zodipy 0.1.8

Zodipy is a python tool that simulates the Zodiacal emission.

Zodipy

Description

Zodipy is a python tool that simulates the Zodiacal emission.

Installing

Zodipy is installed with pip.

pip install zodipy

Usage

The following examples are meant to provide an overview of how Zodipy may be used to produce simulations of the Zodiacal emission. A more in-depth documentation will be available in the near future.

Simulating the instantaneous emission from a single observation

The simplest use case of Zodipy is to simulate the instantaneous emission as seen from a major body or a location in the Solar system, as of today:

import zodipy

zodi = zodipy.Zodi()
emission = zodi.get_emission(nside=128, freq=800)

Calling the Zodi object with no arguments will by default set up the initial conditions of the simulation for an observer at L2 today. The get_emission method of the Zodi object, is then called to simulate and return the emission for a given nside and frequency.

We can visualize the above simulated emission using Healpy:

Alternatively, a specific observer and specific epochs can be passed as arguments to the Zodi object. The epochs object must match one of the possible formats defined in astroquery's JPL Horizons api.

import zodipy

MJD = 59215  # 2010-01-01 in Modified Julian dates
zodi = zodipy.Zodi(observer='Planck', epochs=MJD)
emission = zodi.get_emission(nside=128, freq=800)

To return the component-wise emission the keyword return_comps in the get_emission function may be set to True.

Simulating the pixel weighted average over multiple observations

By providing multiple dates in the epochs argument to Zodi, the get_emission function will return the emission averaged over all observations.

It is possible to provide hit maps for each respective observation given by epochs. This is done by passing a sequence of hit maps through the hit_counts argument in Zodi.

Below is an example where we simulate the pixel weighted average over daily observations over a year:

import zodipy

epochs = {
    'start': '2010-01-01', 
    'stop': '2011-01-01', 
    'step' : '1d'
}
hit_counts = ... # Your sequence of hit_counts for each observation in epochs 

zodi = zodipy.Zodi(observer='Planck', epochs=epochs, hit_counts=hit_counts)
emission = zodi.get_emission(nside=128, freq=800)

This simulation closely resembles map making in the time-ordered domain, with the hit maps playing a significant role on the outputted emission due to the motion of Earth through the interplanetary dust.

The hit maps used in the above example was somewhat arbitrarily chosen (stripes of 10 degrees perpendicular to the ecliptic).

Interplanetary dust models

Zodipy uses the Kelsall et al. (1998) Interplanetary dust model. The line-of-sight integrals are computed using the definition in Planck 2013 results. XIV. Zodiacal emission. During the Planck analysis, three different sets of emissivities were fit to describe the emission. These can be selected by providing the keyword argument model to the Zodi object:

import zodipy

zodi = zodipy.Zodi(model='planck 2013')

The available models are 'planck 2013', 'planck 2015', and 'planck 2018'. The default is the 2018 model. Note that selecting the 2013 model will include the Circumsolar and Earth-trailing components, which were left out in the 2015 and 2018 Planck analyses.