HealPixEffectiveArea

class gdt.core.healpix.HealPixEffectiveArea

Bases: HealPix

Class for effective area HEALPix files

Attributes Summary

eff_area	The effective area HEALPix array
npix	Number of pixels in the HEALPix map
nside	The HEALPix resolution
pixel_area	The area of each pixel in square degrees
trigtime	The reference time

Methods Summary

convolve(model, *args, **kwargs)	Convolve the map with a model kernel.
effective_area(az, zen)	Calculate the effective area at a given point.
from_cosine(az, zen, eff_area_normal[, ...])	Create an object with effective area that has a cosine angular depndence.
from_data(hpx_arr[, trigtime, filename])	Create a HealPix object from healpix arrays
from_uniform(eff_area[, nside, filename])	Create an object with uniform effective area.
make_grid([numpts_az, numpts_zen])	Return the effective area mapped to a grid.
multiply(healpix1, healpix2[, primary, ...])	Multiply two HealPix maps and return a new HealPix object
sum(healpix1, healpix2[, primary, output_nside])	Add two HealPixEffectiveArea maps and return a new object

Attributes Documentation

eff_area

The effective area HEALPix array

Type:

(np.array)

npix

Number of pixels in the HEALPix map

Type:

(int)

nside

The HEALPix resolution

Type:

(int)

pixel_area

The area of each pixel in square degrees

Type:

(float)

trigtime

The reference time

Type:

(float)

Methods Documentation

convolve(model, *args, **kwargs)

Convolve the map with a model kernel. The model can be a Gaussian kernel or any mixture of Gaussian kernels. Uses healpy.smoothing.

An example of a model kernel with a 50%/50% mixture of two Gaussians, one with a 1-deg width, and the other with a 3-deg width:

def gauss_mix_example():
    sigma1 = np.deg2rad(1.0)
    sigma2 = np.deg2rad(3.0)
    frac1 = 0.50
    return ([sigma1, sigma2], [frac1])

Parameters:

• model (<function>) – The function representing the model kernel

• *args – Arguments to be passed to the model kernel function

Returns:

(HealPix)

effective_area(az, zen)

Calculate the effective area at a given point. This function interpolates the map at the requested point rather than providing the vale at the nearest pixel center.

Parameters:

• az (float) – The Azimuth

• zen (float) – The Zenith

Returns:

(float)

classmethod from_cosine(az, zen, eff_area_normal, coeff=1.0, nside=64, filename=None, **kwargs)

Create an object with effective area that has a cosine angular depndence.

Parameters:

• az (float) – The azimuth of the detector normal

• zen (float) – The zenith of the detector normal

• eff_area_normal (float) – The effective area at the detector normal

• coeff (float, optional) – The cosine coefficient to use. Default is 1

• nside (int, optional) – The nside of the HEALPix to make. Default is 64

• filename (str, optional) – The filename

Returns:

(HealPixEffectiveArea)

classmethod from_data(hpx_arr, trigtime=None, filename=None, **kwargs)

Create a HealPix object from healpix arrays

Parameters:

• hpx_arr (np.array) – The HEALPix array

• trigtime (float, optional) – The reference time for the map

• filename (str, optional) – The filename

Returns:

(HealPix)

classmethod from_uniform(eff_area, nside=64, filename=None, **kwargs)

Create an object with uniform effective area.

Parameters:

• eff_area (float) – The effective area.

• nside (int, optional) – The nside of the HEALPix to make.

• filename (str, optional) – The filename

Returns:

(HealPixEffectiveArea)

make_grid(numpts_az=360, numpts_zen=180)

Return the effective area mapped to a grid.

Parameters:

• numpts_az (int, optional) – The number of grid points along the Az axis. Default is 360.

• numpts_zen (int, optional) – The number of grid points along the Zen axis. Default is 180.

Returns:

3-tuple containing –

• np.array: The effective area array with shape

  (numpts_zen, numpts_az)

• np.array: The Az grid points

• np.array: The Zen grid points

classmethod multiply(healpix1, healpix2, primary=0, output_nside=128, **kwargs)

Multiply two HealPix maps and return a new HealPix object

Parameters:

• healpix1 (HealPix) – One of the HEALPix maps to multiply

• healpix2 (HealPix) – The other HEALPix map to multiply

• primary (int, optional) – If 0, use the first map metadata, or if 1, use the second map metadata. Default is 0.

• output_nside (int, optional) – The nside of the multiplied map. Default is 128.

Returns

(HealPix)

classmethod sum(healpix1, healpix2, primary=0, output_nside=128, **kwargs)

Add two HealPixEffectiveArea maps and return a new object

Parameters:

• healpix1 (HealPixEffectiveArea) – One of the HEALPix maps to sum

• healpix2 (HealPixEffectiveArea) – The other HEALPix map to sum

• primary (int, optional) – If 0, use the first map metadata, or if 1, use the second map metadata. Default is 0.

• output_nside (int, optional) – The nside of the multiplied map. Default is 128.

Returns

(HealPixEffectiveArea)