FRB example

v2 – Using PATH object

[1]:

# imports
from importlib import reload
import os
from pkg_resources import resource_filename

import numpy as np

import pandas

from astropy.coordinates import SkyCoord
#from astropy.io import fits

from astropath import path
from astropath import localization

Dummy FRB (based on 180924)

Instantiate PATH

[2]:

Path = path.PATH()

Localization

Here is the full data model for the localization options

[3]:

localization.localization_dmodel

[3]:

{'type': {'dtype': str,
  'options': ['eellipse', 'wcs', 'healpix'],
  'help': 'Localization type.'},
 'center_coord': {'dtype': astropy.coordinates.sky_coordinate.SkyCoord,
  'help': '"Central" coordinate'},
 'eellipse': {'dtype': dict,
  'help': 'Error ellipse with keys "a [arcsec]", "b [arcsec]", "theta [deg]"'},
 'healpix_data': {'dtype': (numpy.ndarray, astropy.table.table.Table),
  'help': 'Data containing the healpix information. Input either as a simple numpy array for a full NESTED array or an astropy Table for NUNIQ format with columns UNIQ and PROBDENSITY.'},
 'healpix_nside': {'dtype': int, 'help': 'NSIDE value of healpix map.'},
 'healpix_ordering': {'dtype': str,
  'options': ['NESTED', 'NUNIQ'],
  'help': 'Ordering of the healpix information.'},
 'healpix_coord': {'dtype': str,
  'options': ['C'],
  'help': 'Coordinate system of the healpix.'},
 'wcs_data': {'dtype': numpy.ndarray, 'help': 'PDF of localization.'},
 'wcs_WCS': {'dtype': astropy.wcs.wcs.WCS, 'help': 'WCS of the localization.'}}

We will use the Error Ellipse type

[4]:

## FRB Coord
frb_coord = SkyCoord('21h44m25.255s -40d54m00.10s', frame='icrs')
frb_coord

[4]:

<SkyCoord (ICRS): (ra, dec) in deg
    (326.10522917, -40.90002778)>

Error ellipse

[5]:

#eellipse = dict(a=0.3, b=0.1, theta=45.)
#eellipse = dict(a=3, b=3, theta=90.)
eellipse = dict(a=0.1, b=0.1, theta=0.)

Set it

[6]:

Path.init_localization('eellipse', center_coord=frb_coord, eellipse=eellipse)

[7]:

Path.localiz

[7]:

{'type': 'eellipse',
 'center_coord': <SkyCoord (ICRS): (ra, dec) in deg
     (326.10522917, -40.90002778)>,
 'eellipse': {'a': 0.1, 'b': 0.1, 'theta': 0.0}}

Candidates

Load

[8]:

cand_file = os.path.join(resource_filename('astropath', 'data'), 'frb_example', 'frb180924_candidates.csv')

[9]:

candidates = pandas.read_csv(cand_file, index_col=0)
candidates.head()

[9]:
ra dec half_light VLT_FORS2_g
3 326.101738 -40.899771 0.458869 25.295416
7 326.105365 -40.900239 1.308629 21.319569
8 326.104186 -40.900180 0.814683 24.272838
9 326.106237 -40.899279 0.501247 25.474828

Init in PATH

[10]:

Path.init_candidates(candidates.ra.values,
                     candidates.dec.values,
                     candidates.half_light.values,
                     mag=candidates.VLT_FORS2_g.values)

[11]:

Path.candidates

[11]:
ra dec ang_size mag
0 326.101738 -40.899771 0.458869 25.295416
1 326.105365 -40.900239 1.308629 21.319569
2 326.104186 -40.900180 0.814683 24.272838
3 326.106237 -40.899279 0.501247 25.474828

Priors

Candidate prior

[12]:

Path.init_cand_prior('inverse', P_U=0.)

Offset prior

[13]:

Path.init_theta_prior('exp', 6.)

Calculate

[14]:

Path.calc_priors()

[14]:

array([0.0316325 , 0.87225473, 0.06831713, 0.02779563])

[15]:

Path.candidates

[15]:
ra dec ang_size mag P_O
0 326.101738 -40.899771 0.458869 25.295416 0.031633
1 326.105365 -40.900239 1.308629 21.319569 0.872255
2 326.104186 -40.900180 0.814683 24.272838 0.068317
3 326.106237 -40.899279 0.501247 25.474828 0.027796

Posteriors

Calculate

[16]:

P_Ox, P_Ux = Path.calc_posteriors('fixed', box_hwidth=30.)

Show

[17]:

Path.candidates

[17]:
ra dec ang_size mag P_O p_xO P_Ox
0 326.101738 -40.899771 0.458869 25.295416 0.031633 0.000000e+00 0.000000e+00
1 326.105365 -40.900239 1.308629 21.319569 0.872255 5.156772e-02 9.895195e-01
2 326.104186 -40.900180 0.814683 24.272838 0.068317 6.973468e-03 1.048049e-02
3 326.106237 -40.899279 0.501247 25.474828 0.027796 9.296108e-20 5.684350e-20 
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