Astronomer of the Month: Amber Straughn

Each month we will highlight a member of the CANDELS team by presenting an interview introducing them and what it's like to be an astronomer. This month's Astronomer is Amber Straughn.

Tell us a little about yourself!

Hi! I’m Amber Straughn. I work at NASA’s Goddard Space Flight Center in Greenbelt, MD as a Civil Servant Scientist (my formal title is “Research Astrophysicist”) and as the Deputy Project Scientist for James Webb Space Telescope Science Communications. I’m also on Goddard’s WFIRST science team. I grew up in a tiny rural farming town in north-central Arkansas (Bee Branch, to be specific, not that anyone ever knows where that is!). I got my B.S. in Physics at University of Arkansas (Go Razorbacks!) and my M.S. and Ph.D. in Physics at Arizona State University, all the while focusing on astrophysics. I did my first postdoc at Goddard through the NASA Postdoctoral Program, and was hired by NASA in 2011.

What is your specific area of research? What is your role within the CANDELS team? 

I am broadly interested in galaxy evolution, and specifically how galaxies gain their mass over time; as well as the interplay between galaxy interactions, star formation, and supermassive black hole growth. I’ve done work on both galaxy morphologies and also looking at emission-line galaxies using HST grism spectra. I am an original co-I on the CANDELS proposal, which was submitted back when I was a postdoc at Goddard.

What made you want to become an astronomer? At what age did you know you were interested in astronomy? 

I really have always known I wanted to be an astronomer. As I mentioned above, I grew up in an extremely rural part of the US. There wasn’t a lot to do in my hometown, but the night sky was -- and still is -- breathtaking. I was pulled in by the night sky from as early as I can remember. I would drag my family outside to watch meteor showers and eclipses, and I remember asking my parents ridiculous questions about how the Universe worked… I distinctly remember at one point when I was very young and asked my mom something that she didn’t know the answer to, that she told me: “I don’t know. But you can find out the answer yourself someday.” That gave me the initial motivation I needed to pursue this very privileged path of studying the Universe for a living.

What obstacles have you encountered on your path to becoming an astronomer and how did you overcome them? 

Aside from the very real obstacles of getting through the first year of grad school (and qualifying exams, and full loads of classes and TA’ing, etc., that everyone goes through!), I would say that I’m lucky to not have had any huge obstacles. I am, however, a first generation college student. So that did present its own challenges. Coming from a small town, with a tight-knit extended blue-collar family where nobody really ventures too far from home, I did encounter some skepticism and negative feedback from people close to me that didn’t understand what I wanted to do. It was a weird thing to “leave”…leave your hometown, your family. But I’m grateful that my immediate family -- especially my mom -- has always been extremely supportive of me! And of course being a woman in a male-dominated field has at times been challenging. I’m grateful that I’ve never experienced overt harassment or discrimination, but as others have more eloquently elaborated on…sometimes it’s the constant “small” things that add up.

 

Who has been your biggest scientific role model and why? 

I’m very grateful for many role models and mentors I’ve had along my career path. My undergrad academic physics advisor at the University of Arkansas (Lin Oliver) was one of my earliest and most influential mentors. He helped convince me that I could succeed on this path very early on as a not-very-well prepared college student, when I was sometimes worried about my capabilities (imposter syndrome is real!). I’m happy to say that we’re still in contact! 

What is it like to be an astronomer? What is your favorite aspect? 

Is there anything better than doing something you love as a career? It’s wonderful. In my current job at NASA, I do a lot of work on future space missions that enable astronomy, and science communications work, in addition to my own research. I mostly use Hubble data for my research. And for me, Hubble’s always “been up there” (it was launched when I was in elementary school). Working at Goddard, I get to see hardware for the James Webb Space Telescope as it’s being developed, and there’s something that’s so cool about that. 

What motivates you in your research? 

I think it’s generally just the drive to find out something new, and to feel like I’ve contributed -- even if it’s only a tiny bit -- to this grand endeavor of understanding our Universe. 

What is your favorite astronomical facility? 

Well, that would have to be Hubble! I think it’s amazing that not only has Hubble so profoundly changed the way we understand the Universe, but it’s also completely captivated the imagination of the public.

Where do you see yourself in the future? What are your career aspirations? 

