SIMBAD references

2019MNRAS.485.2447M - Mon. Not. R. Astron. Soc., 485, 2447-2456 (2019/May-2)

GMRT observations of extragalactic radio sources with steeply inverted spectra.


Abstract (from CDS):

We report quasi-simultaneous Giant Metrewave Radio Telescope observations of seven extragalactic radio sources at 150, 325, 610, and 1400 MHz, in an attempt to accurately define their radio continuum spectra, particularly at frequencies below the observed spectral turnover. We had previously identified these sources as candidates for a sharply inverted integrated radio spectrum whose slope is close to, or even exceeds αc = +2.5, the theoretical limit due to synchrotron self-absorption (SSA) in a source of incoherent synchrotron radiation arising from relativistic particles with the canonical (i.e. power law) energy distribution. We find that four of the seven candidates have an inverted radio spectrum with a slope close to or exceeding +2.0, while the critical spectral slope αc is exceeded in at least one case. These sources, together with another one or two reported in very recent literature, may well be the archetypes of an extremely rare class, from the standpoint of violation of the SSA limit in compact extragalactic radio sources. However, the alternative possibility that free-free absorption is responsible for their ultra-sharp spectral turnover cannot yet be discounted.

Abstract Copyright: © 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society

Journal keyword(s): radiation mechanisms: non thermal - galaxies: ISM - galaxies: jets - galaxies: nuclei - quasars: general - radio continuum: galaxies

Simbad objects: 24

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