10.6.8 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).

abToJansky( magAB )

Converts AB magnitude to flux in Jansky.

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

• Parameters:
  • magAB (floating point): AB magnitude value
• Return value
  • (floating point): equivalent flux in Jansky

janskyToAb( fluxJansky )

Converts flux in Jansky to AB magnitude.

AB=2.5*(23-log₁₀(F/Jy))-48.6

• Parameters:
  • fluxJansky (floating point): flux in Jansky
• Return value
  • (floating point): equivalent AB magnitude

luminosityToFlux( lumin, dist )

Converts luminosity to flux given a luminosity distance.

F=lumin/(4 x Pi x dist²)

• Parameters:
  • lumin (floating point): luminosity
  • dist (floating point): luminosity distance
• Return value
  • (floating point): equivalent flux

fluxToLuminosity( flux, dist )

Converts flux to luminosity given a luminosity distance.

lumin=(4 x Pi x dist²) F

• Parameters:
  • flux (floating point): flux
  • dist (floating point): luminosity distance
• Return value
  • (floating point): equivalent luminosity

JOHNSON_AB_V

Approximate offset between Johnson and AB magnitudes in V band. V_J~=V_AB+JOHNSON_AB_V.

JOHNSON_AB_B

Approximate offset between Johnson and AB magnitudes in B band. B_J~=B_AB+JOHNSON_AB_B.

JOHNSON_AB_Bj

Approximate offset between Johnson and AB magnitudes in Bj band. Bj_J~=Bj_AB+JOHNSON_AB_Bj.

JOHNSON_AB_R

Approximate offset between Johnson and AB magnitudes in R band. R_J~=R_AB+JOHNSON_AB_R.

JOHNSON_AB_I

Approximate offset between Johnson and AB magnitudes in I band. I_J~=I_AB+JOHNSON_AB_I.

JOHNSON_AB_g

Approximate offset between Johnson and AB magnitudes in g band. g_J~=g_AB+JOHNSON_AB_g.

JOHNSON_AB_r

Approximate offset between Johnson and AB magnitudes in r band. r_J~=r_AB+JOHNSON_AB_r.

JOHNSON_AB_i

Approximate offset between Johnson and AB magnitudes in i band. i_J~=i_AB+JOHNSON_AB_i.

JOHNSON_AB_Rc

Approximate offset between Johnson and AB magnitudes in Rc band. Rc_J~=Rc_AB+JOHNSON_AB_Rc.

JOHNSON_AB_Ic

Approximate offset between Johnson and AB magnitudes in Ic band. Ic_J~=Ic_AB+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. J_Vega~=J_AB+VEGA_AB_J.

VEGA_AB_H

Approximate offset between Vega (as in 2MASS) and AB magnitudes in H band. H_Vega~=H_AB+VEGA_AB_H.

VEGA_AB_K

Approximate offset between Vega (as in 2MASS) and AB magnitudes in K band. K_Vega~=K_AB+VEGA_AB_K.