Browsing by Author "Lidman, C"

Now showing 1 - 7 of 7
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    An optical time-delay for the lensed BAL quasar HE 2149-2745
    (2002) Burud, I; Courbin, F; Magain, P; Lidman, C; Hutsemékers, D; Kneib, JP; Hjorth, J; Brewer, J; Pompei, E; Germany, L; Pritchard, J; Jaunsen, AO; Letawe, G; Meylan, G
    We present optical V and i-band light curves of the gravitationally lensed BAL quasar HE 2149-2745. The data, obtained with the 1.5 m Danish Telescope (ESO-La Silla) between October 1998 and December 2000, are the first from a long-term project aimed at monitoring selected lensed quasars in the Southern Hemisphere. A time delay of 103+/-12 days is determined from the light curves. In addition, VLT/FORS1 spectra of HE 2149 2745 are deconvolved in order to obtain the spectrum of the faint lensing galaxy, free of any contamination by the bright nearby two quasar images. By cross-correlating the spectrum with galaxy-templates we obtain a tentative redshift estimate of z = 0.495+/-0:01. Adopting this redshift, a Omega = 0.3, Lambda = 0.7 cosmology, and a chosen analytical lens model, our time-delay measurement yields a Hubble constant of H-0 = 66+/-8 km s(-1) Mpc(-1) (1sigma error) with an estimated systematic error of +/-3 km s(-1) Mpc(-1). Using non-parametric models yields H-0 = 65+/-8 km s(-1) Mpc(-1) (1sigma error) and confirms that the lens exhibits a very dense/concentrated mass profile. Finally, we note, as in other cases, that the flux ratio between the two quasar components is wavelength dependent. While the flux ratio in the broad emission lines-equal to 3.7-remains constant with wavelength, the continuum of the brighter component is bluer. Although the data do not rule out extinction of one quasar image relative to the other as a possible explanation, the effect could also be produced by differential microlensing by stars in the lensing galaxy.
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    Deep imaging of AX J2019+112
    (1999) Benítez, N; Broadhurst, T; Rosati, P; Courbin, F; Squires, G; Lidman, C; Magain, P
    We detect a distant cluster of galaxies centered on the QSO lens and luminous X-ray source AX J2019 + 112, a.k.a. the "Dark Cluster." Using deep V and I Keck images and wide-held K-s imaging from the New Technology Telescope (NTT), a tight red sequence of galaxies is identified within a radius of 0.2 h(-1) Mpc of the known z = 1.01 elliptical lensing galaxy. The sequence, which includes the central elliptical galaxy, has a slope in good agreement with the model predictions of Kodama et al. for z similar to 1. We estimate the integrated rest-frame luminosity of the cluster to be L-V greater than or equal to 3.2 x 10(11) h(-2) L. (after accounting for significant extinction at the low latitude of this field), more than an order of magnitude higher than previous estimates. The central region of the cluster is deconvolved using the technique of Magain, Courbin, & Sohy, revealing a thick central are coincident with an extended radio source. All the observed lensing features are readily explained by differential magnification of a radio-loud active galactic nucleus by a shallow elliptical potential. The QSO must lie just outside the diamond caustic, producing two images; the are is a highly magnified image formed from a region close to the center of the host galaxy, projecting inside the caustic. The mass-to-light ratio within an aperture of 0.4 h(-1) Mpc is M-X/L-V = 224(-78)(+112)h(M/L-V)., using the X-ray temperature. The strong lens model yields a compatible value, M/L-V = 372(-94)(+94)h(M/L-V)., whereas an independent weak-lensing analysis sets an upper limit of M/L-V < 520h(M/L-V)., typical of massive clusters.
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    Discovery of a high-redshift Einstein ring
    (2005) Cabanac, RA; Valls-Gabaud, D; Jaunsen, AO; Lidman, C; Jerjen, H
    We report the discovery of a partial Einstein ring of radius 1.''48 produced by a massive (and seemingly isolated) elliptical galaxy. The spectroscopic follow-up at the VLT reveals a 2L(star) galaxy at z = 0.986, which is lensing a post-starburst galaxy at z = 3.773. This unique configuration yields a very precise measure of the mass of the lens within the Einstein radius, (8.3 +/- 0.4) x 10(11)h(70)(-1) M-circle dot. The fundamental plane relation indicates an evolution rate of dlog(M/L)(B)/dz = -0.57 +/- 0.04, similar to other massive ellipticals at this redshift. The source galaxy shows strong interstellar absorption lines indicative of large gas-phase metallicities, with fading st phase populations after a burst stellar Higher resolution spectra and will allow the detailed imaging study of an unbiased representative of the galaxy population when the universe was just 12% of its current age.
