Source code for gammapy.irf.irf_reduce

# Licensed under a 3-clause BSD style license - see LICENSE.rst
import logging
import numpy as np
from astropy import units as u
from . import EnergyDependentTablePSF, IRFStacker, EffectiveAreaTable

__all__ = [
    "make_psf",
    "make_mean_psf",
    "make_mean_edisp",
    "apply_containment_fraction",
    "compute_energy_thresholds",
]

log = logging.getLogger(__name__)


[docs]def make_psf(observation, position, energy=None, rad=None): """Make energy-dependent PSF for a given source position. Parameters ---------- observation : `~gammapy.data.DataStoreObservation` Observation for which to compute the PSF position : `~astropy.coordinates.SkyCoord` Position at which to compute the PSF energy : `~astropy.units.Quantity` 1-dim energy array for the output PSF. If none is given, the energy array of the PSF from the observation is used. rad : `~astropy.coordinates.Angle` 1-dim offset wrt source position array for the output PSF. If none is given, the offset array of the PSF from the observation is used. Returns ------- psf : `~gammapy.irf.EnergyDependentTablePSF` Energy dependent psf table """ offset = position.separation(observation.pointing_radec) if energy is None: energy = observation.psf.to_energy_dependent_table_psf(theta=offset).energy if rad is None: rad = observation.psf.to_energy_dependent_table_psf(theta=offset).rad psf_value = observation.psf.to_energy_dependent_table_psf( theta=offset, rad=rad ).evaluate(energy) arf = observation.aeff.data.evaluate(offset=offset, energy=energy) exposure = arf * observation.observation_live_time_duration psf = EnergyDependentTablePSF( energy=energy, rad=rad, exposure=exposure, psf_value=psf_value ) return psf
[docs]def make_mean_psf(observations, position, energy=None, rad=None): """Compute mean energy-dependent PSF. Parameters ---------- observations : `~gammapy.data.Observations` Observations for which to compute the PSF position : `~astropy.coordinates.SkyCoord` Position at which to compute the PSF energy : `~astropy.units.Quantity` 1-dim energy array for the output PSF. If none is given, the energy array of the PSF from the first observation is used. rad : `~astropy.coordinates.Angle` 1-dim offset wrt source position array for the output PSF. If none is given, the energy array of the PSF from the first observation is used. Returns ------- psf : `~gammapy.irf.EnergyDependentTablePSF` Mean PSF """ for idx, observation in enumerate(observations): psf = make_psf(observation, position, energy, rad) if idx == 0: stacked_psf = psf else: stacked_psf = stacked_psf.stack(psf) return stacked_psf
[docs]def make_mean_edisp( observations, position, e_true, e_reco, low_reco_threshold="0.002 TeV", high_reco_threshold="150 TeV", ): """Compute mean energy dispersion. Compute the mean edisp of a set of observations j at a given position The stacking is implemented in :func:`~gammapy.irf.IRFStacker.stack_edisp` Parameters ---------- observations : `~gammapy.data.Observations` Observations for which to compute the EDISP position : `~astropy.coordinates.SkyCoord` Position at which to compute the EDISP e_true : `~astropy.units.Quantity` True energy axis e_reco : `~astropy.units.Quantity` Reconstructed energy axis low_reco_threshold : `~astropy.units.Quantity` low energy threshold in reco energy high_reco_threshold : `~astropy.units.Quantity` high energy threshold in reco energy Returns ------- stacked_edisp : `~gammapy.irf.EnergyDispersion` Stacked EDISP for a set of observation """ low_reco_threshold = u.Quantity(low_reco_threshold) high_reco_threshold = u.Quantity(high_reco_threshold) list_aeff = [] list_edisp = [] list_livetime = [] list_low_threshold = [low_reco_threshold] * len(observations) list_high_threshold = [high_reco_threshold] * len(observations) for obs in observations: offset = position.separation(obs.pointing_radec) list_aeff.append(obs.aeff.to_effective_area_table(offset, energy=e_true)) list_edisp.append( obs.edisp.to_energy_dispersion(offset, e_reco=e_reco, e_true=e_true) ) list_livetime.append(obs.observation_live_time_duration) irf_stack = IRFStacker( list_aeff=list_aeff, list_edisp=list_edisp, list_livetime=list_livetime, list_low_threshold=list_low_threshold, list_high_threshold=list_high_threshold, ) irf_stack.stack_edisp() return irf_stack.stacked_edisp
