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Register a new userProbing 3-D matter distribution at z~2 with QSO multiple lines of sight
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We investigate the 3-D matter distribution at z~2 with high resolution (R ~ 40000) spectra of QSO pairs and groups obtained with the UVES spectrograph at ESO VLT. Our sample is unique for the number density of objects and the variety of separations, between 0.5 and 7 proper Mpc. We compute the real space cross-correlation function of the Lyman-alpha forest transmitted fluxes. There is a significant clustering signal up to ~2 proper Mpc, which is still present when absorption lines with high column density (log N > 13.8) are excluded.
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Broad Absorption Line (BAL) QSOs have been suggested to be youthful super-accretors based on their powerful radiatively driven absorbing outflows and often reddened continua. To test this hypothesis, we observed near IR spectra of the H$beta$ region for 11 bright BAL QSOs at redshift z ~ 2. We measured these and literature spectra for 6 BAL QSOs, 13 radio-loud and 7 radio-quiet non-BAL QSOs. Using the luminosity and H$beta$ broad line width to derive black hole mass and accretion rate, we find that both BAL and non-BAL QSOs at z ~ 2 tend to have higher $L/L_{Edd}$ than those at low z -- probably a result of selecting the brightest QSOs. However, we find that the high z QSOs, in particular the BAL QSOs, have extremely strong Fe II and very weak [O III], extending the inverse relationship found for low z QSOs. This suggests that, even while radiating near $L_{Edd}$, the BAL QSOs have a more plentiful fuel supply than non-BAL QSOs. Comparison with low z QSOs shows for the first time that the inverse Fe II -- [O III] relationship is indeed related to $L/L_{Edd}$, rather than black hole mass.
Absorption spectroscopy of gravitationally lensed quasars (GLQs) enables study of spatial variations in the interstellar and/or circumgalactic medium of foreground galaxies. We report observations of 4 GLQs, each with two images separated by 0.8-3.0, that show strong absorbers at redshifts 0.4$<$$z_{abs}$$<$1.3 in their spectra, including some at the lens redshift with impact parameters 1.5-6.9 kpc. We measure H I Lyman lines along two sight lines each in five absorbers (10 sight lines in total) using HST STIS, and metal lines using Magellan Echellette or Sloan Digital Sky Survey. Our data have doubled the lens galaxy sample with measurements of H I column densities ($N_{rm H I}$) and metal abundances along multiple sight lines. Our data, combined with the literature, show no strong correlation between absolute values of differences in $N_{rm H I}$, $N_{rm Fe II}$, or [Fe/H] and the sight line separations at the absorber redshifts for separations of 0-8 kpc. The estimated abundance gradients show a tentative anti-correlation with abundances at galaxy centers. Some lens galaxies show inverted gradients, possibly suggesting central dilution by mergers or infall of metal-poor gas. [Fe/H] measurements and masses estimated from GLQ astrometry suggest the lens galaxies lie below the total mass-metallicity relation for early-type galaxies as well as measurements for quasar-galaxy pairs and gravitationally lensed galaxies at comparable redshifts. This difference may arise in part from the dust depletion of Fe. Higher resolution measurements of H and metals (especially undepleted elements) for more GLQ absorbers and accurate lens redshifts are needed to confirm these trends.
Absorption-line spectroscopy is an effective probe for cold ejecta within an SNR, provided that suitable background UV sources can be identified. For the SN 1006 remnant we have identified four such sources, in addition to the much-studied Schweitzer-Middleditch (SM) star. We have used STIS on HST to obtain UV spectra of all four sources, to study core samples of the SN 1006 interior. The line of sight closest to the center of the SNR shell, passing only 2.0 arcmin away, is to a V = 19.5 QSO at z = 1.026. Its spectrum shows broad Fe II absorption lines, asymmetric with red wings broader than blue. The similarity of these profiles to those seen in the SM star, which is 2.8 arcmin from the center in the opposite direction, confirms the existence of a bulge on the far side of SN 1006. The Fe II equivalent widths in the QSO spectrum are ~ 50% greater than in the SM star, suggesting that somewhat more iron may be present within SN 1006 than studies of the SM star alone have indicated, but this is still far short of what most SNIa models require. The absorption spectrum against a brighter z = 0.337 QSO seen at 57% of the shell radius shows broad silicon absorption lines but no iron other than narrow, probably interstellar lines. The cold iron expanding in this direction must be confined within v <~ 5200 km/s, also consistent with a high-velocity bulge on the far side only. The broad silicon lines indicate that the silicon layer has expanded beyond this point, and that it has probably been heated by a reverse shock. Finally, the spectra of two ~ A0V stars near the southern shell rim show no broad or unusually strong absorption lines, suggesting that the low-ionization ejecta are confined within 83% of the shell radius, at least at the azimuths of these background sources.
We present a direct detection of the growth of large-scale structure, using weak gravitational lensing and photometric redshift data from the COMBO-17 survey. We use deep R-band imaging of two 0.25 square degree fields, affording shear estimates for over 52000 galaxies; we combine these with photometric redshift estimates from our 17 band survey, in order to obtain a 3-D shear field. We find theoretical models for evolving matter power spectra and correlation functions, and fit the corresponding shear correlation functions to the data as a function of redshift. We detect the evolution of the power at the 7.7 sigma level given minimal priors, and measure the rate of evolution for 0<z<1. We also fit correlation functions to our 3-D data as a function of cosmological parameters sigma_8 and Omega_Lambda. We find joint constraints on Omega_Lambda and sigma_8, demonstrating an improvement in accuracy by a factor of 2 over that available from 2D weak lensing for the same area.
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 2dF QSO Redshift Survey allows us to select a sample of QSOs at z=1.75-2.5 which have nearby (<12 arcsecond separation) bright stars suitable for use as AO guide stars. We have observed a sample of 9 QSOs. The images of these sources have AO corrected full-width at half-maximum of between 0.11 and 0.25 arcseconds. We use multiple observations of point spread function (PSF) calibration star pairs in order to quantify any uncertainty in the PSF. We then factored these uncertainties into our modelling 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, r_e=0.55+-0.1, equivalent to ~3L*_gal assuming a simple passively evolving model. From detailed simulations of our host galaxy modelling 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 non-detections 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 AGN 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.
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