Address PR comments.

src/tdastro/astro_utils/cosmology.py

@@ -5,7 +5,7 @@
 
 
 def redshift_to_distance(redshift, cosmology, kind="comoving"):
-    """Compute a source's distance given its redshift and a
+    """Compute a source's luminosity distance given its redshift and a
     specified cosmology using astropy's redshift_distance().
 
     Parameters
@@ -21,7 +21,7 @@ def redshift_to_distance(redshift, cosmology, kind="comoving"):
     Returns
     -------
     distance : `float`
-        The distance (in pc)
+        The luminosity distance (in pc)
     """
     z = redshift * cu.redshift
     distance = z.to(u.pc, cu.redshift_distance(cosmology, kind=kind))

src/tdastro/sources/physical_model.py

@@ -22,7 +22,7 @@ class PhysicalModel(ParameterizedNode):
     redshift : `float`
         The object's redshift.
     distance : `float`
-        The object's distance (in pc). If the distance is not provided and
+        The object's luminosity distance (in pc). If no value is provided and
         a ``cosmology`` parameter is given, the model will try to derive from
         the redshift and the cosmology.
     background : `PhysicalModel`
@@ -40,8 +40,8 @@ def __init__(self, ra=None, dec=None, redshift=None, distance=None, background=N
         self.add_parameter("dec", dec)
         self.add_parameter("redshift", redshift)
 
-        # If the distance is provided, use that. Otherwise try the redshift value
-        # using the cosmology (if given). Finally, default to None.
+        # If the luminosity distance is provided, use that. Otherwise try the
+        # redshift value using the cosmology (if given). Finally, default to None.
         if distance is not None:
             self.add_parameter("distance", distance)
         elif redshift is not None and kwargs.get("cosmology", None) is not None:

tests/tdastro/astro_utils/test_cosmology.py

@@ -1,5 +1,5 @@
 import pytest
-from astropy.cosmology import WMAP9
+from astropy.cosmology import WMAP9, Planck18
 from tdastro.astro_utils.cosmology import redshift_to_distance
 
 
@@ -8,3 +8,6 @@ def test_redshift_to_distance():
     # 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)
+
+    # Try the Planck18 cosmology.
+    assert redshift_to_distance(1100, cosmology=Planck18) == pytest.approx(13886.327957 * 1e6)

tests/tdastro/sources/test_physical_models.py

@@ -1,5 +1,5 @@
 import pytest
-from astropy.cosmology import WMAP9
+from astropy.cosmology import Planck18
 from tdastro.sources.physical_model import PhysicalModel
 
 
@@ -12,13 +12,12 @@ def test_physical_model():
     assert model1.distance == 3.0
     assert model1.redshift == 0.0
 
-    # Derive the distance from the redshift using the example from:
-    # https://docs.astropy.org/en/stable/api/astropy.cosmology.units.redshift_distance.html
-    model2 = PhysicalModel(ra=1.0, dec=2.0, redshift=1100.0, cosmology=WMAP9)
+    # Derive the distance from the redshift:
+    model2 = PhysicalModel(ra=1.0, dec=2.0, redshift=1100.0, cosmology=Planck18)
     assert model2.ra == 1.0
     assert model2.dec == 2.0
     assert model2.redshift == 1100.0
-    assert model2.distance == pytest.approx(14004.03157418 * 1e6)
+    assert model2.distance == pytest.approx(13886.327957 * 1e6)
 
     # Neither distance nor redshift are specified.
     model3 = PhysicalModel(ra=1.0, dec=2.0)