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    Evolution in the cluster early-type galaxy size-surface brightness relation at z ≃ 1
    (2005) Holden, BP; Blakeslee, JP; Postman, M; Illingworth, GD; Demarco, R; Franx, M; Rosati, P; Bouwens, RJ; Martel, AR; Ford, H; Clampin, M; Hartig, GF; Benítez, N; Cross, NJG; Homeier, N; Lidman, C; Menanteau, F; Zirm, A; Ardila, DR; Bartko, F; Bradley, LD; Broadhurst, TJ; Brown, RA; Burrows, CJ; Cheng, ES; Feldman, PD; Golimowski, DA; Goto, T; Gronwall, C; Infante, L; Kimble, RA; Krist, JE; Lesser, MP; Magee, D; Mei, S; Meurer, GR; Miley, GK; Motta, V; Sirianni, M; Sparks, WB; Tran, HD; Tsvetanov, ZI; White, RL; Zheng, W
    We investigate the evolution in the distribution of surface brightness, as a function of size, for elliptical and S0 galaxies in the two clusters RDCS J1252.9 - 2927 ( z = 1: 237) and RX J0152.7 - 1357 ( z = 0: 837). We use multicolor imaging with the Advanced Camera for Surveys on the Hubble Space Telescope to determine these sizes and surface brightnesses. Using three different estimates of the surface brightnesses, we find that we reliably estimate the surface brightness for the galaxies in our sample with a scatter of < 0.2 mag and with systematic shifts of <= 0.05 mag. We construct samples of galaxies with early- type morphologies in both clusters. For each cluster, we use a magnitude limit in a band that closely corresponds to the rest- frame B, to magnitude limit of M-B = - 18: 8 at z = 0, and select only those galaxies within the color- magnitude sequence of the cluster or by using our spectroscopic redshifts. We measure evolution in the rest- frame B surface brightness and find - 1: 41 +/- 0: 14 mag from the Coma Cluster of galaxies for RDCS J1252.9 - 2927 and - 0: 90 +/- 0: 12 mag of evolution for RX J0152.7 - 1357, or an average evolution of ( - 1: 13 +/- 0: 15) z mag. Our statistical errors are dominated by the observed scatter in the size - surface brightness relation, sigma = 0: 42 +/- 0: 05 mag for RX J0152.7 - 1357 and sigma = 0: 76 +/- 0: 10 mag for RDCS J1252.9 - 2927. We find no statistically significant evolution in this scatter, although an increase in the scatter could be expected. Overall, the pace of luminosity evolution we measure agrees with that of the fundamental plane of early- type galaxies, implying that the majority of massive early- type galaxies observed at z similar or equal to 1 formed at high redshifts.
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    Exploring the gravitationally lensed system HE 1104-1805: near-IR spectroscopy
    (2000) Courbin, F; Lidman, C; Meylan, G; Kneib, JP; Magain, P
    A new technique for the spatial deconvolution of spectra is applied to near-IR (0.95-2.50 mu m) NTT/SOFI spec tra of the lensed, radio-quiet quasar HE 1104-1805. The continuum of the lensing galaxy is revealed between 1.5 mu m and 2.5 mu m Although the spectrum does not show strong emission features, it is used in combination with previous optical and IR photometry to infer a plausible redshift in the range 0.8 < z < 1.2. Modeling of the system shows that the lens is complex, probably composed of the red galaxy seen between the quasar images and a more extended component associated with a galaxy cluster with fairly low velocity dispersion (575 km s(-1)). Unless more constrains can be put on the mass distribution of the cluster, e.g. from deep X-ray observations, HE 1104-1805 will not be a good system to determine H-0. We stress that multiply imaged quasars with known time delays may prove more useful as tools for detecting dark mass in distant lenses than for determining cosmological parameters.
