Clustering of Lyman-alpha Emitters Around Quasars at z∼4z\sim4

The strong observed clustering of $z>3.5$ quasars indicates they are hosted by massive ($M_{\rm{halo}}\gtrsim10^{12}\,h^{-1}\,\rm{M_{\odot}}$) dark matter halos. Assuming quasars and galaxies trace the same large-scale structures, this should also manifest as strong clustering of galaxies around quasars. Previous work on high-redshift quasar environments, mostly focused at $z>5$, have failed to find convincing evidence for these overdensities. Here we conduct a survey for Lyman alpha emitters (LAEs) in the environs of 17 quasars at $z\sim4$ probing scales of $R\lesssim7\,h^{-1}\,{\rm{Mpc}}$. We measure an average LAE overdensity around quasars of 1.4 for our full sample, which we quantify by fitting the quasar-LAE cross-correlation function. We find consistency with a power-law shape with correlation length of $r^{QG}_{0}=2.78^{+1.16}_{-1.05}\,h^{-1}\,{\rm{cMpc}}$ for a fixed slope of $\gamma=1.8$. We also measure the LAE auto-correlation length and find $r^{GG}_{0}=9.12^{+1.32}_{-1.31}\,h^{-1}$\,cMpc ($\gamma=1.8$), which is $3.3$ times higher than the value measured in blank fields. Taken together our results clearly indicate that LAEs are significantly clustered around $z\sim4$ quasars. We compare the observed clustering with the expectation from a deterministic bias model, whereby LAEs and quasars probe the same underlying dark matter overdensities, and find that our measurements fall short of the predicted overdensities by a factor of 2.1. We discuss possible explanations for this discrepancy including large-scale quenching or the presence of excess dust in galaxies near quasars. Finally, the large cosmic variance from field-to-field observed in our sample (10/17 fields are actually underdense) cautions one from over-interpreting studies of $z\sim6$ quasar environments based on a single or handful of quasar fields.Comment: 19 pages, 12 figures, submitted to the Ap

Evolution of Cluster Ellipticals at 0.2 < z < 1.2 from Hubble Space Telescope Imaging

Two-dimensional surface photometry derived from Hubble Space Telescope imaging is presented for a sample of 225 early-type galaxies (assumed to be cluster members) in the fields of 9 clusters at redshifts $0.17 < z < 1.21$. The 94 luminous ellipticals ($M_{AB}(B)<-20$; selected by morphology alone with no reference to color) form tight sequences in the size-luminosity plane. The position of these sequences shifts, on average, with redshift so that an object of a given size at z=0.55 is brighter by $\Delta M(B)=-0.57 \pm 0.13$ mag than its counterpart (measured with the same techniques) in nearby clusters. At z=0.9 the shift is $\Delta M(B)=-0.96 \pm 0.22$ mag. If the relation between size and luminosity is universal so that the local cluster galaxies represent the evolutionary endpoints of those at high redshift, and if the size-luminosity relation is not modified by dynamical processes then this population of galaxies has undergone significant luminosity evolution since z=1 consistent with expectations based on models of passively evolving, old stellar populations.Comment: 7 pages, 3 figures, and 1 Tabl

A highly elongated prominent lens at z=0.87: first strong lensing analysis of El Gordo