Right now, I can’t imagine a place I’d rather work than NASA. But maybe…astronaut? Who knows!

If you could have any astronomy related wish, what would it be? 

Sort of unrelated to actual astronomy research, but if I could wave the magic wand, I’d totally go to Mars.

What is your favorite, most mind-boggling astronomy fact? 

That our physical bodies are literally made of exploded stars. There’s something so poetic about that…and it’s actually literal fact. To get a bit more philosophical…I think it speaks to our interconnectedness as human beings -- to each other, and to the cosmos itself! 

Is there anything else you would like for the public to know about you or astronomy in general? 

I think sometimes the public, and/or kids who think about becoming scientists, think that scientists are these super-intelligent socially-awkward genius loners who spend all their time in the lab or “doing science”. And it’s not surprising that people think that way…that’s often the way that scientists are portrayed in the media. But the reality is that the vast majority of us are regular, everyday people (who do have an aptitude for science and math, and certainly an increased interest in it) -- people who have families, outside hobbies (I’m both a pilot and a faithful yoga practitioner!), and hopes and dreams unrelated to science. Science is a big part of our lives, to be sure, but feel free to talk to us…we’re a lot like you!

Exploring How Galaxies are Transformed

Fig 1: Spiral galaxy M74. Image
Credit: NASA

When we look at galaxies out in the universe, we find that they come in many different types. Some galaxies have beautiful spiral structure (see Figure 1), while others look like irregular blobs of stars and gas. Still others look like featureless spheres of light (see Figure 2). These galaxies aren't only different in appearance, however. We find that we can separate galaxies into broad classes based not only on their shape (or morphology), but also on their stellar mass and how quickly they are forming stars (their star formation rate, or SFR). We find that galaxies with disky morphologies, such as the spiral galaxies mentioned above, tend to be relatively star-forming compared to galaxies with more elliptical morphologies, which appear smooth, round, and featureless and are often no longer forming stars.

Fig 2: Elliptical galaxy ESO 325-
G004. Image Credit: NASA

Since morphology and star formation rate often appear to be correlated in this way, it has been suggested by many that perhaps the processes responsible for shutting off star formation in galaxies are also associated with the formation of an elliptical component, called a "bulge." One such process for shutting off star formation is AGN feedback, which is the name for when a supermassive black hole at the center of a galaxy affects the galaxy around it. When a supermassive black hole accretes material, large amounts of energy are released from the regions near the black hole, which can then heat up or drive out gas from the surrounding galaxy by launching winds or relativistic jets of plasma. The gas that is driven out or heated up is then no longer available to form stars, so the galaxy becomes "quiescent," which is the term we use for galaxies which have stopped forming stars.

Fig 3: Artist's rendition of a galaxy with
AGN-driven outflows. Image Credit:
ESA/ATG medialab

So how does the morphology of the galaxy change, and what triggers the AGN feedback? Here we rely on galaxy mergers and disk instabilities to drive material toward the center of a galaxy in order to both build a bulge component and feed the central supermassive black hole. During a galaxy merger, gas will be driven toward the center of the merger remnant, whereas a disk instability will lead to material being moved to the center of an isolated disk galaxy. In either case, the result is a galaxy with a significant bulge component that is no longer forming stars.

Fig 4: Galaxies in three different redshift bins being

split into the four quadrants of the specific star formation rate-

morphology plane. On the left are galaxies from our model

and on the right are observed galaxies. The greyscale 2D

histogram and contours indicate the density of galaxies

across the plane.

In order to test these ideas, we implemented a merger and disk instability-based AGN feedback prescription in our semi-analytic model (SAM) of galaxy formation and evolution in order to see how well we could reproduce the fraction of galaxies that are star-forming and disk-dominated (SFD) or quiescent and spheroid-dominated (QS) as compared with data from the CANDELS survey (as well as a local sample of galaxies from the GAMA survey). SAMs are a type of simulation which model large numbers of galaxies over the history of the universe. Our SAM evolves a cosmological sample of galaxies forward in time with relatively simple prescriptions for physical processes like the hierarchical growth of structure formation due to the merging of dark matter halos, the heating and cooling of gas, star formation, stellar evolution, supernovae, chemical enrichment of galactic and intergalactic gas, AGN feedback, and starbursts and morphological transformation due to galaxy mergers and disk instabilities. We divided galaxies based on their specific star formation rates (star formation rate divided by stellar mass) and their Sersic index, which is a measure of morphology. A Sersic index of 1 indicates a pure disk, while a Sersic index of 4 indicates a pure bulge. The distribution of galaxies in this plane, as well as our dividing lines for a few of our redshift bins, can be seen in Figure 4. By focusing on this plane, we also found ourselves studying the more "outlying populations": star-forming and spheroid-dominated (SFS) and quiescent and disk-dominated (QD). These populations are more rare but must still be explained by our evolutionary models.

