Data Analysis and Image Reconstruction

John Monnier (Smithsonian Astrophysical Observatory)

Abstract:

Aperture masking allows a large number of visibilities and closure phases to be measured simultaneously, allowing aperture synthesis imaging to be performed for complex sources where model-fitting is not appropriate. This talk will review the principles behind closure phase imaging and discuss how CLEAN and Maximimum Entropy algorithms can be used to produce diffraction-limited images of complex sources. Currently, most imaging applications require the use of routines written for radio interferometers (VLBMEM, DIFFMAP, AIPS), and we will discuss the challenges and compromises when following this approach. Lastly, we will discuss how calibration errors affect the imaging reconstruction process for various types of sources.

Realaudio of lecture.
Viewgraphs: Pages 1-19 PDF 4352k Bytes.
Viewgraphs: Pages 20-45 PDF 5328k Bytes.

References:

• Infrared Interferometry and Spectroscopy of Circumstellar Envelopes

John D. Monnier
PhD thesis, University of California, Berkeley (1999)
See Chapters 10-13.
• An Introduction to Closure Phases, John Monnier, Chapt. 13 in
  Principles of Long Baseline Stellar Interferometry
  P.R. Lawson, ed.
  JPL Publication 00-9 (JPL Publications: Pasadena, California, 2000).

• Radio-interferometric imaging of weak objects in conditions of poor phase stability: the relationship between speckle masking and phase closure methods
  T. Cornwell
  Astron. Astrophys 180, 269-274 (1987)

• Synthetic aperture imaging at infrared wavelengths
  C.A. Haniff, D.F. Buscher, J.C. Christou, and S.T. Ridgway
  Mon. Not. R. Astron. Soc. 241, 51P-56P (1989)

• The mapping of compact radio sources from VLBI data
  A.C.S. Readhead P.N. Wilkinson
  Astrophys. J. 223, 25-36 (1978)

• Diffraction-limited imaging with ground-based optical telescopes
  A.C.S. Readhead, T.S. Nakajima, T.J. Pearson, G. Neugebauer, J.B. Oke, and W.L.W. Sargent
  Astron. J. 95 1278-1296 (1988)

• Maximum entropy image reconstruction: general algorithm
  J. Skilling and R.K. Bryan
  Mon. Not. R. Astron. Soc 211, 111-124 (1984).