def _vega_source(mag=0, x=0, y=0):
specs = [vega_spectrum(mag)]
tbl = Table(names=["x", "y", "ref", "weight"],
data=[[x] * u.arcsec, [y] * u.arcsec, [0], [1]])
tbl_source = Source(table=tbl, spectra=specs)
return tbl_source
def test_all_zero_spectra_line_up():
mag = 0
vega = src_ts.vega_spectrum(mag)
ab = src_ts.ab_spectrum(mag)
st = src_ts.st_spectrum(mag)
wave = 0.55 * u.um
assert st(wave).value == approx(vega(wave).value, rel=0.03)
assert ab(wave).value == approx(vega(wave).value, rel=0.03)
def get_zero_mag_spectrum(system_name="AB"):
if system_name.lower() in ["vega"]:
spec = vega_spectrum()
elif system_name.lower() in ["ab"]:
spec = ab_spectrum()
elif system_name.lower() in ["st", "hst"]:
spec = st_spectrum()
return spec
def test_scales_vega_spectrum_to_vega_ab_or_jansky(self):
spec = src_ts.vega_spectrum()
vega_185 = ter_utils.scale_spectrum(spec, "Ks", -1.85 * u.mag)
ab_0 = ter_utils.scale_spectrum(spec, "Ks", 0 * u.ABmag)
jy_3630 = ter_utils.scale_spectrum(spec, "Ks", 3630 * u.Jy)
wave = np.linspace(1.8, 2.5, 1000) * u.um
assert vega_185(wave).value == approx(ab_0(wave).value, rel=1e-2)
assert vega_185(wave).value == approx(jy_3630(wave).value, rel=1e-2)
if PLOTS:
plt.plot(wave, spec(wave), "b")
plt.plot(wave, vega_185(wave), "r:")
plt.plot(wave, ab_0(wave), "g--")
plt.plot(wave, jy_3630(wave), "y-.")
plt.semilogy()
plt.show()
def photons_in_vega_spectrum(self):
for filter_name in ["J", "H", "Ks", "Lp", "Mp"]:
vega = vega_spectrum()
kwargs = {
"observatory": "Paranal",
"instrument": "NACO",
"filter_name": filter_name
}
filt = sim.effects.SpanishVOFilterCurve(**kwargs)
wave = filt.surface.table["wavelength"]
trans = filt.surface.table["transmission"]
dwave = 0.5 * (np.r_[[0], np.diff(wave)] +
np.r_[np.diff(wave), [0]]) * u.AA
flux = vega(wave) # ph/s/cm2/AA
flux *= trans * dwave # ph/s
sum_flux = np.sum(flux.to(u.ph / u.s / u.m**2).value)
print(f"\nVega spectrum over the {filter_name} band "
f"({filter_name}=0mag) has a flux of "
f"{int(sum_flux * 1e-6)}e6 ph/s/m2")
def scale_spectrum(spectrum, filter_name, amplitude):
"""
Scales a SourceSpectrum to a value in a filter
Parameters
----------
spectrum : synphot.SourceSpectrum
filter_name : str
Name of a filter from
- a local instrument package (available in ``rc.__search_path__``)
- a generic filter name (see ``ter_curves_utils.FILTER_DEFAULTS``)
- a spanish-vo filter service reference (e.g. ``"Paranal/HAWKI.Ks"``)
amplitude : ``astropy.Quantity``, float
The value that the spectrum should have in the given filter. Acceptable
astropy quantities are:
- u.mag : Vega magnitudes
- u.ABmag : AB magnitudes
- u.STmag : HST magnitudes
- u.Jy : Jansky per filter bandpass
Additionally the ``FLAM`` and ``FNU`` units from ``synphot.units`` can
be used when passing the quantity for ``amplitude``:
Returns
-------
spectrum : synphot.SourceSpectrum
Input spectrum scaled to the given amplitude in the given filter
Examples
--------
::
>>> from scopesim.source.source_templates import vega_spectrum
>>> from scopesim.effects.ter_curves_utils as ter_utils
>>>
>>> spec = vega_spectrum()
>>> vega_185 = ter_utils.scale_spectrum(spec, "Ks", -1.85 * u.mag)
>>> ab_0 = ter_utils.scale_spectrum(spec, "Ks", 0 * u.ABmag)
>>> jy_3630 = ter_utils.scale_spectrum(spec, "Ks", 3630 * u.Jy)
"""
if isinstance(amplitude, u.Quantity):
if amplitude.unit.physical_type == "spectral flux density":
if amplitude.unit != u.ABmag:
amplitude = amplitude.to(u.ABmag)
ref_spec = ab_spectrum(amplitude.value)
elif amplitude.unit.physical_type == "spectral flux density wav":
if amplitude.unit != u.STmag:
amplitude = amplitude.to(u.STmag)
ref_spec = st_spectrum(amplitude.value)
elif amplitude.unit == u.mag:
ref_spec = vega_spectrum(amplitude.value)
else:
raise ValueError(f"Units of amplitude must be one of "
f"[u.mag, u.ABmag, u.STmag, u.Jy]: {amplitude}")
else:
ref_spec = vega_spectrum(amplitude)
filt = get_filter(filter_name)
ref_flux = Observation(ref_spec, filt).effstim(flux_unit=PHOTLAM)
real_flux = Observation(spectrum, filt).effstim(flux_unit=PHOTLAM)
scale_factor = ref_flux / real_flux
spectrum *= scale_factor.value
return spectrum