Fig 5: The fraction of galaxies in each of the four populations.
The solid black line represents the observations, while the dashed
red line represents our primary model which includes AGN feedback
and bulge formation triggered by both mergers and disk instabilities.
The dotted blue line represents our model which only includes mergers.

In Figure 5, we can see the evolution of the fraction of galaxies in each of these four populations for both our model and the observations. Our model, which includes disk instabilities as a driver of bulge formation and AGN feedback, reproduces the fraction of SFDs and QSs much better than our model with a merger-only picture. Meanwhile, we reproduce the rough fractions of SFSs and QDs, although we do not quite match how the fractions evolve.

Our model suggests that SFDs are galaxies which have had very quiet histories; they've avoided major mergers and if they have ever been disturbed, they were able to accrete new gas and continue forming stars. QSs, on the other hand, are very likely to have undergone at least one major merger, or perhaps very many minor mergers, which built up a large bulge component and triggered AGN feedback, eventually leading to the cessation of star formation. SFSs in our model are a very short-lived population, the result of a recent merger which has led to bulge formation and a post-trauma starburst. These are likely soon to experience AGN feedback which will transform them into QSs. Finally, QDs are the result of SFDs which have stopped accreting new gas (perhaps due to environmental effects) or are very large and extended, causing their gas not to be dense enough to form stars.

While we do not match the evolution of these populations exactly, it seems we are beginning to be able to capture the very complicated processes responsible for the diverse galaxy population we see all around us.

Astronomer of the Month: Tim Hamilton

Each month we will highlight a member of the CANDELS team by presenting an interview introducing them and what it's like to be an astronomer. This month's Astronomer is Tim Hamilton.

I'm Tim Hamilton, a professor at Ohio's Shawnee State University. In addition to my research, I teach physics and astronomy, and I run the university's Clyde W. Clark Planetarium.

I'm a hillbilly from the Smoky Mountains of East Tennessee, where I grew up on a small farm (mostly forest, actually) bordering the national park. We have a wonderful view of the skies from the pasture, where we'd sometimes take a blanket and a thermos of hot chocolate and lie out to watch the stars. It's dark enough there to see even some globular clusters (a kind of star cluster) with the naked eye, and the Milky Way really stands out well. That was probably what made me interested in astronomy, although I never  became much of an "amateur astronomer" -- no telescopes or astrophotography as a kid. I went to Rhodes College, where I majored in physics. At the time, our program there was geared towards astronomy. Almost all of the physics professors were astronomers, and that gave me my big push into the subject. I went on to the University of Pittsburgh for my  doctorate - -a big change in moving from a tiny college to a big, urban campus. And I did much of my graduate research at the Space Telescope Science Institute, which operates the Hubble Space Telescope. After graduation, I worked at NASA for two years and then started my current job.  I met my wife at a black hole conference about that time, and we were lucky that after we married, we were able to get jobs in similar fields within a reasonable commuting distance of each other. I know some couples who have to live states or even countries away for a few years at a time, and that's rough. As it is, we live close to the college where she teaches, and I have an hour's drive to work, following the Ohio River valley the entire way. It's a beautiful and relaxing commute, and I usually take my camera.

There are several different areas I work on in astronomy. First, I've made a specialty of looking at the galaxies that have quasars in them. The bright glare from the quasar in the galaxy's center poses a real challenge in seeing the fainter galaxy around it, so I've developed ways of erasing that glare from the pictures. Lately, I've branched out into other kinds of galaxies, but I especially enjoy what we call "active galaxies," like quasars, Seyferts, and radio galaxies. On the side, I do a bit of work with "exoplanets" -- planets around other stars.  I'm part of the PANOPTES project, which uses a network of hobbyist digital cameras to find these.  We've got a Canon EOS Rebel with an 85 mm lens mounted on a tripod that tracks the motion of the sky, and we take a series of pictures at night. If an exoplanet eclipses its star, then the star will dim for a few hours, and we can see that in the photos. Ultimately, we want to make this into a global project that will include amateur astronomers, colleges, and even high school students.

