From 2b8dda20b1737794c82ab29a0221e3ffe96cd26c Mon Sep 17 00:00:00 2001
From: Aaron LI <aly@aaronly.me>
Date: Thu, 1 Feb 2018 21:54:52 +0800
Subject: utils/convert.py: Add flux_to_power() to calculate power from flux
density
---
fg21sim/utils/convert.py | 35 ++++++++++++++++++++++++++++++++++-
1 file changed, 34 insertions(+), 1 deletion(-)
(limited to 'fg21sim')
diff --git a/fg21sim/utils/convert.py b/fg21sim/utils/convert.py
index 0fd08b4..85240f8 100644
--- a/fg21sim/utils/convert.py
+++ b/fg21sim/utils/convert.py
@@ -1,11 +1,14 @@
-# Copyright (c) 2016-2017 Weitian LI <weitian@aaronly.me>
+# Copyright (c) 2016-2018 Weitian LI <weitian@aaronly.me>
# MIT license
"""
Utilities for conversion among common astronomical quantities.
"""
+import numpy as np
+
from .units import (UnitConversions as AUC, Constants as AC)
+from ..share import COSMO
def Sb_to_Tb(Sb, freq):
@@ -108,3 +111,33 @@ def JyPerPix_to_K(freq, pixelsize):
"""
factor = Fnu_to_Tb(Fnu=1.0, omega=pixelsize**2, freq=freq)
return factor
+
+
+def flux_to_power(flux, z, index=1.0):
+ """
+ Calculate the (spectral) power from the measured flux density at
+ the same frequency with K-correction taking into account, if the
+ spectral index is given.
+
+ Parameters
+ ----------
+ flux : float
+ The measured flux density at a frequency.
+ Unit: [mJy]
+ z : float
+ The redshift to the source.
+ index : float, optional
+ The spectral index (α) of the source flux: S(ν) ∝ ν^(-α)
+ If given, the K-correction is taken into account.
+
+ Returns
+ -------
+ power : float
+ The calculated (spectral) power at the same frequency as
+ the flux density measured.
+ Unit: [W/Hz]
+ """
+ flux *= 1e-29 # [mJy] -> [W/Hz/m^2]
+ DL = COSMO.DL(z) * AUC.Mpc2m # [m]
+ power = 4*np.pi * DL**2 * (1+z)**(index-1) * flux # [W/Hz]
+ return power
--
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