The low-frequency properties of FR 0 radio galaxies
Using the alternative data release of the TIFR GMRT Sky Survey (TGSS), we studied the low-frequency properties of FR 0 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 FR...
Saved in:
Published in | Astronomy and astrophysics (Berlin) Vol. 631; p. A176 |
---|---|
Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
Heidelberg
EDP Sciences
01.11.2019
|
Subjects | |
Online Access | Get full text |
Cover
Loading…
Summary: | Using the alternative data release of the TIFR GMRT Sky Survey (TGSS), we studied the low-frequency properties of FR 0 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 FR 0s at z < 0.05: all but one of them are covered by the TGSS, and 43 of them are detected above a 5σ limit of 17.5 mJy. No extended emission has been detected around the FR 0s, corresponding to a luminosity limit of ≲4 × 1023 W Hz−1 over an area of 100 kpc × 100 kpc. All but eight FR 0s have a flat or inverted spectral shape (α < 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 FR 0s 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 FR 0s 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. |
---|---|
Bibliography: | dkey:10.1051/0004-6361/201936254 href:https://www.aanda.org/articles/aa/abs/2019/11/aa36254-19/aa36254-19.html ark:/67375/80W-4WVPHM13-4 publisher-ID:aa36254-19 e-mail: capetti@oato.inaf.it bibcode:2019A%26A...631A.176C istex:78B3EDF736E04EBAD5A4CF97967AD042A865CBF2 |
ISSN: | 0004-6361 1432-0746 |
DOI: | 10.1051/0004-6361/201936254 |