References of "Courbin, Frédéric"
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See detailH0LiCOW. VI. Testing the fidelity of lensed quasar host galaxy reconstruction
Ding, Xuheng; Liao, Kai; Treu, Tommaso et al

in Monthly Notices of the Royal Astronomical Society (2017), 465

The empirical correlation between the mass of a supermassive black hole (M_BH) and its host galaxy properties is widely considered to be an evidence of their co-evolution. A powerful way to test the co ... [more ▼]

The empirical correlation between the mass of a supermassive black hole (M_BH) and its host galaxy properties is widely considered to be an evidence of their co-evolution. A powerful way to test the co-evolution scenario and learn about the feedback processes linking galaxies and nuclear activity is to measure these correlations as a function of redshift. Unfortunately, currently M_BH can only be estimated in active galaxies at cosmological distances. At these distances, bright active galactic nuclei (AGNs) can outshine the host galaxy, making it extremely difficult to measure the host's luminosity. Strongly lensed AGNs provide in principle a great opportunity to improve the sensitivity and accuracy of the host galaxy luminosity measurements as the host galaxy is magnified and more easily separated from the point source, provided the lens model is sufficiently accurate. In order to measure the M_BH-L correlation with strong lensing, it is necessary to ensure that the lens modelling is accurate, and that the host galaxy luminosity can be recovered to at least a precision and accuracy better than that of the typical M_BH measurement. We carry out extensive and realistic simulations of deep Hubble Space Telescope observations of lensed AGNs obtained by our collaboration. We show that the host galaxy luminosity can be recovered with better accuracy and precision than the typical uncertainty in M_BH(˜0.5 dex) for hosts as faint as 2-4 mag dimmer than the AGN itself. Our simulations will be used to estimate bias and uncertainties in the actual measurements to be presented in a future paper. [less ▲]

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See detailH0LiCOW - IV. Lens mass model of HE 0435-1223 and blind measurement of its time-delay distance for cosmology
Wong, Kenneth C.; Suyu, Sherry H.; Auger, Matthew W. et al

in Monthly Notices of the Royal Astronomical Society (2017), 465

Strong gravitational lenses with measured time delays between the multiple images allow a direct measurement of the time-delay distance to the lens, and thus a measure of cosmological parameters ... [more ▼]

Strong gravitational lenses with measured time delays between the multiple images allow a direct measurement of the time-delay distance to the lens, and thus a measure of cosmological parameters, particularly the Hubble constant, H[SUB]0[/SUB]. We present a blind lens model analysis of the quadruply imaged quasar lens HE 0435-1223 using deep Hubble Space Telescope imaging, updated time-delay measurements from the COSmological MOnitoring of GRAvItational Lenses (COSMOGRAIL), a measurement of the velocity dispersion of the lens galaxy based on Keck data, and a characterization of the mass distribution along the line of sight. HE 0435-1223 is the third lens analysed as a part of the H[SUB]0[/SUB] Lenses in COSMOGRAIL's Wellspring (H0LiCOW) project. We account for various sources of systematic uncertainty, including the detailed treatment of nearby perturbers, the parametrization of the galaxy light and mass profile, and the regions used for lens modelling. We constrain the effective time-delay distance to be D_{Δ t}= 2612_{-191}^{+208} Mpc, a precision of 7.6 per cent. From HE 0435-1223 alone, we infer a Hubble constant of H[SUB]0[/SUB] = 73.1_{-6.0}^{+5.7} km s^{-1 Mpc^{-1}} assuming a flat ΛCDM cosmology. The cosmographic inference based on the three lenses analysed by H0LiCOW to date is presented in a companion paper (H0LiCOW Paper V). [less ▲]

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See detailCOSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses: XII. Time delays of the doubly lensed quasars SDSS~J1206+4332 and HS~2209+1914
Eulaers, Eva ULg; Tewes, Malte; Magain, Pierre ULg et al

in Astronomy and Astrophysics (2013)

Aims. Within the framework of the COSMOGRAIL collaboration we present 7- and 8.5-year-long light curves and time-delay esti- mates for two gravitationally lensed quasars: SDSS J1206+4332 and HS 2209+1914 ... [more ▼]

