Issue |
A&A
Volume 376, Number 3, September IV 2001
|
|
---|---|---|
Page(s) | L35 - L38 | |
Section | Letters | |
DOI | https://doi.org/10.1051/0004-6361:20011085 | |
Published online | 15 September 2001 |
Mid infrared polarisation of Ultraluminous Infrared Galaxies*
1
European Southern Observatory, Karl-Schwarzschildstr. 2, 85748 Garching b.München, Germany
2
Astrophysics Group, Blackett Laboratory, Imperial College of Science Technology & Medicine, Prince Consort Rd., London. SW7 2BZ, UK
Corresponding author: R. Siebenmorgen, rsiebenm@eso.org
Received:
25
May
2001
Accepted:
30
July
2001
The mid infrared polarisation properties of four Ultraluminous Infrared Galaxies (ULIRGs) have been investigated by broad band filter observations with the ISOCAM instrument on board the Infrared Space Observatory (ISO). The wavelength region from 5 to 18 μm was selected where the emission from the putative torus peaks. We report detection of polarisation for all ULIRGs studied. The fractional polarisation ranges from ~3% up to 8% . The highest polarisation is recorded in Mrk 231 which has a clear AGN signature, whereas the lowest is for Arp 220, which is generally thought to be powered predominantly by star formation. We discuss the various mechanisms that could give rise to the polarisation and conclude that the most likely interpretation is that it is due to magnetically aligned elongated dust grains. This is the same mechanism believed to be operating in a number of galactic sources. The position angle of polarisation could give the projected magnetic field direction and therefore constrain models for the formation of the tori.
Key words: polarization / infrared: galaxies / galaxies: ISM / galaxies: individual: Mrk 231, Arp 220, IRAS 15250+3609, Mrk 273
© ESO, 2001
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.