def test_from_mag_unit_error(self):
bp = synphot.SpectralElement(synphot.Box1D,
x_0=11.7 * u.um,
width=0.1 * u.um)
with pytest.raises(ValueError):
Efrho.from_mag(5, 'asdf', 1 * u.arcsec, bp,
dict(rh=1.5 * u.au, delta=1.0 * u.au))
def test_from_mag_bandpass(self, unit, efrho0):
aper = 1 * u.arcsec
# width = 0.1 um for speed
bp = synphot.SpectralElement(synphot.Box1D,
x_0=11.7 * u.um,
width=0.1 * u.um)
eph = dict(rh=1.0 * u.au, delta=1.0 * u.au)
Tscale = 1.1
efrho = Efrho.from_mag(5, unit, aper, eph, bandpass=bp, Tscale=Tscale)
assert np.isclose(efrho.cm, efrho0, rtol=0.001)
def test_observe_bandpass(self):
w = u.Quantity(np.linspace(0.3, 1.0), 'um')
f = u.Quantity(np.ones(len(w)), 'W/(m2 um)')
s = Star.from_array(w, f)
bp = synphot.SpectralElement(synphot.Box1D,
x_0=0.55 * u.um,
width=0.1 * u.um)
fluxd = s.observe(bp)
assert np.allclose(fluxd.value, [1])
bps = [
synphot.SpectralElement(synphot.Box1D,
x_0=0.55 * u.um,
width=0.1 * u.um),
synphot.SpectralElement(synphot.Box1D,
x_0=0.65 * u.um,
width=0.1 * u.um)
]
fluxd = s.observe(bps, unit='W/(m2 um)')
assert np.allclose(fluxd.value, [1, 1])
def __call__(self, wave_or_freq, unit=None):
"""Evaluate the source spectrum.
Parameters
----------
wave_or_freq : `~astropy.units.Quantity`
Requested wavelength or frequencies of the resulting
spectrum. If an array, `wave_or_freq` specifies bin
centers. If a single value, fluxd will be interpolated to
this wavelength/frequency.
unit : string, `~astropy.units.Unit`, optional
Spectral units of the output: flux density, 'vegamag',
'ABmag', or 'STmag'. If ``None``, return units are W/(m2
μm) for ``wave_or_freq`` as wavelength, otherwise return Jy.
Returns
-------
fluxd : `~astropy.units.Quantity`
The spectrum binned to match `wave_or_freq`. If a single
point is requested, the original spectrum is interpolated to
it.
"""
import numpy as np
import synphot
if unit is None:
if wave_or_freq.unit.is_equivalent('m'):
unit = u.Unit('W/(m2 um)')
else:
unit = u.Jy
if np.size(wave_or_freq) > 1:
# Method adapted from http://www.astrobetter.com/blog/2013/08/12/python-tip-re-sampling-spectra-with-pysynphot/
specele = synphot.SpectralElement(synphot.ConstFlux1D(1))
obs = synphot.Observation(self.source,
specele,
binset=wave_or_freq,
force='taper')
# The following is the same as obs.binflux, except sample_binned
# will do the unit coversions.
fluxd = obs.sample_binned(flux_unit=unit)
else:
fluxd = self.source(wave_or_freq, unit)
return fluxd
def test_mag(self):
# compare to sbpy
g = {'rh': 2.0 * u.au, 'delta': 1.0 * u.au, 'phase': 0 * u.deg}
afrho = Afrho(100 * 2**-2, 'cm')
tab = np.loadtxt(os.path.join(__path__[0], 'lsst-total-r.dat')).T
r = synphot.SpectralElement(synphot.Empirical1D,
points=tab[0] * u.nm,
lookup_table=tab[1])
rap = 1 * u.arcsec
m0 = afrho.to_fluxd(r, rap, g, unit=u.ABmag).value
comet = Comet(R=1, afrho1=100, k=-2)
m = comet.mag(g, 'r', rap=rap.value, nucleus=False)
assert np.isclose(m, m0, atol=0.05)
def test_mag_fluxd0_bandpass(self):
# comapre with test_mag_bandpass
aper = 1 * u.arcsec
# width = 0.1 um for speed
bp = synphot.SpectralElement(synphot.Box1D,
x_0=11.7 * u.um,
width=0.1 * u.um)
eph = dict(rh=1.0 * u.au, delta=1.0 * u.au)
Tscale = 1.1
fluxd0 = u.Quantity(3631, 'Jy')
efrho = Efrho(78750, 'cm')
mag = efrho.mag(None,
aper,
eph,
bandpass=bp,
fluxd0=fluxd0,
Tscale=Tscale)
assert np.isclose(mag, 5, rtol=0.001)
def observe(self, wfb, unit=None, **kwargs):
"""Observe source as through filters or spectrometer.
