Euclid

Abstract:

We review the current status of QSO clustering measurements, particular with respect to their relevance in understanding AGN physics. Measurements based on the 2dF QSO Redshift Survey (2QZ) find a scale length for QSO clustering of s_0=5.76(+0.17-0.27) h-1 Mpc at a redshift ~1.5, very similar to low redshift galaxies. There is no evidence of evolution in the clustering of QSOs from z~0.5 to z~2.2. This lack of evolution and low clustering amplitude suggests a short life time for AGN activity of the order ~10^6-10^7 years. Large surveys such at the 2QZ and SDSS also allow the the study of QSO environments in 3D for the first time (at least at low redshift), early results from this work seem to show no difference between the environments of QSOs and normal galaxies. Future studies e.g. measuring clustering as a function of black hole mass, and deep QSO surveys should provide further insight into the formation and evolution of AGN.

Abstract:

We present results of a Gemini adaptive optics (AO) imaging program to investigate the host galaxies of typical QSOs at z ∼ 2. Our aim is to study the host galaxies of typical L*QSO QSOs at the epoch of peak QSO and star formation activity. The large database of faint QSOs provided by the Two-Degree Field QSO Redshift Survey allows us to select a sample of QSOs at z = 1.75-2.5 that have nearby (<12″ separation) bright stars suitable for use as AO guide stars. We have observed a sample of nine QSOs. The images of these sources have AO-corrected FWHM of between 0″.11 and 0″.25. We use multiple observations of point-spread function (PSF) calibration star pairs to quantify any uncertainty in the PSF. We then factored these uncertainties into our modeling of the QSO plus host galaxy. In only one case did we convincingly detect a host (2QZ J133311.4+001949, at z = 1.93). This host galaxy has K = 18.5 ± 0.2 mag with a half-light radius Re = 0″.55 ± 0″.1 equivalent to ∼3L*gal, assuming a simple passively evolving model. From detailed simulations of our host galaxy modeling process, we find that for four of our targets we should be sensitive to host galaxies that are equivalent to ∼2L*gal (passively evolved). Our nondetections therefore place tight constraints on the properties of L*QSO QSO host galaxies, which can be no brighter (after allowing for passive evolution) than the host galaxies of L*QSO active galactic nuclei at low redshift, although the QSOs themselves are a factor of ∼50 brighter. This implies that either the fueling efficiency is much greater at high redshift or that more massive black holes are active at high redshift.

Abstract:

The completed 2dF QSO Redshift (2QZ) Survey has been used to search for extreme large-scale cosmological structure (around 200 Mpc) over the redshift range 0100Mpc are in the linear or only weakly non-linear regime and do not represent collapsed non-linear structures. We compare the measurements with the expectation of a standard LCDM model by measuring the variance of counts in cells and find that, provided the distribution of QSOs on large scales exhibits a mild bias with respect to the distribution of dark matter, the observed fluctuations are found to be in good agreement with the model. There is no evidence on such scales for any extreme structures that might require, for example, departures from the assumption of Gaussian initial perturbations. Thus the power-spectrum derived from the 2QZ Survey appears to provide a complete description of the distribution of QSOs. The amount of bias and its redshift dependence that is required is consistent with that found from studying the clustering of 2QZ QSOs on 10 Mpc scales, and may be adequately described by an approximately redshift-invariant power spectrum with normalisation sigma_8=1.0 corresponding to a bias at z=0 of b=1.1 rising to b=2 at the survey's mean redshift z=1.5.

Abstract:

We report on measurements of the cosmological constant, Λ, and the redshift space distortion parameter β= Ωm0.6/b, based on an analysis of the quasi-stellar object (QSO) power spectrum parallel and perpendicular to the observer's line of sight, Ps(k≺, k⊥), from the final catalogue of the Two-Degree Field (2dF) QSO Redshift Survey. We derive a joint Λ - β constraint from the geometric and redshift-space distortions in the power spectrum. By combining this result with a second constraint based on mass clustering evolution, we break this degeneracy and obtain strong constraints on both parameters. Assuming a flat (Ωm + Ωλ = 1) cosmology and a Λ cosmology r(z) function to convert from redshift into comoving distance, we find best-fitting values of Ωλ = 0.71 -0.17+0.09 and βq(z ∼ 1.4) = 0.45 -0.11+0.09 Assuming instead an Einstein-de Sitter cosmology r(z) we find that the best-fitting model obtained, with Ω λ = 0.64+0.16+0.11 and β q(z ∼ 1.4) = 0-40-0.09+0.09, is consistent with the Λ r(z) results, and inconsistent with a Ω λ = 0 flat cosmology at over 95 per cent confidence.