Within CANDELS, I'm making simulations of that glare pattern I mentioned earlier. Whether the glare is from a quasar or a star, the pattern will be the same. By making a simulation -- a model of it -- we can either remove the glare from the picture (showing us what else is around that area), or we can measure just how bright the star or quasar is.  That can tell us how massive it is and how much energy it puts out.

Math is my weakest point, academically (I'm actually best at history and foreign language). I'd actually wandered off into particle physics for a couple of years at the beginning of grad school, but I wasn't doing that well in calculating the reactions. So I switched back into astronomy and found my niche. I'm much better at visual things, and analyzing images -- pictures -- is a satisfying piece of work. I'm using plenty of math, of course, but it helps now that I'm applying it to a purpose I understand better.

I don't have a real role model in science. But I enjoy the biographies and anecdotes of scientists; they humanize the work. The one I've enjoyed the most -- maybe the closest one to a role model -- is Richard Feynman, who won the Nobel Prize in 1965.  But it isn't so much his research; it was reading his memoirs, Surely You're Joking, Mr. Feynman!, that inspired me. He was simply interesting and funny.

My institution is is mostly for teaching undergraduates, so research has to be fit into a full lecturing schedule. My enthusiasm for keeping active in astronomy is partly a matter of wanting to succeed personally (ego can be a wonderful motivator when you're not paid for research!) and partly the desire to find out how the universe works. You can get so bogged down in the weeds in a research project -- spending days trying to make software work, or figure out the best way to clean up a picture -- that it's important to keep a perspective on your work and remember where it fits into the big picture. What bigger questions is your research going to answer, and what will that lead to?

Contrary to how astronomers are usually pictured, I spend very little time at a telescope. Much to my great disappointment. Actually, the only telescope I get to use in person is the 8" one I have on campus for the students. See, about the time I was in grad school, the biggest observatories stopped having you come out to the telescope and take the observations yourself.  So instead of you needing to fly out to, say, Hawaii(!) for four days, they'd just take the pictures for you and email you the results. Nuts. Now, the smaller telescopes still do have people go there in person, but for my quasar work, those just can't get the sharp picture I need. Really, though, almost all of my work has been with the Hubble, and since it's in space, I wouldn't get to travel there, anyway. Now, once I have my galaxy pictures, I work on my laptop to analyze them. A MacBook has everything I need to do the work, so I can sit out on my deck at home and do the research without having to be stuck in my college office, staring at the concrete block wall. It makes up a little for the lack of observatory travel.

Since I haven't traveled to observatories, my favorite astronomical facility is the Space Telescope Science Institute, since I did most of my graduate research there. They operate the Hubble Space Telescope now, and when its successor is launched (the James Webb Space Telescope), they will run it, too. In the meantime, they also maintain an enormous archive of images not only from the Hubble but from several other space observatories. Having an archive of digital images changes how some of us do astronomy. The fact that they're all digital means they can be immediately put on a computer and analyzed. (Until about the 1980s, you'd have to scan in the glass plate negatives.) And by keeping all of the old pictures available, you have free access to everything the Hubble has ever looked at. Nobody exhausts all that can be done with the original pictures, and later scientists find lots of new things to discover in them.

I plan to make my career where I am, at Shawnee State. It's not a research-heavy institution, but I'm tenured and the most senior physics professor there, and that gives me the job stability that I want. I attend conferences often enough to stay in the loop. Some research-only people wind up moving every few years, and I wouldn't like that. I also enjoy teaching (grading is another matter), and I'd miss that if I went back to Space Telescope or NASA.  But I do hope to make some bigger discoveries at some point, and if a Nobel prize is out of my reach, I'd settle for publishing a paper that lots of people cited.

