Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 1998
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998baas...30..763b&link_type=abstract
American Astronomical Society Meeting, 191, #127.04
Astronomy and Astrophysics
Astronomy
Scientific paper
We report on the detection of a highly significant excess of foreground galaxies near the lines of sight to luminous quasars (R mag ~ 19(m) ) at z > 4. Our spectroscopy of some of these galaxies shows that they are foreground objects, typically with z ~ 1, although a few are quasar companions at z > 4. This excess also appears to be correlated with the apparent luminosity of the QSO - brighter QSOs have more foreground galaxies associated with them than faint QSOs. This suggests that gravitational (micro)lensing may be systematically affecting our inferred luminosities of these objects. These foreground galaxies have typical R magnitudes of ~ 25 and impact parameters of about 100 comoving kpc depending on the choice of cosmology. The number of galaxies detected near the sample of bright QSOs was compared with counts of faint galaxies found in surveys of blank fields of sky, and two-point correlation functions are determined for individual fields and the sample as a whole. We also find a correlation between the observed rest-frame B-band luminosity of the QSOs to their spectral indices, in the sense that brighter QSOs are redder. This is consistent with observing the brighter QSOs through slightly dusty foreground galaxies. This result may have significant implications for our understanding of the evolution of the quasar luminosity function. We may be overestimating the number of bright quasars due to this magnification. In addition, our understanding of the evolution of high-redhisft absorbers may change. Damped Lyman alpha absorbers are studied along the lines of sights to bright high-redshift quasars, and if there is an overdensity of galaxies along these lines of sight, we are overestimating the comoving density of H I in DLAs. However, if a population of thick lenses/absorbers exists, we would see the opposite effect.
Banas Kenneth R.
de Carvalho Reinaldo R.
Djorgovski Stanislav G.
Gal Roy R.
Kennefick Daniel J.
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