Browsing by Author "Koekemoer, A."

Now showing 1 - 7 of 7
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    Black Hole Growth Is Mainly Linked to Host-galaxy Stellar Mass Rather Than Star Formation Rate
    (2017) Wang, J.; Yang, G.; Chen, C.; Vito, F.; Brandt, W.; Alexander, D.; Luo, B.; Sun, M.; Xue, Y.; Bauer, Franz Erik; Koekemoer, A.; Lehmer, B.; Liu, T.; Schneider, D.; Shemmer, O.; Trump J.; Vignali, C.
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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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    CLASH : the concentration-mass relation of galaxy clusters
    (2015) Merten, J.; Meneghetti, M.; Postman, M.; Umetsu, K.; Zitrin, A.; Medezinski, E.; Nonino, M.; Koekemoer, A.; Melchior, P.; Infante Lira, Leopoldo; Gruen, D.; Moustakas, L.; Bartelmann, M.; Host, O.; Donahue, M.; Coe, D.; Carrasco, M.
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    CLASH-VLT: spectroscopic confirmation of z=6.11 quintuply lensed galaxy in the Frontier Fields cluster RXC J2248.7-4431
    (2013) Balestra, I.; Vanzella, E.; Rosati, P.; Monna, A.; Grillo, C.; Nonino, M.; Mercurio, A.; Biviano, A.; Bradley, L.; Coe, D.; Fritz, A.; Postman, M.; Seitz, S.; Scodeggio, M.; Tozzi, P.; Zhengll, W.; Ziegler, B.; Zitrin, A.; Annunziatella, M.; Bartelmann, M.; Benitez, N.; Broadhurst, T.; Bouwens, R.; Czoske, O.; Donahue, M.; Ford, H.; Girardi, M.; Infante, L.; Jouvel, S.; Kelson, D.; Koekemoer, A.; Kuchner, U.; Lemze, D.; Lombardi, M.; Maier, C.; Medezinski, E.; Melchior, P.; Meneghetti, M.; Merten, J.; Molino, A.; Moustakas, L.; Presotto, V.; Smit, R.; Umetsu, K.
    We present VIsible Multi-Object Spectrograph (VIMOS) observations of a z similar to 6 galaxy quintuply imaged by the Frontier Fields galaxy cluster RXC J2248.7-4431 (z = 0.348). This sub-L*, high-z galaxy has been recently discovered by Monna et al. (2013) using dropout techniques with the 16-band HST photometry acquired as part of the Cluster Lensing And Supernova survey with Hubble (CLASH). Obtained as part of the CLASH-VLT survey, the VIMOS medium-resolution spectra of this source show a very faint continuum between similar to 8700 angstrom and similar to 9300 angstrom and a prominent emission line at 8643 angstrom, which can be readily identified with Lyman-alpha at z = 6.110 +/- 0.002. The emission line exhibits an asymmetric profile, with a more pronounced red wing. The rest-frame equivalent width of the line is EW = 79 +/- 10 angstrom, relatively well constrained thanks to the detection of the UV continuum, which is rarely achieved for a sub-L* galaxy at this redshift. After correcting for magnification, the star formation rate (SFR) estimated from the Ly alpha line is SFR(Ly alpha) = 11 M-circle dot yr(-l) and that estimated from the UV data is SFR(UV) = 3 M-circle dot yr(-1). We estimate that the effective radius of the source is R-e less than or similar to 0.4 kpc, which implies a star formation surface mass density Sigma(SFR) > 6 M(circle dot)yr(-1) kpc(-2) and, using the Kennicutt-Schmidt relation, a gas surface mass density Sigma(gas) > 10(3) M(circle dot)pc(-2). Our results support the idea that this magnified, distant galaxy is a young and compact object with luminosity 0.4 L* at z = 6, when the Universe was just 1 Gyr old, with a similar amount of mass in gas and stars. In the spirit of the Frontier Fields initiative, we also publish the redshifts of several multiply imaged sources and other background objects, which will help improving the strong-lensing model of this galaxy cluster.
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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.
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    The Space Density of High-redshift QSOs in the Great Observatories Origins Deep Survey
    (2004) Cristiani, S.; Bauer, Franz Erik; Treister, Ezequiel; Alexander, D. M.; Brandt, W N.; Chatzichristou, E. T.; Fontanot, F.; Grazian, A.; Koekemoer, A.; Lucas, R. A.; Monaco, P.
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    X-Ray Unveiling Events in a z ≈ 1.6 Active Galactic Nucleus in the 7 Ms Chandra Deep Field-South
    (2023) Yu, Li-Ming; Luo, Bin; Brandt, W. N.; Bauer, Franz E.; De Cicco, D.; Fabian, A.; Gilli, R.; Koekemoer, A.; Paolillo, M.; Schneider, D. P.; Shemmer, O.; Tozzi, P.; Trump, Jonathan R.; Vignali, C.; Vito, F.; Wang, J. -x.; Xue, Y. Q.
    We investigate the extreme X-ray variability of a z = 1.608 active galactic nucleus in the 7 Ms Chandra Deep Field-South (XID 403), which showed two significant X-ray brightening events. In the first event, XID 403 brightened by a factor of >2.5 in less than or similar to 6.1 rest-frame days in the observed-frame 0.5-5 keV band. The event lasted for approximate to 5.0-7.3 days, and then XID 403 dimmed by a factor of >6.0 in less than or similar to 6.1 days. After approximate to 1.1-2.5 yr in the rest frame (including long observational gaps), it brightened again, with the 0.5-5 keV flux increasing by a factor of >12.6. The second event lasted over 251 days, and the source remained bright until the end of the 7 Ms exposure. The spectrum is a steep power law (photon index Gamma = 2.8 +/- 0.3) without obscuration during the second outburst, and the rest-frame 2-10 keV luminosity reaches 1.5(-0.5)(+0.8) x 10(43) erg s(-1); there is no significant spectral evolution within this epoch. The infrared-to-UV spectral energy distribution of XID 403 is dominated by the host galaxy. There is no significant optical/UV variability and R-band (rest-frame approximate to 2500 angstrom) brightening contemporaneous with the X-ray brightening. The extreme X-ray variability is likely due to two X-ray unveiling events, where the line of sight to the corona is no longer shielded by high-density gas clumps in a small-scale dust-free absorber. XID 403 is probably a high-redshift analog of local narrow-line Seyfert 1 galaxies, and the X-ray absorber is a powerful accretion disk wind. On the other hand, we cannot exclude the possibility that XID 403 is an unusual candidate for tidal disruption events.