We present the first strong-lensing (SL) analysis of the galaxy cluster ACT-CL J0102-4915 (\emph{El Gordo}), in recent \emph{HST}/ACS images, revealing a prominent strong lens at a redshift of $z=0.87$. This finding adds to the already-established unique properties of \emph{El Gordo}: it is the most massive, hot, X-ray luminous, and bright Sunyaev-Zeldovich effect cluster at $z\gtrsim0.6$, and the only `bullet'-like merging cluster known at these redshifts. The lens consists of two merging massive clumps, where for a source redshift of $z_{s}\sim2$ each clump exhibits only a small, separate critical area, with a total area of 0.69\pm0.11\sq\arcmin over the two clumps. For a higher source redshift, $z_{s}\sim4$, the critical curves of the two clumps merge together into one bigger and very elongated lens (axis ratio $\simeq5.5$), enclosing an effective area of 1.44\pm0.22\sq\arcmin. The critical curves continue expanding with increasing redshift so that for high-redshift sources ($z_{s}\gtrsim9$) they enclose an area of \sim1.91\pm0.30\sq\arcmin (effective \theta_{e}\simeq46.8\pm3.7\arcsec) and a mass of $6.09\pm1.04\times10^{14}M_{\odot}$. According to our model, the area of high magnification ($\mu>10$) for such high redshift sources is \simeq1.2\sq\arcmin, and the area with $\mu>5$ is \simeq2.3\sq\arcmin, making \emph{El Gordo} a compelling target for studying the high-redshift Universe. We obtain a strong lower limit on the total mass of \emph{El Gordo}, $\gtrsim1.7\times10^{15}M_{\odot}$ from the SL regime alone, suggesting a total mass of, roughly, $M_{200}\sim2.3\times10^{15}M_{\odot}$. Our results should be revisited when additional spectroscopic and \emph{HST} imaging data are available.Comment: 7 pages, 3 figures, 1 table; accepted to ApJ Letters; V2: minor changes, figure added, typos fixe

Strong Clustering of Lyman Break Galaxies around Luminous Quasars at z~4

In the standard picture of structure formation, the first massive galaxies are expected to form at the highest peaks of the density field, which constitute the cores of massive proto-clusters. Luminous quasars (QSOs) at z~4 are the most strongly clustered population known, and should thus reside in massive dark matter halos surrounded by large overdensities of galaxies, implying a strong QSO-galaxy cross-correlation function. We observed six z~4 QSO fields with VLT/FORS exploiting a novel set of narrow band filters custom designed to select Lyman Break Galaxies (LBGs) in a thin redshift slice of Delta_z~0.3, mitigating the projection effects that have limited the sensitivity of previous searches for galaxies around z>~4 QSOs. We find that LBGs are strongly clustered around QSOs, and present the first measurement of the QSO-LBG cross-correlation function at z~4, on scales of 0.1<~R<~9 Mpc/h (comoving). Assuming a power law form for the cross-correlation function xi=(r/r0_QG)^gamma, we measure r0_QG=8.83^{+1.39}_{-1.51} Mpc/h for a fixed slope of gamma=2.0. This result is in agreement with the expected cross-correlation length deduced from measurements of the QSO and LBG auto-correlation function, and assuming a linear bias model. We also measure a strong auto-correlation of LBGs in our QSO fields finding r0_GG=21.59^{+1.72}_{-1.69} Mpc/h for a fixed slope of gamma=1.5, which is ~4 times larger than the LBG auto-correlation length in random fields, providing further evidence that QSOs reside in overdensities of LBGs. Our results qualitatively support a picture where luminous QSOs inhabit exceptionally massive (M_halo>10^12 M_sun) dark matter halos at z~4.Comment: 25 pages, 22 figures, submitted to the Ap

Spectroscopy of moderately high-redshift RCS-1 clusters

We present spectroscopic observations of 11 moderately high-redshift (z~0.7- 1.0) clusters from the first Red-Sequence Cluster Survey (RCS-1). We find excellent agreement between the red-sequence estimated redshift and the spectroscopic redshift, with a scatter of 10% at z>0.7. At the high-redshift end (z>~0.9) of the sample, we find two of the systems selected are projections of pairs of comparably rich systems, with red-sequences too close to discriminate in (R-z') colour. In one of these systems, the two components are close enough to be physically associated. For a subsample of clusters with sufficient spectroscopic members, we examine the correlation between B_gcR (optical richness) and the dynamical mass inferred from the velocity dispersion. We find these measurements to be compatible, within the relatively large uncertainties, with the correlation established at lower redshift for the X-ray selected CNOC1 clusters and also for a lower redshift sample of RCS-1 clusters. Confirmation of this and calibration of the scatter in the relation will require larger samples of clusters at these and higher redshifts. [abridged]Comment: AJ accepted. 30 pages, 7 figures (figure 5 reduced quality

