NICMOS Instrument Handbook for Cycle 11

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 A2.1, we see that the conversion constant is 3x10^-13 and the wavelength is 1350Å = 0.135µm. Thus:

   

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 A2.2, the zero-point flux in the UKIRT system for K is 657Jy. Thus the 2.2µm flux is:

   

3. Given a surface brightness of 21.1 magnitudes arcsec^-2 at J, convert this into Jy arcsec^-2. Taking the zero-point for the J band from Table A2.2, we determine that the surface brightness is:

   

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 A2.3 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