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                              G C N E W S
                             * Newsflash *

            - The Newsletter for Galactic Center Research -

gcnews@mpifr-bonn.mpg.de             http://www.mpifr-bonn.mpg.de/gcnews
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Vol. 10, No. 21                                              Oct 28, 1999


Recently submitted papers:
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Email    : lazio@sne.nrl.navy.mil
Title    : A Wide Field 90 cm VLA Image of the Galactic Center Region
Author(s): T. N. LaRosa, Namir E. Kassim, T. Joseph W. Lazio,  \&  S. 
           D. Hyman
Paper    : Astronomical Journal, 2000 January
Weblink  : http://rsd-www.nrl.navy.mil/7213/lazio/GCatlas/

Abstract:
We present a wide-field, high dynamic range, high resolution long
wavelength (lambda = 90 cm) VLA image of the Galactic center region.
The image is centered on Sgr A, covers an area of 4^o * 5^o with an
angular resolution of 43'' and has a rms sensitivity of ~ 5 mJy/beam.
The image was constructed from archival VLA data of Pedlar et
al. (1989) and Anantharamaiah et al. (1991) using new 3-D image
restoration techniques.  These 3-D imaging techniques resolve the
problem of non-coplanar baselines encountered at long wavelengths and
yield distortion free imaging of far-field sources with improved
sensitivity.  At lambda = 90 cm the VLA is sensitive to both thermal
and nonthermal emission and the resulting image gives an unprecedented
contextual perspective of the large-scale radio structure in this
unique and complicated region.  We have catalogued over a hundred
sources from this image and present for each source its 90 cm flux
density, position, and size.  For many of the small- diameter sources,
we also derive the 20/90 cm spectral index.  The spectral index as a
function of length along several of the isolated nonthermal filaments
has been estimated and found to be constant.  We have found six new
small-diameter sources as well as several extended regions of emission
that are clearly distinct sources that have not been previously
identified at higher frequencies.  These data are presented as a first
epoch of VLA observations that can be used to search for source
variability in conjunction with a second epoch of observations that
were recently initiated.
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			       Edited by
Angela Cotera                                Heino Falcke
(cotera@ipac.caltech.edu)                    (hfalcke@mpifr-bonn.mpg.de)
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