Voila. The size of the shell from this image is ~1 kpc, and the velocity difference across the shell is ~7 / sin(i) km/s ~ 10 km/s. This is a bit smaller than the 15 km/s from before. Interesting. In any case, there's still a shell visible!
We can also look at the moment 0 (total intensity) and 2 (velocity dispersion) maps for these. A shell should have high velocity dispersion (but other things can show up with high velocity dispersion, so it's not a sufficient indicator for a hole). Here's the moment 0 map:
Dark colors mean more HI (except for the central black spot - that's NO HI) and white means less HI. Notice that the hole is now an oval instead of a circle due to the inclination of the galaxy - the y-axis that's labeled kpc is actually a projected kpc, not a measure of kpc in the plane of the galaxy.
And the velocity dispersion map:
Awesome.
2 comments:
these are great :)
thanks!
Very impressed that the scale of the shell is puts it right in with observed shells :)
For those reading this blogg:
for ref.. shell number 13 is the largest in Walter and Brinks 1998, for DWARF GALAXY IC 2574 and they get diameter 1992 pc, but no value for expansion velocity, while shell number 4 is 1116x1240pc with Vexp=14km/s.........
IC2574 has M_HI~9eMsol and Vrot=58km/s while the simulation that Adrienne is analysing, h516 has M_HI~5e8Msol and Vrot~50km/s....
Walter & Brinks measure multiple shells, and the simulation shells seem to be very much within the bounds of those observed, both in diameter and expansion velocity :)
this is good stuff1
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