diff options
Diffstat (limited to 'fg21sim/utils/convert.py')
| -rw-r--r-- | fg21sim/utils/convert.py | 56 |
1 files changed, 33 insertions, 23 deletions
diff --git a/fg21sim/utils/convert.py b/fg21sim/utils/convert.py index 02a4ffd..13feb8a 100644 --- a/fg21sim/utils/convert.py +++ b/fg21sim/utils/convert.py @@ -1,4 +1,4 @@ -# Copyright (c) 2016 Weitian LI <liweitianux@live.com> +# Copyright (c) 2016-2017 Weitian LI <weitian@aaronly.me> # MIT license """ @@ -11,7 +11,8 @@ import numba def Fnu_to_Tb(Fnu, omega, freq): - """Convert flux density to brightness temperature, using the + """ + Convert flux density to brightness temperature, using the Rayleigh-Jeans law, in the Rayleigh-Jeans limit. Parameters @@ -19,9 +20,9 @@ def Fnu_to_Tb(Fnu, omega, freq): Fnu : `~astropy.units.Quantity` Input flux density, e.g., `1.0*au.Jy` omega : `~astropy.units.Quantity` - Source angular size/area, e.g., `1.0*au.sr` + Source angular size/area, e.g., `100*au.arcsec**2` freq : `~astropy.units.Quantity` - Frequency where the flux density measured, e.g., `1.0*au.MHz` + Frequency where the flux density measured, e.g., `120*au.MHz` Returns ------- @@ -45,15 +46,16 @@ def Fnu_to_Tb(Fnu, omega, freq): def Sb_to_Tb(Sb, freq): - """Convert surface brightness to brightness temperature, using the + """ + Convert surface brightness to brightness temperature, using the Rayleigh-Jeans law, in the Rayleigh-Jeans limit. Parameters ---------- Sb : `~astropy.units.Quantity` - Input surface brightness, e.g., `1.0*au.Jy/au.sr` + Input surface brightness, e.g., `1.0*(au.Jy/au.arcsec**2)` freq : `~astropy.units.Quantity` - Frequency where the flux density measured, e.g., `1.0*au.MHz` + Frequency where the flux density measured, e.g., `120*au.MHz` Returns ------- @@ -67,29 +69,33 @@ def Sb_to_Tb(Sb, freq): @numba.jit(nopython=True) def Sb_to_Tb_fast(Sb, freq): - """Convert surface brightness to brightness temperature, using the + """ + Convert surface brightness to brightness temperature, using the Rayleigh-Jeans law, in the Rayleigh-Jeans limit. This function does the calculations explicitly, and does NOT rely - on the `astropy.units`, therefore it is faster. However, the input - parameters must be in right units. + on the `astropy.units`, therefore it is much faster. However, the + input parameters must be in right units. Tb = Sb * c^2 / (2 * k_B * nu^2) - where `SB` is the surface brightness density measured at a certain + where `Sb` is the surface brightness density measured at a certain frequency (unit: [ Jy/rad^2 ] = [ erg/s/cm^2/Hz/rad^2 ]). Parameters ---------- Sb : float - Input surface brightness, unit [ Jy/deg^2 ] + Input surface brightness + Unit: [Jy/deg^2] freq : float - Frequency where the flux density measured, unit [ MHz ] + Frequency where the flux density measured + Unit: [MHz] Returns ------- Tb : float - Calculated brightness temperature, unit [ K ] + Calculated brightness temperature + Unit: [K] """ # NOTE: `radian` is dimensionless rad2_to_deg2 = np.rad2deg(1.0) * np.rad2deg(1.0) @@ -103,26 +109,30 @@ def Sb_to_Tb_fast(Sb, freq): @numba.jit(nopython=True) def Fnu_to_Tb_fast(Fnu, omega, freq): - """Convert flux density to brightness temperature, using the + """ + Convert flux density to brightness temperature, using the Rayleigh-Jeans law, in the Rayleigh-Jeans limit. - This function does the calculations explicitly, and does NOT rely - on the `astropy.units`, therefore it is faster. However, the input - parameters must be in right units. + This function does NOT invoke the `astropy.units`, therefore it is + much faster. Parameters ---------- Fnu : float - Input flux density, unit [ Jy ] + Input flux density + Unit: [Jy] = 1e-23 [erg/s/cm^2/Hz] = 1e-26 [W/m^2/Hz] omega : float - Source angular size/area, unit [ deg^2 ] + Source angular size/area + Unit: [deg^2] freq : float - Frequency where the flux density measured, unit [ MHz ] + Frequency where the flux density measured + Unit: [MHz] Returns ------- Tb : float - Calculated brightness temperature, unit [ K ] + Calculated brightness temperature + Unit: [K] """ - Sb = Fnu / omega + Sb = Fnu / omega # [Jy/deg^2] return Sb_to_Tb_fast(Sb, freq) |