EDP Sciences
Free Access
Issue
A&A
Volume 414, Number 2, February I 2004
Page(s) 475 - 486
Section Galactic structure and dynamics
DOI https://doi.org/10.1051/0004-6361:20031636


A&A 414, 475-486 (2004)
DOI: 10.1051/0004-6361:20031636

Cold dust in a selected sample of nearby galaxies

I. The interacting galaxy NGC 4631
M. Dumke1, 2, M. Krause1 and R. Wielebinski1

1  Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
2  SMTO, Steward Observatory, The University of Arizona, 933 N. Cherry Avenue, Tucson, Arizona 85721, USA



(Received 14 April 2003 / Accepted 17 October 2003 )

Abstract
We have observed the continuum emission of the interacting galaxy NGC 4631 at $\lambda\lambda$ 870 $\mu$m and 1.23 mm using the Heinrich-Hertz-Telescope on Mt. Graham and the IRAM 30-m telescope on Pico Veleta. We have obtained fully sampled maps which cover the optical emission out to a radius of about 7' at both wavelengths. For a detailed analysis, we carefully subtracted the line contributions and synchrotron and free-free emission from the data, which added up to 6% at 1.23 mm and 10% at 0.87 mm. We combined the flux densities with FIR data to obtain dust spectra and calculate dust temperatures, absorption cross sections, and masses. Assuming a "standard" dust model, which consists of two populations of big grains at moderate and warm temperatures, we obtained temperatures of 18 K and 50 K for the both components. However, such a model suffers from an excess of the radiation at $\lambda\,1.23$ mm, and the dust absorption cross section seems to be enhanced by a factor 3 compared to previous results and theoretical expectations. At large galactocentric radii, where the galaxy shows disturbances as a result of gravitational interaction, this effect seems to be even stronger. Some possibilities to resolve these problems are discussed. The data could be explained by a very cold dust component at a temperature of 4-6 K, an increased abundance of very small grains, or a component of grains with unusual optical properties. We favour the latter possibility, since the first two lead to inconsistencies


Key words: galaxies: ISM -- radio continuum: galaxies -- galaxies: individual: NGC 4631

Offprint request: M. Dumke, mdumke@mpifr-bonn.mpg.de

SIMBAD Objects



© ESO 2004

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.