Today's the Day! The Day We Visit the VLA!

I know it's been a while since my last post, but that's the life of an aspiring scientist--sometimes the results come quickly and sometimes there's almost no progress, making it near impossible to write interesting blog posts about your research. And then there are those times when you don't make much progress in your own research because your job pays to fly you to one of the coolest astronomy-related sites in America!

This past week, I went with 11 other NRAO summer interns to visit the Karl Jansky Very Large Array in New Mexico.  The VLA is an interferometer of 27 radio antenna dishes that are used to take super high-resolution images of objects in our universe.  An interferometer is an array of telescopes that allows astronomers to combine the data coming from each individual dish.  Even if you don't know a lot about radio astronomy, that has to sound pretty freaking cool.

We got a pretty great tour of the facilities.  We started with the normal walking tour of the grounds, where we saw the Ron Bracewell Sundial, made from the pillars of an old telescope array.  Just a short walk away were the VLA's Whisper Dishes, a pair of parabolic dishes designed and placed so that two people standing near them could hear each other whispering from across the field.  A longer walk away, we were able to see the site's backup antenna being repaired in its hangar.  Going back the way we had come, we entered the operating building, the home of the VLA Control Room.  We talked with some of the telescope operators, but didn't get to do any operating (which was probably for the best because this is a multi-million dollar science project).  Our next and final stop was one of the dishes--dish 5 to be exact.  We climbed stairs and ladders until we made our way to the top, and it was such an amazing experience!

But don't worry! We didn't get flown out to New Mexico just to climb telescopes and buy really cool NRAO swag. 

Though I promise we bought plenty of swag

We had to do some science, too.  We had to choose between two projects-- one used the Very Long Baseline Array (VLBA) to image radio galaxies; the other, which I chose, used the VLA to try to identify a nearby dwarf galaxy.  We did this by mapping the neutral hydrogen (HI) in our target area, and depending on what we found, we would be able to determine whether or not the gas cloud was actually a galaxy.

On day one, after we chose our projects, they split us into groups and told us to reduce data.  No one in my group had ever used CASA to reduce data or worked with neutral hydrogen, but our supervisors did point us in the direction of an online CASA guide to follow. It was a slow, frustrating, and educational experience.  I'm far from an expert in CASA data reduction (I'm talking lightyear-scale far), but an image was made. We're not done analyzing yet, and we might have to go back and redo some of the calibration, but we're pretty sure our target is a galaxy.  We think that because on one edge of the target, the hydrogen is coming towards us, and on the other, it's moving away.  This indicates that the hydrogen is part of a larger, cohesive structure, and not just randomly floating out there in the universe. At least, not in this particular area.  

The morals of this post are:

1) If you ever get the chance to visit the VLA, take it in a heartbeat.

2) Reducing data is really hard when you've never done it before.

And, like always,

3) Science is cool!

Size Matters (Of Telescopes, Of Course)

It's really amazing how sometimes old memories are completely off base because you've built them up in your head so much and other times they're spot on.  Luckily for me, this past weekend's trip to NRAO's Green Bank site was even better than I remembered my high school trip being.

It started on Thursday morning.  Tierra (my roommate) and I had decided to go into work early so we could get some work done before we left Charlottesville.  Bad idea.  I didn't realize until I got to the office that I couldn't do anything, anyway, because I didn't have the values I needed to put into my code.  So instead of working, I walked around to the building's various vending machines and gathered snacks for the drive ahead of me.  You can never have too many snacks.

We packed in one suitcase, because we've reached that stage in our roommateship. 

We left Charlottesville a little before 9:00 and got lost almost immediately.  There was some unfortunate miscommunication between the student driving and the one navigating. But we made it to Green Bank in one piece, and just about 30 seconds behind the other van!

