Source

class simcado.source.Source(filename=None, lam=None, spectra=None, x=None, y=None, ref=None, weight=None, **kwargs)

Bases: object

Create a source object from a file or from arrays

Source class generates the arrays needed for source. It takes various inputs and converts them to an array of positions and references to spectra. It also converts spectra to photons/s/voxel. The default units for input data is ph/s/m2/bin.

The internal variables are related like so:

f(x[i], y[i]) = spectra[ref[i]] * weight[i]

Parameters

filenamestr

FITS file that contains either a previously saved Source object or a data cube with dimensions x, y, lambda. A Source object is identified by the header keyword SIMCADO with value SOURCE.

or

lamnp.array

[um] Wavelength bins of length (m)

spectranp.array

[ph/s/m2/bin] A (n, m) array with n spectra, each with m spectral bins

x, ynp.array

[arcsec] coordinates of where the emitting sources are relative to the centre of the field of view

refnp.array

the index for .spectra which connects a position (x, y) to a spectrum f(x[i], y[i]) = spectra[ref[i]] * weight[i]

weightnp.array

A weighting to scale the relevant spectrum for each position

Attributes Summary

info_keys

Return keys of the info dict

Methods Summary

add_background_surface_brightness(self)	Add an EmissionCurve for the background surface brightness of the object
apply_optical_train(self, opt_train, detector)	Apply all effects along the optical path to the source photons
dump(self, filename)	Save to filename as a pickle
image_in_range(self, psf, lam_min, lam_max, …)	Find the sources that fall in the chip area and generate an image for the wavelength range [lam_min, lam_max)
load(filename)	Load :class:’.Source’ object from filename
on_grid(self[, pix_res])	Return an image with the positions of all sources.
photons_in_range(self[, lam_min, lam_max])	Number of photons between lam_min and lam_max in units of [ph/s/m2]
project_onto_chip(self, image, chip)	Re-project the photons onto the same grid as the detectors use
read(self, filename)	Read in a previously saved Source FITS file
rotate(self, angle[, unit, use_orig_xy])	Rotates the x and y coordinates by angle [degrees]
scale_spectrum(self[, idx, mag, filter_name])	Scale a certain spectrum to a certain magnitude
scale_with_distance(self, distance_factor)	Scale the source for a new distance
shift(self[, dx, dy, use_orig_xy])	Shifts the coordinates of the source by (dx, dy) in [arcsec]
write(self, filename)	Write the current Source object out to a FITS file

Attributes Documentation

info_keys

Return keys of the info dict

Methods Documentation

add_background_surface_brightness(self)

Add an EmissionCurve for the background surface brightness of the object

apply_optical_train(self, opt_train, detector, chips='all', sub_pixel=False, **kwargs)

Apply all effects along the optical path to the source photons

Parameters

opt_trainsimcado.OpticalTrain

the object containing all information on what is to happen to the photons as they travel from the source to the detector

detectorsimcado.Detector

the object representing the detector

chipsint, str, list, optional

The IDs of the chips to be readout. “all” is also acceptable

sub_pixelbool, optional

if sub-pixel accuracy is needed, each source is shifted individually. Default is False

Other Parameters

INST_DEROT_PERFORMANCEfloat

[0 .. 100] Percentage of the sky rotation that the derotator removes

SCOPE_JITTER_FWHMfloat

[arcsec] The FWMH of the gaussian blur caused by jitter

SCOPE_DRIFT_DISTANCEfloat

[arcsec] How far from the centre of the field of view has the telescope drifted during a DIT

Notes

Output array is in units of [ph/s/pixel] where the pixel is internal oversampled pixels - not the pixel size of the detector chips

dump(self, filename)

Save to filename as a pickle

image_in_range(self, psf, lam_min, lam_max, chip, **kwargs)

Find the sources that fall in the chip area and generate an image for the wavelength range [lam_min, lam_max)

Output is in [ph/s/pixel]

Parameters

psfpsf.PSF object

The PSF that the sources will be convolved with

lam_min, lam_maxfloat

[um] the wavelength range relevant for the psf

chipstr, detector.Chip

• detector.Chip : the chip that will be seeing this image.

