Browsing by Author "Hertling, G"

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    Advanced camera for surveys observations of a strongly lensed arc in a field elliptical galaxy
    (2004) Blakeslee, JP; Zekser, KC; Benítez, N; Franx, M; White, RL; Ford, HC; Bouwens, RJ; Infante, L; Cross, NJ; Hertling, G; Holden, BP; Illingworth, GD; Motta, V; Menanteau, F; Meurer, GR; Postman, M; Rosati, P; Zheng, W
    We report the discovery of a strongly lensed arc system around a field elliptical galaxy in Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) images of a parallel field observed during NICMOS observations of the HST Ultra Deep Field. The ACS parallel data comprise deep imaging in the F435W, F606W, F775W, and F850LP bandpasses. The main arc is at a radius of 1."6 from the galaxy center and subtends about 120degrees. Spectroscopic follow-up at Magellan Observatory yields a redshift z = 0.6174 for the lensing galaxy, and we photometrically estimate z(phot) = 2.4 +/- 0.3 for the arc. We also identify a likely counterarc at a radius of 0."6 that shows structure similar to that seen in the main arc. We model this system and find a good fit to an elliptical isothermal potential of velocity dispersion a sigma approximate to 300 km s(-1), the value expected from the fundamental plane, and some external shear. Several other galaxies in the field have colors similar to the lensing galaxy and likely make up a small group.
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    Quasars clustering at z ∼ 3 on scales ≲ 10 h-1 Mpc
    (2003) Infante, L; Varela, J; Moles, M; Hertling, G; García, A; Menanteau, F
    We test the hypothesis of whether high-redshift quasi-stellar objects (QSOs) would preferentially appear in small groups or pairs and whether they are associated with massive young clusters. We carried out a photometric search for Lyalpha emitters on scales less than or similar to 10 h(-1) Mpc in the fields of a sample of 47 z approximate to 3 known QSOs. Wide and narrowband filter color-magnitude diagrams were generated for each of the 6'.6 x 6'.6 fields. A total of 13 nonresolved objects with a significant color excess were detected as QSO candidates at a redshift similar to that of the target. All the candidates are significantly fainter than the reference QSOs, with only two of them within 2 mag of the central object. Follow-up spectroscopic observations have shown that five, i.e., about 40% of the candidates, are QSOs at the same redshift of the target; four are QSOs at different z ( two of them probably being a lensed pair at z = 1.47); two candidates are unresolved H II galaxies at z similar to 0.3; and one unclassified and one candidate turned out to be a CCD flaw. These data indicate that at least 10% of the QSOs at z similar to 3 do have companions. We have also detected a number of resolved, rather bright Lyalpha emitter candidates. Most likely, a large fraction of them might be bright galaxies with [O II] emission, at z approximate to 0.3. The fainter population of our candidates corresponds to the current expectations. Thus, there are no strong indications for the existence of an overdensity of Lyalpha galaxies brighter than m approximate to 25 around QSOs at z approximate to 3.
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    RCS 043938-2904.9
    (2004) Barrientos, LF; Gladders, MD; Yee, HKC; Infante, L; Ellingson, E; Hall, PB; Hertling, G
    We present deep imaging and optical spectroscopy of the newly discovered Red-Sequence Cluster Survey cluster RCS 043938 - 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 K-s band exceeding the expected background counts by 9 sigma. The properties of the galaxies in RCS 043938 - 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 known high-redshift clusters 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, most of which have been selected on the basis of X-ray emission.