After eating a much-needed lunch, we got to tour the Green Bank Telescope, the 100-meter, 16 million-pound monstrosity that has the honor of being the largest movable structure in the world. It took three different elevator rides to travel the 450 feet to the top of the telescope, and it was both beautiful and terrifying.  Looking down on the 2-ish-acre surface of the GBT, I found myself trying to contain an unbelievably strong urge to jump down to the dish and slide from one edge to the other.  Of course I didn't do that, but trust me. It was a hard urge to resist.

See that on the right? That's the GBT. And it's huge. 

Later that night, we went to dinner with the Green Bank students and they invited us to a bonfire at their house.  It had been so long since I had been around fire! It brought back memories of camping, home (where I had a wood-burning stove), and going to school every day smelling like wood smoke. It was a great time, only enhanced by the fact that the Green Bank students have their own private playground.  The fun was short-lived, though, because we had to be in the telescope control room at 7:30 the next morning.

Fast forward through the 6 hours of sleep I got and we get to the actual observation.  We had two and a half hours of observing time on the GBT, which may not sound like much, but it's a crapload of time to give to a bunch of college students!  We are talking about one of the most highly sensitive single-dish telescopes in the country.  We mapped the neutral hydrogen in some nearby galaxies for an hour or so, then we improved the location measurement of a pulsar (basically, a collapsed supernova that spins really quickly).  I know, super casual, right? No, it was really, really cool.

That's about it for our Green Bank trip.  We all made it back to Charlottesville safely, the exhausted new owners of lots of NRAO swag.

Really quickly, I just want to say something about my own research.  We got some new data about our galaxy! My mentor was leading a discussion on galaxy formation, and when someone heard what galaxy we're working with, he told my mentor about some archival optical data.  What does this mean? It means pretty pictures!

Isn't it gorgeous?? I've been working with this galaxy for five weeks, and I had no idea what it looked like.  Now that I know it's basically a supermodel among galaxies, I'm even more excited about my work than I was before! 

WiaN? (What's in a Name)

I said before that I would write a post about acronyms in astronomy, and since I haven't made any breakthroughs in my project in the last week, here it is!

First, I need to make a distinction that I've always thought was pretty important, though others rarely share my opinion.  An acronym is an abbreviation made from the first letters of a series of words that can be pronounced as a new word.  An initialism  is an abbreviation that cannot be pronounced as a word.  Now we can start.

On any given day, I swear 10% of my conversations with people are made up of acronyms or initialisms.  NRAO, ALMA, NAASC, REU, VLA, GBT, FIR.... The list goes on and on, so since it would be impossible for me to write a reasonably-lengthed blog post about all of the abbreviations used in astronomy, I'm only going to talk about the ones that are really important to my internship and the ones I think are really cool.

Let's start big and work our way down.  NRAO.  When people ask me what I'm doing this summer, I usually start by telling them I'm doing some astronomy research.  Most people ask where, and I don't know if it's because I'm a lazy speaker or my quick response reflexes just haven't learned their lesson, but I always say "NRAO, in Virginia."  The other person will inevitably ask what NRAO is, and I'll tell them it's the National Radio Astronomy Observatory, and because they've already asked me three questions, they'll usually just smile and nod, even though they still have a slightly confused look on their face.  NRAO is a federally funded research group founded in the 50's whose focus is (surprise!) radio astronomy.  Oh, and it's a pretty freaking awesome organization.

ALMA, VLA, and GBT all stand for NRAO's different (arrays of) telescopes.  ALMA--which is an acronym, by the way--stands for the Atacama Large-Millimeter/submillimeter Array and is located in the Atacama Desert in Chile.  It's a giant international collaboration with the goal of getting super high-resolution radio data from space.  VLA--an initialism--stands for the Very Large Array (astronomers are really creative) and is located in Socorro, New Mexico.  The VLA is the super famous (I'm using this term very loosely) radio telescope array that can be seen in movies like Contact, Terminator Salvation, and 2010, to name a few.  The GBT is the Green Bank Telescope in Green Bank, West Virginia.  Its claim to fame is that it's the largest movable single-dish telescope in the world.

