rhysy.net

Research Interests

My research is prinarily based around the Arecibo Galaxy Environoment Survey. I use the world's largest, most sensitive telescope to hunt for galaxies by detecting their atomic hydrogen (HI) gas. Galaxies are found in different environments, from very low densitiy "voids" where there are hardly any galaxies at all, up to rich clusters thousands strong. AGES is trying to understand how the gas is affected by different enironments, which is important because ultimately it's the gas that determines star fromation.

AGES is not the most sensitive nor the largest survey ever undetaken, but it occupies a happy middle ground. It's pretty sensitive, but so much it will take a bajillion hours of telescope time. It's large enough to give interesting statistics and cover a wide range of galaxy environments, but not so large it needs a huge team to analyse the data (but if you want to join in, let us know !).

Recently I've begun learning the FLASH hydrodynamics code to try and reproduce some of the observations by numerical modelling.

 

My main research interests are :

- Dark galaxies. According to cosmologists, there aren't enpough dwarf galaxy satellites of the Milky Way. Are some of them galaxies with dark matter, gas, but no stars ?

- Morphological evolution. If a spiral galaxy loses gas, after it stops forming stars does it become an elliptical ? Is taking the gas away enough to cause morphological changes ?

- Extended gas streams. How does gas get outside galaxies ? How does it evolve once it's there ?  Is it ripped out of galaxies, or are we seeing primordial gas that hasn't yet formed stars ? Is it possible to produce long streams by high velocity interactions ?

- HI in early-type galaxies. If elliptical galaxies aren't forming any stars, how come some of them have a heck of a lot of gas ? Eh ?

- HI at cosmological redshifts. AGES is one of only a handful of surveys capable of directly detecting HI at z > 0.1. Can we detect any signs of secular evolution from z=0.0 to z=0.16 ? Can we detect very gas-rich, low surface brigthtness galaxies at these redshifts ?

- Star formation. Most galaxies have HI which is more extended than their stellar component. Why doesn't the outer gas form stars ? Is their a connection to extended UV discs ? How significant is star formation outside the main disc, i.e. in extended gas plumes ?

 

In the following pages I will describe some of my key results so far and provide some of the more useful programs I've written.

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