def test_speclite_not_installed():
"""
Regression test for #436
Test that mag_ab raises the correct exception if speclite is not insalled.
"""
from skypy.utils.photometry import mag_ab
wavelength = np.linspace(1, 10, 100)
spectrum = np.ones(10)
filter = 'bessell-B'
with pytest.raises(ImportError):
mag_ab(wavelength, spectrum, filter)
def test_mag_ab_redshift_dependence():
from astropy import units
from speclite.filters import FilterResponse
from skypy.utils.photometry import mag_ab
# make a wide tophat bandpass
filt_lam = [1.0e-10, 1.1e-10, 1.0e0, 0.9e10, 1.0e10]
filt_tx = [0., 1., 1., 1., 0.]
FilterResponse(wavelength=filt_lam,
response=filt_tx,
meta=dict(group_name='test', band_name='filt'))
# create a narrow gaussian source
lam = np.logspace(-11, 11, 1000) * units.AA
flam = np.exp(-((lam - 100 * units.AA) /
(10 * units.AA))**2) * units.Unit('erg s-1 cm-2 AA-1')
# array of redshifts
z = np.linspace(0, 1, 11)
# compute the AB magnitude at different redshifts
m = mag_ab(lam, flam, 'test-filt', redshift=z)
# compare with expected redshift dependence
np.testing.assert_allclose(m, m[0] - 2.5 * np.log10(1 + z))
def test_template_spectra():
from astropy import units
from skypy.utils.photometry import mag_ab, SpectrumTemplates
from astropy.cosmology import Planck15
from speclite.filters import FilterResponse
class TestTemplates(SpectrumTemplates):
'''Three flat templates'''
def __init__(self):
self.wavelength = np.logspace(-1, 4, 1000) * units.AA
A = np.array([[2], [3], [4]]) * 0.10885464149979998
self.templates = A * units.Unit(
'erg s-1 cm-2 AA') / self.wavelength**2
test_templates = TestTemplates()
lam, flam = test_templates.wavelength, test_templates.templates
# Gaussian bandpass
filt_lam = np.logspace(0, 4, 1000) * units.AA
filt_tx = np.exp(-((filt_lam - 1000 * units.AA) / (100 * units.AA))**2)
filt_tx[[0, -1]] = 0
FilterResponse(wavelength=filt_lam,
response=filt_tx,
meta=dict(group_name='test', band_name='filt'))
# Each test galaxy is exactly one of the templates
coefficients = np.eye(3)
# Test absolute magnitudes
mt = test_templates.absolute_magnitudes(coefficients, 'test-filt')
m = mag_ab(lam, flam, 'test-filt')
np.testing.assert_allclose(mt, m)
# Test apparent magnitudes
redshift = np.array([1, 2, 3])
dm = Planck15.distmod(redshift).value
mt = test_templates.apparent_magnitudes(coefficients, redshift,
'test-filt', Planck15)
np.testing.assert_allclose(mt, m - 2.5 * np.log10(1 + redshift) + dm)
# Redshift interpolation test; linear interpolation sufficient over a small
# redshift range at low relative tolerance
z = np.linspace(0.1, 0.2, 3)
m_true = test_templates.apparent_magnitudes(coefficients,
z,
'test-filt',
Planck15,
resolution=4)
m_interp = test_templates.apparent_magnitudes(coefficients,
z,
'test-filt',
Planck15,
resolution=2)
np.testing.assert_allclose(m_true, m_interp, rtol=1e-5)
assert not np.all(m_true == m_interp)
def test_mag_ab_standard_source():
from astropy import units
from speclite.filters import FilterResponse
from skypy.utils.photometry import mag_ab
# create a filter
filt_lam = np.logspace(0, 4, 1000) * units.AA
filt_tx = np.exp(-((filt_lam - 1000 * units.AA) / (100 * units.AA))**2)
filt_tx[[0, -1]] = 0
FilterResponse(wavelength=filt_lam,
response=filt_tx,
meta=dict(group_name='test', band_name='filt'))
# test that the AB standard source has zero magnitude
lam = filt_lam # same grid to prevent interpolation issues
flam = 0.10885464149979998 * units.Unit('erg s-1 cm-2 AA') / lam**2
m = mag_ab(lam, flam, 'test-filt')
assert np.isclose(m, 0)
def test_mag_ab_multi():
from astropy import units
from skypy.utils.photometry import mag_ab
from speclite.filters import FilterResponse
# 5 redshifts
z = np.linspace(0, 1, 5)
# 2 Gaussian bandpasses
filt_lam = np.logspace(0, 4, 1000) * units.AA
filt_mean = np.array([[1000], [2000]]) * units.AA
filt_width = np.array([[100], [10]]) * units.AA
filt_tx = np.exp(-((filt_lam - filt_mean) / filt_width)**2)
filt_tx[:, [0, -1]] = 0
FilterResponse(wavelength=filt_lam,
response=filt_tx[0],
meta=dict(group_name='test', band_name='filt0'))
FilterResponse(wavelength=filt_lam,
response=filt_tx[1],
meta=dict(group_name='test', band_name='filt1'))
# 3 Flat Spectra
# to prevent issues with interpolation, collect all redshifted filt_lam
lam = []
for z_ in z:
lam = np.union1d(lam, filt_lam.value / (1 + z_))
lam = lam * filt_lam.unit
A = np.array([[2], [3], [4]])
flam = A * 0.10885464149979998 * units.Unit('erg s-1 cm-2 AA') / lam**2
# Compare calculated magnitudes with truth
magnitudes = mag_ab(lam, flam, ['test-filt0', 'test-filt1'], redshift=z)
truth = -2.5 * np.log10(A * (1 + z)).T[:, :, np.newaxis]
assert magnitudes.shape == (5, 3, 2)
np.testing.assert_allclose(*np.broadcast_arrays(magnitudes, truth),
rtol=1e-4)
