How to visualize portions of the CMB map?

Use of Healpix, camb, CLASS, cosmomc, compilers, etc.
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Evan B
Posts: 13
Joined: February 27 2015
Affiliation: student

How to visualize portions of the CMB map?

Post by Evan B » February 04 2016

Using Healpix, I am working with patches of a full-sky map. Based on a set nside, we know the pixel indices and (roughly) the coordinates.

I would like to output these patches to see the data. The problem is (based on my understanding), Healpix does not allow one to plot small patches like this. You must output the entire map and mask unwanted pixels, e.g. http://imgur.com/AtH05JR

It appears that many in the community use other software to visualize portions of the CMB map, e.g. this arxiv paper: http://arxiv.org/pdf/1508.07005.pdf

So, I am curious how to visualize Planck data without using this Healpix scheme. There must be software out-there to visualize pixels from FITS without having to write it up from scratch.

Any help appreciated

Antony Lewis
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Joined: September 23 2004
Affiliation: University of Sussex
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Re: How to visualize portions of the CMB map?

Post by Antony Lewis » February 04 2016

You can, see e.g. cartview

Code: Select all

import healpy
healpy.visufunc.cartview(map, lonra=[-135, -130], latra=[-30, -25])

Evan B
Posts: 13
Joined: February 27 2015
Affiliation: student

How to visualize portions of the CMB map?

Post by Evan B » February 05 2016

We may be misunderstanding each other. I am curious how the CMB community plots/visualizes "portions" of the CMB map. For instance, let's say there is a SZ cluster or a point source around a specific coordinate on the full sky map, (l,b) = (24, 45).

Cartview will allow a 2D representation of these pixels, but not only "this patch, i.e. pixel indices [35324, 35325, 35326, 35327, etc.], given some nside resolution".

How do you "splice" the map to only show this cluster of approx. 100-1000 pixels? This must be a standard procedure for doing point source detection, as an example.

Is there another software used to do this? It is basically just selected certain pixels from the full-sky map FITS file and plotting these (selected by index).

Correct me if I'm mistaken, of course.

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