The VLA Low-Frequency Sky Survey Redux (VLSSr)

VLSS-Redux Postage Stamp Server

The National Radio Astronomy Obseratory (NRAO) and the Naval Research Laboratory (NRL) used the NRAO Very Large Array to survey the sky north of a declination of -30 degrees at a frequency of 74 MHz.

This postage stamp server is for images from a re-reduction of the survey data (VLSSr), with maps at a resolution of 75" and a limiting peak source brightness of about 500 mJy/beam. Final sky coverage of the catalog and images is complete above -10 degrees declination, and extends down to -30 degrees declination at most RAs. In some areas data is available down to declinations of -36 degrees.

Redux Overview

The VLSSr represents a major improvement to the original VLSS over most of the sky. It includes six previously unpublished fields, and improved dynamic range in 95% of all fields. The clean bias has been halved and is now 0.66 times the local RMS. The largest angular size imaged has been roughly doubled to 36', and the number of cataloged sources is increased by 35% to %93,000.

An improved primary beam model was applied to correct substantial radially dependent flux errors present in the VLSS.

The VLSSr maps and catalog use the Roger, Costain and Bridle (1973 AJ 78 130) flux scale, based on the source models presented in Scaife and Heald (2012 MNRAS 423 30).

Attribution

If you make use of VLSSr data in your work, please reference this paper:
Lane, W. M., Cotton, W. D., Helmboldt , J. and Kassim, N. E. 2012 "VLSS Redux: Software Improvements applied to the Very Large Array Low-frequency Sky Survey", Radio Science v. 47, RS0K04


For detailed general instructions click here or for more about a form entry click on its label.

Equinox:
Object name [optional]:
Central Right Ascension:
Central declination:
Desired image size (degrees):
See Pixel Spacing for size limit.
Pixel spacing:
Desired pixel size in arcseconds
(Min 0.001; max image size 262144 pixels, e.g. 512 x 512)
Projection:
Desired rotation
(N through E) on the sky in degrees. (Use 0.0 for contour plots)
Image Type:
Don't use "FITS Image" unless you have an external viewer configured to activate for fits files in your browser. Also, for JPEG images, you may need to "reload" the image if you've fetched more than one.

Note: The southern completeness limit is -10 degrees for 18h < RA < 21h, -20 degrees for 15h < RA < 18h, and -30 degrees for the rest of the sky, with decreasing sky coverage to -36 degrees.

Note: these images will have a relatively high dynamic range which will cause them to appear as white dots on a black background unless the viewer used has suitable control over brightness, contrast and the range of values to be displayed. The "noise" level in these images is about 100 mJy/beam.

The FITSview family of FITS image viewers is available for a variety of computer systems. For a short discussion of installing external viewers for FITS files click here.


Other Products

Entire 17 x 17 deg fields can be obtained here or through a simplified form interface. The entire source catalog as a FITS binary table and software is available here. (Reminder: shift-click will generally force your browser to save the requested image to a file rather than displaying it in a text window.) A postage stamp server is also available to obtain FITS images, jpeg or contour plots of smaller regions. Ionospheric climatology using the VLSSr is described here.

Original VLSS

The original survey reduction products (VLSS) can be obtained here. The original survey (VLSS) is documented in: Cohen, A. S., Lane, W. M., Cotton, W. D., Kassim, N. E., Lazio, T. J., Perley, R. A. Condon, J., Erickson, W. C. 2006. "The VLA Low Frequency Sky Survey: Methods and Preliminary Results", 2007, AJ, 134, 1245-1262

Other Sources of FITS Images from Sky Surveys


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?



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Modified on Monday, 03-Jun-2013 16:23:10 EDT
Original by Bill Cotton; markup revisions by Pat Murphy.