Issue |
A&A
Volume 374, Number 1, July IV 2001
|
|
---|---|---|
Page(s) | 42 - 65 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361:20010639 | |
Published online | 15 July 2001 |
Warm dust as a tracer of galaxies with gaseous halos
1
Sterrewacht Leiden, Postbus 9513, 2300 RA Leiden, The Netherlands ( ESO, Alonso de Cordova 3107, Vitacura, Casilla 19001, Santiago 19, Chile.)
2
Astrophysics Department, School of Physics A28, University of Sydney, NSW 2006, Australia
3
Australia Telescope National Facility, PO Box 76, Epping, NSW 2121, Australia
4
XMM-Newton Science Operations Centre, Apartado 50727, 28080 Madrid, Spain
5
Astrophysics Division, Space Science Department of ESA, ESTEC, 2200 AG Noordwijk, The Netherlands
6
IRAM, Avenida Divina Pastora 7, NC, 18012 Granada, Spain
Corresponding author: M. Dahlem, mdahlem@eso.org
Received:
20
December
2000
Accepted:
1
May
2001
We present radio continuum observations conducted with the VLA
and ATCA of a sample of 15 edge-on spiral galaxies. 11 of these
galaxies, with inclination angles of and
neither active galactic nuclei nor nearby interaction partners,
are suitable for studies of halo properties in relation to the
level of star formation in their disks.
In 6 of these 11 galaxies radio halos were detected at the angular
resolution of the current data. In the remaining cases the presence
of halo emission could not be proven unambiguously, partly due to
relatively low angular resolution.
A clear trend was found that galaxies with radio halos are those
with the highest far-infrared 60 μm to 100 μm flux ratios.
This shows the suitability of high
ratios of
≥
0.4 as a reliable tracer of galaxies with high star
formation rates and related disk-halo interactions, leading to
the presence of extraplanar emission, e.g. from cosmic ray
electrons. The measured exponential scale heights of those 6
radio halos that were clearly detected range from about 1.4 to
3.1 kpc.
All 4 physically small galaxies in our sample do show extraplanar
synchrotron radio emission, indicating that their more shallow
gravitational potential compared to normal-sized spirals might
facilitate the escape of cosmic-ray electrons from the sites of
star formation in their disks.
Although the galaxies with the highest energy input rates into
the ISM of their disks are those that have the most prominent
radio halos, there is no direct relation between the halo scale
heights and the energy input rates. Instead, the scale heights
of the radio halos are dominated by the energy losses of the
cosmic ray electrons on their way out of the galaxy disks.
Key words: ISM: general / galaxies: evolution / galaxies: halos / galaxies: starburst / radio continuum: galaxies
© ESO, 2001
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