Somak Raychaudhury
Research Interests

Gravitational Lensing

High-redshift quasars are often lensed into multiple images by galaxies,  as is shown in this image (from Castles). They can be used for accurate measurements of various global cosmological parameters, provided that the mass distribution of the gravitational lens system is well constrained. Since the light travel time along the path to the various images is different, observing delayed versions of the same source event in its various images provides a direct way to measure the Hubble constant, independent of local calibrators. The cleanest systems to do these are in the four-image systems as above. However, in many of these cases, it is obvious that the lensing effect is not due to a single galaxy, but contributions from the group or cluster it belongs to are significant.

My Publications in this field           

  1. Observing high-redshift Supernovae in lensed galaxies
    Saini, Tarun Deep, Raychaudhury, Somak & Shchekinov, Y., 2000, Astron. Astrophys., 363, 349-354
  2. A lens mapping algorithm for weak lensing
    Saini, Tarun Deep, and Raychaudhury, Somak, 2001, ApJ, 560, L9-L13 [a slightly expanded version in astro-ph/0002416]
  3. Is B1422+231 a Golden Lens?
    Raychaudhury Somak, Saha Prasenjit, and Williams Liliya L.R., 2003, AJ, 126, 29-36 (astro-ph/0303366)
    Featured in the September 2003 issue of
    Natural History magazine!
  4. Short time-delays in the gravitational lens system B1422+231
    Raychaudhury Somak, Saha Prasenjit, and Fenton, Joe, 2005, MNRAS, submitted. 
  5. A Bayesian approach to estimating time delays between gravitationally lensed multiple images
    Harva Markus O. and Raychaudhury Somak, 2005, MNRAS, in preparation.
  6. How accurate are the time delay estimates in gravitational lensing?
    Juan C. Cuevas-Tello, Peter Tino & Raychaudhury Somak, 2005, Astron. Astrophys., in preparation.
  7. Kernel-based methods applied to irregularly sampled time series
    Cuevas-Tello Juan C., Tino, Peter, Raychaudhury, Somak, 2005, in "The Analysis of Patterns", Centre Ettore Majorana for Scientific Culture, Erice, Italy October 28 - November 6, 2005.

Full List of publications