Selden,
many thanks for your latest version of the ATNF pulsar add-on.
The best evidence for a 4 arm structure came originally from Prof. Urquhart's MYSO data that were both published and sent by him in numerical form to me in 2014. An amazing and perfectly compatible further evidence then came from combining the MYSO data with the
transversely cut ATNF pulsar population! This work I did in 2014 together with Christophe.
Here is a summary image:
[click on image by all means!]Attachment:
best_MYSO_cutATNF_MW.png [ 652.75 KiB | Viewed 974 times ]
The bluish sketched lines are best interpolations by Christophe of the MYSO data, while the various yellow-orange-red squares denote the subset of ATNF pulsars that
lives close to the galactic plane. Mainly these combined data are the sought for best messengers of the detailed MW arm structure. As you may see, there is barely any deviation of the selected ATNF pulars and the MYSO data. This exciting joint result has formed the basis of the MW template in
celestia.Sci!
By projecting the full ATNF data set
transversely to the galactic plane, on can easily see that quite a number of the pulsars are located significantly outside the galactic plane and hence their presence will obscure the arms pattern in the plane! These pulsars in the bulge have practically nothing to do with the arms. These findings rest also on quite convincing astrophysical arguments...
See e.g. again Prof. M. Hoare's argumentation about MYSOs:
viewtopic.php?f=11&t=875#p14526 Here is an illustration, how a simple
b-cut filters out the pulsars closest to the galactic plane:
Attachment:
MW_pulsars_bcut.jpg [ 156.44 KiB | Viewed 974 times ]
If I had a little more spare time besides celestia.Sci coding

I had long written a scientific paper about these results.
Fridger