Now, while I've avoided writing this up in the question-and-answer style, there are a couple or three questions they have for me that I just can't fit into a narrative, so let me put them here:

If I could have any astronomy-related wish, what would it be? I'm going to stretch the bounds of "astronomy" a bit here. I would wish to be an astronaut. I don't even want to do that to see the stars better or anything else that ties in with my interests in astronomy. I just want to fly a rocket into space. That would be the biggest thrill I can imagine. I went to Space Camp in high school, I read The Space Shuttle Operator's Manual, and I built model rockets. If you haven't seen them already, watch the movies The Right Stuff and Apollo 13. Despite the disasters and near-disasters you see in our early space program, those just made me want to be an astronaut even more.

What is my favorite, most mind-boggling astronomy fact? That might be the slowing of timed down to a stop, as something falls into a black hole. From the view of someone outside the black hole, nothing has ever fallen completely into it! Maybe. See, how would the black hole form in the first place, if that were true? That's actually my wife's field, and there's thinking that the black hole's event horizon is more complicated than that.

What else would I like the public to know about astronomy? Astronomy might be the area of physics that uses the broadest range of knowledge. Any area of physics you can think of can probably be applied to astronomy in some way, and this makes it useful to talk to people in different fields. Astronomy is like the liberal arts of physics, all in itself. On top of the physicists, there are artists who paint renditions of our discoveries, chemists who study the molecules in nebulae, and there are even biologists who work out what kind of life could survive on different planets.

OK, I'd like people to know that and one other thing: There are lots -- LOTS -- of astronomers who are rock climbers. I don't know why. I was at a wedding of two astronomers, and the groomsmen all went climbing the morning of the ceremony. This was not considered unusual. I've got a colleague across the hall who works on stars and has written an instruction book on climbing, and I've got another friend who does mission planning for the New Horizons space probe and has written a guide book on climbing. And then there are just a bunch of others who climb without writing books about it, a correlation that has gone back several decades. If anyone can come up with a theory that explains the connection, I'll be interested.

CANDELS Detects First Light Galaxies

This is a guest post by Ketron Mitchell-Wayne, graduate student at the University of California-Irvine. He and other CANDELS team member recently published a paper in Nature. This paper was the subject of a recent press release. Here, Ketron describes the project and the role that he played.

The cosmic extragalactic background light is a product of many different component emissions throughout all cosmic times. Recent CANDELS observations have opened up a new window of opportunity for measuring this cosmic background light at optical and near infrared wavelengths. We have assembled Hubble frames taken over a 10 year period and mosaiced them to produce some of the deepest images suitable for such a study. With the mosaics, we can study this diffuse, clumpy light that resides behind all the resolved stars and galaxies in the mosaics. With statistics, we have attributed a fraction of this diffuse background to the first light galaxies during reionization. Here's a short summary of the work that I did, over the course of two years, in order to make these very interesting measurements.

My main job for this paper was generating the mosaics and making the statistical measurements. I started working on the data reduction in the summer of 2013 and have spent the better part of the last two years working on the project. Anton Koekemoer had a data reduction pipeline set up for all the incoming CANDELS data, but I wanted to incorporate archival data in our analysis too. So I had a number of reduction steps to complete on thousands of frames, even before making the mosaics (which is in itself very difficult).

Once we had mosaics in multiple bands (left panel of Figure 1), I generated a source mask. We want to isolate the background light signal, so foreground stars and galaxies need to be removed from the image. The dark areas in the second panel of Figure 1 is the source mask (just zeros in the array).

Figure 1: These three panels show different components of near-infrared background light. The one on the left is a mosaic of images taken, the one in the middle shows the intrahalo light seen when masking out all the stars and galaxies, and the one on the right shows the signature of the first galaxies. Credit: Ketron Mitchell-Wynne / UCI

At this point I could start making statistical measurements of the background light in the mosaiced, source-subtracted maps. The methods we used aren't new, but much of the dataset was. We used a very similar method to what was used in the Cosmic Microwave Background (CMB) studies. We look at "empty pixels" (what's left over after source removal) and measure whether or not some group of pixels in one part of the image is correlated with another group of pixels in a different part of the image. This is the angular power spectrum, which quantifies these correlations, as a function of angular scale. This is exactly what the CMB team did to measure the microwave background power spectrum, which is paramount in our understanding of cosmology. 

