Image Masking

hostphot.image_masking.mask_image(data, objects, r=5, sigma=20)

Masks objects in an image (2D array) by convolving it with a 2D Gaussian kernel.

Parameters

  • data (2D array) – Image data.

  • objects (array) – Objects extracted with sep.extract().

  • r (float, default 5) – Scale of the semi-mayor and semi-minor axes of the ellipse of the obejcts.

  • sigma (float, default 20) – Standard deviation in pixel units of the 2D Gaussian kernel used to convolve the image.

Returns

masked_data – Masked image data.

Return type

2D array

hostphot.image_masking.create_mask(name, host_ra, host_dec, filt, survey, ra=None, dec=None, bkg_sub=False, threshold=15, sigma=8, crossmatch=False, extract_params=False, common_params=None, save_plots=True)

Calculates the aperture parameters for common aperture.

Parameters

  • name (str) – Name of the object to find the path of the fits file.

  • host_ra (float) – Host-galaxy right ascension in degrees.

  • host_dec (float) – Host-galaxy declination in degrees.

  • filt (str or list) – Filter to use to load the fits file. List is commonly used for coadds.

  • survey (str) – Survey to use for the zero-points and correct filter path.

  • ra (float, default None) – Right ascension of an object, in degrees. Used for plotting.

  • dec (float, default None) – Declination of an object, in degrees. Used for plotting.

  • bkg_sub (bool, default False) – If True, the image gets background subtracted.

  • threshold (float, default 15) – Threshold used by sep.extract() to extract objects.

  • sigma (float, default 8) – Standard deviation in pixel units of the 2D Gaussian kernel used to convolve the image.

  • crossmatch (bool, default False) – If True, the detected objects are cross-matched with a Gaia catalog.

  • extract_params (bool, default False) – If True, returns the parameters listed below.

  • common_params (tuple, default None) – Parameters to use for common masking of different filters. These are the same as the outputs of this function.

  • save_plots (bool, default True) – If True, the mask and galaxy aperture figures are saved.

Returns

  • **This are only returned if extract_params==True.**

  • gal_obj (array) – Galaxy object.

  • nogal_obj (array) – Non-galaxy objects.

  • img_wcs (WCS) – Image’s WCS.

  • pixel_scale (float) – Pixel scale for the survey.

hostphot.image_masking.plot_masked_image(data, masked_data, objects, img_wcs, ra=None, dec=None, outfile=None)

Plots the masked image together with the original image and the detected objects.

Parameters

  • data (2D array) – Image data.

  • masked_data (2D array) – Masked image data.

  • objects (array) – Objects extracted with sep.extract().

  • img_wcs (WCS) – Image’s WCS.

  • ra (float, default None) – Right ascension of an object, in degrees. Used for plotting the position of the object.

  • dec (float, default None) – Declination of an object, in degrees. Used for plotting the position of the object.

  • outfile (str, default None) – If given, path where to save the output figure.