Next Previous Up Contents
Next: Coords
Up: General Functions
Previous: Strings

### B.1.10 Fluxes

Functions for conversion between flux and magnitude values. Functions are provided for conversion between flux in Janskys and AB magnitudes.

Some constants for approximate conversions between different magnitude scales are also provided:

- Constants `JOHNSON_AB_*`, for Johnson <-> AB magnitude conversions, from Frei and Gunn, Astronomical Journal 108, 1476 (1994), Table 2 (1994AJ....108.1476F).
- Constants `VEGA_AB_*`, for Vega <-> AB magnitude conversions, from Blanton et al., Astronomical Journal 129, 2562 (2005), Eqs. (5) (2005AJ....129.2562B).

JOHNSON_AB_V
  Approximate offset between Johnson and AB magnitudes in V band. VJ~=VAB+`JOHNSON_AB_V`.
JOHNSON_AB_B
  Approximate offset between Johnson and AB magnitudes in B band. BJ~=BAB+`JOHNSON_AB_B`.
JOHNSON_AB_Bj
  Approximate offset between Johnson and AB magnitudes in Bj band. BjJ~=BjAB+`JOHNSON_AB_Bj`.
JOHNSON_AB_R
  Approximate offset between Johnson and AB magnitudes in R band. RJ~=RAB+`JOHNSON_AB_R`.
JOHNSON_AB_I
  Approximate offset between Johnson and AB magnitudes in I band. IJ~=IAB+`JOHNSON_AB_I`.
JOHNSON_AB_g
  Approximate offset between Johnson and AB magnitudes in g band. gJ~=gAB+`JOHNSON_AB_g`.
JOHNSON_AB_r
  Approximate offset between Johnson and AB magnitudes in r band. rJ~=rAB+`JOHNSON_AB_r`.
JOHNSON_AB_i
  Approximate offset between Johnson and AB magnitudes in i band. iJ~=iAB+`JOHNSON_AB_i`.
JOHNSON_AB_Rc
  Approximate offset between Johnson and AB magnitudes in Rc band. RcJ~=RcAB+`JOHNSON_AB_Rc`.
JOHNSON_AB_Ic
  Approximate offset between Johnson and AB magnitudes in Ic band. IcJ~=IcAB+`JOHNSON_AB_Ic`.
JOHNSON_AB_uPrime
  Offset between Johnson and AB magnitudes in u' band (zero). u'J=u'AB+`JOHNSON_AB_uPrime`=u'AB.
JOHNSON_AB_gPrime
  Offset between Johnson and AB magnitudes in g' band (zero). g'J=g'AB+`JOHNSON_AB_gPrime`=g'AB.
JOHNSON_AB_rPrime
  Offset between Johnson and AB magnitudes in r' band (zero). r'J=r'AB+`JOHNSON_AB_rPrime`=r'AB.
JOHNSON_AB_iPrime
  Offset between Johnson and AB magnitudes in i' band (zero). i'J=i'AB+`JOHNSON_AB_iPrime`=i'AB.
JOHNSON_AB_zPrime
  Offset between Johnson and AB magnitudes in z' band (zero). z'J=z'AB+`JOHNSON_AB_zPrime`=z'AB.
VEGA_AB_J
  Approximate offset between Vega (as in 2MASS) and AB magnitudes in J band. JVega~=JAB+`VEGA_AB_J`.
VEGA_AB_H
  Approximate offset between Vega (as in 2MASS) and AB magnitudes in H band. HVega~=HAB+`VEGA_AB_H`.
VEGA_AB_K
  Approximate offset between Vega (as in 2MASS) and AB magnitudes in K band. KVega~=KAB+`VEGA_AB_K`.
abToJansky( magAB )
  Converts AB magnitude to flux in Jansky.

  F/Jy=10(23-(AB+48.6)/2.5)

janskyToAb( fluxJansky )
  Converts flux in Jansky to AB magnitude.

  AB=2.5*(23-log10(F/Jy))-48.6

luminosityToFlux( lumin, dist )
  Converts luminosity to flux given a luminosity distance.

  F=lumin/(4 x Pi x dist2)

fluxToLuminosity( flux, dist )
  Converts flux to luminosity given a luminosity distance.

  lumin=(4 x Pi x dist2) F

Next Previous Up Contents
Next: Coords
Up: General Functions
Previous: Strings

TOPCAT - Tool for OPerations on Catalogues And Tables
Starlink User Note253
TOPCAT web page: http://www.starlink.ac.uk/topcat/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@bristol.ac.uk