Details

Autor(en) / Beteiligte

• Muller, C
• Burd, P R
• Schulz, R
• Coppejans, R
• Falcke, H
• Intema, H
• Kadler, M
• Krauss, F
• Ojha, R

Titel

The MHz-peaked radio spectrum of the unusual gamma -ray source PMNJ1603-4904

Ist Teil von

• Astronomy and astrophysics (Berlin), 2016-09, Vol.593

Erscheinungsjahr

2016

Link zum Volltext

Quelle

EZB*

Beschreibungen/Notizen

• Context. The majority of bright extragalactic gamma -ray sources are blazars. Only a few radio galaxies have been detected by Fermi/LAT. Recently, the GHz-peaked spectrum source PKS1718-649 was confirmed to be gamma -ray bright, providing further evidence for the existence of a population of gamma -ray loud, compact radio galaxies. A spectral turnover in the radio spectrum in the MHz to GHz range is a characteristic feature of these objects, which are thought to be young due to their small linear sizes. The multiwavelength properties of the gamma -ray source PMNJ1603-4904 suggest that it is a member of this source class. Aims. The known radio spectrum of PMNJ1603-4904 can be described by a power law above 1GHz. Using observations from the Giant Metrewave Radio Telescope (GMRT) at 150, 325, and 610MHz, we investigate the behavior of the spectrum at lower frequencies to search for a low-frequency turnover. Methods. Data from the TIFR GMRT Sky Survey (TGSS ADR) catalog and archival GMRT observations were used to construct the first MHz to GHz spectrum of PMNJ1603-4904. Results. We detect a low-frequency turnover of the spectrum and measure the peak position at about 490MHz (rest-frame), which, using the known relation of peak frequency and linear size, translates into a maximum linear source size of ~1.4kpc. Conclusions. The detection of the MHz peak indicates that PMNJ1603-4904 is part of this population of radio galaxies with turnover frequencies in the MHz to GHz regime. Therefore it can be considered the second confirmed object of this kind detected in gamma -rays. Establishing this gamma -ray source class will help to investigate the gamma -ray production sites and to test broadband emission models.