Merge pull request #669 from Andrew-Robertson/fix_lightconeRedshiftOb…

…served Fix lightcone redshift observed
galacticusorg · Aug 19, 2024 · bd363d5 · bd363d5
2 parents d6740de + 5c6540f
commit bd363d5
Showing 1 changed file with 10 additions and 11 deletions.
diff --git a/source/nodes.property_extractor.lightcone.F90 b/source/nodes.property_extractor.lightcone.F90
@@ -17,6 +17,8 @@
 !!    You should have received a copy of the GNU General Public License
 !!    along with Galacticus.  If not, see <http://www.gnu.org/licenses/>.
 
+!+    Contributions to this file made by: Andrew Robertson, Andrew Benson
+
   use            :: Cosmology_Functions, only : cosmologyFunctions, cosmologyFunctionsClass
   use            :: Geometry_Lightcones, only : geometryLightcone , geometryLightconeClass
   use, intrinsic :: ISO_C_Binding      , only : c_size_t
@@ -274,24 +276,21 @@ function lightconeExtract(self,node,time,instance)
          &                                                                          )
     lightconeExtract   (8  )=self%geometryLightcone_%solidAngle()/degreesToRadians**2
     if (self%includeObservedRedshift) then
-       ! Compute the relativistic velocity β=v/c.
+       ! Compute the line-of-sight peculiar velocity divided by the speed of light: β_los=v_los/c.
        velocityBeta                                     =+Dot_Product     (lightconeExtract(4:6),lightconeExtract(1:3)) &
             &                                            /Vector_Magnitude(                      lightconeExtract(1:3)) &
             &                                            *kilo                                                          &
             &                                            /speedLight
        ! Compute the observed redshift. This is given by:
        !  1 + zₒ = (1 + zₕ) (1 + zₚ),
-       ! where zₒ is observed redshift, zₕ is cosmological redshift (due to Hubble expansion), and zₚ is the peculiar redshift,
-       ! given by
-       !  1 + zₚ = √[(1+βₚ)/(1-βₚ)]
-       ! where βₚ=vₚ/c is the dimensionless peculiar velocity (e.g. Davis et al.; 2011; ApJ; 741; 67; eqn. 4;
+       ! where zₒ is observed redshift, zₕ is cosmological redshift (due
+       ! to Hubble expansion), and zₚ is the peculiar redshift, given by
+       ! (in the non-relativistic limit) zₚ = β_los (e.g. Davis et al.;
+       ! 2011; ApJ; 741; 67; below eqn. 4;
        ! https://ui.adsabs.harvard.edu/abs/2011ApJ...741...67D).
-       lightconeExtract(self%redshiftObservedOffset  +1)=+                                       lightconeExtract(7  )  &
-            &                                            +    (+1.0d0                           +lightconeExtract(7  )) &
-            &                                            *sqrt(                                                         &
-            &                                                  +(+1.0d0+velocityBeta)                                   &
-            &                                                  /(+1.0d0-velocityBeta)                                   &
-            &                                                 )
+       lightconeExtract(self%redshiftObservedOffset+1)=  -1.0d0                      &
+            &                                          +(+1.0d0+lightconeExtract(7)) &
+            &                                          *(+1.0d0+velocityBeta       )
     end if
     if (self%includeAngularCoordinates) then
        lightconeExtract(self%angularCoordinatesOffset+1)=atan2(                              &