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#!/usr/bin/env python3
#
# Copyright (c) 2018 Aaron LI <aly@aaronly.me>
# MIT License
#
"""
Montage a list of sky patches (e.g., simulated sky maps of radio halos
of 10x10 deg^2) to create a large map (e.g., hemisphere) for OSKAR
simulation to help investigate the far side confusion noise (FSCN).
Configuration file (YAML format)
--------------------------------
nside: 8 # npix=768, pixsize~7.33[deg]
region:
center: [0.0, -27.0] # [deg]
rmin: 10.0 # [deg]
rmax: 80.0 # [deg]
threshold:
min: 0.0001 # [K]
max: null
frequency:
type: calc
start: 154.0 # [MHz]
stop: 162.0
step: 0.16
input:
filename: '{dir}/cluster_{freq:06.2f}.fits'
dirlist: 'dir.list' # filename of the directory list file
pixelsize: 20 # [arcsec]
output:
filename: 'skymodel/cluster_{freq:06.2f}.osm'
clobber: true
"""
import os
import argparse
import logging
from functools import lru_cache
import yaml
import numpy as np
import healpy as hp
import astropy.units as au
from astropy.io import fits
from astropy.wcs import WCS
logging.basicConfig(level=logging.INFO,
format='[%(levelname)s:%(lineno)d] %(message)s')
logger = logging.getLogger()
def get_frequencies(config):
config_freq = config['frequency']
if config_freq['type'] == 'custom':
return np.array(config_freq['frequencies'])
else:
start = config_freq['start']
stop = config_freq['stop']
step = config_freq['step']
return np.arange(start, stop+step/2, step)
def central_angle(points, p0):
"""
Calculate the central angles between the points with respect to the
reference point (p0) on the sphere.
Input parameters:
points: (longitude, latitude) [deg]
point coordinates, two columns
p0: (longitude, latitude) [deg]
coordinate of reference point
Algorithm:
(radial, azimuthal, polar): (r, theta, phi)
central_angle: alpha
longitude: lambda = theta
latitude: delta = 90 - phi
colatitude: phi
Unit vector:
\hat{r}_1 = (cos(theta1) sin(phi1), sin(theta1) sin(phi1), cos(phi1))
= (cos(lambda1) cos(delta1), sin(lambda1) cos(delta1), sin(delta1))
\hat{r}_2 = (cos(theta2) sin(phi2), sin(theta2) sin(phi2), cos(phi2))
= (cos(lambda2) cos(delta2), sin(lambda2) cos(delta2), sin(delta2))
Therefore the angle (alpha) between \hat{r}_1 and \hat{r}_2:
cos(alpha) = \hat{r}_1 \cdot \hat{r}_2
= cos(delta1) cos(delta2) cos(lambda1-lambda2)
+ sin(delta1) sin(delta2)
References:
[1] Spherical Coordinates - Wolfram MathWorld
http://mathworld.wolfram.com/SphericalCoordinates.html
Equation (19)
[2] Great Circle - Wolfram MathWorld
http://mathworld.wolfram.com/GreatCircle.html
Equation (1), (2), (4)
"""
points = np.deg2rad(points)
if points.ndim == 1:
lbd1, delta1 = points[0], points[1]
elif points.ndim == 2:
lbd1, delta1 = points[:, 0], points[:, 1]
else:
raise ValueError('invalid input points')
lbd0, delta0 = np.deg2rad(p0)
dotvalue = (np.cos(delta1) * np.cos(delta0) * np.cos(lbd1-lbd0) +
np.sin(delta1) * np.sin(delta0))
alpha = np.arccos(dotvalue)
return np.rad2deg(alpha) # [deg]
def get_healpix_coords(nside):
npix = hp.nside2npix(nside)
lon, lat = hp.pix2ang(nside, np.arange(npix), lonlat=True)
return (lon, lat) # [deg]
class Patches:
def __init__(self, config):
config_input = config['input']
self._filename = config_input['filename']
self._dirlist = [d.strip()
for d in open(config_input['dirlist']).readlines()]
def get_image(self, freq, i):
i = i % len(self._dirlist)
fn = self._filename.format(freq=freq, dir=self._dirlist[i])
logger.info('Load image: %s' % fn)
with fits.open(fn) as f:
return (f[0].data, f[0].header)
class SkyModel:
