TY  - JOUR
A1  - Wambsganß, Joachim
A1  - Hasinger, Günther
A1  - Giacconi, R.
A1  - Gunn, J. E.
A1  - Lehmann, Ingo
A1  - Schmidt, M.
A1  - Schneider, D. P.
A1  - Stanke, Thomas
A1  - Trümper, J.
A1  - Woods, D.
A1  - Zamorani, G.
T1  - A Distant X-ray Selected, Gravitationally-Lensing Galaxy Cluster
Y1  - 2000
ER  - 
TY  - JOUR
A1  - Koopmans, L. V. E.
A1  - Bruyn, A. G.
A1  - Wambsganß, Joachim
A1  - Fassnacht, C. D.
T1  - A radio-microlensing caustic crossing in B1600+434?
N2  - First, we review the current status of the detection of strong `external' variability in the CLASS gravitational B1600+434, focusing on the 1998 VLA 8.5-GHz and 1998/9 WSRT multi-frequency observations. We show that this data can best be explained in terms of radio-microlensing. We then proceed to show some preliminary results from our new multi-frequency VLA monitoring program, in particular the detection of a strong feature (~30%) in the light curve of the lensed image which passes predominantly through the dark-matter halo of the lens galaxy. We tentatively interpret this event, which lasted for several weeks, as a radio-microlensing caustic crossing, i.e. the superluminal motion of a micro-arcsec-scale jet-component in the lensed source over a single caustic in the magnification pattern, that has been created by massive compact objects along the line-of-sight to the lensed image.
Y1  - 2001
UR  - http://xxx.uni-augsburg.de/pdf/astro-ph/0004285
SN  - 1-538-81076-5
ER  - 
TY  - JOUR
A1  - Schmidt, Robert W.
A1  - Wambsganß, Joachim
A1  - Pen, U.-L.
A1  - Turner, E. L.
T1  - APO monitoring of Q2237+0305 in 1995-97 : evidence for microlensing
Y1  - 2001
SN  - 1-583-81074-9
ER  - 
TY  - JOUR
A1  - Wambsganß, Joachim
T1  - Cosmological microlensing
Y1  - 2001
SN  - 1-583-81076-5
ER  - 
TY  - JOUR
A1  - Puga, E.
A1  - Alcalde, D.
A1  - Barrena, R.
A1  - Mediavilla, E.
A1  - Motta, V.
A1  - Munoz, J. A.
A1  - Oscoz, Alejandro
A1  - Serra-Ricart, M.
A1  - Gil-Merino, Rodrigo
A1  - Goicoechea, Luis Julian
A1  - Lewis, G. f
A1  - Libbrecht, C.
A1  - Moreau, O.
A1  - Surdej, J.
A1  - Wambsganß, Joachim
T1  - Daily monitoring of the gravitational lens QSO 2237+0305 at the Nordic Optical Telescope
Y1  - 2001
SN  - 0-7923-6974-2
ER  - 
TY  - JOUR
A1  - Schindler, Sabine
A1  - Castillo-Morales, A.
A1  - De Filippis, E.
A1  - Schwope, A. D.
A1  - Wambsganß, Joachim
T1  - Discovery of depressions in the X-ray emission of the distant galaxy cluster RBS797 in a CHANDRA observation
N2  - We present CHANDRA observations of the X-ray luminous, distant galaxy cluster RBS797 at z=0.35. In the central region the X-ray emission shows two pronounced X-ray minima, which are located opposite to each other with respect to the cluster centre. These depressions suggest an interaction between the central radio galaxy and the intra-cluster medium, which would be the first detection in such a distant cluster. The minima are symmetric relative to the cluster centre and very deep compared to similar features found in a few other nearby clusters. A spectral and morphological analysis of the overall cluster emission shows that RBS797 is a hot cluster (T=7.7+1.2-1.0 keV) with a total mass of Mtot(r500)= 6.5+1.6-1.2 *E14Msun.
Y1  - 2001
ER  - 
TY  - JOUR
A1  - de Filippis, E.
A1  - Schindler, Sabine
A1  - Castillo-Morales, A.
A1  - Schwope, A. D
A1  - Wambsganß, Joachim
T1  - Discovery of holes in the core of the distant galaxy cluster RBS797 in a CHANDRA observation
Y1  - 2002
SN  - 1-583-81108-7
ER  - 
TY  - JOUR
A1  - Wambsganß, Joachim
A1  - Cen, Renyue
A1  - Xu, Guohong
A1  - Ostriker, Jeremiah P.
T1  - Effects of Weak Gravitational Lensing from Large-Scale Structure of the Determination of Q 0
N2  - Weak gravitational lensing by large-scale structure affects the determination of the cosmological deceleration parameter q0. We find that the lensing induced dispersions on truly standard candles are 0.04 and 0.02 mag at redshift z = 1 and z = 0.5, respectively, in a COBE-normalized cold dark matter universe with Omega 0 = 0.40, Lamda 0 = 0.6, H = 65 km s-1 Mpc-1, and sigma 8 = 0.79. It is shown that one would observe q0 = -0.395^{+0.125}_{-0.095} and q0 = - 0.398^{+0.048}_{-0.077} (the error bars are 2 sigma limits) with standard candles with zero intrinsic dispersion at redshift z = 1 and z = 0.5, respectively, compared to the truth of q0 = -0.400. A standard COBE normalized Omega 0 = 1 CDM model would produce three times as much variance and a mixed (hot and cold) dark matter model would lead to an intermediate result. One unique signature of this dispersion effect is its non-Gaussianity. Although the lensing induced dispersion at lower redshift is still significantly smaller than the currently best observed (total) dispersion of 0.12 mag in a sample of type Ia supernovae, selected with the multicolor light curve shape method, it becomes significant at higher redshift. We show that there is an optimal redshift, in the range z ~ 0.5--2.0 depending on the amplitude of the intrinsic dispersion of the standard candles, at which q0 can be most accurately determined.
Y1  - 1997
ER  - 
TY  - JOUR
A1  - Wambsganß, Joachim
T1  - Gravitational Lensing : a universal astrophysical tool
N2  - In the roughly 20 years of its existence as an observational science, gravitational lensing has established itself as a valuable tool in many astrophysical fields. In the introduction of this review we briefly present the basics of lensing. Then it is shown that the two propagation effects, lensing and scintillation, have a number of properties in common. In the main part various lensing phenomena are discussed with emphasis on recent observations.
Y1  - 2001
ER  - 
TY  - JOUR
A1  - Wambsganß, Joachim
T1  - Gravitational lensing : numerical simulations with a hierarchical tree code
Y1  - 1999
ER  -