Figure 2: The brightness of the near-infrared background light as a function
of wavelength. Our new Hubble measurements are highlighted in orange.
The components from the "intrahalo light" (shown above in middle panel)
and the first light galaxies (right panel above) are shown as the blue
and red line, respectively.

I made maps in five different wavelength ranges, or "bands": 0.6, 0.7, 0.85, 1.25 and 1.6 microns. The shortest band is in the yellow range of visible light, and the longest two are in the near-infrared (NIR), which our eyes aren't sensitive to. This wavelength range (1 micron) is special because it is sensitive to Lyman break signatures with a multi-wavelength study, and it is the wavelength at which we expect a signal from the reionization epoch. Figure 2 shows the brightness of the background light in each of these bands. Each of the bands has a common component - what we call "intrahalo light" - which is the light emitted by stars which have been tidally stripped from their host galaxies via mergers or interactions. But in Figure 2 you can see that the brightness drops significantly from the two NIR bands to the shorter bands. We think this is because the NIR bands are picking up, in addition to intrahalo light, a high-redshift signal from the first light galaxies. Because the photons from the reionization era have been redshifted by a factor of about 10, we expect their signal to peak between 0.9 and 1.1 microns, with no shortward contribution below the Lyman break at about 0.8 microns.

We're studying the background light, which traces emission from many different kinds of sources over all cosmological times. So we don't have a direct image of only the first galaxies. With sophisticated modeling, we were able to separate the different component emissions, and isolate the signal from the first galaxies. So what we have, via statistical methods, is a description of the astrophysical environment 500 million years after the big bang. The third panel in Fig 1 is a reconstruction of what they would look like based on our statistical measurements. Cosmological theory suggests that these first light galaxies are the progenitors to our milky way, and all other evolved galaxies.

Astronomer of the Month: Brett Salmon

Each month we will highlight a member of the CANDELS team by presenting an interview introducing them and what it's like to be an astronomer. This month's Astronomer is Brett Salmon.

Tell us a little about yourself!

Hi! My name is Brett Salmon and I’m a finishing graduate student at Texas A&M University. I was born and raised in New Jersey and I am primarily from Washington Township, just outside of Philadelphia. I received my Bachelors degree in Astronomy from Rutgers University in 2010. While at Rutgers I ran for the varsity cross country team, where my fastest 8 km race was 26 and a half minutes. I originally intended on taking a year after undergrad to build my research experience, but applied to Texas A&M on a whim. The program looked great so I decided to go, and I’ve been here for 5 years. 

What is your specific area of research? What is your role within the CANDELS team? 

I am a junior scientist member of the CANDELS team, and have been a part of the high redshift and phot-z working groups. I’ve also been involved in several CANDELS projects on the evolution of distant galaxies. Specifically, I study the physical properties of galaxies in the early universe, including their star-formation rates, stellar masses, star-formation histories, nebular emission, and dust. For the most distant galaxies these features cannot be observed directly, so a chunk of my work involves developing statistical techniques to infer galaxy properties from broadband photometric data, and the limitations of those techniques. 

What made you want to become an astronomer? At what age did you know you were interested in astronomy? 

Like most astronomers, I was hooked at a young age. I recall my mom getting a small (refracting!) telescope when I was about 6. The night sky flourished above our rural home, and our wonder instilled a passion for astronomy. I knew I wanted to learn about the cosmos. However, to be fair, I was 6 and also wanted to be a policeman, fireman, and astronaut. 

What obstacles have you encountered on your path to becoming an astronomer and how did you overcome them? 

The Physics GRE knocked me down. I should have prepared differently and my resulting poor score nearly scared me away from an astro-track. Thankfully, support from professors Andrew Baker and Chuck Keeton at Rutgers reassured me that such standardized tests aren’t reflective of success in the field of astronomy. 

 

Who has been your biggest scientific role model and why? 

The mentors and advisors I’ve had in undergrad and grad school (Casey Papovich) have certainly been influential in shaping my career as a scientist. As far as role models, I’ve always admired those that can purvey complicated scientific phenomena in a way that is fun and understandable to the public, like Carl Sagan, Neil deGrasse Tyson, and Michio Kaku. 

What is it like to be an astronomer? What is your favorite aspect? 

