Research

I’m broadly interested in observational astrophysics, especially if it is extragalactic and large-scale in nature. I most often use a combination of ultraviolet and visible spectroscopy with photoionization modeling to study the intergalactic medium, galaxies (especially active galaxies), and the interplay between the two. You can find my publications (and all of the papers which cite them) via this ADS search. You will also find links to the arXiv versions of all of my papers via that search. If you prefer, you can also usually find all of my papers at Google Scholar, but it sometimes is not as complete as ADS. You can see papers in which I am acknowledged via this ADS search.

Non-jargon version for non-scientists:

Our sun is one of billions of stars in our galaxy, the Milky Way, which itself is just one of billions of galaxies which have huge distances of almost empty space between them. These galaxies come in many shapes and sizes, and most of them have a really big black hole at their centers. A black hole is just what you get when you pack a really huge amount of stuff into a really small space - nothing especially mysterious, although still pretty cool! Anyway, in some of the galaxies, the black hole does neat things. Sometimes, a lot of stuff is falling onto the black hole - specifically, gas, made of all the same elements you find in air on earth (albeit in different amounts). This alone wouldn’t be too interesting, but as the gas falls onto the black hole, it kinda squeezes closer together, which makes it heat up and eventually emit light, kinda like a stove burner does as it gets hot. And it turns out that this gas makes a lot of light of all different colors, even colors outside what our eyes can see (like x-rays and radio waves!). The way I’ve described it, it doesn’t sound too complicated, but in reality, it’s a bit messier. Gas sometimes flies out instead of in, we don’t know much about how big the black holes really are, and all of these galaxies look and work kinda differently from each other. Part of my work is trying to understand how and why these things do the things they do.

To do that, I just measure the light that comes from them, and try to piece together after the fact how that light ended up looking how it does. I do that in the same way that a rainbow or prism or reflection on a CD does. If you let the light hit the right material, you can split it up into all the colors that it is made of, the same way that a raindrop splits up the white light of the sun into all the colors in a rainbow (splitting up the light like that, by the way, is called making a spectrum, but that’s just a fancy word for a rainbow, basically). With the help of computers, I can measure all these colors very carefully, and figure out how they were made, and learn something about the galaxy that they came from.

There’s one other neat part of my research. Remember how I said that there are lots of galaxies which have huge distances of almost empty space between them? I lied a little bit. Turns out that that space isn’t quite empty. There are little tiny amounts of gas out there in some places. Like, really tiny amounts. But there is so much space out there that there are tons and tons of those little tiny bits of gas. In fact, there’s so many tiny bits, that altogether there is more gas and atoms out there than there is in all the galaxies and stars and planets combined! I try to figure out what that gas is like, but there’s a problem with doing that. This gas doesn’t make any light that we can look for with telescopes, like a star would, for example. But it does block light. So if I can find something really bright behind the gas I want to study, like, say, the glowing gas falling onto black holes that I talked about earlier, then I can study that gas by seeing how it blocks and changes the background light. So that’s what I do, again using the whole split-up-the-light-like-a-rainbow technique.

Those things that I study sound really specialized and irrelevant to almost anything, but it turns out that everything is kinda connected in nature. These two little subjects are small pieces of much bigger questions, like why galaxies and stars and planets exist the way they do at all. If you want to know why we live on a planet like Earth, near a star like the Sun, in a galaxy like the Milky Way, then you have to first understand lots of other little problems, like why the silly bits of gas that I study look the way they do when you split up their light like a rainbow.