ETC

class pyetc.etc.ETC(log=20)

Bases: object

Generic class for Exposure Time Computation (ETC)

Methods Summary

`adaptative_circular_aperture`(ins, ima, kfwhm)	truncate the image with a window size relative to the image FWHM
`fixed_circular_aperture`(ins, ima, radius[, cut])	truncate the image with a fixed size aperture
`flux_from_source`(ins, snr, ima, spec[, ...])	compute the flux needed to achieve a given S/N
`fun`(flux, snr0, ins, ima, spec, krange)	minimizing function used by flux_from_source
`get_ima`(ins, dima[, oversamp, uneven])	compute source image from the model parameters
`get_image_psf`(ins, wave[, oversamp])	compute PSF image
`get_image_quality`(ins[, spec])	compute image quality evolution with wavelength
`get_psf_frac_ima`(ins, flux, spec[, lrange, ...])	compute the flux fraction evolution with seeing for a point source
`get_sky`(ins, moon)	return sky emission and tranmission spectra
`get_spec`(ins, dspec[, oversamp, lsfconv])	compute source spectrum from the model parameters
`get_spectral_resolution`(ins)	return spectral resolving power
`optimum_circular_aperture`(ins, flux, ima, spec)	compute the optimum aperture which maximize the S/N
`optimum_spectral_range`(ins, flux, ima, spec)	compute the optimum window range which maximize the S/N
`print_aper`(res, names)	pretty print the apertures results for a set of results
`set_logging`(log)	Change logging value
`set_obs`(obs)	save obs dictionary to self
`snr_from_cube`(ins, cube)	compute S/N from a data cube
`snr_from_ima`(ins, ima, wave)	compute S/N from an image
`snr_from_ps_spec`(ins, spec, frac_ima, nspaxels)	compute S/N for a point source define by a spectrum in flux/spectel
`snr_from_source`(ins, flux, ima, spec[, ...])	main routine to perform the S/N computation for a given source
`snr_from_spec`(ins, spec)	compute S/N from a spectrum in flux/spectel
`square_aperture`(ins, ima, nsp)	truncate an image on a squared aperture
`truncate_spec_adaptative`(ins, spec, kfwhm)	truncate an emission line spectrum as function of the line FWHM
`truncate_spec_fixed`(ins, spec, nsp)	truncate the spectrum to a fixed spectral window size

Methods Documentation

adaptative_circular_aperture(ins, ima, kfwhm)

truncate the image with a window size relative to the image FWHM

Parameters:

insdict: instrument (eg self.ifs[‘blue’] or self.moslr[‘red’])
imaMPDAF image: source image
kfwhmfloat: factor relative to FWHM to define the truncation aperture

Returns:

tuple: tima truncated MPDAF image nspaxels (int) number of spaxels size (float) aperture size (diameter, arcsec) frac_flux (float) fraction flux kept after truncation+

fixed_circular_aperture(ins, ima, radius, cut=0.0625)

truncate the image with a fixed size aperture

Parameters:

insdict: instrument (eg self.ifs[‘blue’] or self.moslr[‘red’])
imaMPDAF image: source image
radiusfloat: aperture radius in arcsec
cutfloat: spaxels with flux below cut will not be counted (Default value = 1/16)

Returns:

tuple: tima truncated MPDAF image nspaxels (int) number of spaxels size (float) aperture size (diameter, arcsec) frac_flux (float) fraction flux kept after truncation

flux_from_source(ins, snr, ima, spec, snrcomp=None, flux=None, bracket=(0.1, 100000))

compute the flux needed to achieve a given S/N

Parameters:

insdict: instrument (eg self.ifs[‘blue’] or self.moslr[‘red’])
fluxfloat: flux value in erg/s/cm2 (for line), in erg/s/cm2/A (for cont), / arcsec2 (for sb)
imaMPDAF image: source image, can be None for surface brightness source or point source
specMPDAF spectrum: source spectrum
snrcompdict: method and parameters to derive the S/N target value from the cont spectrum (Default value = None)
flux: starting value of the flux (Default value = None)
brackettuple of float: interval of flux*1.e-20 for the zero finding routine (Default value = (0.1,100000) :

