From 12a9e21fa2c135f9d90fc49134211dec6a705baf Mon Sep 17 00:00:00 2001
From: Aaron LI <aly@aaronly.me>
Date: Thu, 3 Aug 2017 20:54:06 +0800
Subject: utils/convert.py: Improve various comments/descriptions
Signed-off-by: Aaron LI <aly@aaronly.me>
---
fg21sim/utils/convert.py | 56 ++++++++++++++++++++++++++++--------------------
1 file changed, 33 insertions(+), 23 deletions(-)
(limited to 'fg21sim/utils')
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)
--
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