Understanding the Relations between QSOs and Their Host Galaxies from Combined<i>HST</i>Imaging and VLT Spectroscopy

Letawe, Yannick; Magain, Pierre; Letawe, Géraldine; Courbin, F.; Hutsemékers, Damien

doi:10.1086/587866

Cited by 25 publications

(42 citation statements)

References 43 publications

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“…Burud et al 2000;Letawe et al 2008). The basic principle of this technique is the following: it does not try to reach an infinite resolution in the resulting deconvolved frame, in order to conform to the sampling theorem.…”

Section: Methodsmentioning

confidence: 99%

COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses

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Magain

et al. 2012

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Gravitationally lensed quasars can be used as powerful cosmological and astrophysical probes. We can (i) infer the Hubble constant H 0 based on the so-called time-delay technique, (ii) unveil substructures along the line-of-sight toward distant galaxies, and (iii) compare the shape and the slope of baryons and dark matter distributions in the inner regions of galaxies. To reach these goals, we need highaccuracy astrometry of the quasar images relative to the lensing galaxy and morphology measurements of the lens. In this work, we first present new astrometry for 11 lenses with measured time delays, namely, JVAS B0218+357, SBS 0909+532, RX J0911.4+0551, FBQS J0951+2635, HE 1104-1805, PG 1115+080, JVAS B1422+231, SBS 1520+530, CLASS B1600+434, CLASS B1608+656, and HE 2149-2745. These measurements proceed from the use of the Magain-Courbin-Sohy (MCS) deconvolution algorithm applied in an iterative way (ISMCS) to near-IR HST images. We obtain a typical astrometric accuracy of about 1-2.5 mas and an accurate shape measurement of the lens galaxy. Second, we combined these measurements with those of 14 other lensing systems, mostly from the COSMOGRAIL set of targets, to present new mass models of these lenses. The modeling of these 25 gravitational lenses led to the following results: 1) in four double-image quasars (HE0047-1746, J1226-006, SBS 1520+530, and HE 2149-2745), we show that the influence of the lens environment on the time delay can easily be quantified and modeled, hence putting these lenses with high priority for time-delay determination; 2) for quadruple-image quasars, the difficulty often encountered in reproducing the image positions to milli-arcsec accuracy (astrometric anomaly problem) is overcome by explicitly including the nearest visible galaxy/satellite in the lens model. However, one anomalous system (RXS J1131-1231) does not show any luminous perturber in its vicinity, and three others (WFI 2026-4536, WFI 2033, and B2045+265) have problematic modeling. These four systems are the best candidates for a pertubation by a dark matter substructure along the line-of-sight; 3) we revisit the correlation between the position angle (PA) and ellipticity of the light and of the mass distribution in lensing galaxies. As in previous studies, we find a significant correlation between the PA of the light and of the mass distributions. However, in contrast with these same studies, we find that the ellipticity of the light and of the mass also correlate well, suggesting that the overall spatial distribution of matter is not very different from the baryon distribution in the inner ∼5 kpc of lensing galaxies. This offers a new test for high-resolution hydrodynamical simulations.

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Section: Methodsmentioning

confidence: 99%

COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses

Sluse

Chantry

Magain

et al. 2012

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“…This software has been successfully applied to a variety of astrophysical problems ranging from gravitationally lensed quasars (e.g., Burud et al 2000Burud et al , 2002 to the study of quasar host galaxies (e.g., Letawe et al 2008), or to the search for extrasolar planets using the transit technique (e.g., Gillon et al 2007a,b). Image deconvolution requires accurate knowledge of the instrumental and atmospheric point spread function (PSF).…”

