Changeset 36079 for trunk/ppSim/src/ppSimMakeGalaxies.c

Timestamp:

Aug 31, 2013, 5:20:18 AM (13 years ago)

Author:

eugene

Message:

fix the normalization of a sersic-like model

File:

• trunk/ppSim/src/ppSimMakeGalaxies.c (modified) (1 diff)

trunk/ppSim/src/ppSimMakeGalaxies.c

@@ -219 +219 @@
     }
 
+    // exponential
+    // f = I0 exp (sqrt(z)) (index = 1.0)
+
+    // f = I0 exp (-0.5*z) 
+
     if (isSersicType) {
         // for a sersic model, 
-        float bn = 1.9992*index - 0.3271;
-        float Io = exp(bn);
+        // float bn = 1.9992*index - 0.3271;
+        // float Io = exp(bn);
                     
         // the integral of a Sersic has an analytical form as follows:
-        float logGamma = lgamma(2.0*index);
-        float bnFactor = pow(bn, 2.0*index);
-        float norm = 2.0 * M_PI * PS_SQR(galaxy->Rmaj) * index * Io * exp(logGamma) / bnFactor;
+        // float logGamma = lgamma(2.0*index);
+        // float bnFactor = pow(bn, 2.0*index);
+        // float norm = 2.0 * M_PI * PS_SQR(galaxy->Rmaj) * index * Io * exp(logGamma) / bnFactor;
                     
+        // find the flux of a sersic with peak = 1.0:
+        float norm = pmSersicNorm (index);
+        float flux = 2.0 * M_PI * galaxy->Rmaj * galaxy->Rmin * norm;
+
         // XXX probably should limit the allowed thinness of a galaxy
-        galaxy->peak = galaxy->flux / norm / (galaxy->Rmin / galaxy->Rmaj);
+        galaxy->peak = galaxy->flux / flux;
         return true;
     }