Questions from the Lorentz Workshop "The Passage of Light through Spiral Disks"

While the Lorentz Center workshop was going on, we identified some outstanding issues with the modelling of edge-on spirals. There are the questions that ended up on the board:

1. What is the morphology of the dusty clumps?
2. How are the cold and hot dust related to each other?
3. What is the minimum physical scale we need?
4. How to integrate MW constraints into Radiative Transfer?
5. What other extinction curves can we get?
6. What other data would we like?
7. Does the IRSF harden with radius?
8. What is our Southern NC 891? - NGC 5746 appears to be a great candidate.

1. What is the morphology of the dusty clumps?

Richard Tuffs already picked on this one. So far, too many of the models have to assume "spherical cows" for the already horribly computationally costly radiative transfer model.
But we all know they are not spherical. Far from it. So what is better? Ilse's talk on Friday already points to a better model: many many little spheres that are also allowed to overlap. Still not there I feel. I like "headlights", where a heating source is off-center from the GMC. And of course filamentary structure. Kenny Wood's talk also points to how much ISM structure dicatates the results from RT. Much will happen here. 

2. How are the cold and hot dust related to each other?

In a very complicated way. FIR colors may point to as to how (George Bendo's second talk).

 3. What is the minimum physical scale we need?

 This went back & forth quite a bit. Waad Safty's and the DART-RAY talk for example were all about extremely high resolution simulations (e.g. EAGLES) that took it down to supparsec resolution. In reality, good data can be obtained (with effort) to below the kpc scale. That kpc scale seems to be important. Then individual GMCs are affecting the RT, not just whole spiral arms etc.

4. How to integrate MW constraints into Radiative Transfer?

This is going to be tricky and may need its own workshop. There are plenty of things we know from MW RT models but how well to these translate into global RT models? 

5. What other extinction curves can we get?

This is easier. For one thing, the occulting galaxy technique (my talk!) promises to measure these statistically and specifically with IFU observations. The new generation of IFUs will certainly be able to resolve GMCs in nearby disks. That is likely to give us actual extinction curves.

6. What other data would we like?

IFUs and ALMA! These are obvious next choices. ALMA mosaicing is going to be tough. As is MUSE IFU observations. 

7. Does the IRSF harden with radius?

yes. George canvassed everyone and this was unanimous.

8. What is our Southern NC 891?

NGC 5746 appears to be a great candidate.

I'm sure we will come up with many more soon.

We had a count which galaxies was mentioned most. Edge-on favorites are NGC 891, NGC 4244, the Sombrero, and NGC 4565. Of these four, obviously NGC 891 won. By a landslide.