Notes from meeting with Ted on 31 October

I met with Ted today. My PhD committee meeting is next Wednesday.

Context:
over the last week, my priority has been to get h13cn column density measurements for IRAS 16293, which has meant compiling data from a few different sources. I found the Herschel CHESS HIFI spectral scans of this source in the Herschel Science Archive, "reduced" them lightly (really this only involved downloading, converting to CLASS format, doing simple baselining and single-component Gaussian fitting to the h13cn lines, and extracting integrated fluxes in K km /s units). I also fetched low-J line fluxes (single-dish) from the Caux+11 paper, which had IRAM-30m and JCMT data for J=1-0, 3-2 and 4-3.

In the pursuit of getting a source size measurement for the h13cn emission, I tracked down the ALMA science verification data for this source - turns out they had an already-reduced h13cn 8–7 datacube sitting and ready to analyze on their server, and it even has a whole CASA tutorial attached to it. Screenshot of the moment-0 map of the h13cn line is shown below, where the beam is a filled white ellipse, and "component A" is in the bottom-left while "component B" is in the top-right.

I started the meeting by discussing with Ted whether the inclusion of all this extra data (lots of Herschel, this ALMA dataset, and the Caux fluxes so far) justifies turning this h13cn analysis of IRAS 16293 into its own separate (small) paper. He says "unless there is additional info (another interferometric h13cn map of this source at a different line, or some other substantial additional data) I don't agree." Basically the idea right now (from my point of view) is to stick the details of the abundance measurement in the appendix of the Nitrogen accounting paper. Maybe multiple appendices for multiple sources.

We discussed how I'd get the CO column density. A few ideas, including "look it up in a Jørgensen paper" were thrown around, but Ted settled on this:
(New task for me.)
Since I have all the Herschel HIFI spectral data in-hand already, I can (almost trivially) replicate the exact analysis that Plume+2012 does towards Orion KL, for CO. I'd have to track down the C17O and C18O lines in the spectrum but since the analysis is already completely described in Plume+12, I wouldn't be easily misguided. If the CO isotopg. lines are comparable in strength to the HCN isotopg. lines, then we should be in great shape.

I also need to track down the hc15n lines at IRAS 16293 in order to confirm (or debunk) the "optically thin" assumption that goes into using h13cn lines for column density analysis. This would be in the HIFI data somewhere - hopefully they're not too weak. This table should help me estimate the expected line strengths -  it looks like I'd expect the hc15n lines to be (12c/13c) x (15n/14n) = ~0.18 times as strong as the h13cn lines, assuming "local ISM" isotopic ratios.

Another thing: I mentioned that I felt like the Kama+2013 paper (CHESS molecular line identification towards the intermediate-mass young star OMC-2 FIR4) probably didn't identify ALL the h13cn lines that were probably present in the data - I suspect that 1-2 more could be identified and extracted by someone dedicated enough. He suggested that I email Mikhail Kama about it. I said I could probably just download the Herschel data myself

Pretty much we want to do the h13cn column density + abundance measurement for ANY source that has (a) Herschel data with h13cn lines in it and (b) a reasonable source size measurement or estimation. This partially rules out Orion S since its hot-core source size is v. unconstrained.