Generic Drone Control Platform for Autonomous Capture of Cinema Scenes

The movie industry has been using Unmanned Aerial Vehicles as a new tool to produce more and more complex and aesthetic camera shots. However, the shooting process currently rely on manual control of the drones which makes it difficult and sometimes inconvenient to work with. In this paper we address the lack of autonomous system to operate generic rotary-wing drones for shooting purposes. We propose a global control architecture based on a high-level generic API used by many UAV. Our solution integrates a compound and coupled model of a generic rotary-wing drone and a Full State Feedback strategy. To address the specific task of capturing cinema scenes, we combine the control architecture with an automatic camera path planning approach that encompasses cinematographic techniques. The possibilities offered by our system are demonstrated through a series of experiments

RCS043938-2904.9: A New Rich Cluster of Galaxies at z=0.951

We present deep I, J_s, K_s imaging and optical spectroscopy of the newly discovered Red-Sequence Cluster Survey cluster RCS043938-2904.9. This cluster, drawn from an extensive preliminary list, was selected for detailed study on the basis of its apparent optical richness. Spectroscopy of 11 members places the cluster at z=0.951 +- 0.006, and confirms the photometric redshift estimate from the (R-z) color-magnitude diagram. Analysis of the infrared imaging data demonstrates that the cluster is extremely rich, with excess counts in the Ks-band exceeding the expected background counts by 9 sigma. The properties of the galaxies in RCS043938-2904.9 are consistent with those seen in other clusters at similar redshifts. Specifically, the red-sequence color, slope and scatter, and the size-magnitude relation of these galaxies are all consistent with that seen in the few other high redshift clusters known, and indeed are consistent with appropriately evolved properties of local cluster galaxies. The apparent consistency of these systems implies that the rich, high-redshift RCS clusters are directly comparable to the few other systems known at z ~ 1, most of which have been selected on the basis of X-ray emission.Comment: 12 pages, 1 color figure. Accepted for publication on The ApJ Letter

Constraining the Redshift Evolution of FIRST Radio Sources in RCS1 Galaxy Clusters

We conduct a statistical analysis of the radio source population in galaxy clusters as a function of redshift by matching radio sources from the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) catalog with 618 optically-selected galaxy clusters from the first Red-Sequence Cluster Survey (RCS1). The number of excess radio sources (above the background level) per cluster is 0.14 +/- 0.02 for clusters with 0.35 < z < 0.65 and is 0.10 +/- 0.02 for clusters with 0.65 < z < 0.95. The richest clusters in the sample have more radio sources than clusters with low or intermediate richness. When we divide our sample into bins according to cluster richness, we do not observe any significant difference (> 1.5 sigma) in the number of radio sources per unit of cluster mass for the galaxy clusters with 0.35 < z < 0.65 as compared to the galaxy clusters with 0.65 < z < 0.95. Thus the entire sample can be characterized by the number of (L(1.4 GHz) > 4.1 X 10^(24) W/Hz) radio sources per unit (10^14 solar masses) mass, which we measure to be 0.031 +/- 0.004. We further characterize the population of galaxy cluster-related radio sources through visual inspection of the RCS1 images, finding that although the radio activity of brightest cluster galaxies (BCGs) also does not strongly evolve between our high and low redshift samples, the lower-redshift, richest clusters are more likely to host radio-loud BCGs than the higher-redshift, richest clusters or poorer clusters at the 2-sigma level.Comment: submitted to ApJ, revised versio

Squark Loop Correction to W^{+-} H^{-+} Associated Hadroproduction

We study the squark loop correction to W^{+-} H^{-+} associated hadroproduction via gluon-gluon fusion within the minimal supersymmetric extension of the standard model. We list full analytic results and quantitatively analyze the resulting shift in the cross section at the CERN Large Hadron Collider assuming a supergravity-inspired scenario.Comment: 13 pages (Latex), 5 figures (Postscript