Aims. Within the framework of the COSMOGRAIL collaboration we present 7- and 8.5-year-long light curves and time-delay esti- mates for two gravitationally lensed quasars: SDSS J1206+4332 and HS 2209+1914. Methods. We monitored these doubly lensed quasars in the R-band using four telescopes: the Mercator, Maidanak, Himalayan Chandra, and Euler Telescopes, together spanning a period of 7 to 8.5 observing seasons from mid-2004 to mid-2011. The pho- tometry of the quasar images was obtained through simultaneous deconvolution of these data. The time delays were determined from these resulting light curves using four very different techniques: a dispersion method, a spline fit, a regression difference technique, and a numerical model fit. This minimizes the bias that might be introduced by the use of a single method. Results. The time delay for SDSS J1206+4332 is ∆tAB = 111.3 ± 3 days with A leading B, confirming a previously published result within the error bars. For HS 2209+1914 we present a new time delay of ∆tBA = 20.0 ± 5 days with B leading A. Conclusions. The combination of data from up to four telescopes have led to well-sampled and nearly 9-season-long light curves, which were necessary to obtain these results, especially for the compact doubly lensed quasar HS 2209+1914. [less ▲]

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See detailCOSMOGRAIL: Measuring Time Delays of Gravitationally Lensed Quasars to Constrain Cosmology
Tewes, Malte; Courbin, Frédéric; Meylan, Georges et al

in The Messenger (2012)

COSMOGRAIL is a long-term programme for the photometric monitoring of gravitationally lensed quasars. It makes use of several medium-size telescopes to derive long and well-sampled light curves of lensed ... [more ▼]

COSMOGRAIL is a long-term programme for the photometric monitoring of gravitationally lensed quasars. It makes use of several medium-size telescopes to derive long and well-sampled light curves of lensed quasars, in order to measure the time delays between the quasar images. These delays directly relate to the Hubble constant H0, without any need for secondary distance calibrations. COSMOGRAIL was initiated in 2004, and has now secured almost a decade of data, resulting in cosmological constraints that are very complementary to other cosmological probes. [less ▲]

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See detailNew insights on the quasars central region from microlensed quasars
Sluse, Dominique ULg; Hutsemekers, Damien ULg; Wambsganss, Joachim et al

Conference (2012, March 21)

Our detailed understanding of the working engine of quasars is still incomplete. Several basic questions remain such as: How is the supermassive black hole in the center of quasars fed ? What is the ... [more ▼]

Our detailed understanding of the working engine of quasars is still incomplete. Several basic questions remain such as: How is the supermassive black hole in the center of quasars fed ? What is the geometry and kinematics of the gas flow near the black hole ? The slow advances in answering these questions during the last decades advocates for new research methods. The analysis of the microlensing-induced deformations of multiply-imaged quasars is one such technique. It starts to be used as a tool to measure the temperature profile of the accretion disk, to estimate the size and study the geometry of the region emitting the broad emission lines. However, up to now, these applications have concerned mostly a handful of systems. In this talk, I will discuss the occurence of microlensing in a sample known strongly-lensed quasars and present the variety of emission-line deformations which is observed. I will also explain how spectroscopic follow-up of strongly-lensed quasars in the survey era should provide important insights on the quasar structure. [less ▲]

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See detailThe Host Galaxies of the Brightest Quasars: Gas-Rich Galaxies, Mergers, and Young Stars
Courbin, Frédéric; Letawe, Géraldine ULg; Meylan, Georges et al

in The Messenger (2006), 124

Because they are faint and hidden in the glare of a much brighter unresolved source, quasar host galaxies still challenge the most powerful telescopes, instrumentation and processing techniques ... [more ▼]

Because they are faint and hidden in the glare of a much brighter unresolved source, quasar host galaxies still challenge the most powerful telescopes, instrumentation and processing techniques. Determining their basic morphological parameters and their integrated colours is feasible, but difficult, from imaging alone. However, detailed information on their stellar and gas contents and on their dynamics is achievable with deep spectroscopy. [less ▲]

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See detailHigh precision photometry in crowded stellar fields
Magain, Pierre ULg; Courbin, Frédéric; Gillon, Michaël ULg et al

in SPIE Newsroom (2006)

A deconvolution-based method which allows to derive high-precision photometry of stars in crowded fields, proves very useful for a variety of astronomical projects, including transit searches for ... [more ▼]

A deconvolution-based method which allows to derive high-precision photometry of stars in crowded fields, proves very useful for a variety of astronomical projects, including transit searches for extrasolar planets. [less ▲]

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