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Examples

  1. Given a source with a flux of 0.9mJy at 1350Å, convert this flux to erg s-1cm-2Å-1. From section 3, Table 12.1, we see that the conversion constant is 3x10-13 and the wavelength is 1350Å = 0.135µm. Thus: F=3x10-13 x 9x10-4 / 0.1352 = 1.48x10-14erg s-1cm-2Å-1

  2. Given a V magnitude of 15.6, and knowledge that V-K=2.5 in the UKIRT system, estimate the flux in Jy at K. Since V-K=2.5 we know that K=13.1. From Table 12.2, the zero-point flux in the UKIRT system for K is 657Jy. Thus the 2.2µm flux is: F=10-13.1/2.5 x 657 = 3.8x10-3Jy

  3. Given a surface brightness of 21.1 magnitudes arcsec-2 at J, convert this into Jy arcsec-2 and into MJy steradian-1. Taking the zero-point for the J band from Table 12.2, we determine that the surface brightness is: 10-21.1/2.5 x 1670 = 6.06x10-6Jy arcsec-2, or 6.06x10-6/0.084616 = 7.17x10-5MJy ster-1

  4. Given a flux at 0.9µm of 2.3x10-7Jy, estimate the I magnitude. 2.3x10-7Jy is less than 2.3x10-1Jy by three powers of a hundred, or 15 magnitudes. From Table 12.3 we see that 0.25Jy is equivalent to an I-band magnitude of 9.89. Thus 2.3x10-7 is roughly 15 magnitudes fainter than this, or of order I=24.9.

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stevens@stsci.edu
Copyright © 1997, Association of Universities for Research in Astronomy. All rights reserved. Last updated: 07/24/97 15:35:28