It is hard to distinguish between two changes in my life that happened during the early years of grad school: learning how to think like a scientist, and working like an astronomer. The former is an idea that has broad impact; ideas and concepts are validated (or refuted) through evidence, not artful rhetoric. I think this scientific mindset takes time and experience to fully appreciate. 

The second change involved learning what daily work in astronomy is really like.  I learned that each day is like a crash course in learning new programming, statistics, or data visualization techniques. Every day is different. 

My favorite aspect of astronomy is that it is, at heart, an observational science. Physics, math, and computer science are valuable subjects themselves, but in astronomy they become tools invoked to explain a particular phenomena. Although astronomers draw from multiple disciplines, they do so to figure out how and why a galaxy exploded 10 billion years ago. It feels grounded in context. 

What motivates you in your research? 

I’m motivated by that nagging feeling of wanting to see the answer to a puzzle you’ve been working on for 5 years. There are rarely finite results thanks to the incremental nature of science. As a result, that itch to figure out what’s going on in the data never really goes away. 

What is your favorite astronomical facility? (This could include telescopes or super computers, for example) 

Any telescope on Mauna Kea, Hawaii. I had the pleasure to do some observing at the summit at Gemini Observatory, and the experience was surreal. The clouds illuminated beautiful sunsets and sunrises, which was bittersweet since it also meant poor weather for observations. 

Where do you see yourself in the future? What are your career aspirations? 

In the immediate future I am applying for postdoc positions. I have a passion for astronomy as well as outreach and teaching, so we’ll see where that takes me. 

If you could have any astronomy related wish, what would it be? 

A realistic wish: more funding and public support. A supernatural hypothetical wish: I’d like to see a really bright supernovae go off in the Milky Way (aren’t we due for one?).

What is your favorite, most mind-boggling astronomy fact? 

There are more stars in our Milky Way galaxy like the Sun, than there are people on Earth that have ever lived. 

Is there anything else you would like for the public to know about you or astronomy in general? 

If you want to get into astronomy professionally one day, take computer science and statistics courses. Most, if not all, undergrad curriculum for physics/astronomy does not include these courses, yet I use statistics and programming on a daily basis. Thanks for reading!

BICEP2: Pinning Down Cosmic Inflation

Last month, the scientific collaboration working with the BICEP2 telescope in Antarctica (Background Imaging of Cosmic Extragalactic Polarization) published a surprising first result: after three years of deep microwave imaging of 6% of the sky, they may have found the smoking gun* of the theory of inflation. That smoking gun consists of a series of ripples or fluctuations of the microwave polarization in this part of the sky. These ripples signify that within the first trillionth of a trillionth of a trillionth of second, the universe underwent a rapid, exponential spatial inflation, making its temperature and density nearly homogenous, corresponding to the large-scale density-uniformity of our own observable universe today. Because the universe started out on such a small spatial scale before inflation, quantum alternations in the fabric of spacetime were present. As the universe rapidly inflated in this 10^-32 second of time, those alterations were magnified and manifested themselves as large-scale gravitational waves. These gravitational waves made their imprint in the cosmic microwave background, that image of the hot early universe we see today, in that same background’s polarization information. (Just like ordinary polarized light you can see by turning your head 90 degrees while wearing polarized glasses, radio waves, including microwave radio emission from the early universe, can be polarized in perpendicular directions.) As a result of this imprint, there are patches of sky in which the CMB’s polarization goes one way, and other patches in which the polarization goes the other way:

Fluctuations in the polarization of the cosmic microwave background observed with the BICEP2 telescope. The high and low ripples (orange and blue) indicate a signature of gravitational waves from the era of inflation.

...the orange areas corresponding to one direction of polarization and the blue areas corresponding to another direction of polarization. The width and number of the orange and blue blobs is where the inflationary theory (conceived in the 1980s by Guth and Linde and others) comes in. That theory predicts that if inflation happened and if it produced large-scale gravitational waves, the number of widths of the blobs should be such-and-such. Now take a look at the next image:

Detailed analysis of the above fluctuation image.
The number and size of the blue and orange peaks and troughs
matches theoretical predictions closely.

...now, this image is fairly complicated and was of course given for the target audience of professional cosmologists. What it essentially means, though, is that the number and widths of blue and orange blobs (the black data points with error plusses overlaid) exactly corresponds to the predictions of the theory of inflation (the red curve which they follow).