Section: Image Processing and Deconvolution Photometrymentioning

confidence: 99%

COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses

Courbin

Chantry

Revaz

et al. 2011

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We present accurate time delays for the quadruply imaged quasar HE 0435-1223. The delays were measured from 575 independent photometric points obtained in the R-band between January 2004 and March 2010. With seven years of data, we clearly show that quasar image A is affected by strong microlensing variations and that the time delays are best expressed relative to quasar image B. We measured Δt BC = 7.8 ± 0.8 days, Δt BD = −6.5 ± 0.7 days and Δt CD = −14.3 ± 0.8 days. We spacially deconvolved HST NICMOS2 F160W images to derive accurate astrometry of the quasar images and to infer the light profile of the lensing galaxy. We combined these images with a stellar population fitting of a deep VLT spectrum of the lensing galaxy to estimate the baryonic fraction, f b , in the Einstein radius. We measured f b = 0.65 The spectrum also allowed us to estimate the velocity dispersion of the lensing galaxy, σ ap = 222 ± 34 km s −1 . We used f b and σ ap to constrain an analytical model of the lensing galaxy composed of an Hernquist plus generalized NFW profile. We solved the Jeans equations numerically for the model and explored the parameter space under the additional requirement that the model must predict the correct astrometry for the quasar images. Given the current error bars on f b and σ ap , we did not constrain H 0 yet with high accuracy, i.e., we found a broad range of models with χ 2 < 1. However, narrowing this range is possible, provided a better velocity dispersion measurement becomes available. In addition, increasing the depth of the current HST imaging data of HE 0435-1223 will allow us to combine our constraints with lens reconstruction techniques that make use of the full Einstein ring that is visible in this object. Key words. cosmological parameters -gravitational lensing: strong Based on observations made with the 1.2 m Euler Swiss Telescope, the 1.5 m telescope of Maidanak Observatory in Uzbekistan, and with the 1.2 m Mercator Telescope, operated on the island of La Palma by the Flemish Community, at the Spanish Observatorio del Roque de los

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“…We compared the quality of our method with the MCS deconvolution technique developed by Magain, Courbin, & Sohy (Magain et al 1998) used in Letawe et al (2008;see also Courbin et al 2000). This method requires an unblended star to be observed with the identical instrument setup.…”

Section: Spectroscopymentioning

confidence: 99%

Galaxy counterparts of intervening high-zsub-DLAs/DLAs and Mg ii absorbers towards gamma-ray bursts

Schulze

Fynbo

Milvang-Jensen

et al. 2012

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We present the first search for galaxy counterparts of intervening high-z (2 < z < 3.6) sub-damped Lyα absorbers (sub-DLAs) and DLAs towards gamma-ray bursts (GRBs). Our final sample comprises five intervening sub-DLAs and DLAs in four GRB fields. To identify candidate galaxy counterparts of the absorbers we used deep optical-and near-infrared imaging, and low-, mid-and highresolution spectroscopy acquired with 6-m to 10-m class telescopes, the Hubble and the Spitzer Space Telescopes. Furthermore, we used the spectroscopic information and spectral-energy-distribution fitting techniques to study them in detail. Our main result is the detection and spectroscopic confirmation of the galaxy counterpart of the intervening DLA at z = 3.096 in the field of GRB 070721B (z GRB = 3.6298) as proposed by other authors. We also identify good candidates for the galaxy counterparts of the two strong Mg ii absorbers at z = 0.6915 and 1.4288 towards GRB 050820A (z GRB = 2.615). The properties of the detected DLA galaxy are typical for Lyman-break galaxies (LBGs) at similar redshifts; a young, highly star-forming galaxy that shows evidence for a galactic outflow. This supports the hypothesis that a DLA can be the gaseous halo of an LBG. In addition, we report a redshift coincidence of different objects associated with metal lines in the same field, separated by 130-161 kpc. The high detection rate of three correlated structures on a length scale as short as ∼150 kpc in two pairs of lines of sight is intriguing. The absorbers in each of these are most likely not part of the same gravitationally bound structure. They more likely represent groups of galaxies.

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Understanding the Relations between QSOs and Their Host Galaxies from CombinedHSTImaging and VLT Spectroscopy

Cited by 25 publications

References 43 publications

COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses

COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses

COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses

Galaxy counterparts of intervening high-zsub-DLAs/DLAs and Mg ii absorbers towards gamma-ray bursts

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