Include the HEALPix pixel window in map-based pseudo-Cℓ bandpower windows

src/sp_validation/cosmo_val/pseudo_cl.py

@@ -610,7 +610,7 @@ def calculate_pseudo_cl_map(self, ver, nside, out_path):
         cl_shear = cl_shear - cl_noise
 
         self.print_cyan("Saving pseudo-Cl's...")
-        self.pseudo_cl_to_sacc_part(ver, out_path, ell_eff, cl_shear, wsp)
+        self.pseudo_cl_to_sacc_part(ver, out_path, ell_eff, cl_shear, wsp, nside=nside)
 
         self._pseudo_cls[ver]["pseudo_cl"] = self._load_pseudo_cl_sacc(out_path)
 
@@ -716,19 +716,23 @@ def apply_random_rotation(self, e1, e2, rng=None):
         """
         return apply_random_rotation(e1, e2, rng)
 
-    def pseudo_cl_to_sacc_part(self, version, out_path, ell_eff, cl_all, wsp):
+    def pseudo_cl_to_sacc_part(
+        self, version, out_path, ell_eff, cl_all, wsp, nside=None
+    ):
         """Write the pseudo-Cl SACC part (EE/BB/EB + shared bandpower window).
 
         ``cl_all`` is NaMaster's decoupled ``(4, nbp)`` array (EE, EB, BE, BB);
-        the writer takes the shared bandpower window from ``wsp``. No covariance
-        is attached here.
+        the writer takes the shared bandpower window from ``wsp``, with the
+        pixel window of maps at ``nside`` for a map-based spectrum. No
+        covariance is attached here.
         """
         s = pseudo_cl_to_sacc(
             self.sacc_nz(version),
             self.sacc_metadata(version),
             ell_eff,
             cl_all,
             wsp,
+            nside=nside,
         )
         sacc_io.save(s, out_path, type="data")
 

src/sp_validation/cosmo_val/sacc_writers.py

@@ -68,14 +68,15 @@ def xi_to_sacc(
     return s
 
 
-def pseudo_cl_to_sacc(nz, metadata, ell_eff, cl_all, wsp, covariance=None):
+def pseudo_cl_to_sacc(nz, metadata, ell_eff, cl_all, wsp, covariance=None, nside=None):
     """One pseudo-Cℓ part: EE/BB/EB with the shared bandpower window.
 
     ``cl_all`` is NaMaster's decoupled ``(4, nbp)`` array (EE, EB, BE, BB); the
-    window comes from :func:`bandpower_window_from_workspace`. ``covariance``,
-    when given, is the dense ``[EE; BB; EB]``-ordered block matching insertion.
+    window comes from :func:`bandpower_window_from_workspace`, with the pixel
+    window of maps at ``nside`` when given. ``covariance``, when given, is the
+    dense ``[EE; BB; EB]``-ordered block matching insertion.
     """
-    window_ells, window_weights = bandpower_window_from_workspace(wsp)
+    window_ells, window_weights = bandpower_window_from_workspace(wsp, nside)
     s = sio.new_sacc(nz, metadata)
     sio.add_pseudo_cl(
         s,

src/sp_validation/pseudo_cl.py

@@ -286,7 +286,7 @@ def get_pseudo_cls_catalog(
 _NMT_EE = 0
 
 
-def bandpower_window_from_workspace(wsp):
+def bandpower_window_from_workspace(wsp, nside=None):
     """Extract the bandpower window matrix ``W`` for a spin-2×spin-2 workspace.
 
     NaMaster's ``get_bandpower_windows()`` returns a four-index array
@@ -303,9 +303,14 @@ def bandpower_window_from_workspace(wsp):
         ``compute_coupled_cell``.
     window_weights : np.ndarray
         ``W`` of shape ``(n_ell, n_bpw)`` — one column per bandpower, the layout
-        :func:`sp_validation.sacc_io.add_pseudo_cl` expects.
+        :func:`sp_validation.sacc_io.add_pseudo_cl` expects. For a spectrum of
+        HEALPix maps at ``nside``, ``W`` includes the pixel window pw²(ℓ), so it
+        maps a C_ℓ to the measured bandpower.
     """
     bpw = wsp.get_bandpower_windows()  # (n_cl_out, n_bpw, n_cl_in, n_ell)
     diagonal = bpw[_NMT_EE, :, _NMT_EE, :]  # (n_bpw, n_ell)
     window_ells = np.arange(diagonal.shape[1], dtype=float)
+    if nside is not None:
+        pixwin = hp.pixwin(nside, lmax=diagonal.shape[1] - 1)
+        diagonal = diagonal * pixwin**2
     return window_ells, diagonal.T

src/sp_validation/tests/test_sacc_writers.py

@@ -171,6 +171,16 @@ def test_pseudo_cl_to_sacc_real_namaster(tmp_path):
     assert np.array_equal(ee, cl_all[0]) and np.array_equal(bb, cl_all[3])
     # window columns correspond to the bandpowers, one per ell_eff
     assert window.weight.shape[1] == len(ell_eff)
+    # a map-based spectrum's window carries the pixel window pw²(ℓ)
+    import healpy as hp
+
+    mapped = sw.pseudo_cl_to_sacc({0: _nz()}, META, ell_eff, cl_all, wsp, nside=nside)
+    pw2 = hp.pixwin(nside, lmax=len(window.values) - 1) ** 2
+    np.testing.assert_allclose(
+        mapped.get_bandpower_windows(mapped.indices(sio.CL_EE)).weight,
+        pw2[:, None] * window.weight,
+        rtol=1e-12,
+    )
 
 
 def test_cosebis_to_sacc(tmp_path):