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HI Rogues

As I follow the endless path, looking for references in papers, I came across this - the HI rogues gallery. It is a "Collection of maps of HI in Weird Galaxies and Weird HI in otherwise Normal Galaxies" and wow is it a beautiful collection.

The whole reason astronomers are interested in HI (neutral Hydrogen) in the universe is because it is the fundamental fuel that makes stars. Also, there's loads and loads of it in galaxies and in the Inter-galactic medium (theoretically).  And in galaxies, this HI extends wayy beyond the boundary defined by the stellar population of the galaxy. This fact can be used to understand the (baryonic) gravitational potential of the galaxy it is embedded in, and the dark matter halo it is embedded in. If you dig through the gallery, you will come across interesting examples showing intergalactic debris with no optical counterparts! This is interesting as it helps us understand the history of the galaxies, their environments and the distribution of dark matter cusps in the galactic environment.

Now I'm reminded of how I came across this gallery. I was reading through the paper by Kilborn et al. 2006 on Gaseous Tidal Debris found in the NGC 3783 group. They used the ASKAP to study the galaxy group surrounding NGC 3783 and used the ACTA to do a follow up survey on objects whose ASKAP observations clashed with those from legacy Parkes radio telescope data. They discovered new radio counterparts to optical galaxies in literature and they discovered a new HI cloud without any optical counterpart. They expect the cloud to have been part of another galaxy closeby, one that looks to have been disrupted tidally (with significant evidence).

A rough idea for a PhD project has started forming in my head. I am currently applying to a professor who wants to work on simulating the neutral HI in the universe and understand how galaxy evolution works : through feedback and given an environment. And apart from simulations, there are more and more interesting observations, in the optical and the radio domain, where people are discovering lower and lower mass galaxies. A thorough study of dwarf/satellite galaxies, stellar tidal streams, intergalactic HI clouds and HI in tidally interacting galaxies is going to become accessible over the next decade, with the upcoming ASKAP/Apertif(WSRT) in the radio domain and the LSST/GMT/TMT in the optical domain. It is going to be rich in observations and it looks like something I'm interested in working on for the next decade or so. Now to see if I find a prof who is as interested in working on it as I am...

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