QSO cool gaseous haloes
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Absorption lines in quasar (QSO) spectra provide a unique tool for probing the gas and dust content of foreground galaxies and of intergalactic medium at almost any redshift. These features are considered to be linked to large gaseous haloes around galaxies extending up to 100 kpc. We investigate the MgII 2800 and CIV 1540 absorption features of the gas in the halo of a foreground QSO through the absorption imprinting on the spectra of a background QSO that is closely aligned with the nearest quasar .
Despite a number of studies aimed at connecting metal absorption systems (in particular Mg II and C IV) with galaxy properties the origin of the absorbing gas is still unclear. However, in the last decades, it is progressively emerging a scenario in which the stronger absorption lines (rest frame equivalent width EWr∼> 1 A) are linked to winds driven by the star formation activity, while the weaker one are associated with inflows of gas onto the host galaxies.
RESULTS:
At variance with the case of inactive and less massive galaxies we find that relatively strong (EW ~ 1 Ang) absorption features are present out to a radius of 100 kpc. This suggests that a large extended halo is associated with massive galaxies. When account is taken for different masses we find no difference between absorptions properties associated with inactive (less massive) and active (more massive) galaxies. Since in the spectra of the foreground QSO there are no signs of MgII absorptions of the same strength seen in the background QSO, we argue that the absorbing gas around the QSO is not homogeneous, as a possible consequence of the non isotropic emission from the QSO.
Publications:
- Farina, E.P., Falomo, R. Decarli, R. Treves, A. Kotilainen J.K., 2012 MNRAS in press arXiv:1211.3433
- Falomo, R. , Farina, E.P., Decarli, R. Treves, A. Kotilainen J.K., 2012 IAU Symp 295 - XXVIII IAU-GA , Beijing