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http://hdl.handle.net/20.500.12386/29933
Title: | The low-frequency properties of FR0 radio galaxies | Authors: | CAPETTI, Alessandro Ranieri D. Baldi BRIENZA, MARISA MORGANTI, RAFFAELLA Gabriele Giovannini |
Issue Date: | 2019 | Journal: | ASTRONOMY & ASTROPHYSICS | Number: | 631 | First Page: | A176 | Abstract: | Using the Alternative Data Release of the TIFR GMRT Sky Survey (TGSS), we studied the low-frequency properties of FR0 radio galaxies, the large population of compact radio sources associated with red massive early-type galaxies revealed by surveys at 1.4 GHz. We considered TGSS observations from FR0CAT, a sample formed by 104 FR0s at z<0.05: all but one of them are covered by the TGSS, and 43 of them are detected above a 5 sigma limit of 17.5 mJy. No extended emission has been detected around the FR0s, corresponding to a luminosity limit of < 4 10^23 W/Hz over an area of 100 kpc x 100 kpc. All but eight FR0s have a flat or inverted spectral shape (alpha < 0.5) between 150 MHz and 1.4 GHz: this spectral behavior confirms the general paucity of optically thin extended emission within the TGSS beam, as is expected for their compact 1.4 GHz morphology. Data at 5 GHz were used to build their radio spectra, which are also generally flat at higher frequencies. By focusing on a sub-sample of FR0s with flux density > 50 mJy at 1.4 GHz, we found that ~75% of them have a convex spectrum, but with a smaller curvature than the more powerful gigahertz peaked-spectrum sources (GPS). The typical FR0s radio spectrum is better described by a gradual steepening toward high frequencies, rather than to a transition from an optically-thick to an optically-thin regime, possibly observed in only ~15% of the sample. | URI: | http://hdl.handle.net/20.500.12386/29933 | URL: | https://www.aanda.org/articles/aa/full_html/2019/11/aa36254-19/aa36254-19.html | ISSN: | 0004-6361 | DOI: | 10.1051/0004-6361/201936254 | Bibcode ADS: | 2019A&A...631A.176C | Fulltext: | open |
Appears in Collections: | 1.01 Articoli in rivista |
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