Resolution of the Compact Radio Continuum Sources in Arp220

Дата и время публикации : 2011-09-29T09:01:16Z

Авторы публикации и институты :
Fabien Batejat
John E. Conway
Rossa Hurley
Rodrigo Parra
Philip J. Diamond
Colin J. Lonsdale
Carol J. Lonsdale

Ссылка на журнал-издание: Ссылка на журнал-издание не найдена
Коментарии к cтатье: 16 pages, 5 figures
Первичная категория: astro-ph.CO

Все категории : astro-ph.CO

Краткий обзор статьи: 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 {geq} 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 10^4 cm^{-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 {propto} D^{-9/4}. Revised equipartition arguments adjusted to a magnetic field to 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 ~ 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.

Category: Physics