EDP Sciences
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Volume 416, Number 2, March III 2004
Page(s) 441 - 446
Section Cosmology (including clusters of galaxies)
DOI http://dx.doi.org/10.1051/0004-6361:20031725

A&A 416, 441-446 (2004)
DOI: 10.1051/0004-6361:20031725

On the L $\mathsf{_x - \sigma_{v}}$ relation of groups of galaxies

M. Plionis1, 2 and H. M. Tovmassian2

1  Institute of Astronomy & Astrophysics, National Observatory of Athens, I. Metaxa & B. Pavlou, P. Penteli 152 36, Athens, Greece
    e-mail: mplionis@astro.noa.gr
2  Instituto Nacional de Astrofísica Óptica y Electrónica, AP 51 y 216, 72000, Puebla, Pue, México

(Received 9 April 2003 / Accepted 6 November 2003 )

We analyse the $L_{\rm x}-\sigma_{\rm v}$ relation for the new Mulchaey et al. group Atlas. We find that once we take into account the possible statistical bias introduced by the cutoff in luminosity, we recover a relation that is consistent with that of clusters, i.e., $L_{\rm x} \propto \sigma^{4.1}$. The larger scatter of this relation for groups of galaxies could be attributed to an orientation effect, due to which the radial velocity dispersion of groups oriented close to orthogonal to the line of sight, would be underestimated. This effect could also contribute to flattening the slope of the group $L_{\rm x}-\sigma_{\rm v}$ relation.

Key words: galaxies: clusters: general -- X-rays: galaxies

Offprint request: H. M. Tovmassian, hrant@inaoep.mx

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