Triplets of Quasars at high redshift I: Photometric data

We have conducted an optical and infrared imaging in the neighbourhoods of 4 triplets of quasars. R, z', J and Ks images were obtained with MOSAIC II and ISPI at Cerro Tololo Interamerican Observatory. Accurate relative photometry and astrometry were obtained from these images for subsequent use in deriving photometric redshifts. We analyzed the homogeneity and depth of the photometric catalog by comparing with results coming from the literature. The good agreement shows that our magnitudes are reliable to study large scale structure reaching limiting magnitudes of R = 24.5, z' = 22.5, J = 20.5 and Ks = 19.0. With this catalog we can study the neighbourhoods of the triplets of quasars searching for galaxy overdensities such as groups and galaxy clusters.Comment: The paper contains 12 figures and 3 table

Evidence of increased UV Fe II emission in quasars in candidate overdense regions

We present evidence for a skewed distribution of UV Fe ii emission in quasars within candidate overdense regions spanning spatial scales of ∼50 Mpc at 1.11 42 Å) and a dearth of low-equivalent-width sources. There are various possible explanations for this effect, including dust, Lyα fluorescence, microturbulence and iron abundance. We find that the most plausible of these is enhanced iron abundance in the overdense regions, consistent with an enhanced star formation rate in the overdense regions compared to the field

Observations across nearby spiral bulges

The bulges of spiral galaxies may be old, as in our Galaxy, or may possess younger stars, as evidenced in spectroscopic line strengths in some external bulges. Bulges look similar to elliptical galaxies, but their formation history is expected to differ due to the presence of the disc and different formation mechanisms. This project extends the numbers of high signal-to-noise, broad coverage spectra to a larger sample of bulges in order to test conflicting ideas about their age distributions. New Gemini long-slit observations will be used to derive stellar population ages and histories across 30 bulges. Here we present preliminary results from the sample. © 2008 Copyright International Astronomical Union 2008

The Clowes-Campusano large quasar group survey. I.Galexselected sample of lyman Break Galaxies ATz∼ 1

The Clowes & Campusano Large Quasar Group (LQG, MNRAS 1991, 249, 218) at z = 1.28 has been re-examined using the quasar data from the DR5QSO catalog of the Sloan Digital Sky Survey. In the 1991 discovery, the LQG impinged on the northern, southern and eastern limits of the survey. In the DR5QSO data, the western, northern and southern boundaries of the LQG remain essentially unchanged, but an extension eastwards of 2 deg. is indicated. In the DR5QSO data, the LQG has 31 members, with z = 1.27, and a characteristic size 250 Mpc. Its quasar density contrast is δρ/ρ 0.94, suggesting either that it is approaching the non-linear regime or that quasar formation is substantially enhanced in LQGs. A new LQG of 41 members is indicated at z = 1.11 and within 0.8 deg. of the Clowes & Campusano LQG. A further LQG, at z = 1.53 and within 1.5 deg. of the Clowes & Campusano LQG, was previously known but is found here with membership increased to 20. The characteristic sizes and quasar density contrasts of these two additional LQGs are (325 Mpc, 0.42) and (200 Mpc, 0.66) respectively. This concentration of three LQGs in the same cosmological neighborhood, with centroids that are almost co-linear, raises the possibility that large-scale structure can itself be associated on scales 350 Mpc