[docs]def apply_containment_fraction(aeff, psf, radius): """Estimate PSF containment inside a given radius and correct effective area for leaking flux. The PSF and effective area must have the same binning in energy. Parameters ---------- aeff : `~gammapy.irf.EffectiveAreaTable` the input 1D effective area psf : `~gammapy.irf.EnergyDependentTablePSF` the input 1D PSF radius : `~astropy.coordinates.Angle` the maximum angle Returns ------- correct_aeff : `~gammapy.irf.EffectiveAreaTable` the output corrected 1D effective area """ energy_center = aeff.energy.center energy_edges = aeff.energy.edges containment = psf.containment(energy_center, radius) corrected_aeff = EffectiveAreaTable( energy_lo=energy_edges[:-1], energy_hi=energy_edges[1:], data=aeff.data.data * np.squeeze(containment), meta=aeff.meta, ) return corrected_aeff
[docs]def compute_energy_thresholds( aeff, edisp, method_lo="none", method_hi="none", **kwargs ): """Compute safe energy thresholds from 1D energy dispersion and effective area. Set the high and low energy threshold based on a chosen method. For now the methods return thresholds assuming true and reco energy are comparable. Available methods for setting the low energy threshold: * area_max : Set energy threshold at x percent of the maximum effective area (x given as kwargs['area_percent_lo']) * energy_bias : Set energy threshold at energy where the energy bias exceeds a value of x percent (given as kwargs['bias_percent_lo']) * none : Do not apply a lower threshold Available methods for setting the high energy threshold: * area_max : Set energy threshold at x percent of the maximum effective area (x given as kwargs['area_percent_hi']). The threshold is searched in the last true energy decade of the effective area. * energy_bias : Set energy threshold at energy where the energy bias exceeds a value of x percent (given as kwargs['bias_percent_hi']). The threshold is searched in the last true energy decade of the energy dispersion. * none : Do not apply a higher energy threshold Parameters ---------- aeff : `~gammapy.irf.EffectiveAreaTable` the 1D effective area edisp : `~gammapy.irf.EnergyDispersion` the energy dispersion used method_lo : {'area_max', 'energy_bias', 'none'} Method for defining the low energy threshold method_hi : {'area_max', 'energy_bias', 'none'} Method for defining the high energy threshold """ # Low threshold if method_lo == "area_max": aeff_thres = kwargs["area_percent_lo"] / 100 * aeff.max_area thres_lo = aeff.find_energy(aeff_thres) elif method_lo == "energy_bias": thres_lo = edisp.get_bias_energy(kwargs["bias_percent_lo"] / 100) elif method_lo == "none": thres_lo = aeff.energy.edges[0] else: raise ValueError("Invalid method_lo: {}".format(method_lo)) # High threshold if method_hi == "area_max": aeff_thres = kwargs["area_percent_hi"] / 100 * aeff.max_area e_max = aeff.energy.edges[-1] try: thres_hi = aeff.find_energy(aeff_thres, emin=0.1 * e_max, emax=e_max) except ValueError: thres_hi = e_max elif method_hi == "energy_bias": e_max = aeff.energy.edges[-1] try: thres_hi = edisp.get_bias_energy( kwargs["bias_percent_hi"] / 100, emin=0.1 * e_max, emax=e_max ) except ValueError: thres_hi = e_max elif method_hi == "none": thres_hi = aeff.energy.edges[-1] else: raise ValueError("Invalid method_hi: {}".format(method_hi)) return thres_lo, thres_hi