The optical–infrared colors of corals qsos: searching for dust reddening associated with high-redshift damped lya systems
Author
dc.contributor.author
Ellison, Sara L.
Author
dc.contributor.author
Hall, Patrick B.
es_CL
Author
dc.contributor.author
Lira Teillery, Paulina
es_CL
Admission date
dc.date.accessioned
2014-01-03T13:16:07Z
Available date
dc.date.available
2014-01-03T13:16:07Z
Publication date
dc.date.issued
2005-11
Cita de ítem
dc.identifier.citation
The Astronomical Journal, 130:1345–1357, 2005 October
en_US
Identifier
dc.identifier.uri
https://repositorio.uchile.cl/handle/2250/125941
Abstract
dc.description.abstract
The presence of dust in quasar absorbers, such as damped Ly (DLA) systems, may cause the background QSO to
appear reddened.We investigate the extent of this potential reddening by comparing the optical-to-infrared colors of
QSOs with and without intervening absorbers. Our QSO sample is based on the Complete Optical and Radio
Absorption Line System (CORALS) survey of Ellison and coworkers. The CORALS data set consists of 66 radioselected
QSOs at zem 2:2 with complete optical identifications.We have obtained near-simultaneous B- and K-band
magnitudes for a subset of the CORALS sample and supplemented our observations with further measurements
published in the literature. In total, we have B K colors for 42 of the 66 QSOs, of which 14 have intervening DLA
systems. To account for redshift-related color changes, the B K colors are normalized using the Sloan Digital Sky
Survey QSO composite. The mean normalized B K color of the DLA subsample is +0.12, whereas the mean for the
no-DLA sample is 0.10; both distributions have rms scatters of 0.5. Neither a Student’s t-test nor a Kolmogorov-
Smirnov test indicate that there is any significant difference between the two color distributions. Based on simulations
that redden the colors of QSOs with intervening DLA systems, we determine a reddening limit that corresponds to
E(B V )<0:04 (SMC-like extinction) at 99% confidence (3 ), assuming that E(B V ) is the same for all DLA
systems. Finally, we do not find any general correlation between absorber properties (such as [Fe/Zn] or neutral
hydrogen column density) and B K color. The two reddest QSOs with DLA systems in our sample have H i column
densities that differ from each other by an order of magnitude and moderate gas-to-dust ratios as inferred from
chemical abundances. One of these two QSOs shows evidence for strong associated absorption from X-ray observations,
an alternative explanation for its very red color.We conclude that the presence of intervening galaxies causes
a minimal reddening of the background QSO.