Returns:

dict: result dictionary (see documentation)

fun(flux, snr0, ins, ima, spec, krange)

minimizing function used by flux_from_source

Parameters:

fluxfloat: flux value * 1.e-20
snr0float: target S/N
insdict: instrument (eg self.ifs[‘blue’] or self.moslr[‘red’])
imaMPDAF image: source image, can be None for surface brightness source or point source
specMPDAF spectrum: source spectrum
krangetuple of int: wavelength range in spectel to compute the S/N

Returns:

float: S/N - target S/N

get_ima(ins, dima, oversamp=10, uneven=1)

compute source image from the model parameters

Parameters:

insdict: instrument (eg self.ifs[‘blue’] or self.moslr[‘red’])
dimadict: dictionary of parameters describing the source spectrum
oversampint: oversampling factor (Default value = 10)
unevenint: if 1 the size of the image will be uneven (Default value = 1)

Returns:

MPDAF image: image of the source

get_image_psf(ins, wave, oversamp=10)

compute PSF image

Parameters:

insdict: instrument (eg self.ifs[‘blue’] or self.moslr[‘red’])
wavefloat: wavelength in A
oversampint: oversampling factor (Default value = 10)

Returns:

MPDAF image: PSF image

get_image_quality(ins, spec=None)

compute image quality evolution with wavelength

Parameters:

insdict: instrument (eg self.ifs[‘blue’] or self.moslr[‘red’])
specMPDAF spectrum: use wavelengths from spec, if None use all instrument wavelengths

Returns:

numpy array of float: image quality

get_psf_frac_ima(ins, flux, spec, lrange=None, oversamp=10, lbin=1)

compute the flux fraction evolution with seeing for a point source

Parameters:

insdict: instrument (eg self.ifs[‘blue’] or self.moslr[‘red’])
fluxfloat: flux value in erg/s/cm2 (for line), in erg/s/cm2/A (for cont), / arcsec2 (for sb)
imaMPDAF image: source image
specMPDAF spectrum: source spectrum
lrangetuple: wavelength range to compute S/N for cont spectrum (Default value = None)
oversampint: oversampling factor (Default value = 10)
lbinint: step in wavelength (Default value = 1)

Returns:

tuple: frac_ima (MPDAF spectrum) fraction of flux as function of wavelength size_ima (MPDAF spectrum) diameter in arcsec of the aperture nspaxels (numpy array of int) corresponding number of spaxels within the aperture

get_sky(ins, moon)

return sky emission and tranmission spectra

Parameters:

insdict: instrument (eg self.ifs[‘blue’] or self.moslr[‘red’])
moonstr: moon observing condition (e.g “darksky”)

Returns:

tuple of MPDAF spectra: emission and absorption sky spectra

get_spec(ins, dspec, oversamp=10, lsfconv=True)

compute source spectrum from the model parameters

Parameters:

insdict: instrument (eg self.ifs[‘blue’] or self.moslr[‘red’])
dspecdict: dictionary of parameters describing the source spectrum
oversampint: oversampling factor (Default value = 10)
lsfconvbool: apply LSF convolution (Default value = True)

Returns:

MPDAF spectrum: resulting source spectrum

get_spectral_resolution(ins)

return spectral resolving power

Parameters:

insdict: instrument (eg self.ifs[‘blue’] or self.moslr[‘red’])

Returns:

numpy array: spectral resoving power (lbda/dlbda)

optimum_circular_aperture(ins, flux, ima, spec, bracket=[1, 5], lrange=None)

compute the optimum aperture which maximize the S/N

Parameters:

insdict: instrument (eg self.ifs[‘blue’] or self.moslr[‘red’])
fluxfloat: flux value in erg/s/cm2 (for line), in erg/s/cm2/A (for cont), / arcsec2 (for sb)
imaMPDAF image: source image
specMPDAF spectrum: source spectrum
brackettuple: (Default value = [1,5]) :
lrangetuple: wavelength range to compute S/N for cont spectrum (Default value = None)

Returns:

float

factor relative to FWHM (kfwhm)

the kfwhm value is also updated into the obs dictionary

optimum_spectral_range(ins, flux, ima, spec)

compute the optimum window range which maximize the S/N

Parameters:

insdict: instrument (eg self.ifs[‘blue’] or self.moslr[‘red’])
fluxfloat: flux value in erg/s/cm2 (for line), in erg/s/cm2/A (for cont), / arcsec2 (for sb)
imaMPDAF image: source image
specMPDAF spectrum: source spectrum

