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We report the discovery of a giant Lya emitter (LAE) with a Spitzer/Infrared Array Camera (IRAC) counterpart near the reionization epoch at z = 6.595. The giant LAE is found from the extensive 1 deg2 Subaru narrowband survey for z = 6.6 LAEs in the Subaru/XMM-Newton Deep Survey (SXDS) field, and subsequently identified by deep spectroscopy of Keck/DEIMOS and Magellan/IMACS. Among our 207 LAE candidates, this LAE is not only the brightest narrowband object with L(Lya) = 3.9 +- 0.2 x 1043 erg s-1 in our survey volume of 106 Mpc3, but also a spatially extended Lya nebula with the largest isophotal area whose major axis is at least [?]3''. This object is more likely to be a large Lya nebula with a size of [?]17 kpc than to be a strongly lensed galaxy by a foreground object. Our Keck spectrum with medium-high spectral and spatial resolutions suggests that the velocity width is v FWHM = 251 +- 21 km s-1, and that the line-center velocity changes by [?]60 km s-1 in a 10 kpc range. The stellar mass and star formation rate are estimated to be 0.9-5.0 x 1010 M and >34 M yr-1, respectively, from the combination of deep optical to infrared images of Subaru, UKIDSS-Ultra Deep Survey, and Spitzer/IRAC. Although the nature of this object is not yet clearly understood, this could be an important object for studying cooling clouds accreting onto a massive halo, or forming-massive galaxies with significant outflows contributing to cosmic reionization and metal enrichment of intergalactic medium.

Many strong gravitational lenses lie in complex environments, such as poor groups of galaxies, that significantly bias conclusions from lens analyses. We are undertaking a photometric survey of all known galaxy-mass strong lenses to characterize their environments and include them in careful lens modeling, as well as to build a large, uniform sample of galaxy groups at intermediate redshifts for evolutionary studies. In this paper we present wide-field photometry of the environments of 12 lens systems with 0.24 [?] zlens [?] 0.5. Using a red sequence identifying technique, we find that 8 of the 12 lenses lie in groups and that 10 group-like structures are projected along the line of sight toward 7 of these lenses. Follow-up spectroscopy of a subset of these fields confirms these results. For lenses in groups, the group centroid position is consistent with the direction of the external tidal shear required by lens models. Lens galaxies are not all super-L* elliptical galaxies; the median lens luminosity is [?]L*, and the distribution of lens luminosities extends 3 mag below L* (in agreement with theoretical models). Only two of the lenses in groups are the brightest group galaxy, in qualitative agreement with theoretical predictions. As in the local universe, the highest velocity dispersion (s) groups contain a brightest member spatially coincident with the group centroid, whereas lower s groups tend to have an offset brightest group galaxy. This suggests that higher s groups are more dynamically relaxed than lower s groups and that at least some evolved groups exist by z ~ 0.5.

We present the first results from our spectroscopic survey of strong gravitational lens environments. Six of the eight lens galaxies in our sample belong to a poor group of galaxies, three of which are newly discovered here (those associated with BRI 0952-0115, MG 1654+1346, and B2114+022). For the three previously known groups (surrounding MG 0751+2716, PG 1115+080, and B1422+231), we more than double the number of group members. The group velocity dispersions range from 110img1.gif to 470img2.gif km s-1. The higher velocity dispersions of the richer groups (MG 0751, PG 1115, and B1422) are consistent with those of nearby X-ray-luminous groups; the lower velocity dispersions of the other groups are more typical of dynamically younger groups. The lens galaxy is the brightest member in fewer than half of the groups. The brightest group galaxy is an early-type galaxy that, at least for the poorer groups, lies outside the group centroid and on an orbit indistinguishable from other group members. In at least three cases, MG 0751, PG 1115, and B1422, the group environment significantly affects the lens potential. These happen to be the quadruply imaged lenses in our sample, suggesting a connection between image configuration and environment. Finally, we assess the importance of line-of-sight mass structures, showing that, in principle, the lens potential may be affected by structures lying at a wide range of spatial and redshift offsets from the lens. We quantify the real line-of-sight effects, finding that four of the eight systems have substantial interloping structures and that at least one of those (behind MG 0751) significantly affects the lens potential.

