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.  

The Future's Gettin' Kinda Close

This past week has been pretty busy.  I've...

~Started working with entirely new data for my research project
~Produced two new codes
~Tried to write a proposal to get observing time on the VLBA (I'm definitely going to have to write a blog post about astronomers and their acronyms)
~Listened to a really hard-to-follow lecture on how to take data and turn it into an image
~Gone on a (short) tour of the tattoo shops in Charlottesville within bussing distance of my apartment (that has nothing to do with astronomy; it was just really fun)

But, most importantly, I've learned a lot about graduate school and the different paths that exist thereafter.

Let's start with last Friday.  A scientist at NRAO invited all of the summer students to his house for an informal discussion about grad school, career paths, networking, and all things future-related.  We were there for about five hours, but I learned so much (and I got to eat Indian food, which is always a positive in my book)!  We discussed GPAs, the GRE, how publishing papers works, the different career options after graduation, and a whole bunch of other stuff.  I left that night with two things on my brain:

1) I need to start meeting more people
2) OH MY GOD I HAVE TO GO TO GRAD SCHOOL AND FIGURE OUT WHAT I'M DOING WITH MY LIFE!!!

(Yes, the caps lock was necessary, because I was that frantic.)

So I took some deep breaths and emailed the TF from the astro classes I took last year.  He was a huge help and pretty much got rid of the crisis altogether.

Come Monday, I was ready for the next discussion about grad schools, and this time, I was excited.  Afterwards, trying to take care of that first thought, I asked someone if they could put me in contact with anyone who did astronomy education and public outreach.  They did, and this morning I met Tania Burchell, the wonderful woman who further opened my eyes to EPO.  She had so much great knowledge and advice to share, and is completely responsible for the creation of my new twitter page (@GoAstroMo because shameless plugs are great).

I guess I should probably say a little something about my research... I'm still coding.  That's about all I can say.  But I have found my new pump-up song.  Every time I hit a roadblock in my project, I listen to this, dance like an idiot, and continue typing away.

Coding Can Be...Fun!

Week 2 is done and it was even better than the first!  If I recall correctly, I was just starting my data analysis the last time I posted.  Here's what I've been up to since:

I finished that code I was working on at the end of the first week!  It took a couple days, but I finally figured out how to loop through the data I had reduced and add up the flux values for a range of selected wavelengths.  I was definitely making it more difficult than it had to be when I first tried to tackle the problem.  The hard part was actually identifying and calculating the different factors that contributed to the error in my intensity measurement.  But I did it!  It was my first solo-constructed script, and I was really damn proud.

Once I was done with that, my mentor had me start learning about modeling right away.  We're using these spectral lines to determine characteristics--temperature, density, metallicity, etc.--of a starburst galaxy, so one of the things I have to do is use the data that's been collected (by the Herschel telescope) to actually create a theoretical model of this galaxy.  My mentor told me to read a paper by Robert Rubin on modeling HII regions.  Most of the paper was filled with pages-long tables of data, which I was then asked to turn into a meaningful model with a code of my own creation.  And that's where it got really fun!

Simplified diagram of an HII Region from this University of California website

HII regions are large clouds of ionized hydrogen gas where a lot of star formation has just happened

Rubin's data came to me in 4-dimensional cubes with dimensions corresponding to metallicity, photon-number, temperature, and density.  My task was to turn it into a 5-dimensional "cube" with an extra axis representing the number of HII clouds in the galaxy model.  I had to do this because we don't know how many clouds the galaxy we're studying has, and creating a fifth dimension of data allows us to see which number of HII clouds most closely matches our own data.  After adding the extra dimension, I had to create chi square grids (which I now understand a lot better than I ever did when they tried to explain it in my introductory mechanics class) and calculate the probability that each model in Rubin's data actually matched our own.  So far, I've been working on this script for two days, and I'm still not done.  But every time I do something right, I can't help but do a little dance in my seat, and that's a great feeling!

On top of all that, I've been to two discussions about grad school and career paths in astronomy in the past 5 days.  I've barely been here for two weeks and they've already managed to convince me that I should pursue a Ph.D in astronomy.  But more on that in the next post, where I'll tell you all about my (new and very tentative) future plans.

Welcome to NRAO

I thought I was done with all of this blogging stuff for a while, but then my advisor suggested that I use this blog to document my summer internship.  It seemed like a pretty excellent idea, and his advice hasn't steered me wrong yet, so here I am. 

For those of you who don't know, I was granted the opportunity to work at the National radio Astronomy Observatory (NRAO) this summer.  When I boarded my train a little over a week ago, I literally only knew two things about the summer ahead:
1) My roommate's name was Tierra (there will almost definitely be more about her in future blogs).
2) My research project had something to do with a galaxy...somewhere in the universe.  

 

I was pretty terrified.  But I had already signed all of the official papers agreeing to show up, and I didn't want to find out what would happen if I didn't.  And I'm so glad I got on that train, because this last week has been amazing!

First, I'll give a quick description of the project I'm working on.  I'm using radio spectral lines to determine the physical characteristics of a galaxy, IRAS 08339+6517.  It's at a redshift of about 0.02, so it's far enough away that it looks like a point source in our images, but close enough that we can get some really good data from it.  Please, please, please ask me questions about the project!  Answering them will help me better understand what I'm doing. 

I started out last week with a bunch of data.  The program I was using, the Herschel Interactive Processing Environment (HIPE), provided the data in varying levels of reduction.  My first assignment was to go through the most processed level and see if I could find and identify the spectral lines.  It was actually pretty simple--look at the graphs and mark where there's a spike.  I found 6! 

My next assignment was to figure out how to reduce the data myself.  That was interesting.  It involved some coding, though since I was provided with a skeleton script, the bulk of my job was to add some values and do some debugging. 

Finally I got to do some analysis!  After 4 days of reducing data (which I understand is nowhere near as long as some people have to do it) to a useable form, I was asked to find the intensity of each spectral line.  I got to make my own script (with some help from my research mentor) and go through what I have identified as the typical stages of coding:

excitement
confusion
annoyance
hair-tearing anger
utter elation

And that was my first week!  I'm not completely sure what the next step is, but I'm here for 10 weeks, so I know I have a lot left to do.