• str : [“tiny”, “small”, “center”] -> [128, 1024, 4096] pixel chips

Returns

slice_arraynp.ndarray

the image of the source convolved with the PSF for the given range

classmethod load(filename)

Load :class:’.Source’ object from filename

on_grid(self, pix_res=0.004)

Return an image with the positions of all sources.

The pixel values correspond to the number of emitting objects in that pixel

Parameters

pix_resfloat

[arcsec] The grid spacing

Returns

im2D array

A numpy array containing an image of where the sources are

photons_in_range(self, lam_min=None, lam_max=None)

Number of photons between lam_min and lam_max in units of [ph/s/m2]

Calculate how many photons for each source exist in the wavelength range defined by lam_min and lam_max.

Parameters

lam_min, lam_maxfloat, optional

[um] integrate photons between these two limits. If both are None, limits are set at lam[0], lam[-1] for the source’s wavelength range

Returns

slice_photonsfloat

[ph/s/m2] The number of photons in the wavelength range

project_onto_chip(self, image, chip)

Re-project the photons onto the same grid as the detectors use

Parameters

imagenp.ndarray

the image to be re-projected

chipdetector.Chip

the chip object where the image will land

read(self, filename)

Read in a previously saved Source FITS file

Parameters

filenamestr

Path to the file

rotate(self, angle, unit='degree', use_orig_xy=False)

Rotates the x and y coordinates by angle [degrees]

Parameters

anglefloat

Default is in degrees, this can set with unit

unitstr, astropy.Unit

Either a string with the unit name, or an astropy.unit.Unit object

use_orig_xybool

If the rotation should be based on the original coordinates or the current coordinates (e.g. if rotation has already been applied)

scale_spectrum(self, idx=0, mag=20, filter_name='Ks')

Scale a certain spectrum to a certain magnitude

See simcado.source.scale_spectrum() for examples

Parameters

idxint

The index of the spectrum to be scaled: <Source>.spectra[idx] Default is <Source>.spectra[0]

magfloat

[mag] new magnitude of spectrum

filter_namestr, TransmissionCurve

Any filter name from SimCADO or a TransmissionCurve object (see get_filter_set())

scale_with_distance(self, distance_factor)

Scale the source for a new distance

Scales the positions and brightnesses of the Source object according to the ratio of the new and old distances

i.e. distance_factor = new_distance / current_distance

Warning

This does not yet take into account redshift

Todo

Implement redshift

Parameters

distance_factorfloat

The ratio of the new distance to the current distance i.e. distance_factor = new_distance / current_distance

Examples

 >>> from simcado.source import cluster
 >>>
 >>> curr_dist = 50000  # pc, i.e. LMC
 >>> new_dist = 770000  # pc, i.e. M31
>>> src = cluster(distance=curr_dist)
 >>> src.scale_with_distance( new_dist/curr_dist )

shift(self, dx=0, dy=0, use_orig_xy=False)

Shifts the coordinates of the source by (dx, dy) in [arcsec]

Parameters

dx, dyfloat, array

[arcsec] The offsets for each coordinate in the arrays x, y. - If dx, dy are floats, the same offset is applied to all coordinates - If dx, dy are arrays, they must be the same length as x, y

use_orig_xybool

If the shift should be based on the original coordinates or the current coordinates (e.g. if shift has already been applied)

write(self, filename)

Write the current Source object out to a FITS file

Parameters

filenamestr

where to save the FITS file

Notes

Just a place holder so that I know what’s going on with the input table * The first extension [0] contains an “image” of size 4 x N where N is the number of sources. The 4 columns are x, y, ref, weight. * The second extension [1] contains an “image” with the spectra of all sources. The image is M x len(spectrum), where M is the number of unique spectra in the source list. M = max(ref) - 1