ISO-SWS spectra of galaxies: continuum and features
E. Sturm, D. Lutz, D. Tran, H. Feuchtgruber,
R. Genzel, D. Kunze,
A.F.M. Moorwood, M.D. Thornley
Abstract:
We present an inventory of mid-infrared spectral features detected in high
resolution 2.4 to 45 µm ISO-SWS spectra of the galaxies M82,
NGC253, Circinus,
NGC1068, and the 30Doradus region of the LMC. We discuss their identifications
and highlight possible relations between these features and the physical state
of the interstellar medium in galaxies.
In the 5-13 µm region, emission from unidentified infrared
bands (UIBs),
usually ascribed to aromatic molecules, and apparent silicate absorption
dominate the spectrum. We demonstrate the danger of overestimating the amount
of silicate absorption by comparing the spectrum of M82 to the (absorption
free) spectrum of the reflection nebula NGC7023. No strong silicate absorption
is present in M82. The (very small grain) dust continuum under the UIB
emission in our starburst templates can be modeled by a simple power law,
starting at wavelengths between 8 and 9 µm.
The spectra are valuable templates for future mid-infrared missions. We smooth
our data to simulate low resolution spectra as obtained with ISOCAM-CVF,
ISOPHOT-S, and in the future with the low resolution mode of SIRTF-IRS, and
use our high spectral resolution information to highlight possible
identification problems at low resolving power that are caused by coincidences
of lines and features.
Keywords: Infrared: ISM: continuum -- Infrared: ISM: lines and bands --
Galaxies: ISM -- Galaxies: individual: M82 -- Galaxies: individual:
NGC253 -- Galaxies: individual: Circinus -- Galaxies: individual: NGC1068 --
Galaxies: individual: LMC 30 Doradus
Status: A&A accepted
Address:mailto:
sturm@mpe.mpg.de
Full text
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