Euclid

Abstract:

(ABRIDGED) We present a power spectrum analysis of the 10K catalogue from the 2dF QSO Redshift Survey. We compare the redshift-space power spectra of QSOs to those measured for galaxies and Abell clusters at low redshift and find that they show similar shapes in their overlap range, 50-150h^{-1}Mpc, with P_QSO(k)\propto k^{-1.4}. The amplitude of the QSO power spectrum at z~1.4 is almost comparable to that of galaxies at the present day if Omega_m=0.3 and Omega_Lambda=0.7 (the Lambda cosmology), and a factor of ~3 lower if Omega_m=1 (the EdS cosmology) is assumed. The amplitude of the QSO power spectrum is a factor of ~10 lower than that measured for Abell clusters at the present day. At larger scales, the QSO power spectra continue to rise robustly to ~400 h^{-1}Mpc, implying more power at large scales than in the APM galaxy power spectrum measured by Baugh & Efstathiou. We split the QSO sample into two redshift bins and find little evolution in the amplitude of the power spectrum. The QSO power spectrum may show a spike feature at ~90h^{-1}Mpc assuming the Lambda cosmology or ~65 h^{-1}Mpc assuming an EdS cosmology. Although the spike appears to reproduce in both the North and South strips and in two independent redshift ranges, its statistical significance is still marginal and more data is needed to test further its reality. We compare the QSO power spectra to CDM models to obtain a constraint on the shape parameter, Gamma. For two choices of cosmology (Omega_m=1, Omega_Lambda=0 and Omega_m=0.3, Omega_Lambda=0.7), we find the best fit model has Gamma~0.1 +-0.1.

Abstract:

We report the determination of the 2dF spectroscopic selection function as a function of both redshift and magnitude per observed field. Variations in number densities between fields due to intrinsic clustering in the QSO population can then be disentangled from those caused by varying completenesses in fields observed under differing weather conditions.

Abstract:

We present the first results from a major Hubble Space Telescope program designed to investigate the cosmological evolution of quasar host galaxies from z~2 to the present day. Here we describe J and H-band NICMOS imaging of two quasar samples at redshifts of 0.9 and 1.9 respectively. Each sample contains equal numbers of radio-loud and radio-quiet quasars, selected to lie within the same narrow range of optical absolute magnitude (-24 > M_V > -25). Filter and target selection were designed to ensure that at each redshift the images sample the same part of the object's rest-frame spectrum, avoiding potential contamination by [OIII]lambda5007 and H-alpha emission lines. At z=1 the hosts of both radio-loud and radio-quiet quasars lie on the same Kormendy relation described by 3CR radio galaxies at comparable redshift. There is some evidence for a gap of ~1 mag between the host luminosities of RLQs and RQQs, a difference that cannot be due to emission-line contamination given the design of our study. However, within current uncertainties, simple passive stellar evolution is sufficient to link these galaxies with the elliptical hosts of low-redshift quasars of comparable nuclear output, implying that the hosts are virtually fully assembled by z=1. At z=2 the luminosity gap appears to have widened further to ~1.5 mag. Thus while the hosts of radio-loud quasars remain consistent with a formation epoch of z>3, allowing for passive evolution implies that the hosts of radio-quiet quasars are ~2-4 times less massive at z=2 than at low z.