Move "ChandraPixel" from "deproject_sbp.py" to "astro_params.py"

1 files changed, 38 insertions, 0 deletions

diff --git a/astro_params.py b/astro_params.py
index a272ba4..b3b733b 100644
--- a/astro_params.py
+++ b/astro_params.py
@@ -4,6 +4,10 @@
 # Created: 2016-06-24
 # Updated: 2016-06-24
 #
+# Change logs:
+# 2016-06-24:
+#   * Add class 'ChandraPixel', moved from 'deproject_sbp.py'
+#
 
 """
 This module contains the parameters/constants used in astronomy
@@ -11,6 +15,7 @@ and astrophysics.
 """
 
 import astropy.units as au
+from astropy.cosmology import FlatLambdaCDM
 
 
 class AstroParams:
@@ -31,3 +36,36 @@ class AstroParams:
     mu_e = 1.155
     # atomic mass unit
     m_atom = au.u.to(au.g)  # [ g ]
+
+
+class ChandraPixel:
+    """
+    Chandra pixel unit conversions.
+    """
+    angle = 0.492 * au.arcsec
+    z = None
+    # cosmology calculator
+    cosmo = None
+    # angular diameter distance
+    D_A = None
+    # length of one pixel at the given redshift
+    length = None
+
+    def __init__(self, z=None):
+        self.z = z
+        self.cosmo = FlatLambdaCDM(H0=AstroParams.H0,
+                                   Om0=AstroParams.OmegaM0)
+        if z is not None:
+            self.D_A = self.cosmo.angular_diameter_distance(z)
+            self.length = self.D_A * self.angle.to(au.radian).value
+
+    def get_angle(self):
+        return self.angle
+
+    def get_length(self, z=None):
+        if z is None:
+            length = self.length
+        else:
+            D_A = self.cosmo.angular_diameter_distance(z)
+            length = D_A * self.angle.to(au.radian).value
+        return length