Address more PR comments

Fix the distance kind as "luminosity"

src/tdastro/astro_utils/cosmology.py

@@ -4,7 +4,7 @@
 from tdastro.base_models import FunctionNode
 
 
-def redshift_to_distance(redshift, cosmology, kind="comoving"):
+def redshift_to_distance(redshift, cosmology):
     """Compute a source's luminosity distance given its redshift and a
     specified cosmology using astropy's redshift_distance().
 
@@ -14,17 +14,14 @@ def redshift_to_distance(redshift, cosmology, kind="comoving"):
         The redshift value.
     cosmology : `astropy.cosmology`
         The cosmology specification.
-    kind : `str`
-        The distance type for the Equivalency as defined by
-        astropy.cosmology.units.redshift_distance.
 
     Returns
     -------
     distance : `float`
         The luminosity distance (in pc)
     """
     z = redshift * cu.redshift
-    distance = z.to(u.pc, cu.redshift_distance(cosmology, kind=kind))
+    distance = z.to(u.pc, cu.redshift_distance(cosmology, kind="luminosity"))
     return distance.value
 
 
@@ -45,18 +42,14 @@ class RedshiftDistFunc(FunctionNode):
         The function or constant providing the redshift value.
     cosmology : `astropy.cosmology`
         The cosmology specification.
-    kind : `str`
-        The distance type for the Equivalency as defined by
-        astropy.cosmology.units.redshift_distance.
     """
 
-    def __init__(self, redshift, cosmology, kind="comoving"):
+    def __init__(self, redshift, cosmology):
         # Call the super class's constructor with the needed information.
         super().__init__(
             func=redshift_to_distance,
             redshift=redshift,
             cosmology=cosmology,
-            kind=kind,
         )
 
     def __str__(self):

tests/tdastro/astro_utils/test_cosmology.py

@@ -1,13 +1,12 @@
-import pytest
 from astropy.cosmology import WMAP9, Planck18
 from tdastro.astro_utils.cosmology import redshift_to_distance
 
 
 def test_redshift_to_distance():
     """Test that we can convert the redshift to a distance using a given cosmology."""
-    # Use the example from:
-    # https://docs.astropy.org/en/stable/api/astropy.cosmology.units.redshift_distance.html
-    assert redshift_to_distance(1100, cosmology=WMAP9) == pytest.approx(14004.03157418 * 1e6)
+    wmap9_val = redshift_to_distance(1100, cosmology=WMAP9)
+    planck18_val = redshift_to_distance(1100, cosmology=Planck18)
 
-    # Try the Planck18 cosmology.
-    assert redshift_to_distance(1100, cosmology=Planck18) == pytest.approx(13886.327957 * 1e6)
+    assert abs(planck18_val - wmap9_val) > 1000.0
+    assert 13.0 * 1e12 < wmap9_val < 16.0 * 1e12
+    assert 13.0 * 1e12 < planck18_val < 16.0 * 1e12

tests/tdastro/sources/test_physical_models.py

@@ -1,4 +1,3 @@
-import pytest
 from astropy.cosmology import Planck18
 from tdastro.sources.physical_model import PhysicalModel
 
@@ -17,7 +16,7 @@ def test_physical_model():
     assert model2.ra == 1.0
     assert model2.dec == 2.0
     assert model2.redshift == 1100.0
-    assert model2.distance == pytest.approx(13886.327957 * 1e6)
+    assert 13.0 * 1e12 < model2.distance < 16.0 * 1e12
 
     # Neither distance nor redshift are specified.
     model3 = PhysicalModel(ra=1.0, dec=2.0)