Free Form: Blog 12, Dust Disks in Elliptical Galaxies

Long ago - last semester - in Astronomy 16, I wrote a free form blog post on an astronomy research experience I had before my junior year of high school. I researched Lyman-alpha emitting galaxies from the beginning of the universe. If you are interested I recommend reading that post here.  The post ends with the sentence:

"This experience caused me to take a position in an astronomy lab the next summer researching black holes, but I will talk about that in my next blog post."

But I lied! We never actually had another free form blog post for Astronomy 16 so I will now talk about the second high school research experience that got me interested in astronomy. The summer before senior year, I emailed around to different labs at the University of California, Irvine (where I grew up) to see if any labs doing interesting research wanted some assistance for the summer. I ended up working at the lab of Aaron Barth, a physics and astronomy professor at UCI. Dr. Barth researches super massive black holes and had recently turned his attention to black holes at the center of elliptical galaxies. That is where I come in. My job was to look through all the pictures the Hubble Space Telescope and ALMA telescope had taken of elliptical galaxies - yes all of them - to look for evidence of black holes. If that wasn't enough, I also looked through many, many pictures that were not of elliptical galaxies. Often times, pictures of other galaxies, stars, and even our own planets have elliptical galaxies "photobombing" in the background, which can potentially mean a lot of useful data.

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Once I had a clear, or often very blurry, image of an elliptical galaxy, the first step would be to look for evidence of a dust disk. A dust disk is basically exactly what is sounds like, a disk of dust circling the galaxy due to an extremely heavy object pulling it in, most likely a black hole. The problem with black holes is that we cannot analyze them if we cannot see them, so astronomers settle for analyzing the material around them. A clear example of a dust disk in an elliptical galaxy looks like this:

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However, my images were hardly that clear on average. A lot of lab time that summer was spent learning how to search in different wavelengths, adjust contrasts, and adjusting wavelength colors to try to get a glimpse of a dust disk. Most of them ended up looking something like this:

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And those are normal dust disks. Many of them are distorted by the gravity of another object:

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My favorites were the galaxies with two dust disks:

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After spending so long looking at questionable candidates finding a nearly perfect dusk disk like the one below was a thing of beauty:

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The end results were amazing, but to get there was a lot of tedium. Most of my time was spent searching through NASA databases, making very long spreadsheets of candidates and their properties, and painstakingly adjusting image parameters. By the end of the project I had looked over more than 1,000 galaxies across 6 luminosity "bins."

So many spreadsheets

In the end, it is worth it. By analyzing the mass, density, or speed of the dust disk we can begin to collect data on the black hole at the center of the galaxy, something that still mystifies astronomers. Additionally, the project was worth it just because I spent my time looking at gorgeous pictures from the Hubble Space Telescope. Not just of elliptical galaxies but also of exploding supernovae and beauiful spiral galaxies.

 

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Additionally, I learned many new things along the way. For example, I constantly saw arcs of light that I could not explain, which is how I first learned about gravitational lensing and some of the crazy effects relativity can have on our observations. I even found evidence for a dust disk in a lensed galaxy.

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I finished my project in August of 2014. The professor analyzed the data further in order to write a research proposal. In January of 2015, he wrote me an email to inform me that the project was approved for time on the HUBBLE SPACE TELESCOPE in order to get clearer pictures of some of the better candidates I found. In a few months, the data should be coming in from the telescope and I can't wait to see the pictures.

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Overall, those two research projects definitely solidified my interest in astronomy and led me to where I am today: sitting in a Harvard dorm, writing a blog post for Astronomy 17.