The VLSS Bright Source Spectral CalculatorThe forms below allow you to search the VLSS Bright Source Spectral Catalog (VBSSC), a catalog of 388 sources with peak intensities at 74 MHz larger than 15 Jy taken from the VLA Low Frequency Sky Survey (VLSS), and returns the flux density at a specified frequency (in MHz). The flux density for the closest match to a given position, or the position of a given 3C source, is computed using both the model fit (see the VBSSC paper) and an interpolation of the data. A plot of the spectrum and the fitted curve is also provided to help you decide which flux density to use. For sources with data at less than 5 frequencies, a power-law was fit only to frequencies greater than 300 MHz. For our purposes here, the "model" curve below 300 MHz for these sources is simply a line connecting the 74 MHz flux density and the value of the power-law fit at 300 MHz. The spectra and the parameters derived from the model fits can be downloaded here. These files contain udated versions of this data since it was discovered that the data presented in the VBSSC paper used the wrong factors to put the 6C and 7C flux densities on the Baars et al. (1977) scale and the data from the WENSS survey was read in incorrectly. For the position search, the default search radius is set to 1,000 arcmin since this form is primarily intended to provide a calibration source for a low-frequency observation at a given postion. For the 3C search, the default radius is set to 10 arcmin since the intent is to provide a spectrum of a particular 3C source. If you enter a 3C source which does not have a match in the VBSSC but which does have data from Keuhr et al. (1981), that reference is used to provide you with a spectrum. For the special cases of 3C 461 (Cas A), 3C 405 (Cyg A), and 3C 144 (The Crab/Tau A), the spectral data from Baars et al. (1977) are used. Note that for Cas A, no attempt has been made to evolve the flux densities to the current epoch. |