TY - JOUR
T1 - Nature and statistical properties of quasar associated absorption systems in the XQ-100 Legacy Survey
AU - Perrotta, Serena
AU - D'Odorico, Valentina
AU - Prochaska, J. Xavier
AU - Cristiani, Stefano
AU - Cupani, Guido
AU - Ellison, Sara
AU - Lòpez, Sebastian
AU - Becker, George D.
AU - Berg, Trystyn A. M.
AU - Christensen, Lise
AU - Denney, Kelly D.
AU - Hamann, Frederick
AU - Pâris, Isabelle
AU - Vestergaard, Marianne
AU - Worseck, Gábor
N1 - 18 pages, 13 figures, 5 tables
PY - 2016/11/1
Y1 - 2016/11/1
N2 - We statistically study the physical properties of a sample of narrow absorption line (NAL) systems looking for empirical evidences to distinguish between intrinsic and interveningNALs without taking into account any a priori definition or velocity cut-off. We analyse the spectra of 100 quasars with 3.5 < zem < 4.5, observed with X-shooter/Very Large Telescope in the context of the XQ-100 Legacy Survey. We detect an ~8s excess in the CIV number density within 10 000 km s-1 of the quasar emission redshift with respect to the random occurrence of NALs. This excess does not show a dependence on the quasar bolometric luminosity and it is not due to the redshift evolution of NALs. It extends far beyond the standard 5000 km s-1 cutoff traditionally defined for associated absorption lines. We propose to modify this definition, extending the threshold to 10 000 km s-1 when weak absorbers (equivalent width < 0.2Å) are also considered. We infer NV is the ion that better traces the effects of the quasar ionization field, offering the best statistical tool to identify intrinsic systems. Following this criterion, we estimate that the fraction of quasars in our sample hosting an intrinsic NAL system is 33 per cent. Lastly, we compare the properties of the material along the quasar line of sight, derived from our sample, with results based on close quasar pairs investigating the transverse direction. We find a deficiency of cool gas (traced by C II) along the line of sight connected to the quasar host galaxy, in contrast with what is observed in the transverse direction.
AB - We statistically study the physical properties of a sample of narrow absorption line (NAL) systems looking for empirical evidences to distinguish between intrinsic and interveningNALs without taking into account any a priori definition or velocity cut-off. We analyse the spectra of 100 quasars with 3.5 < zem < 4.5, observed with X-shooter/Very Large Telescope in the context of the XQ-100 Legacy Survey. We detect an ~8s excess in the CIV number density within 10 000 km s-1 of the quasar emission redshift with respect to the random occurrence of NALs. This excess does not show a dependence on the quasar bolometric luminosity and it is not due to the redshift evolution of NALs. It extends far beyond the standard 5000 km s-1 cutoff traditionally defined for associated absorption lines. We propose to modify this definition, extending the threshold to 10 000 km s-1 when weak absorbers (equivalent width < 0.2Å) are also considered. We infer NV is the ion that better traces the effects of the quasar ionization field, offering the best statistical tool to identify intrinsic systems. Following this criterion, we estimate that the fraction of quasars in our sample hosting an intrinsic NAL system is 33 per cent. Lastly, we compare the properties of the material along the quasar line of sight, derived from our sample, with results based on close quasar pairs investigating the transverse direction. We find a deficiency of cool gas (traced by C II) along the line of sight connected to the quasar host galaxy, in contrast with what is observed in the transverse direction.
KW - astro-ph.GA
KW - astro-ph.CO
U2 - 10.1093/mnras/stw1703
DO - 10.1093/mnras/stw1703
M3 - Journal article
SN - 0035-8711
VL - 462
SP - 3285
EP - 3301
JO - Royal Astronomical Society. Monthly Notices
JF - Royal Astronomical Society. Monthly Notices
ER -