zod-light

A tool for estimating Galactic zodiacal light emission for Spitzer Space Telescope observations.

Background

This is a Python wrapper for querying the Zodiacal Light Model (written in C) by W. Reach, J. Bennett, & B. Hartley (SSC): see https://irsa.ipac.caltech.edu/data/SPITZER/docs/dataanalysistools/tools/contributed/general/zodiacallight/.

Please note that the C code has been modified to account for a couple of bugs, hence why the C code itself is included here (all rights of the C model remain with the authors as mentioned above).

Typical use case

A common use for this package is to determine the zodiacal light towards a given position (RA, Dec) during a Spitzer observation. For instance, in [Shannon et al. (2018)][http://adsabs.harvard.edu/abs/2018ApJ...855...32S] we examined diffuse background emission from the Galactic bulge region. Since we were only interested in the background itself (and not the on-star observations), no background-subtraction was performed. Depending on how close to the Galactic center one looks, the zodiacal light can be an important if not dominant component of the mid-infrared continuum.

For instance, here is an estimate of the zodiacal light continuum from the paper (using this tool):

And here's an example of how some observations can be dominated by zodiacal light (dashed line):

What you'll need to use this tool

Essentially, all you need to know is when your Spitzer observation was taken and where (in RA, Dec) the telescope was pointed. Specifically, you'll want the following information before you proceed (for each observation in which you want an output mid-IR spectrum):

• year
• month
• day
• right ascension (in HMS or degrees)
• declination (in HMS or degrees)

Typical outputs

Installation

1. First, download this repository. Your best bet is to just clone it. From the terminal:

   • git clone https://github.com/mattjshannon/zod-light.git

2. Next, you need to ensure that you have the ephem data, i.e., model/ephem/de.bsp and model/ephem/sirtf.bsp.

   • Note that these files are quite large (140MB and 225MB, respectively). They are linked here (in this repository) through the git-lfs (Large File Storage) service. However, if you do not have git-lfs installed (or if the bandwidth amount has been exceeded):
   • Extract them from the model/ephem/ folder of the Spitzer-hosted (old) Zodiacal Light Model, which you can download from https://irsa.ipac.caltech.edu/data/SPITZER/docs/dataanalysistools/tools/contributed/general/zodiacallight/. Just dump them into the model/ephem/ folder of this repository.

3. Next, you need to make the ZL Model. To do so:

   • cd model
   • And followed by the appropriate command (choose as appropriate):
     • make mac
     • make linux
     • make solaris

Running an example

Inputs

How to format your queries

Outputs