Separate VLA images:
NRAO VLA Archive Survey Images Page
Before using the menuPlease take some time to read this page before using the menu links and buttons on the left. In particular you really would want to read the Cone search section. If all this is still confusing or you have other remarks or suggestions, please contact us.
PurposeThis page is to guide you through the images and (calibrated) data processed with the latest VLA pipeline (by Lorant Sjouwerman, NRAO), on a subset of the raw, non-proprietary uvdata in the VLA archive. The pilot project contains all calibratable X- and C-band (8 and 5 GHz) continuum data taken with the VLA in it's B-configuration (baselines shorter than 11 km), between 1999 October 29 (UT 00h) and 2000 February 14 (UT 23h). A draft report on the pilot (compressed postscript) was completed. Since it's completion we've continued processing data for all arrays, for all continuum data sets at frequencies above a GigaHertz (so no 4-band nor P-band, i.e., no 74 nor 300 MHz), starting 2000 March 1, and will do so until 2003 May 15 before tackling earlier dates. A-array takes long to process, which means their processing is lagging so far.
Let's call it "NVAS", for "NRAO VLA Archive Survey"..
(2010-Jul-12) we have
VLA images of
Images and data may be freely downloaded, copied and redistributed
as part of scientific research or non-profit educational purposes. For
other purposes please contact the NRAO director directly
(434-296-0225, or see the
director's office web pages) before using this material.
Menu ButtonsYou have several options to choose from on the menu on the left hand side:
LinksThese will take you to the main National Radio Astronomy Observatory (NRAO) page, to NRAO's Data Archive System, NRAO's Very Large Array (VLA) or NRAO's Astronomical Image Processing System (AIPS) pages, this NVAS (NRAO VLA Archive Survey) page, or to the VLA Large proposal page (that may include data that NVAS might have skipped).
SearchWhether or not you have the sky position of your source or region of interest, you can check (in a pop-up window) what the "NASA/IPAC Extragalactic Database" (NED) or the SIMBAD database (at the "Centre de Données astronomiques de Strasbourg") have collected. Use SIMBAD for Galactic sources and either NED or SIMBAD for Extragalactic sources. Type the name in the NED or SIMBAD field and hit return (NOT Search!). The results of either NED or SIMBAD are displayed in the same pop-up window, in case you wonder where the results are.... This name look up is in particular useful if you know the source's name but not its position. Grab the J2000 (!) position and paste it as is in the position search field directly following the name lookup and click search (after reading the next paragraph).
Use the position search to enter a position, a search radius of up to 900 arcminutes (15 degrees), an upper limit to the RMS (default ≤10 mJy, which however may be too restrictive for complicated sources like Cas A), and perhaps a frequency range (see the list for frequency ranges within each observing band) and click search. By default the search radius entered is a fixed numerical angular distance, though you have the option to scale the search radius with highest frequency of the observing band (e.g., if you entered 0.25 arcmin and 20.4-25.5 GHz for K-band, the search will return matches at 20.4 GHz within up to 0.31 arcminutes and matches at 25.5 GHz within the requested 0.25 arcmin). If you do not explicitly ask for one observing band, the entered search radius above is assumed to be the search radius at 5.0 GHz and the search scales relative to 5.0 GHz (e.g., if you entered 0.25 arcmin, the search will return matches at 1.4 GHz within up to 0.89 arcminutes and matches at 43 GHz within only 0.03 arcmin). If you have allowed this web site to set cookies, entrered values should remain following your search in the menu when the page returns the search results. You can graphically check the current coverage.
Note that this VLA Archive Image pipeline does not try to reproduce the conserted efforts done already by the proposers of the big VLA surveys; "The NRAO VLA Sky Survey" (NVSS), "Faint Images of the Radio Sky at Twenty-centimeters" (The VLA FIRST Survey), "The Spitzer/SIRTF First-Look Survey" (FLS), and "The VLA Low-frequency Sky Survey" (VLSS, a.k.a. 4MASS). Also, over the years many observers have submitted their images to the "NRAO Image Gallery". Data and images from these surveys and submissions may be retrieved from the home pages of these surveys. Their links are give in the menu on the left below the "Cone Search".
BrouwseHere you can browse the files in the archive, in case you're not looking for images but for uvdata (e.g. if you want to combine multiple calibrated data sets), or want to see the logs for a particular pipelined experiment. In any case you would want to have a look at the README file, which explains the naming of the files, and should show up in a pop-up window. If you don't allow pop-up windows, you can also see it in your browser. Have fun!
NVAS ContactContact Lorant Sjouwerman for any remarks, suggestions and/or reasonable complaints. Compliments and encouragements should go to the division head (C. Chandler). Thanks for using this service! Modified on 2007-Apr-21 (text), 2006-Oct-31 (canvas)