Now for some fun ones. One of the things that keeps me awake when I'm reading scientific papers is seeing all of the cool abbreviations. HERMES, GOALS, ZEUS, and SKA are just a few.  My favorite, though, is ALFALFA.  I saw this in a paper once and it immediately woke me up and kept me interested for the rest of the paper.  ALFALFA is the Arecibo Legacy Fast ALFA survey to find more pulsars.  (I know I just used an acronym in the description of an acronym, which is kind of copping out, but I couldn't find ALFA's definition to save my life.  If you know it, please let me know!)

Like I said, there's no way I could talk about all of the acronyms and initialisms, because I'm pretty sure that that blog post would take years to write, let alone read.  But now you (hopefully) know a little bit more than you did before.  And please feel free to comment back with questions about abbreviations I mentioned but didn't explain or ones I didn't even name that you want to know more about!  I'd love to help spread the knowledge.


Just FYI, I'm actually heading to do some observing with the GBT tomorrow, so you should definitely come back in a few days to read about those adventures!

It's All Coming Together!

I figured that it was probably time for me to talk about my research project again, and I actually have something to say today! So that's good timing.

Remember that code I was working on for all of last week?  Crushed it!! But I have to say that my greatest accomplishment of the week is finally putting all of the puzzle pieces together and seeing the big picture that is this project.  And I'm going to share that epiphany with you!

I'm going to start with another description of my project.  I'm determining the physical characteristics of a starburst galaxy--a galaxy that's undergone a lot of intense star formation--in the hopes that we'll be able to use it as a template for high-redshift galaxies.  The problem, though, is that galaxies aren't homogeneous creatures.  They vary in density, temperature, and composition throughout.   And that's great and all, but it's really annoying to model.

I'm particularly interested in the variances that come from two different regions of the galaxy--HII regions and PDRs.  HII regions are clumps of ionized hydrogen gas that occur when new stars are formed.  PDRs (Photodissociation Regions) are a little bit harder to explain.  Basically, they're regions in the inter-stellar medium (a fancy phrase for the space between stars) where UV light photons knock electrons off of dust grains.

Diagram of a PDR from Hollenbachs's Article on Dense PDRs

I intentionally made my explanation pretty light, so if you have questions, feel free to comment with them, and hopefully I'll be able to answer. 

Okay, now that you know that, on to my epiphany!  Until this week, I was kind of just going with the flow of my various assignments.  Reduce this data.  Identify these lines. Make these plots. And I did it all, faster than  and with more enjoyment than I expected, but I didn't really know why. But now I do, and here it is, step-by-step.  

1) Take this data, reduce it (this, I've learned, is a simple way of saying "take a massive glob of data and cut out all of the useless stuff to get down to the pretty information that will make you happy").  Why did I have to do this? I was looking for the spectral lines that I would then use to actually figure out the characteristics of the galaxy.  Pretty simple, actually.  

2) Take the newly reduced data and compare it to the models created by a scientist named Rubin.  Why?  Well, apparently, Rubin was modeling the HII regions with different parameters (density, temperature, composition, etc.) and recorded the intensities of different lines that for each individual model.  I compared my data to his to see which model of an HII region most accurately represented the data I had.  

3) Take the intensity values for each line and enter them into an online program that spits out contour maps of the PDRs.  I did this to model the PDRs...not too hard to understand in the grand scheme of things.

4) Use a program called CLOUDY (I will probably write a post in the near future about how much I hate this program) which is usually used to model nebulas.  It turns out that CLOUDY can also be used to model galaxies.  And since we don't know how much of each line's intensity comes from HII regions and how much comes from PDRs, we're using CLOUDY to (basically) figure out the how the galaxy is divided between the two.  

And that's it. Looking back now, I realize that it probably shouldn't have been to hard to see, but that's hindsight bias for you.  I guess the important bit is that I know why I did this stuff now.