VLA Low frequency Sky Survey (VLSS formerly 4MASS)
Work on VLSS is in collaboration with Jim Condon, Rick Perley and
Namir Kassim's group at NRL.
The 4 Meter All Sky Survey is a proposed survey to be made with the
VLA at a wavelength of 4 meters (74 MHz).
This will be made in the B and AnB configurations with 80" resolution
and approximately 100 mJy RMS noise.
My work on this has been in the area of calibration and imaging.
The behavior of the ionosphere at this low frequency makes calibration
challenging.
Results are available:
VLA observations of the Spitzer FLS field.
This is a project with Jim Condon, Q. F. Yin and the SIRTF team.
The
Spitzer First Look Survey
lies inside the Spitzer "constant viewing
zone" near the north ecliptic pole.
It covers about 5 square degrees in a region having a relatively faint
cirrus foreground, centered on J2000 RA = 17 18 00., declination = +59
30 00. The VLA image of this field has a resolution of 5 arcseconds
FWHM and an RMS noise of 23 microJy/beam at 1.4 GHz.
The VLA survey results are available:
-
I've worked on this project with Jim Condon, J. Broderick, Q.
F. Yin, R. Perley and G. Taylor (Condon et al. 1998, AJ, 115, 1693).
This radio survey uses the NRAO Very Large Array telescope and will
cover the sky north of a declination of -40 degrees at a frequency of
1.4 GHz, a resolution of 45" and a limiting peak source brightness of
about 3 mJy/beam.
Linear polarization as well as total intensity measurments are made.
Results are released as soon as they are available.
See the following available data products.
Note: holding the shift key down when clicking on a link to
a file generally causes a Web browser to download to a disk file
rather than doing something silly like displaying a binary file in a
text window.
Obit: Merx mollis mortibus nuper
This package is my personal research project intended to facilitate
the development and testing of algorithms for calibration and imaging
of astronomical (mostly radio) data.
It may be of interest to others and is offered on an "as is" basis
under the GNU General License.
This package consists of a c language base library of classes many of
which also have bindings to python.
The library has an abstract external data model and can currently use
either AIPS or FITS data structures as native formats.
More detail and access are available
here.
Other astronomy related activities
- Continuing involvement in the definition of FITS formats for the
interchange of optical/IR interferometry data.
FITSview FITS image viewers
As part of an effort to make the NVSS images available to the
general public as well as astronomers I've developed an familly of
graphical FITS image viewers for a variety of types of computers.
These are distributed free by NRAO.
The FITSview family of viewers for FITS format astronomical
images are available for Microsoft Windows (FITSview),
Apple Macintosh (MacFITSview) and Unix/X-Windows (XFITSview) computer
systems.
These viewers have easy to use graphical controls and will display
astronomical images in the Flexible Image Transport System (FITS)
format allowing zooming, scrolling, modifying the brightness, contrast
and pseudo color and allow determination of celestial positions and
the physical brightness units in the image.
Both standard World Coordinate System (WCS) and Digitized Sky Survey
(DSS) coordinates are supported.
Positions and brightnesses of selected pixels may be logged to a text
file and specified positions in the image may be marked.
Images may be compared by "blinking" them and 3 dimensional images may
be viewed a plane at a time or in the form of a movie.
Blanked pixels and all defined FITS image data types are supported.
Normal or gzip compressed files may be used.
The programs contain extensive online documentation and are suitable for use
as external FITS image viewers for Web browsers.
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Other FITS related software
I've developed a number of other FITS image related software packages.
These are mostly for geometric transformations or to convert other
coordinates into WCS.
These packages are in Fortran and/or c and are distributed as installation
kits in the form of gzipped tar files.
All use the fitsio or cfitsio libraries to access FITS files for which links
are included but I do not support fitsio, cfitsio or libjpeg software.
Some modification of a Makefile is required; I have only built these on Unix
systems but there is some chance the will work on others.
The WCS coordinates supported are of the old style.
-
postage
- makes subimages ("postage stamps") of FITS files allowing changes between WCS
geometries and full resampling. Supports B1950 and J2000 epochs.
This package is mostly in Fortran with some c and needs the
cfitsio
package.
-
wcsFITS
- has programs dss2wcs and iraf2wcs which convert Digital Sky Survey (DSS) images
with astrometric plate constants to the closest approximation WCS coordinates
without regridding the image (dss2wcs) and converts IRAF images with CD-MATRIX
coordinates to the closest WCS coordinates (iraf2wcs) also without
regridding.
Also corrects some errors in the dates introduced by the STScI.
This package is all in the c language and needs the
cfitsio
package.
-
FITS2jpeg
- converts FITS images to jpeg format with control over pixel range and mapping.
This package is all in the c language and needs the
cfitsio
and
libjpeg
packages.
-
FITScont
- Make contour plots in a postscript file of a selected portion of a FITS image.
This program is in Fortran and needs the
fitsio
and
pgplot
packages.
Note: holding the shift key down when clicking on a link to
a file generally causes a Web browser to download to a disk file
rather than doing something silly like displaying a binary file in a
text window.
Current Astronomical Research Areas
- VLBI studies of low power (FRI) radio galaxies in collaboration
with G. Giovannini in Bologna, Italy.
- Radio polarization studies of steep spectrum compact radio sources
and NGC315.
- VLA/GBT studies of NGC315 in collaboration with Bridle and Laing et al.
- SiO maser and IR interferometric studies of Mira variables using
the VLBA and the IOTA interferometer.
- Imaging the Galactic center region with F. Yusef-Zadeh.
Nonastronomy
Activities
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The (USA) National Radio Astronomy Observatory
(NRAO)
is operated by Associated Universities, Inc. and is a Facility of
the (USA) National Science Foundation.
Comments? Questions? Problems?