Utils¶

Other support functions are documented bellow:

hostphot.utils.adapt_aperture(objects, img_wcs, img_wcs2, flip=False)¶

Changes the aperture parameters to consider differences in WCS between surveys.

The values of center, a and b should in pixel units. DES images are flipped, so these need to be corrected with theta -> -theta, i.e. using flip=True.

Parameters:

objects (ndarray) – Objects with apertures.
img_wcs (WCS) – WCS of the image from where the objects were extracted.
img_wcs2 (WCS) – WCS used to adapt the apertures.
flip (bool, default False) – Whether to flip the orientation of the aperture. Only used for DES images.

Returns:

objects_ (ndarray) – Objects with adapted apertures.
conv_factor (float) – Convertion factor between the resolutions of the images.

hostphot.utils.calc_sky_unc(image, exptime)¶

Calculates the uncertainty of the image from the sky standard deviation, sigma-clipped STD.

Parameters:

image (ndarray) – Image in a 2D numpy array.
exptime (float) – Exposure time of the image.

Returns:

error – Estimated error of the image.

Return type:

float

hostphot.utils.check_HST_filters(filt)¶

Check whether the given filter is whithin the valid options for HST.

Parameters:: filt (str) – Filter to use, e,g, WFC3_UVIS_F225W.

hostphot.utils.check_filters_validity(filters, survey)¶

Check whether the given filters are whithin the valid options for the given survey.

Parameters:

filters (str or list) – Filters to use, e,g, griz.
survey (str) – Survey name: e.g. PS1, GALEX.

hostphot.utils.check_survey_validity(survey)¶

Check whether the given survey is whithin the valid options.

Parameters:: survey (str) – Survey name: e.g. PS1, GALEX.

hostphot.utils.check_work_dir(wokrdir)¶

Checks if the working directory exists. If it does not, one is created.

Parameters:: wokrdir (str) – Working directory path.

hostphot.utils.clean_dir(directory)¶

Removes the directory if it is empty.

Parameters:: directory (str) – Directory path.

hostphot.utils.correct_HST_aperture(filt, ap_area, header)¶

Get the aperture correction for the given configuration.

Parameters:

filt (str) – HST filter, e.g. WFC3_UVIS_F225W.
ap_area (float) – Aperture area.
header (fits header) – Header of an image.

Returns:

correction – Aperture correction (encircled energy fraction).

Return type:

float

hostphot.utils.extract_filter(filt, survey, version=None)¶

Extracts the transmission function for the filter.

Parameters:

filt (str) – Filter to extract.
survey (str) – Survey of the filters.
version (str, default None) – Version of the filters to use. E.g. for the Legacy Survey as it uses DECam for the south and BASS+MzLS for the north.

Returns:

wave (array) – Wavelength range of the filter.
transmission (array) – Transmission function.

hostphot.utils.get_HST_err(filt, header)¶

Obtaines the error propagation from the zeropoint.

Parameters:

filt (str) – HST filter, e.g. WFC3_UVIS_F225W.
header (fits header) – Header of an image.

Returns:

mag_err – Magnitude error on PHOTFLAM.

Return type:

float

hostphot.utils.get_image_exptime(header, survey)¶

Returns the exposure time from an image’s header.

Parameters:

header (fits header) – Header of an image.
survey (str) – Survey name: e.g. PS1, GALEX.

Returns:

exptime – Exposure time in seconds.

Return type:

float

hostphot.utils.get_image_gain(header, survey)¶

Returns the gain from an image’s header.

Note: for SDSS this is assumed to be one as it should already be included.

Parameters:

header (fits header) – Header of an image.
survey (str) – Survey name: e.g. PS1, GALEX.

Returns:

gain – Gain value.

Return type:

float

hostphot.utils.get_image_readnoise(header, survey)¶

Returns the read noise from an image’s header. All values are per-pixel values.

Note: for SDSS this is assumed to be zero as it should already be included.

Parameters:

header (fits header) – Header of an image.
survey (str) – Survey name: e.g. PS1, GALEX.

