Publications by Malte Tewes | EPFL Graph Search

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In this paper, we present results from the weak-lensing shape measurement GRavitational lEnsing Accuracy Testing 2010 (GREAT10) Galaxy Challenge. This marks an order of magnitude step change in the level of scrutiny employed in weak-lensing shape measureme ...

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 ...

Cosmic shear, that is weak gravitational lensing by the large-scale matter structure of the Universe, is a primary cosmological probe for several present and upcoming surveys investigating dark matter and dark energy, such as Euclid or WFIRST. The probe re ...

Context. Since 1998, a planet-search program around main sequence stars within 50 pc in the southern hemisphere has been carried out with the CORALIE echelle spectrograph at La Silla Observatory. Aims. With an observing time span of more than 14 years, the ...

We present the first case of strong gravitational lensing by a QSO: SDSS J0013 + 1523 at z = 0.120. The discovery is the result of a systematic search for emission lines redshifted behind QSOs, among 22 298 spectra of the SDSS data release 7. Apart from th ...

We present a new measurement of the Hubble Constant H-0 and other cosmological parameters based on the joint analysis of three multiply imaged quasar systems with measured gravitational time delays. First, we measure the time delay of HE 0435-1223 from 13- ...

We present the results of 15 years of monitoring lensed quasars, which was conducted by the COSMOGRAIL programme at the Leonhard Euler 1.2 m Swiss Telescope. The decade-long light curves of 23 lensed systems are presented for the first time. We complement ...

Information on the spectral types of stars is of great interest in view of the exploitation of space-based imaging surveys. In this article, we investigate the classification of stars into spectral types using only the shape of their diffraction pattern in ...

Weak gravitational lensing has the potential to place tight constraints on the equation of the state of dark energy. However, this will only be possible if shear measurement methods can reach the required level of accuracy. We present a new method for meas ...

We present first results from the third GRavitational lEnsing Accuracy Testing (GREAT3) challenge, the third in a sequence of challenges for testing methods of inferring weak gravitational lensing shear distortions from simulated galaxy images. GREAT3 was ...

COSMOGRAIL is a long-term photometric monitoring of gravitationally lensed quasars aimed at implementing Refsdal's time-delay method to measure cosmological parameters, in particular H-0. Given the long and well sampled light curves of strongly lensed quas ...

We analyze the optical, UV, and X-ray microlensing variability of the lensed quasar SDSS J0924+ 0219 using six epochs of Chandra data in two energy bands (spanning 0.4-8.0 keV, or 1-20 keV in the quasar rest frame), 10 epochs of F275W (rest-frame 1089 angs ...

We report the discovery of three new cases of quasi-stellar objects (QSOs) acting as strong gravitational lenses on background emission line galaxies: SDSS J0827+5224 (z(QSO) = 0.293, z(s) = 0.412), SDSS J0919+2720 (z(QSO) = 0.209, z(s) = 0.558), SDSS J100 ...

We present four new seasons of optical monitoring data and six epochs of X-ray photometry for the doubly imaged lensed quasar Q J0158-4325. The high-amplitude, short-period microlensing variability for which this system is known has historically precluded ...

Aims. Within the framework of the COSMOGRAIL collaboration we present 7- and 8.5-year-long light curves and time-delay estimates for two gravitationally lensed quasars: SDSS J1206+4332 and HS 2209+1914. Methods. We monitored these doubly lensed quasars in ...

Under the assumption of a flat Lambda CDM cosmology, recent data from the Planck satellite point toward a Hubble constant that is in tension with that measured by gravitational lens time delays and by the local distance ladder. Prosaically, this difference ...

We describe a simple and fast method to correct ellipticity measurements of galaxies from the distortion by the instrumental and atmospheric point spread function (PSF), in view of weak lensing shear measurements. The method performs a classification of ga ...

Strong gravitational lenses with measured time delays between the multiple images and models of the lens mass distribution allow a one-step determination of the time-delay distance, and thus a measure of cosmological parameters. We present a blind analysis ...

We present a two-channel deconvolution method that decomposes images into a parametric point-source channel and a pixelized extended-source channel. Based on the central idea of the deconvolution algorithm proposed by Magain et al. (1998, ApJ, 494, 472), t ...

A rare case of a quasar acting as a gravitational lens allows a precise determination of the mass of the quasar's host galaxy and offers a new path to studying the connections between supermassive black holes and their host galaxies. ...

Malte Tewes

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Image analysis for cosmology: results from the GREAT10 Galaxy Challenge

COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses

Weak-lensing shear measurement with machine learning Teaching artificial neural networks about feature noise

The CORALIE survey for southern extrasolar planets XVII. New and updated long period and massive planets

First case of strong gravitational lensing by a QSO: SDSS J0013+1523 at z=0.120

H0LiCOW-V. New COSMOGRAIL time delays of HE 0435-1223: H-0 to 3.8 per cent precision from strong lensing in a flat Lambda CDM model

COSMOGRAIL: XIX. Time delays in 18 strongly lensed quasars from 15 years of optical monitoring star

Stellar classification from single-band imaging using machine learning

Hopfield neural network deconvolution for weak lensing measurement

GREAT3 results - I. Systematic errors in shear estimation and the impact of real galaxy morphology

COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses XV. Assessing the achievability and precision of time-delay measurements

A Consistent Picture Emerges: A Compact X-Ray Continuum Emission Region In The Gravitationally Lensed Quasar Sdss J0924+0219

Three quasi-stellar objects acting as strong gravitational lenses

Further Evidence That Quasar X-Ray Emitting Regions Are Compact: X-Ray And Optical Microlensing In The Lensed Quasar Q J0158-4325

COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses XII. Time delays of the doubly lensed quasars SDSS J1206+4332 and HS 2209+1914

Cosmology From Gravitational Lens Time Delays And Planck Data

A fast empirical method for galaxy shape measurements in weak lensing surveys

Two Accurate Time-Delay Distances From Strong Lensing: Implications For Cosmology

Firedec: a two-channel finite-resolution image deconvolution algorithm

Strong gravitational lensing by AGNs as a probe of the quasar-host relations in the distant Universe