These are quick notes summarizing our December 4, 2012 Google Hangout.

1--mass is likely ~10x more than what IRDC analysis shows, according to: Kainulainen, J., Alves, J., Beuther, H., Henning, T., Schuller, F., 2011. Mass reservoirs surrounding massive infrared dark clouds: A view by near-infrared dust extinction. eprint arXiv:1109.6017.

2--analysis of velocity gradient using glue shows that position within the arm is more likely than position across arm--send Tom Dame HOPS data for Nessie positions, l,b,v by saving subsets and giving them to Chris who will give them to Tom. Tom will analyze how these compare with CO velocity structure & give his best estimate on "armieness"

3--Andi will (with input from Clare Dobbs, who we should add to the paper), look at simulations to see what mass/velocity structures would be associated with real "backbone" of the arm scenario, even as viewed from ~25 pc above the plane ... see Dobbs, C.L., Burkert, A., Pringle, J.E., 2011. Why are most molecular clouds not gravitationally bound? Monthly Notices of the Royal Astronomical Society 413, 2935–2942. http://doi.wiley.com/10.1111/j.1365-2966.2011.18371.x

4--AG will move all materials to Authorea, from their currently scattered locations, including the "Nessie Paper" shared Google Drive.

More soon!

Alyssa

P.S. I sent this update to CfA Press Officer (Christine Pulliam), after the meeting:

Hi Christine,

I just got off a long Google Hangout with my collaborators on the Nessie/Bones project. We are leaning much more toward the idea that Nessie is really more of "backbone" of spiral arm than a between-the-arms like feature. The IC342 image you mentioned shows both, but it highlights the between-the-arms option a bit too much in my opinion. So, if you prefer, I'd suggest you have a look at the simulations we're now using to understand what's going on, at:

http://empslocal.ex.ac.uk/people/staff/cld214/movies.html

http://empslocal.ex.ac.uk/people/staff/cld214/eff005whole.mov

In the second movie, stills from which are in,
Dobbs, C.L., Burkert, A., Pringle, J.E., 2011. Why are most molecular clouds not gravitationally bound? Monthly Notices of the Royal Astronomical Society 413, 2935–2942, we now think Nessie is likely to be part of the dark red "skeleton" you see mostly within the arms.

Synthetic observations of these simulations are shown here: http://empslocal.ex.ac.uk/people/staff/cld214/synthetic.html.

If you decide to use any of the simulation images, then we can highlight for you just how tiny a piece of galaxy we are talking about for you on a high-res image! And, we are planning to include Clare Dobbs, creator of the visualizations & lead author, on the paper now. Andi Burkert, cc'd, is going to invite Clare.

Thanks!

Alyssa