def __init__(self, image, freq, pixelsize, p0, min_=1e-4, max_=None):
self._image = image
self._freq = freq # [MHz]
self._pixelsize = pixelsize # [arcsec]
self._p0 = p0 # (lon, lat) [deg]
self._min = min_ # [K]
self._max = max_ # [K]
@property
def K2JyPixel(self):
pixarea = (self._pixelsize * au.arcsec) ** 2
equiv = au.brightness_temperature(pixarea, self._freq*au.MHz)
return au.K.to(au.Jy, equivalencies=equiv)
@property
def mask(self):
_max = self._max or np.inf
return ((np.abs(self._image) >= self._min) &
(np.abs(self._image) <= _max))
@property
def wcs(self):
shape = self._image.shape
delta = self._pixelsize / 3600.0 # [deg]
wcs = WCS(naxis=2)
projection = 'SIN'
wcs.wcs.ctype = ['RA---'+projection, 'DEC--'+projection]
wcs.wcs.crval = np.array(self._p0)
wcs.wcs.crpix = np.array([shape[1], shape[0]]) / 2.0 + 1
wcs.wcs.cdelt = np.array([-delta, delta])
return wcs
@property
def sky(self):
shape = self._image.shape
idx = self.mask.flatten()
wcs = self.wcs
x, y = np.meshgrid(np.arange(shape[1]), np.arange(shape[0]))
pix = np.column_stack([x.flatten()[idx], y.flatten()[idx]])
world = wcs.wcs_pix2world(pix, 0)
ra, dec = world[:, 0], world[:, 1]
flux = self._image.flatten()[idx] * self.K2JyPixel
return np.column_stack([ra, dec, flux])
if __name__ == '__main__':
parser = argparse.ArgumentParser(
description='Montage sky patches to make a large OSKAR sky model')
parser.add_argument('config', help='configuration file in YAML format')
args = parser.parse_args()
config = yaml.load(open(args.config))
patches = Patches(config)
frequencies = get_frequencies(config) # [MHz]
nfreq = len(frequencies)
pcenter = config['region']['center'] # [deg]
rmin = config['region']['rmin'] # [deg]
rmax = config['region']['rmax'] # [deg]
min_ = config['threshold']['min'] # [K]
max_ = config['threshold']['max'] # [K]
pixelsize = config['input']['pixelsize'] # [arcsec]
clobber = config['output']['clobber']
nside = config['nside']
logger.info('Nside: %d' % nside)
resol = hp.nside2resol(nside, arcmin=True) # [arcmin]
logger.info('HEALPix resolution: %.2f [arcmin]' % resol)
imgsize = int(round(resol * 60 / pixelsize))
logger.info('Image patch size: %d' % imgsize)
plon, plat = get_healpix_coords(nside) # [deg]
npatch = len(plon)
for i, freq in enumerate(frequencies):
logger.info('[%d/%d] %.2f[MHz] ...' % (i+1, nfreq, freq))
outfile = config['output']['filename'].format(freq=freq)
os.makedirs(os.path.dirname(outfile), exist_ok=True)
if os.path.exists(outfile) and (not clobber):
raise FileExistsError(outfile)
results = []
jj = 0
for j, p0 in enumerate(zip(plon, plat)):
logger.info('[%d/%d|%d] patch @ (%.2f, %.2f)' %
(j+1, jj+1, npatch, p0[0], p0[1]))
if central_angle(p0, pcenter) > rmax:
logger.info('skip')
continue
image, header = patches.get_image(freq, jj)
skymodel = SkyModel(image[:imgsize, :imgsize],
freq, pixelsize=pixelsize,
p0=p0, min_=min_, max_=max_)
sky = skymodel.sky
points = sky[:, 0:2] # (lon, lat)
angles = central_angle(points, pcenter) # [deg]
idx = ((angles >= rmin) & (angles <= rmax))
sky = sky[idx, :]
logger.info('Source counts: %d' % len(sky))
results.append(sky)
jj += 1
sky = np.row_stack(results)
logger.info('Total source counts: %d' % len(sky))
header = ('Frequency = %.2f [MHz]\n' % freq +
'Source counts = %d\n\n' % len(sky) +
'R.A.[deg] Dec.[deg] flux[Jy]')
logger.info('Writing sky model to file: %s ...' % outfile)
np.savetxt(outfile, sky, fmt='%.10e, %.10e, %.10e', header=header)
logger.info("Wrote OSKAR sky model to file: %s" % outfile)
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