The nature of radio continuum emission in the dwarf starburst galaxy NGC 625

John M Cannon; Evan D Skillman

doi:10.1086/421903

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The nature of radio continuum emission in the dwarf starburst galaxy NGC 625

Journal article

Open access

Peer reviewed

The nature of radio continuum emission in the dwarf starburst galaxy NGC 625

John M Cannon and Evan D Skillman

The Astrophysical journal, Vol.610(2), pp.772-780

08/01/2004

DOI: 10.1086/421903

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Abstract

We present new multifrequency radio continuum imaging of the dwarf starburst galaxy NGC 625 obtained with the Very Large Array. Data at 20, 6, and 3.6 cm reveal global continuum emission dominated by free-free emission, with only mild synchrotron components. Each of the major H II regions is detected; the individual spectral indices are thermal for the youngest regions (showing largest Hα emission) and nonthermal for the oldest. We do not detect any sources that appear to be associated with deeply embedded, dense, young clusters, although we have discovered one low-luminosity, obscured source that has no luminous optical counterpart and resides in the region of highest optical extinction. Since NGC 625 is a Wolf-Rayet galaxy with strong recent star formation, these radio properties suggest that the youngest star formation complexes have not yet evolved to the point where their thermal spectra are significantly contaminated by synchrotron emission. The nonthermal components are associated with regions of older star formation that have smaller ionized gas components. These results imply a range of ages for the H II regions and radio components that agrees with our previous resolved stellar population analysis, where an extended burst of star formation has pervaded the disk of NGC 625 over the last ~50 Myr. We compare the nature of radio continuum emission in selected nearby dwarf starburst and Wolf-Rayet galaxies, demonstrating that thermal radio continuum emission appears to be more common in these systems than in typical H II galaxies with less recent star formation and more evolved stellar clusters.

Astronomy

Astronomical observations

Earth, ocean, space

Exact sciences and technology

Fundamental astronomy and astrophysics. Instrumentation, techniques, and astronomical observations

Quasars. Active or peculiar galaxies, objects, and systems

Radio, microwave (> 1 mm)

Starburst galaxies and infrared excess galaxies

Stellar systems. Galactic and extragalactic objects and systems. The universe

Details

Title: Subtitle: The nature of radio continuum emission in the dwarf starburst galaxy NGC 625
Creators: John M Cannon - University of Minnesota
Evan D Skillman - University of Minnesota
Resource Type: Journal article
Publication Details: The Astrophysical journal, Vol.610(2), pp.772-780
Publisher: University of Chicago Press
DOI: 10.1086/421903
ISSN: 0004-637X
eISSN: 1538-4357
Language: English
Date published: 08/01/2004
Academic Unit: Physics and Astronomy
Record Identifier: 9984627311602771

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