Understanding low and high velocity dispersion compact groups
| dc.creator | Mamon, G. A. | |
| dc.date | 1999-09-01 | |
| dc.date.accessioned | 2026-07-07T02:33:00Z | |
| dc.date.available | 2026-07-07T02:33:00Z | |
| dc.description | A galaxy system must have a minimum velocity dispersion for its mass to be greater than the sum of the masses of its galaxies. Nearly half of the nearby Hickson compact groups (HCGs) have too low a velocity dispersion in comparison with the rotational velocities of their spiral galaxies and internal velocity dispersions of their early types. A detailed study of the low velocity dispersion group, HCG 16 -- the only known group of late-type galaxies with diffuse intergalactic X-ray emitting hot gas -- reveals that half of the diffuse X rays are associated with foreground/background sources and the remaining gas is clumpy and mostly associated with the bright galaxies of the group. The large-scale environment of the group suggests that HCG 16 lies where a cosmological filament falls perpendicularly onto a large-scale sheet. The observed frequency of compact groups is lower than predicted from the extended Press-Schechter formalism, which also predicts that most 10^13 Msun objects in the Universe must be fairly old and hence have already coalesced into single objects, reminiscent of elliptical galaxies over-luminous in X-rays that are now being discovered. Thus, the low survival time of dense groups against the merging instability is no longer a worry for compact groups, as they form in large enough numbers. I show why other arguments against the reality of HCGs no longer hold, partly because of the biases of Hickson's sample. | |
| dc.description | To appear in IAU Colloq. 174, Small Galaxy Groups (meeting held in Turku, Finland, June 1999), ed. M. Valtonen & Chris Flynn (San Francisco: ASP). 8 pages LaTeX2e, uses graphics.sty and journals.sty (included), 5 encapsulated PS figures. Full resolution paper available at ftp://ftp.iap.fr/pub/from_users/gam/PAPERS/iau174.ps.gz (1261967 bytes) | |
| dc.identifier | https://arxiv.org/abs/astro-ph/9909019 | |
| dc.identifier | http://arxiv.org/abs/astro-ph/9909019 | |
| dc.identifier | ASP 209, pp. 217-225 (2000) | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/14673 | |
| dc.subject | Astrophysics | |
| dc.title | Understanding low and high velocity dispersion compact groups | |
| dc.type | text |