Comparison of the Radio, Optical, and X-Ray Structures of the cD Galaxy in Abell 2597
Abstract
We present new, high spatial resolution X-ray and radio observations of the cD galaxy in A2597. The X-ray observations confirm that this is a cooling flow with a cooling rate of Mcool 327 Msun yr-1 within a radius of rcool ≈ 130 kpc. The central X-ray emission is elongated parallel to the major axis of the cD galaxy. Our radio observations are the first to resolve the structure of the small, powerful radio source PKS 2322- 122 associated with the central cD. The radio source consists of unresolved nuclear emission, a strongly bent radio jet to the southwest of the nucleus, and two diffuse lobes to the northeast and southwest of the nucleus. The radio source has a steep spectral index of α ≈ -1.35 for the entire source and α ≈ -1.5 for the diffuse lobes. The minimum nonthermal pressures of the diffuse lobes are in very good agreement with the measured pressure of the ambient X-ray-emitting gas. The diffuse morphology of the radio lobes, their steep spectral indices, and the apparent pressure equilibrium with the ambient gas all indicate that the radio lobes are confined by the ambient hot gas. The radio jets emerge perpendicular to the elongation in the inner X-ray structure. We suggest that the X-ray-emitting gas forms an inflowing disk which feeds the radio source. The radio jet to the southeast is disrupted and turned through a large projected angle roughly 1" away from the nucleus. We suggest that the jet was bent either by ram pressure due to motions in the ambient thermal gas or due to a collision with a dense, massive cloud. Both of the radio lobes have been deflected in the same direction in which the jet is bent; this is more consistent with ram pressure from motions of the ambient gas. The cD galaxy in A2597 has two blue optical lobes located on either side of the nucleus (McNamara & O'Connell 1993). The radio observations show that the lobes cannot be due to synchrotron or inverse Compton emission. The lobes are aligned with the initial directions of the radio jet. This morphology and the brightness of the jets are in agreement with a model in which the lobes are scattered light from an anisotropically beamed nucleus. It is also possible that the lobes might be produced by stars formed recently by interactions of the radio jets with the ambient gas.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 1995
- DOI:
- 10.1086/175899
- Bibcode:
- 1995ApJ...447..559S
- Keywords:
-
- GALAXIES: COOLING FLOWS;
- GALAXIES: CLUSTERS: INDIVIDUAL NAME: ABELL 2597;
- GALAXIES: ELLIPTICAL AND LENTICULAR;
- CD;
- RADIO CONTINUUM: GALAXIES;
- X-RAYS: GALAXIES