Returns:

float

factor relative to FWHM (kfwhm)

the kfwhm value is also updated into the obs dictionary

print_aper(res, names)

pretty print the apertures results for a set of results

Parameters:

resdict or list of dict: result dictionaries deliver by snr_from_source or flux_from_source
namesstr or list of str: name to identify the result

Returns:

astropy table: table with one column by result

set_logging(log)

Change logging value

Parameters:

logstr: desired log mode “DEBUG”,”INFO”,”WARNING”,”ERROR”

set_obs(obs)

save obs dictionary to self

Parameters:

obsdict: dictionary of observation parameters

snr_from_cube(ins, cube)

compute S/N from a data cube

Parameters:

insdict: instrument (eg self.ifs[‘blue’] or self.moslr[‘red’])
cubeMPDAF cube: source data cube in flux/voxels

Returns:

dict

result dictionary

this routine is called by snr_from_source

snr_from_ima(ins, ima, wave)

compute S/N from an image

Parameters:

insdict: instrument (eg self.ifs[‘blue’] or self.moslr[‘red’])
imaMPDAF image: source image in flux/spaxels
wavefloat: wavelength in A

Returns:

dict

result dictionary

this routine is called by snr_from_source

snr_from_ps_spec(ins, spec, frac_ima, nspaxels)

compute S/N for a point source define by a spectrum in flux/spectel

Parameters:

insdict: instrument (eg self.ifs[‘blue’] or self.moslr[‘red’])
specMPDAF spectrum: point source spectrul in flux/spectel
frac_imaMPDAF spectrum: flux fraction recovered in the aperture as function of wavelength
nspaxelsnumpy array of int: corresponding number of spaxels in the aperture

Returns:

dict

result dictionary

this routine is called by snr_from_source

snr_from_source(ins, flux, ima, spec, loop=False, debug=True)

main routine to perform the S/N computation for a given source

Parameters:

insdict: instrument (eg self.ifs[‘blue’] or self.moslr[‘red’])
fluxfloat: flux value in erg/s/cm2 (for line), in erg/s/cm2/A (for cont), / arcsec2 (for sb)
imaMPDAF image: source image, can be None for surface brightness source or point source
specMPDAF spectrum: source spectrum
loopbool: set to True for multiple call (used only in ps and cont, Default value = False)
debug: if True print some info in logger.debug mode (Default value = True)

Returns:

dict: result dictionary (see documentation)

snr_from_spec(ins, spec)

compute S/N from a spectrum in flux/spectel

Parameters:

insdict: instrument (eg self.ifs[‘blue’] or self.moslr[‘red’])
specMPDAF spectrum: source spectrum in flux/spectel

Returns:

dict

result dictionary

this routine is called by snr_from_source

square_aperture(ins, ima, nsp)

truncate an image on a squared aperture

Parameters:

insdict: instrument (eg self.ifs[‘blue’] or self.moslr[‘red’])
imaMPDAF image: source image
nspint: the number of spaxels to use is 2 * nsp +1

Returns:

tuple: tima truncated MPDAF image nspaxels (int) number of spaxels size (float) aperture size (diameter, arcsec) frac_flux (float) fraction flux kept after truncation

truncate_spec_adaptative(ins, spec, kfwhm)

truncate an emission line spectrum as function of the line FWHM: the window size is compute as center +/- kfwhm*fwhm

Parameters:

insdict: instrument (eg self.ifs[‘blue’] or self.moslr[‘red’])
specMPFAF spectrum: source spectrum
kfwhmfloat: factor relative to the line FWHM,
Returns
——-
tuple: tspec truncated MPDAF spectrum waves numpy array of corresponding wavelengths (A) nspectels (int) number of spectels kept size (float) wavelength range (A) frac_flux (float) fraction flux kept after truncation

truncate_spec_fixed(ins, spec, nsp)

truncate the spectrum to a fixed spectral window size

Parameters:

insdict: instrument (eg self.ifs[‘blue’] or self.moslr[‘red’])
specMPDAF spectrum: source spectrum
nspint: half number of spectels to use (size is 2 * nsp + 1)

Returns:

tuple: tspec truncated MPDAF spectrum waves numpy array of corresponding wavelengths (A) nspectels (int) number of spectels kept size (float) wavelength range (A) frac_flux (float) fraction flux kept after truncation