Browsing by Author "Jha, S."

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    CLASH : Accurate photometric redshifts with 14 HST bands in massive galaxy cluster cores
    (2017) Lazkoz, R.; Lemze, D.; Maoz, D.; Mercurio, A.; Meneghetti, M.; Merten, J.; Moustakas, L.; Nonino, M.; Orgaz, S.; Infante Lira, Leopoldo; Riess, A.; Rodney, S.; Sayers, J.; Umetsu, K.; Zheng, W.; Zitrin, A.; Molino, A.; Benítez, N.; Ascaso, B.; Coe, D.; Postman M.; Jouvel, S.; Host, O.; Lahav O.; Seitz, S.; Medezinski, E.; Rosati, P.; Schoenell, W.; Koekemoer, A.; Jiménez-Teja, Y.; Broadhurst, T.; Melchior, P.; Balestra, I.; Bartelmann, M.; Bouwens, R.; Bradley, L.; Czakon, N.; Donahue, M.; Ford, H.; Graur, O.; Graves, G.; Grillo, C.; Jha, S.; Kelson, D.
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    Discovery of the Low-Redshift Optical Afterglow of Grb 011121 and Its Progenitor Supernova Sn 2001ke1
    (2003) Garnavich, P.M.; Stanek, K.Z.; Wyrzykowski, L.; Infante, L.; Bendek, E.; Bersier, D.; Holland, S.T.; Jha, S.; Matheson, T.; Kirshner, R.P.; Krisciunas, K.; Phillips, M.M.; Carlberg, R.G.
    We present the discovery and follow-up observations of the afterglow of the gamma-ray burst GRB 011121 and its associated supernova SN 2001ke. Images were obtained with the Optical Gravitational Lensing Experiment 1.3 m telescope in BVRI passbands, starting 10.3 hr after the burst. The temporal analysis of our early data indicates a steep decay, independent of wavelength, with F-nu proportional to t(-1.72+/-0.05). There is no evidence for a break in the light curve earlier than 2.5 days after the burst. The spectral energy distribution determined from the early broadband photometry is a power law with Fnu proportional to nu(-0.66+/-0.13) after correcting for a large reddening. Spectra obtained with the Magellan 6.5 m Baade telescope reveal narrow emission lines from the host galaxy that provide a redshift of z = 0.362 +/- 0.001 to the GRB. We also present late R - and J-band observations of the afterglow similar to7-17 days after the burst. The late-time photometry shows a large deviation from the initial decline, and our data combined with Hubble Space Telescope photometry provide strong evidence for a supernova peaking about 12 rest-frame days after the GRB. The first spectrum ever obtained of a GRB supernova at cosmological distance revealed a blue continuum. SN 2001ke was more blue near maximum than SN 1998bw and faded more quickly, which demonstrates that a range of properties are possible in supernovae that generate GRBs. The blue color is consistent with a supernova interacting with circumstellar gas, and this progenitor wind is also evident in the optical afterglow. This is the best evidence to date that classical, long GRBs are generated by core-collapse supernovae.
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    THE CLUSTER LENSING AND SUPERNOVA SURVEY WITH HUBBLE (CLASH): STRONG-LENSING ANALYSIS OF A383 FROM 16-BAND HST/WFC3/ACS IMAGING
    (2011) Zitrin, A.; Broadhurst, T.; Coe, D.; Umetsu, K.; Postman, M.; Benitez, N.; Meneghetti, M.; Medezinski, E.; Jouvel, S.; Bradley, L.; Koekemoer, A.; Zheng, W.; Ford, H.; Merten, J.; Kelson, D.; Lahav, O.; Lemze, D.; Molino, A.; Nonino, M.; Donahue, M.; Rosati, P.; Van der Wel, A.; Bartelmann, M.; Bouwens, R.; Graur, O.; Graves, G.; Host, O.; Infante, L.; Jha, S.; Jimenez-Teja, Y.; Lazkoz, R.; Maoz, D.; McCully, C.; Melchior, P.; Moustakas, L. A.; Ogaz, S.; Patel, B.; Regoes, E.; Riess, A.; Rodney, S.; Seitz, S.
    We examine the inner mass distribution of the relaxed galaxy cluster A383 (z = 0.189), in deep 16 band Hubble Space Telescope/ACS+WFC3 imaging taken as part of the Cluster Lensing And Supernova survey with Hubble (CLASH) multi-cycle treasury program. Our program is designed to study the dark matter distribution in 25 massive clusters, and balances depth with a wide wavelength coverage, 2000-16000 angstrom, to better identify lensed systems and generate precise photometric redshifts. This photometric information together with the predictive strength of our strong-lensing analysis method identifies 13 new multiply lensed images and candidates, so that a total of 27 multiple images of nine systems are used to tightly constrain the inner mass profile gradient, d log Sigma/d log r similar or equal to -0.6 +/- 0.1 (r < 160 kpc). We find consistency with the standard distance-redshift relation for the full range spanned by the lensed images, 1.01 < z < 6.03, with the higher-redshift sources deflected through larger angles as expected. The inner mass profile derived here is consistent with the results of our independent weak-lensing analysis of wide-field Subaru images, with good agreement in the region of overlap (similar to 0.7-1 arcmin). Combining weak and strong lensing, the overall mass profile is well fitted by a Navarro-Frenk-White profile with M-vir = (5.37(-0.63)(+0.70) +/- 0.26) x 10(14) M-circle dot h(-1) and a relatively high concentration, c(vir) = 8.77(-0.42)(+0.44) +/- 0.23, which lies above the standard c-M relation similar to other well-studied clusters. The critical radius of A383 is modest by the standards of other lensing clusters, r(E) similar or equal to 16 +/- 2 '' (for z(s) = 2.55), so the relatively large number of lensed images uncovered here with precise photometric redshifts validates our imaging strategy for the CLASH survey. In total we aim to provide similarly high-quality lensing data for 25 clusters, 20 of which are X-ray-selected relaxed clusters, enabling a precise determination of the representative mass profile free from lensing bias.