Updating GALFA and Planck
By Elijah Bernstein-Cooper, June 28, 2015, 0 comments.

Data Update


We are now using the GALFA data release 2. Some words from Josh Peek about the data:

  • Credit to Kevin Douglas, Brian Babler, Yong Zheng and Josh Peek

  • The data are largely taken from commensal observations with GALFACTS, and are in our shallowest (“gear 6”) mode, which results in noise of about 140 mK / 1 km/s channel, covering almost all of the Arecibo sky. The data are supplemented from three sources to fully fill in the Arecibo sky:

    1. A small region of sky near RA = 60, dec 10 is filled in with data from DR1.

    2. A small region near RA 50, dec 18 is filled in with data provided by the EBHIS collaboration. These data are marked in the equivalent T.fits files with a -1

    3. Small holes throughout are patched with data from LAB. These data are marked in the equivalent T.fits files with a -2

The GALFA DR1 and DR2 have comparable noise present both ranging from K to K.


We will now be using the map only instead of the Radiance + combined map. This is because the radiance map is only accurate for the most diffuse regions where the interstellar radiation field does not vary much. The dust opacity (which depends on) is shown to vary less than the radiation field for molecular clouds. See Section 6.3 and Figure 24 of the Planck paper which shows correlates better with 2MASS stellar extinction maps in Taurus than the radiance.

Perseus Intercept Test

Below are likelihood spaces for Perseus.

Planck Results

Judging by the background of all three clouds, Perseus seems to have the most constant background . It is odd that there is no intercept calculated however, because inspecting the map visually, it looks like there is at least a mag background in the Planck map.

Lee+12 Results

We expect that the intercept be mag since the background has already been subtracted from Perseus manually. Indeed we have agreement, no intercept was found.

2MASS / Planck Relationship

Here is a 2D histogram plot including all three clouds of Planck vs. 2MASS . The Planck map is systematically offset from the 2MASS values. An empirical fit for each of the three clouds will come tomorrow.