def load_vega(vegafile=None, **kwargs):
"""Convenience function to load Vega spectrum that is
used throughout `stsynphot`.
Parameters
----------
vegafile : str or `None`, optional
Vega spectrum filename.
If `None`, use ``synphot.config.conf.vega_file``.
kwargs : dict
Keywords acceptable by :func:`synphot.specio.read_remote_spec`.
Returns
-------
sp : `synphot.spectrum.SourceSpectrum` or `None`
Vega spectrum. `None` if failed.
"""
global Vega
if vegafile is None:
vegafile = synconf.vega_file
with synconf.set_temp('vega_file', vegafile):
try:
Vega = SourceSpectrum.from_vega(**kwargs)
except Exception as e:
Vega = None
warnings.warn(
'Failed to load Vega spectrum from {0}; Functionality '
'involving Vega will be cripped: {1}'.format(
vegafile, str(e)), AstropyUserWarning)
def load_vega(vegafile=None, **kwargs):
"""Convenience function to load Vega spectrum that is
used throughout `stsynphot`.
Parameters
----------
vegafile : str or `None`, optional
Vega spectrum filename.
If `None`, use ``synphot.config.conf.vega_file``.
kwargs : dict
Keywords acceptable by :func:`synphot.specio.read_remote_spec`.
Returns
-------
sp : `synphot.spectrum.SourceSpectrum` or `None`
Vega spectrum. `None` if failed.
"""
global Vega
if vegafile is None:
vegafile = synconf.vega_file
with synconf.set_temp('vega_file', vegafile):
try:
Vega = SourceSpectrum.from_vega(**kwargs)
except Exception as e:
Vega = None
warnings.warn(
'Failed to load Vega spectrum from {0}; Functionality '
'involving Vega will be cripped: {1}'.format(
vegafile, str(e)), AstropyUserWarning)
def rescale_normalized_spectra(spectra, catalog_info, magnitude_system,
bandpass_file, gain_value):
"""Rescale any input spectra that are normalized
Parameters
----------
spectra : OrderedDict
Dictionary containing spectra for some/all targets. Dictionary
keys are the object indexes (such as from the index column in
the catalog_file. Entries must be e.g.
d[1] = {"wavelengths": <wavelength_list>,
"fluxes": <List of spectral flux densities>}
Wavelengths and fluxes can be lists, or lists with astropy units
attached. If no units are supplied, Mirage assumes wavelengths
in microns and flux densities in Flambda units.
catalog_info : astropy.table.Table
Index column and magnitude column to use for rescaling. Extracted
from the original input catalog.
magnitude_system : str
Magnitude system corresponding to the input magnitudes (e.g. 'abmag')
bandpass_file : str
Name of ascii file containing filter throughput curve. (Generally
retrieved from config directory)
gain_value : float
Gain value (e-/ADU) to use to adjust any rescaled spectra to produce
given countrates in ADU/sec rather than e-/sec. This is needed
because the flux calibration info (e.g. photflam, photfnu) were
created such that they translate from magnitudes to ADU/sec rather
than to e-/sec
Returns
-------
spec : OrderedDict
Input dictionary, with flux values rescaled (in FLAM units) to the
requested magnitude, only for spectra where the flux units are
astropy.units.pct
"""
logger = logging.getLogger(
'mirage.catalogs.spectra_from_catalog.rescale_normalized_spectra')
# Get the Vega spectrum from synphot. Use the version that was used
# to create the photom reference files and filter zeropoints
with syn_conf.set_temp(
'vega_file',
'http://ssb.stsci.edu/cdbs/calspec/alpha_lyr_stis_008.fits'):
vegaspec = SourceSpectrum.from_vega()
mag_colname = [col for col in catalog_info.colnames
if 'index' not in col][0]
instrument = mag_colname.split('_')[0].lower()
# Make a copy so we aren't modifying spec in place, which seems to be passed
# by reference back to the calling function
spec = copy.deepcopy(spectra)
for dataset in spec:
waves = spec[dataset]['wavelengths']
flux = spec[dataset]['fluxes']
flux_units = flux.unit
if (flux_units == u.pct):
logger.info(
'SED for source {} is normalized. Rescaling.'.format(dataset))
match = catalog_info['index'] == dataset
if not any(match):
#raise ValueError(('WARNING: No matching target in ascii catalog for normalized source '
# 'number {}. Unable to rescale.').format(dataset))
continue
magnitude = catalog_info[mag_colname].data[match][0]
# Create a synphot source spectrum
fake_flux_units = units.FLAM
source_spectrum = SourceSpectrum(Empirical1D,
points=waves,
lookup_table=flux.value *
fake_flux_units)
# Create a synphot SpectralElement containing the filter bandpass
filter_tp = ascii.read(bandpass_file)
bp_waves = filter_tp['Wavelength_microns'].data * u.micron
bp_waves = bp_waves.to(u.Angstrom)
thru = filter_tp['Throughput'].data
bandpass = SpectralElement(Empirical1D,
points=bp_waves.value,
lookup_table=thru) / gain_value
# Renormalize
magnitude_system = magnitude_system.lower()
if magnitude_system == 'vegamag':
magunits = units.VEGAMAG
vega_spec = vegaspec
elif magnitude_system == 'abmag':
magunits = u.ABmag
vega_spec = None
elif magnitude_system == 'stmag':
magunits = u.STmag
vega_spec = None
elif magnitude_system == 'counts':
raise ValueError(
'ERROR: normalization to a given countrate not yet supported.'
)
if magnitude_system != 'vegamag':
renorm = source_spectrum.normalize(magnitude * magunits,
bandpass,
vegaspec=vega_spec)
else:
if instrument == 'nircam':
# NIRCam vegamag zeropoints are based on synphot's Vega spectrum
renorm = source_spectrum.normalize(magnitude * magunits,
bandpass,
vegaspec=vega_spec)
elif instrument == 'niriss':
# NIRISS vegamag zeropoints are based on Vega having a
# magnitude of 0.02 in all filters
renorm = source_spectrum.normalize(
(magnitude - 0.02) * units.VEGAMAG,
bandpass,
vegaspec=vega_spec)
elif instrument == 'fgs':
# FGS vegamag zeropoints are based on a Sirius spectrum
# rather than Vega
raise NotImplementedError(
"Source spectrum rescaling for FGS not yet supported")
sirius_file = 'sirius_mod_003.txt'
sirius_tab = ascii.read(sirius_file)
sirius_waves = sirius_tab['Wavelength'] * u.Angstrom
sirius_flux = sirius_tab['Flux'] * units.FLAM
sirius_spectrum = SourceSpectrum(Empirical1D,
points=sirius_waves,
lookup_table=sirius_flux)
#sirius_spec_norm = sirius_spectrum.normalize(0. * units.VEGAMAG, bandpass, vegaspec=sirius_spectrum)
renorm = source_spectrum.normalize(
magnitude * units.VEGAMAG,
bandpass,
vegaspec=sirius_spectrum)
spec[dataset]['fluxes'] = renorm(waves, flux_unit='flam')
else:
logger.info(
'SED for source {} is already in physical units. NOT RESCALING'
.format(dataset))
return spec