Different formulas for rmtf FWHM

[miguelcarcamov]

Hi there,

Is there any reason to not use the same formula on functions run_rmsynth on RMtools_1D/do_RMsynth_1D.py and get_rmsf_planes on RMutils/util_RM.py?

If not using super-resolution, the first one calculates the rmtf fwhm as in the Brentjens & Debruyn paper, that is: 2.0 * sqrt(3) / (l2_max - l2_min).

However, the last function uses:

3.8 / (l2_max - l2_min)

I was checking if 2.0 * sqrt(3) was 3.8 but in fact was 3.4641016151377544.

Is there any reason to hardcode it to 3.8?

[Cameron-Van-Eck]

Hi Miguel:

Sorry for the delay in answering; I've been busy traveling. Good catch on the difference in the formulas. The 3.8 value comes from a later paper (Dickey+ 18, I think?) that found that actual RMSFs tend to be slightly wider than predicted by B&dB05. Originally RM-tools used the B&dB05 formula, but at some point I vaguely remember changing it to the new value. I must have changed it in the main function (get_rmsf_planes), but didn't realize that it was also calculated in a different place in run_rmsynth.

I'll make a note to fix it so both use the 3.8 value once I get back from traveling.

Thanks,
Cameron