diff options
Diffstat (limited to 'fg21sim/utils')
| -rw-r--r-- | fg21sim/utils/convert.py | 21 |
1 files changed, 11 insertions, 10 deletions
diff --git a/fg21sim/utils/convert.py b/fg21sim/utils/convert.py index 13feb8a..c36d5fc 100644 --- a/fg21sim/utils/convert.py +++ b/fg21sim/utils/convert.py @@ -80,13 +80,15 @@ def Sb_to_Tb_fast(Sb, freq): Tb = Sb * c^2 / (2 * k_B * nu^2) where `Sb` is the surface brightness density measured at a certain - frequency (unit: [ Jy/rad^2 ] = [ erg/s/cm^2/Hz/rad^2 ]). + frequency, in units of [Jy/arcsec^2]. + + 1 [Jy] = 1e-23 [erg/s/cm^2/Hz] = 1e-26 [W/m^2/Hz] Parameters ---------- Sb : float Input surface brightness - Unit: [Jy/deg^2] + Unit: [Jy/arcsec^2] freq : float Frequency where the flux density measured Unit: [MHz] @@ -97,13 +99,12 @@ def Sb_to_Tb_fast(Sb, freq): Calculated brightness temperature Unit: [K] """ - # NOTE: `radian` is dimensionless - rad2_to_deg2 = np.rad2deg(1.0) * np.rad2deg(1.0) - Sb_rad2 = Sb * rad2_to_deg2 # unit: [ Jy/rad^2 ] -> [ Jy ] - c = 29979245800.0 # speed of light, [ cm/s ] - k_B = 1.3806488e-16 # Boltzmann constant, [ erg/K ] + # NOTE: [rad] & [sr] are dimensionless + arcsec2 = (np.deg2rad(1) / 3600) ** 2 # [sr] + c = 29979245800.0 # speed of light, [cm/s] + k_B = 1.3806488e-16 # Boltzmann constant, [erg/K] coef = 1e-35 # take care the unit conversions - Tb = coef * (Sb_rad2 * c*c) / (2 * k_B * freq*freq) # unit: [ K ] + Tb = coef * (Sb * c*c) / (2 * k_B * freq*freq * arcsec2) # [K] return Tb @@ -123,7 +124,7 @@ def Fnu_to_Tb_fast(Fnu, omega, freq): Unit: [Jy] = 1e-23 [erg/s/cm^2/Hz] = 1e-26 [W/m^2/Hz] omega : float Source angular size/area - Unit: [deg^2] + Unit: [arcsec^2] freq : float Frequency where the flux density measured Unit: [MHz] @@ -134,5 +135,5 @@ def Fnu_to_Tb_fast(Fnu, omega, freq): Calculated brightness temperature Unit: [K] """ - Sb = Fnu / omega # [Jy/deg^2] + Sb = Fnu / omega # [Jy/arcsec^2] return Sb_to_Tb_fast(Sb, freq) |