Parameters
----------
wfb : `~astropy.units.Quantity`, `~synphot.SpectralElement`
Wavelengths, frequencies, or bandpasses. May also be a
list of ``SpectralElement``s.
unit : string, `~astropy.units.Unit`, optional
Spectral units of the output (flux density). If ``None``,
the default depends on ``wfb``: W/(m2 μm) for wavelengths
or bandpasses, Jy for frequencies.
**kwargs
Additional keyword arguments for
`~synphot.observation.Observation`, e.g., ``force``.
Returns
-------
fluxd : `~astropy.units.Quantity`
The spectrum rebinned.
Raises
------
SinglePointSpectrumError - If requested wavelengths or
frequencies has only one value.
Notes
-----
Method adapted from AstroBetter post by Jessica Lu:
http://www.astrobetter.com/blog/2013/08/12/python-tip-re-sampling-spectra-with-pysynphot/
"""
import synphot
from .. import units as sbu # avoid circular dependency
# promote single bandpasses to a list, but preserve number of
# dimensions
if isinstance(wfb, (synphot.SpectralElement, str)):
ndim = 0
wfb = [wfb]
else:
ndim = np.ndim(wfb)
if isinstance(wfb, (tuple, list)):
if unit is None:
unit = u.Unit('W/(m2 um)')
else:
unit = u.Unit(unit)
fluxd = np.ones(len(wfb)) * unit
for i in range(len(wfb)):
fluxd[i] = self.filt(wfb[i], unit=unit, **kwargs)[1]
else:
if np.size(wfb) == 1:
raise SinglePointSpectrumError(
'Multiple wavelengths or frequencies required for '
'observe. Consider interpolation with {}() instead.'.
format(self.__class__.__name__))
if unit is None:
if wfb.unit.is_equivalent('m'):
unit = u.Unit('W/(m2 um)')
else:
unit = u.Jy
else:
unit = u.Unit(unit)
specele = synphot.SpectralElement(synphot.ConstFlux1D(1))
# Use force='taper' to prevent PartialOverlap execption.
# Specele is defined over all wavelengths, but most
# spectral standards are not.
kwargs['force'] = kwargs.get('force', 'taper')
obs = synphot.Observation(self.source,
specele,
binset=wfb,
**kwargs)
if unit.is_equivalent(sbu.VEGAmag):
fluxd = obs.sample_binned(flux_unit='W/(m2 um)').to(
unit, sbu.spectral_density_vega(wfb))
else:
fluxd = obs.sample_binned(flux_unit=unit)
if np.ndim(fluxd) != ndim:
# likely need a squeeze
fluxd = fluxd.squeeze()
return fluxd
def box(center, width):
return synphot.SpectralElement(
synphot.Box1D, x_0=center * u.um, width=width * u.um)
def observe_spectrum(self, wave_or_freq, unit=None, **kwargs):
"""Observe source as through a spectrometer.
.. Important:: This method works best when the requested
spectral resolution is lower than the spectral resolution
of the internal data. If the requested
wavelengths/frequencies are exactly the same as the
internal spectrum, then the internal spectrum will be
returned without binning. This special case does not work
for subsets of the wavelengths.
Parameters
----------
wave_or_freq : `~astropy.units.Quantity`
Wavelengths or frequencies of the spectrum. Spectral bins
will be centered at these values. The length must be
larger than 1.
unit : string, `~astropy.units.Unit`, optional
Spectral flux density units for the output. If ``None``,
the default is W/(m2 μm) for wavelengths, Jy for
frequencies.