This is really big news, and could potentially lead to a Nobel Prize. Of course, the result will be followed up with observations from other telescopes, and will probably take years to verify solidly. However, the results are so far looking incredibly good.

I’ve packed a lot into what I have said so far. Let me try to break it down a bit more, and to point out the relationship of this discovery to the research field of galaxy evolution, which we normally discuss in this blog.

First, what motivated the theory of inflation? A number of things, but most importantly it was the horizon problem. The CMB, even when first discovered in 1964 by Penzias and Wilson (later earning them the Nobel Prize), immediately showed itself as a strangely uniform microwave glow throughout the sky. Because of the CMB’s origin in the early universe, just 3% of the universe’s age after the Big Bang, such a strange uniformity was extremely surprising. 

I say “strange uniformity” for the following reason. The CMB’s overall uniformity (i.e., it is as bright when looking up from the north pole as it is when looking up from Antarctica) means that the early universe, 14 billion years ago, was the same temperature in one faraway volume of space as the other faraway volume of space. But the light-travel time from one side of the universe to the other is much longer than the age of the universe itself! (This conundrum is also called the "horizon problem".)

When I cook scrambled eggs, I have a passionate dislike for the brown, flaky parts that accumulate at the bottom of the frying pan. And so I am an obsessive stirrer. And why do we stir scrambled eggs? Because bringing the hotter parts in contact with the cooler parts equilibrates the temperature everywhere. The hot spots down by the hot frying pan won’t get brown. The fact that the early universe was the same temperature in vastly different parts of the universe means that something must have moved faster than light in order to bring the distant parts of the observable universe into contact with one another. Now we know from special relativity that no information can propagate faster than light. But that fact doesn’t prevent space itself from expanding faster than light. In other words, in very, very, very early times, space itself, i.e., the distance between things, would have stretched out at a rate faster than the speed of light. Thus, by a superluminal stretching, the entire observable universe would have been in causal contact with itself (just like stirred eggs) long before the hot-plasma era of the early universe we see in the CMB.

What would cause such a rapid inflation? An increase in spatial scale by 10²⁶ in 10^-32 seconds (as the theory states) is not reminiscent of any energy source known to us. There is a wealth of theoretical literature on the topic, but the short answer is: we don’t know, but it must have been something. (The best guess is that the mechanism would be something called scalar fields.) Although there are deep reasons in particle physics to look for such forces, doesn’t this sound strangely like magic at the end of the day?

But when the phenomenon known as dark energy was discovered in 1997 by CANDELS team member Adam Riess and collaborators, earning them the 2011 Nobel Prize in Physics, the theory of inflation sounded less like theoretical speculation and more like reality. The discovery, as can be read about in other CANDELS blog posts, showed that the universe in its more recent cosmological history (i.e., the space we see at around a redshift of 1) began accelerating in its expansion. It was certainly a far more gradual acceleration than the rapid inflation at 10^-32 seconds, but nonetheless it was an inflation of sorts.

The BICEP2 facility, located at the South Pole.

The discovery of dark energy gave further impetus to search for the predicted polarization pattern in the CMB that would confirm inflationary theory. Now that a surprisingly strong polarization signal has been found (combining the BICEP2 data with data from the Planck mission), a path of independent confirmations lies ahead. The Planck space mission will confirm the result on larger spatial scales. Other ground-based telescopes such as the SPT and the Keck Array (the expanded BICEP2) will probe more deeply. They will verify that the polarization pattern is due to sources in the early universe and not something nearby – foreground galaxies, or even something in the vicinity of our own galaxy. Finally, the presence of gravitational waves in the early universe gives a bright green light for observations of gravitational waves passing the vicinity of the earth today: through pulsar timing (which, as discussed in previous posts, has significant implications for galaxy evolution models), LIGO, and the space-based eLISA mission.

Although I have not spoken much of galaxy evolution, suffice it to remember that had not the early universe inflated and laid the groundwork in which galaxy clusters, galaxies, stars, planets, and you and me would come to be, then I would not be able to write on this galaxy evolution blog about all that has happened in our universe.

*I don’t really like to use the term “smoking gun” in relation to scientific discoveries, because it usually takes a long time for the story to be over, if it ever is over. In this case, however, the results are rather dramatic, making me unable to resist.