In this contribution we use optical and near-IR images obtained at VLT to investigate the relations between the properties of the circum-galactic medium of the host galaxies and of the large scale galaxy environments of the foreground quasars. Absorption systems of EW ≥0.3 associated with the foreground quasars are revealed up to 200 kpc from the centre of the host galaxy, showing that the structure of the absorbing gas is patchy with a covering fraction quickly decreasing beyond 100 kpc. We used optical spectroscopy of closely aligned pairs of quasars (projected distance ≤ 200 kpc, but at very different redshift) obtained at the VLT and Gran Telescopio Canarias to investigate the distribution of the absorbing gas for a sample of quasars at z ~1. The properties of circum-galactic gas in the halo of quasar host galaxies are investigated analyzing Mg II 2800 and C IV 1540 absorption-line systems along the line of sight close to quasars. 6Max-Planck-Institut für Astronomie, Heidelberg, Germany.5Instituto de Astrofisica de Canarias, La Laguna, Spain.4Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Turku, Finland.3Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano (INAF), Milan, Italy.2Osservatorio Astronomico di Padova (INAF), Padua, Italy.1Dipartimento di Scienza e Alta Tecnologia (DISAT), Università degli Studi dell'Insubria, Como, Italy.Kotilainen 4, Riccardo Scarpa 5 and Emanuele Paolo Farina 6 The intrinsic link between associated absorbers and quasar hosts opens a new window to probe massive galaxy formation and galactic-scale feedback processes, and provides a crucial test of the evolutionary picture of quasars.Riccardo Ottolina 1 *, Renato Falomo 2, Aldo Treves 1, Michela Uslenghi 3, Jari K. This scenario predicts a larger fraction of young bulges, disturbed morphologies, and interactions of AAL quasar hosts compared to normal quasars. We suggest that the unique properties of AAL quasars can be explained if they are the transitional population from heavily dust-reddened quasars to normal quasars in the formation process of quasars and their hosts. AAL quasars also have dust reddening lying between normal quasars and the so-called dust-reddened quasars. = are physically associated with the quasar and its host. Our method for developing quasar spectra models can improve automated classification and predict the intrinsic spectrum in regions affected by intervening absorbers such as Ly α, C iv, and Mg ii, thus benefiting studies of large-scale structure. The redshift estimates from our model are consistent with the Mg ii emission-line redshift with an average offset that displays 51.4% less more » redshift-dependent variation relative to the SDSS eigenspectra. A significant contribution to the relative improvement is from the ability to reconstruct the range of emission-line variation. Our models achieve a median reduced χ 2 on non–broad absorption line quasar spectra that is reduced by 8.5% relative to models using the eigenspectra from the SDSS spectroscopic pipeline.
Quasar spectra free#
We model independent samples of SDSS quasar spectra with the eigenbasis, allowing for a free redshift parameter. Principal component analysis on the library results in an eigenspectrum basis spanning 1067–4007 Å. We compress the quasar populations into a library of 684 high-S/N composite spectra, anchored in redshift space by the Mg ii emission line. Our clustering analysis finds 396 quasar spectra that are not assigned to any population, 15 misclassified spectra, and 6 quasars with incorrect redshifts. We identify populations of spectrally similar quasars through pixel-level clustering on 12,968 high signal-to-noise ratio (S/N) spectra from the Sloan Digital Sky Survey (SDSS) in the redshift range of 1.57 < z < 2.4. Abstract We present a new approach to capturing the broad diversity of emission-line and continuum properties in quasar spectra.