**kwargs
Additional keyword arguments for
`~synphot.observation.Observation`, e.g., ``force``.
Returns
-------
fluxd : `~astropy.units.Quantity`
The spectrum rebinned.
Raises
------
SinglePointSpectrumError - If requested wavelengths or
frequencies has only one value.
Notes
-----
Method for spectra adapted from AstroBetter post by Jessica Lu:
https://www.astrobetter.com/blog/2013/08/12/python-tip-re-sampling-spectra-with-pysynphot/
"""
from .. import units as sbu # avoid circular dependency
if np.size(wave_or_freq) == 1:
raise SinglePointSpectrumError(
'Multiple wavelengths or frequencies required for '
'observe_spectrum. Instead consider interpolation '
'with {}().'.format(self.__class__.__name__))
if unit is None:
if wave_or_freq.unit.is_equivalent('m'):
unit = u.Unit('W/(m2 um)')
else:
unit = u.Jy
else:
unit = u.Unit(unit)
specele = synphot.SpectralElement(synphot.ConstFlux1D, amplitude=1)
# Specele is defined over all wavelengths, but most spectral
# standards are not. force='taper' will affect retrieving
# flux densities at the edges of the spectrum, but is
# preferred to avoid wild extrapolation.
kwargs['force'] = kwargs.get('force', 'taper')
obs = synphot.Observation(self.source,
specele,
binset=wave_or_freq,
**kwargs)
if unit.is_equivalent(sbu.VEGAmag):
fluxd = obs.sample_binned(flux_unit='W/(m2 um)').to(
unit, sbu.spectral_density_vega(wave_or_freq))
else:
fluxd = obs.sample_binned(flux_unit=unit)
return fluxd
def get_sky_spectrum(self, return_type="table", filename=None):
from astropy import table
if filename is None:
filename = "skycalc_temp.fits"
if not self.validate_params():
raise ValueError("Object contains invalid parameters. "
"Not calling ESO")
skm = SkyModel()
skm.callwith(self.values)
skm.write(filename)
with fits.open(filename) as hdu:
tbl = table.Table(hdu[1].data)
tbl["lam"].unit = u.um
for colname in tbl.colnames:
if "flux" in colname:
tbl[colname].unit = u.Unit("ph s-1 m-2 um-1 arcsec-2")
date_created = dt.now().strftime('%Y-%m-%dT%H:%M:%S')
meta_data = {
"DESCRIPT": "Sky transmission and emission curves",
"SOURCE": "ESO Skycalc utility",
"AUTHOR": "ESO Skycalc utility",
"STATUS": "Tested - Generated from ESO Skycalc utility",
"DATE_CRE": date_created,
"ETYPE": "TERCurve",
"EDIM": 1
}
params = {k: (self.values[k], self.comments[k]) for k in self.keys}
meta_data.update(params)
if "tab" in return_type:
tbl.meta.update(meta_data)
if "ext" in return_type:
tbl_return = tbl
else:
tbl_small = table.Table()
tbl_small.add_columns([tbl["lam"], tbl["trans"], tbl["flux"]])
tbl_return = tbl_small
return tbl_return
elif "arr" in return_type:
wave = tbl["lam"].data * tbl["lam"].unit
trans = tbl["trans"].data
flux = tbl["flux"].data * tbl["flux"].unit
return wave, trans, flux
elif "syn" in return_type:
import synphot as sp
trans = sp.SpectralElement(sp.Empirical1D,
points=tbl["lam"].data *
tbl["lam"].unit,
lookup_table=tbl["trans"].data)
funit = u.Unit("ph s-1 m-2 um-1")
flux = sp.SourceSpectrum(sp.Empirical1D,
points=tbl["lam"].data * tbl["lam"].unit,
lookup_table=tbl["flux"].data * funit)
print("Warning: synphot doesn't accept surface brightnesses \n"
"The resulting spectrum should be multiplied by arcsec-2")
return trans, flux
elif "fit" in return_type:
hdu0 = fits.PrimaryHDU()
for key in meta_data:
hdu0.header[key] = meta_data[key]
hdu1 = fits.table_to_hdu(tbl)
hdu = fits.HDUList([hdu0, hdu1])
return hdu
