RESOLUTION OF THE COMPACT RADIO CONTINUUM SOURCES IN Arp220

Journal Article · Thu Oct 20 04:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/740/2/95; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21587352

Batejat, Fabien; Conway, John E; Hurley, Rossa ^[1]; Parra, Rodrigo ^[2]; Diamond, Philip J ^[3]; Lonsdale, Colin J ^[4]

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1. Onsala Space Observatory, SE-439 92 Onsala (Sweden)
2. European Southern Observatory, Alonso de Cordova 3107, Casilla 19001, Santiago 19 (Chile)
3. CSIRO Astronomy and Space Science, P.O. Box 76, Epping, NSW 1710 (Australia)
4. MIT Haystack Observatory, Westford, MA (United States)

We present 2 cm and 3.6 cm wavelength very long baseline interferometry images of the compact radio continuum sources in the nearby ultra-luminous infrared galaxy Arp220. Based on their radio spectra and variability properties, we confirm these sources to be a mixture of supernovae (SNe) and supernova remnants (SNRs). Of the 17 detected sources we resolve 7 at both wavelengths. The SNe generally only have upper size limits. In contrast all the SNRs are resolved with diameters {>=}0.27 pc. This size limit is consistent with them having just entered their Sedov phase while embedded in an interstellar medium (ISM) of density 10{sup 4} cm{sup -3}. These objects lie on the diameter-luminosity correlation for SNRs (and so also on the diameter-surface brightness relation) and extend these correlations to very small sources. The data are consistent with the relation L{proportional_to}D{sup -9/4}. Revised equipartition arguments adjusted to a magnetic field to a relativistic particle energy density ratio of 1% combined with a reasonable synchrotron-emitting volume filling factor of 10% give estimated magnetic field strengths in the SNR shells of {approx}15-50 mG. The SNR shell magnetic fields are unlikely to come from compression of ambient ISM fields and must instead be internally generated. We set an upper limit of 7 mG for the ISM magnetic field. The estimated energy in relativistic particles, 2%-20% of the explosion kinetic energy, is consistent with estimates from models that fit the IR-radio correlation in compact starburst galaxies.

• OSTI ID: 21587352
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 740; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
BINARY STARS
CORRELATIONS
COSMIC RADIO SOURCES
ELECTROMAGNETIC RADIATION
ENERGY DENSITY
ERUPTIVE VARIABLE STARS
GALAXIES
IMAGES
INFRARED RADIATION
INTERFEROMETRY
MAGNETIC FIELDS
RADIATIONS
STARS
SUPERNOVA REMNANTS
SUPERNOVAE
VARIABLE STARS