Issue |
A&A
Volume 441, Number 1, October I 2005
|
|
---|---|---|
Page(s) | 89 - 101 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20053347 | |
Published online | 13 September 2005 |
Low power compact radio galaxies at high angular resolution
1
Dipartimento di Astronomia, Università di Bologna, via Ranzani 1, 40127 Bologna, Italy e-mail: [giroletti;ggiovann]@ira.cnr.it
2
Istituto di Radioastronomia, via Gobetti 101, 40129, Bologna, Italy
3
Kavli Institute of Particle Astrophysics and Cosmology, Menlo Park, CA 94025, USA e-mail: gtaylor@nrao.edu
4
National Radio Astronomy Observatory, PO Box O, Socorro, NM 87801, USA
Received:
2
May
2005
Accepted:
15
June
2005
We present sub-arcsecond resolution multi-frequency (8 and 22 GHz)
VLA images of five low power compact (LPC) radio sources, and phase
referenced VLBA images at 1.6 GHz of their nuclear regions. At the VLA
resolution we resolve the structure and identify component positions and flux
densities. The phase referenced VLBA data at 1.6 GHz reveals flat-spectrum,
compact cores (down to a few milliJansky) in four of the five sources. The
absolute astrometry provided by the phase referencing allows us to identify
the center of activity on the VLA images. Moreover, these data reveal rich
structures, including two-sided jets and secondary components. On the basis
of the arcsecond scale structures and of the nuclear properties, we rule out
the presence of strong relativistic effects in our LPCs, which must be
intrinsically small (deprojected linear sizes 10 kpc). Fits of
continuous injection models reveal break frequencies in the GHz domain, and
ages in the range
yrs. In LPCs, the outermost edge may be
advancing more slowly than in more powerful sources or could even be
stationary; some LPCs might also have ceased their activity. In general, the
properties of LPCs can be related to a number of reasons, including, but not
limited to: youth, frustration, low kinematic power jets, and short-lived
activity in the radio.
Key words: radio continuum: galaxies / galaxies: individual: 1855+37 / galaxies: active / galaxies: jets
© ESO, 2005
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