Subcluster Mergers and Galaxy Infall in A2151
Abstract
We have obtained a 12.5 ks image of the Hercules Cluster, A2151, with the ROSAT PSPC. Comparison of the optical and X-ray data suggest the presence of at least three distinct subclusters in A2151. The brightest X-ray emission coincides with the highest-density peak in the galaxy distribution, and is bimodal. The northern subclump, distinct in position and velocity, has no detectable X-ray gas. The eastern subclump, apparent in the optical contour map, is indistinguishable from the main clump in velocity space, but is clearly visible in the X-ray image. X-ray spectra derived from the central peak of emission yield a best-fit temperature of 1.6 keV. The emission coincident with the eastern clump of galaxies is cooler, 0.8 keV, and is outside the 90% confidence intervals of the central peak temperature. We suggest that the eastern and central subclusters have recently undergone a merger event. The lack of X-ray emission to the north suggests that those galaxies do not form a physically distinct structure (i.e., they are not located within a distinct gravitational potential), but rather that they are falling into the cluster core along the filament defined by the Hercules Supercluster.
- Publication:
-
The Astronomical Journal
- Pub Date:
- March 1995
- DOI:
- 10.1086/117330
- arXiv:
- arXiv:astro-ph/9412004
- Bibcode:
- 1995AJ....109..920B
- Keywords:
-
- Dynamic Characteristics;
- Galactic Clusters;
- Gravitational Effects;
- Intergalactic Media;
- Kinematics;
- Visible Spectrum;
- X Ray Spectra;
- Flux Density;
- Image Analysis;
- Morphology;
- Rosat Mission;
- Spatial Distribution;
- Spectrum Analysis;
- Temperature Distribution;
- Velocity Distribution;
- Astronomy;
- X-RAYS: GALAXIES;
- GALAXIES: KINEMATICS AND DYNAMICS;
- Astrophysics
- E-Print:
- To appear in the March 1995 issue of AJ, LaTeX, PostScript text and figures available by anonymous ftp from kula.phsx.ukans.edu