We present a new technique for wide and shallow observations using the near-infrared channel of Wide Field Camera 3 (WFC3) on the Hubble Space Telescope(HST). Wide-field near-IR surveys with HSTare generally inefficient, as guide star acquisitions make it impractical to observe more than one pointing per orbit. This limitation can be circumvented by guiding with gyros alone, which is possible as long as the telescope has three functional gyros. The method presented here allows us to observe mosaics of eight independent WFC3-IR pointings in a single orbit by utilizing the fact that HSTdrifts by only a very small amount in the 25 s between non-destructive reads of unguided exposures. By shifting the reads and treating them as independent exposures the full resolution of WFC3 can be restored. We use this "drift and shift" (DASH) method in the Cycle 23 COSMOS-DASH program, which will obtain 456 WFC3 H160pointings in 57 orbits, covering an area of 0.6 degree in the COSMOS field down to H160= 25. When completed, the program will more than triple the area of extra-galactic survey fields covered by near-IR imaging at HSTresolution. We demonstrate the viability of the method with the first four orbits (32 pointings) of this program. We show that the resolution of the WFC3 camera is preserved, and that structural parameters of galaxies are consistent with those measured in guided observations.

Using new photometric and spectroscopic data in the fields of nine strong gravitational lenses that lie in galaxy groups, we analyze the effects of both the local group environment and line-of-sight (LOS) galaxies on the lens potential. We use Monte Carlo simulations to derive the shear directly from measurements of the complex lens environment, providing the first detailed independent check of the shear obtained from lens modeling. We account for possible tidal stripping of the group galaxies by varying the fraction of total mass apportioned between the group dark matter halo and individual group galaxies. The environment produces an average shear of g = 0.08 (ranging from 0.02 to 0.17), significant enough to affect quantities derived from lens observables. However, the direction and magnitude of the shears do not match those obtained from lens modeling in three of the six four-image systems in our sample (B1422, RXJ1131, and WFI2033). The source of this disagreement is not clear, implying that the assumptions inherent in both the environment and lens model approaches must be reconsidered. If only the local group environment of the lens is included, the average shear is g = 0.05 (ranging from 0.01 to 0.14), indicating that LOS contributions to the lens potential are not negligible. We isolate the effects of various theoretical and observational uncertainties on our results. Of those uncertainties, the scatter in the Faber-Jackson relation and error in the group centroid position dominate. Future surveys of lens environments should prioritize spectroscopic sampling of both the local lens environment and objects along the LOS, particularly those bright (I< 21.5) galaxies projected within 5' of the lens.

We present new measurements of the Ha luminosity function (LF) and star formation rate (SFR) volume density for galaxies at z [?] 0.8. Our analysis is based on 1.18 mm narrowband data from the NEWFIRM Ha (NewHa) Survey, a comprehensive program designed to capture deep samples of intermediate redshift emission-line galaxies using narrowband imaging in the near-infrared. The combination of depth ([?]1.9 x 10-17 erg s-1 cm-2 in Ha at 3s) and areal coverage (0.82 deg2) of the 1.18 mm observations complements other recent Ha studies at similar redshifts, and enables us to minimize the impact of cosmic variance and place robust constraints on the shape of the LF. The present sample contains 818 NB118 excess objects, 394 of which are selected as Ha emitters. Optical spectroscopy has been obtained for 62% of the NB118 excess objects. Empirical optical broadband color classification is used to sort the remainder of the sample. A comparison of the LFs constructed for the four individual fields covered by the observations reveals significant cosmic variance, emphasizing that multiple, widely separated observations are required for such analyses. The dust-corrected LF is well described by a Schechter function with L [?] = 1043.00+-0.52 erg s-1, Ph[?] = 10-3.20+-0.54 Mpc-3, and a = -1.6 +- 0.19. We compare our Ha LF and SFR density to those at z [?] 1, and find a rise in the SFR density [?](1 + z)3.4, which we attribute to significant L [?] evolution. Our Ha SFR density of 10-1.00+-0.18 M yr-1 Mpc-3 is consistent with UV and [O II] measurements at z [?] 1. We discuss how these results compare to other Ha surveys at z [?] 0.8, and find that the different methods used to determine survey completeness can lead to inconsistent results. This suggests that future surveys probing fainter luminosities are needed, and more rigorous methods of estimating the completeness should be adopted as standard procedure (for example, with simulations which try to simultaneously reproduce the observed Ha LF and equivalent width distributions).