Unusual Radio Structures in the Cooling Flow Cluster 2A 0335+096
Abstract
We present new high-resolution radio images of the 2A 0335+096 cluster of galaxies obtained with the VLA, which we compare to X-ray and optical images of the cluster. In the center of the cluster, there are unresolved radio sources associated with the nucleus of the central D galaxy, with the nucleus of the nearby companion galaxy, and another galaxy that appears to absorb part of the cluster X-ray emission. Two small radio lobes are located approximately 12" on either side of the D galaxy nucleus. We argue that these mark the direction of the emergence of radio jets from the nucleus. A "bar" of X-ray emission coincides with these radio lobes. Most of the radio flux from the central region of the cluster is associated with diffuse, amorphous of emission, which is unpolarized and which has a steep radio spectrum. All of the extended radio components in the center have minimum nonthermal pressures that are much lower than the pressure of the X-ray emitting gas. The low pressure and depolarized emission suggest that the radio plasma is mixed with the thermal plasma. The central radio structure, lack of polarization, low nonthermal pressure, and steep spectral index are all similar to the radio source PKS 0745-191, also associated with the central galaxy in a strong cooling flow cluster. We argue that the weak radio jets in 2A 0335+096 and PKS 0745-191 are disrupted at small radii by the high-pressure ambient gas. The radio plasma from the disrupted jets continues to move outward, but as subsonic, buoyant plumes. These plumes may also entrain a good deal of the ambient thermal gas, which produces the X-ray bar in 2A 0335+096. The radio plasma mixes with the ambient thermal plasma, and continue to move outward buoyantly. In 2A 0335+096, the observed radio lobes are oriented nearly perpendicular to the direction from the D galaxy nucleus to the companion nucleus. There are also elongated optical line and X-ray structures in this same direction. We suggest that this gas forms a rotating disk, which is being accreted onto the D galaxy nucleus and which determines the direction of the radio jets. We also suggest that the activity of the two galactic nuclei and that the orientation of this disk may be due to the merger of the companion galaxy with the central D galaxy.
The cluster also contains a very long Narrow Angle Tail (NAT) radio galaxy. The minimum nonthermal pressures along the tail are in good agreement with the pressure of the surrounding X-ray emitting gas, which indicates that the material in the tail is confined by this gas. The radio spectrum steepens with distance from the galaxy along the tail due to radiative losses. The tail of the NAT radio source changes direction abruptly about 2' from the galaxy. We suggest that is due to buoyant motions of the tail rising out of and away from denser regions of the intracluster gas. In fact, the tail is projected against a region of reduced X-ray emission. The NAT galaxy is also observed to be a moderately strong X-ray source. The source is unresolved and fairly bright, which suggests that the X-ray emission is due to the AGN in this galaxy.- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 1995
- DOI:
- 10.1086/176205
- Bibcode:
- 1995ApJ...451..125S
- Keywords:
-
- GALAXIES: CLUSTERS: INDIVIDUAL ALPHANUMERIC: 2A 0335+096;
- GALAXIES: COOLING FLOWS;
- GALAXIES: ELLIPTICAL AND LENTICULAR;
- CD;
- GALAXIES: INTERGALACTIC MEDIUM;
- RADIO CONTINUUM: GALAXIES