by emission from
something other than normal dust, most likely a mixture of thermal
bremstrahlung from diffuse ionized gas, synchrotron emission, and spinning dust. Furthermore, we find indications of an emissivity
excess at long wavelengths (
850 μm) in the outer
Galaxy (R > 8.9 kpc). This suggests either the existence of a very cold
dust component in the outer Galaxy or a temperature dependence of the
spectral emissivity index. Finally, it is shown that ~80% of
the total FIR luminosity is produced by dust associated with atomic
hydrogen, in agreement with earlier findings.
The work presented here has been carried out as part of the development of analysis tools
for the planned European Space Agency (ESA) Planck mission.
Key words: Galaxy: structure / infrared: ISM / ISM: dust, extinction
© ESO, 2007
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