Warm dust as a tracer of galaxies with gaseous halos

Michael Dahlem, Jasmina Lazendic, Raymond Haynes, Matthias Ehle, Ute Lisenfeld

Research output: Contribution to journalArticleResearchpeer-review

Abstract

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 i >~ 75o 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 mu m to 100 mu m flux ratios. This shows the suitability of high f60/f100 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.
Original languageEnglish
Pages (from-to)42-64
Number of pages21
JournalAstronomy and Astrophysics
Volume374
DOIs
Publication statusPublished - Jul 2001
Externally publishedYes

Keywords

  • ISM: GENERAL, GALAXIES: EVOLUTION, GALAXIES: HALOS, GALAXIES: STARBURST, RADIO CONTINUUM: GALAXIES

Cite this

Dahlem, Michael ; Lazendic, Jasmina ; Haynes, Raymond ; Ehle, Matthias ; Lisenfeld, Ute. / Warm dust as a tracer of galaxies with gaseous halos. In: Astronomy and Astrophysics. 2001 ; Vol. 374. pp. 42-64.
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Warm dust as a tracer of galaxies with gaseous halos. / Dahlem, Michael; Lazendic, Jasmina; Haynes, Raymond; Ehle, Matthias; Lisenfeld, Ute.

In: Astronomy and Astrophysics, Vol. 374, 07.2001, p. 42-64.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Warm dust as a tracer of galaxies with gaseous halos

AU - Dahlem, Michael

AU - Lazendic, Jasmina

AU - Haynes, Raymond

AU - Ehle, Matthias

AU - Lisenfeld, Ute

PY - 2001/7

Y1 - 2001/7

N2 - 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 i >~ 75o 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 mu m to 100 mu m flux ratios. This shows the suitability of high f60/f100 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.

AB - 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 i >~ 75o 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 mu m to 100 mu m flux ratios. This shows the suitability of high f60/f100 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.

KW - ISM: GENERAL, GALAXIES: EVOLUTION, GALAXIES: HALOS, GALAXIES: STARBURST, RADIO CONTINUUM: GALAXIES

U2 - 10.1051/0004-6361:20010639

DO - 10.1051/0004-6361:20010639

M3 - Article

VL - 374

SP - 42

EP - 64

JO - Astronomy and Astrophysics: a European journal

JF - Astronomy and Astrophysics: a European journal

SN - 0004-6361

ER -