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Fix wavelength conversion when filtering SEDs #1366

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Fix wavelength conversion when filtering SEDs #1366

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2 changes: 1 addition & 1 deletion galsim/sed.py
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Original file line number Diff line number Diff line change
Expand Up @@ -533,7 +533,7 @@ def _mul_sed(self, other):
def _mul_bandpass(self, other):
"""Equivalent to self * other when other is a Bandpass"""
wave_list, blue_limit, red_limit = utilities.combine_wave_list(self, other)
zfactor = (1.0+self.redshift) / other.wave_factor
zfactor = (1.0+self.redshift) * other.wave_factor
if self.fast:
if (isinstance(self._fast_spec, LookupTable)
and not self._fast_spec.x_log
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23 changes: 23 additions & 0 deletions tests/test_sed.py
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Expand Up @@ -320,6 +320,29 @@ def test_SED_mul():
np.testing.assert_almost_equal((sed2*sed4)(10), 8.0, 10, "Found wrong value in SED.__mul__")
np.testing.assert_almost_equal((sed3*sed4)(30), 12.0, 10, "Found wrong value in SED.__mul__")

@timer
def test_SED_mul_bandpass():
"""Check wavelength units when filtering an SED. (Issue #1365.)
"""
waves = np.array([400., 500., 600.])
spec_waves = np.arange(100., 1001., 50.)
for fast in [True, False]:
for spec in [lambda w: w / 500.,
galsim.LookupTable(spec_waves, spec_waves / 500., interpolant='linear')]:
for z in [0., 1.]:
sed = galsim.SED(spec, 'nm', 'fphotons', fast=fast).atRedshift(z)
for wave_type, factor in [('nm', 1.), ('Angstrom', 10.), (units.um, 0.001)]:
for throughput in [
lambda w: w / (1000. * factor),
galsim.LookupTable(waves * factor, waves / 1000., interpolant='linear')
]:
bp = galsim.Bandpass(throughput, wave_type,
blue_limit=400. * factor, red_limit=600. * factor)
for filtered in [sed * bp, bp * sed]:
np.testing.assert_allclose(filtered(500.), sed(500.) * bp(500.))
np.testing.assert_allclose(filtered(waves), sed(waves) * bp(waves))


@timer
def test_SED_div():
"""Check that SEDs divide like I think they should...
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