Astronomy and Astrophysics, volume 341, 44 (1999/1-1)
The Mpc-scale radio source associated with the GPS galaxy B 1144+352.
SCHOENMAKERS A.P., DE BRUYN A.G., ROETTGERING H.J.A. and VAN DER LAAN H.
Abstract (from CDS):
We present the results of new observations of the enigmatic radio source B 1144+352 with the WSRT at 1.4GHz. This source is hosted by an mr=14.3±0.1 galaxy at a redshift of z=0.063±0.002 and is one of the lowest redshift Gigahertz Peaked Spectrum (GPS) sources known. It has been known to show radio structure on pc-scale in the radio core and on 20-60kpc-scale in two jet-like radio structures. The WENSS and NVSS surveys have now revealed faint extended radio structures on an even much larger scale. We have investiga ted these large-scale radio components with new 1.4-GHz WSRT observations. Our radio data indicate that the eastern radio structure has a leading hotspot and we conclude that this structure is a radio lobe originating in the galaxy hosting the GPS source. The western radio structure contains two separate radio sources which are superposed on the sky. The first is a low-power radio source, hosted by a mR=15.3±0.5 galaxy at a similar redshift (z=0.065±0.001) to the GPS host galaxy; the second is an extended radio lobe, which we believe is associated with the GPS host galaxy and which contains an elongated tail. The total projected linear size of the extended radio structure associated with B 1144+352 is ∼1.2Mpc. The core of B1144+353 is a known variable radio source: its flux density at 1.4GHz has increased continuously between 1974 and 1994. We have measured the flux density of the core in our WSRT observations (epoch 1997.7) and find a value of 541±10mJy This implies that its flux density has decreased by ∼70mJy between 1994 and 1997. Further, we have retrieved unpublished archival ROSAT HRI data of B1144+352. The source has been detected and appears to be slightly extended in X-rays. We find a luminosity of (1.26±0.15)x1043erg/s between 0.1 and 2.4keV, assumin that the X-ray emission is due to an AGN with a powerlaw spectrum with photon index 1.8, or (0.95±0.11)x1043erg/s if it is due to thermal bremsstrahlung at T=107K. The detection of the X-ray source suggests that the intrinsic HI column density cannot be much larger than a few times 1021cm–2. The non-detection of an extended X-ray halo in a radius of 250 kpc around the host galaxy limits the X-ray luminosity of an intra-cluster gas component within this radius to ≲2.3x1042erg/s (1σ upper limit). This is below the luminosity of an X-ray luminous cluster and is more comparable to that of poor groups of galaxies. Also the optical data show no evidence for a rich cluster around the host galaxy. B 1144+352 is the second GPS galaxy known to be associated with a Mpc-sized radio source, the other being B 1245+676. We argue that the observed structure in both these GPS radio sources must be the result of an interrupted central jet-activity, and that a such they may well be the progenitors of sources belonging to the class of double-double radio galaxy.
galaxies: active - galaxies: individual: B 1144+352 - galaxies: individual: B 1144+353 - galaxies: jets - radio continuum: galaxies - X-rays: galaxies