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    Exploring the gravitationally lensed system HE 1104-1805: VLT spectroscopy of the lens at z=0.729
    (2000) Lidman, C; Courbin, F; Kneib, JP; Golse, G; Castander, F; Soucail, G
    Using FORS2, mounted on Kueyen CUT2 of the VLT), we have obtained the redshift of the lensing galaxy in the gravitational lens system HE 1104-1805. We measure z = 0.729 +/- 0.001, in good agreement with previous estimates based on the time delay and the position of the lens on the fundamental plane. It also coincides with one of the metal line absorption systems that are seen in high resolution spectra of HE 1104-1805.
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    Star formation at z ∼ 6
    (2003) Bouwens, RJ; Illingworth, GD; Rosati, P; Lidman, C; Broadhurst, T; Franx, M; Ford, HC; Magee, D; Benítez, N; Blakeslee, JP; Meurer, GR; Clampin, M; Hartig, GF; Ardila, DR; Bartko, F; Brown, RA; Burrows, CJ; Cheng, ES; Cross, NJG; Feldman, PD; Golimowski, DA; Gronwall, C; Infante, L; Kimble, RA; Krist, JE; Lesser, MP; Martel, AR; Menanteau, F; Miley, GK; Postman, M; Sirianni, M; Sparks, WB; Tran, HD; Tsvetanov, ZI; White, RL; Zheng, W
    Using an i - z dropout criterion, we determine the space density of z similar to 6 galaxies from two deep ACS GTO fields with deep optical-IR imaging. A total of 23 objects are found over 46 arcmin(2), or similar to0.5 +/- 0.1 objects arcmin(-2) down to z(AB) similar to 27.3 (6 sigma), or a completeness-corrected similar to0.5 +/- 0.2 objects arcmin(-2) down to z(AB) similar to 26.5 (including one probable z similar to 6 active galactic nucleus). Combining deep ISAAC data for our RDCS 1252-2927 field (J(AB) similar to 25.7 and K-s;AB similar to 25.0; 5 sigma) and NICMOS data for the Hubble Deep Field North (J(110;AB) and H-160; AB similar to 27.3, 5 sigma), we verify that these dropouts have relatively. at spectral slopes, as one would expect for star-forming objects at z similar to 6. Compared with the average-color (beta = -1.3) U-dropout in the Steidel et al. z similar to 3 sample, i-dropouts in our sample range in luminosity from similar to1.5L(*) (z(AB) similar to 25.6) to similar to0.3L(*) (z(AB) similar to 27.3) with the exception of one very bright candidate at z(850; AB) similar to 24.2. The half-light radii vary from 0."09 to 0."21, or 0.5 kpc to 1.3 kpc. We derive the z similar to 6 rest-frame UV luminosity density (or star formation rate density) by using three different procedures. All three procedures use simulations based on a slightly lower redshift (z similar to 5) V-606-dropout sample from Chandra Deep Field-South ACS images. First, we make a direct comparison of our findings with a no-evolution projection of this V-dropout sample, allowing us to automatically correct for the light lost at faint magnitudes or lower surface brightnesses. We find 23% +/- 25% more i-dropouts than we predict, consistent with no strong evolution over this redshift range. Adopting previous results to z similar to 5, this works out to a mere 20% +/- 29% drop in the luminosity density from z similar to 3 to z similar to 6. Second, we use the same V-dropout simulations to derive a detailed selection function for our i-dropout sample and compute the UV-luminosity density [7.2 +/- 2.5) _x 10(25) ergs s(-1) Hz(-1) Mpc(-3) down to z(AB) similar to 27]. We find a 39% +/- 21% drop over the same redshift range (z similar to 3-6), consistent with the first estimate. This is our preferred value and suggests a star formation rate of 0.0090 +/- 0.0031 M-. yr(-1) Mpc(-3) to z(AB) similar to 27, or similar to 0.036 +/- 0.012 M-. yr(-1) Mpc(-3) by extrapolating the luminosity function to the faint limit, assuming alpha = - 1.6. Third, we follow a very similar procedure, except that we assume no incompleteness, and find a rest-frame continuum luminosity that is similar to2-3 times lower than our other two determinations. This final estimate is to be taken as a lower limit and is important if there are modest changes in the colors or surface brightnesses from z similar to 5 to z similar to 6 (the other estimates assume no large changes in the intrinsic selectability of objects). We note that all three estimates are well within the canonical range of luminosity densities necessary for reionization of the universe at this epoch by star-forming galaxies.