Returns:

readnoise – Read noise value.

Return type:

float

hostphot.utils.get_survey_filters(survey)¶

Gets all the valid filters for the given survey.

Parameters:: survey (str) – Survey name: e.g. PS1, GALEX.
Returns:: filters – Filters for the given survey.
Return type:: str

hostphot.utils.integrate_filter(spectrum_wave, spectrum_flux, filter_wave, filter_response, response_type='photon')¶

Calcultes the flux density of an SED given a filter response.

Parameters:

spectrum_wave (array) – Spectrum’s wavelength range.
spectrum_flux (array) – Spectrum’s flux density distribution.
filter_wave (array) – Filter’s wavelength range.
filter_response (array) – Filter’s response function.
response_type (str, default photon) – Filter’s response type. Either photon or energy.

Returns:

flux_filter – Flux density.

Return type:

float

hostphot.utils.load_pickle(inputfile)¶

Loads a pickle file.

Parameters:: inputfile (str) – Pickle file to load.
Returns:: content – The content of the pickle file
Return type:: any

hostphot.utils.magnitude_calculation(flux, flux_err, survey, filt=None, ap_area=0.0, header=None, bkg_rms=0.0)¶

Calculates the calibrated magnitudes and errors.

Error propagation is included here, both for magnitudes and fluxes.

Parameters:

flux (float) – Aperture flux.
survey (str) – Survey name: e.g. PS1, GALEX.
filt (str, default None) – Survey-specific filter.
ap_area (float, default 0.0) – Aperture area.
header (fits header, default None) – Header of an image.
bkg_rms (float, default 0.0) – Background noise.
invvar_map (ndarray) –

Returns:

mag (float) – Apparent magnitude.
mag_err (float) – Apparent magnitude uncertainty.
flux (float) – Total flux.
flux_err (float) – Total uncertainty in flux.
zp (float) – Zeropoint.

hostphot.utils.pixel2pixel(x1, y1, img_wcs1, img_wcs2)¶: Convert the pixel coordinates from one image to another.

hostphot.utils.plot_fits(fits_file, ext=0)¶

Plots a fits file.

Parameters:

fits_file (str or HDU.) – Path to fits file.
ext (int) – Extension index.

hostphot.utils.plot_image(image_file)¶

Plots an image file.

E.g. ‘.png’ and ‘.jpg’ files.

Parameters:: image_file (str) – Path to an image file.

hostphot.utils.suppress_stdout()¶

Suppresses annoying outputs.

Useful with astroquery and aplpy packages.

hostphot.utils.survey_pixel_scale(survey, filt=None)¶

Returns the pixel scale for a given survey.

Parameters:

survey (str) – Survey name: e.g. PS1, GALEX.
filt (str, default None) – Filter to use by surveys that have different pixel scales for different filters (e.g. Spitzer’s IRAC and MIPS instruments).

Returns:

pixel_scale – Pixel scale in units of arcsec/pixel.

Return type:

float

hostphot.utils.survey_zp(survey)¶

Returns the zero-point for a given survey.

Note: for PS1, an extra \(+2.5*np.log10(exptime)\) needs to be added afterwards.

Parameters:: survey (str) – Survey name: e.g. PS1, GALEX.
Returns:: zp_dict – Zero-points for all the filters in the given survey. If the survey zero-point is different for each image, the string header is returned.
Return type:: dict or str

hostphot.utils.uncertainty_calculation(flux, flux_err, survey, filt=None, ap_area=0.0, header=None, bkg_rms=0.0)¶

Calculates the uncertainty propagation.

Parameters:

flux (float) – Aperture flux.
flux_err (float) – Aperture flux error.
survey (str) – Survey name: e.g. PS1, GALEX.
filt (str, default None) – Survey-specific filter.
ap_area (float, default 0.0) – Aperture area.
header (fits header, default None) – Header of an image.
bkg_rms (float, default 0.0) – Background noise.

Returns:

flux_err – Total uncertainty in flux units.

Return type:

float