Where are they now? 
 -- An Interview with KIPAC alum Chihway Chang

Jun 2, 2015

In the series, "Where are they now?" we check in with KIPAC alumni: where they are now, how they've fared since their days exploring particle astrophysics and cosmology at the Institute, and how their KIPAC experiences have shaped their journeys.

Next up is Chihway Chang, a graduate student at KIPAC from 2007–2013, who is currently a postdoctoral researcher at the Institute for Astronomy at ETH Zürich. Thus far, Chihway's academic career has taken her most of the way around the globe, and that's just counting undergraduate and graduate degrees and her first postdoc. But Chihway is not one for sitting still.

LW:  We always start with a question about background. Tell us a little bit about yourself:  Where are you from? Were you interested in astrophysics or perhaps particle physics as an undergrad?

CC:  I grew up in Taiwan and received all my education through my undergraduate degree there—I graduated from the Physics department at National Taiwan University. I had very little exposure to astrophysics throughout my education, though. In undergrad, I did a few research projects on optical experiments, such as shooting lasers into non-linear crystals and measuring soliton effects. I didn't have a clear idea what area I wanted to end up in, but I did like hands-on lab stuff in general. 

The only astro-related class I took was a pretty relaxed observing class. We stayed in the mountains observing for a week, and I certainly enjoyed the experience.  

LW:  What drew you to KIPAC, then? 

CC:  To be completely honest, I knew very little about Stanford and even less about KIPAC before I came. This isn't uncommon for someone coming from my education system, as the application process is all very tight and there’s not that much time to investigate the research areas available at each school. I pretty much just picked a list of physics departments for schools with a range of rankings and started to fill out applications. The idea was that all of these were great schools and if I manage to get into any of them, things can only be good. (Laughs.) 

After coming to Stanford, I discovered KIPAC and really liked the atmosphere in the group, as well as the semi-romantic idea of studying the history of our majestic Universe. 

LW:  What did you work on while you were here? 

CC:  I was interested in hands-on projects at that time, which led me to instrumentation projects. I started working with [KIPAC professor] Rafe Schindler in 2007. In my second year, I settled on the Large Synoptic Survey Telescope (LSST) group, specifically on LSST-related instrumentation, with both Rafe and [KIPAC professor and LSST Director] Steve Kahn as my joint advisors. I continued with some hardware projects with Rafe, and took on a simulation project with Steve, which later became the main part of my thesis. 

I worked with KIPAC Postdocs Andy Rasmussen and Jack Singal on a system to test possible contamination from materials in the LSST camera's cryostat. Later I also worked with Kirk Gilmore and other people at Brookhaven National Lab on testing early prototype CCDs. 

From the beginning of my third year, however, my focus shifted more to the science side—I became interested in gravitational lensing, one of the main science drivers for LSST. Gravitational lensing is what it's called when light rays are bent as they pass massive structures in the Universe. The effect allows us to indirectly “see” most of the mass in the Universe, which unfortunately does not shine and is impossible to see directly in electromagnetic radiation otherwise (hence the name “dark matter”). 

My main interest was to see how the instrumental and atmospheric effects expected for LSST contaminate the measurement of gravitational lensing. To do this, I used a very sophisticated simulation tool that models the LSST instrument and the atmosphere with great detail and see whether there are ways to get around it. I had a lot of fun working with beautiful simulated images, and was happy that I could still work on “hardware,” though in a very virtual way. 

Above: Abell 2218, a rich galaxy cluster composed of thousands of individual galaxies, acting as a gravitational lens for all the galaxies behind it, several of which appear as long, thin arcs in this image. (Credit: NASA, ESA, and Johan Richard (Caltech, USA).) 

LW:  How did you find the position in at ETH Zürich? What's your research there like? 

CC:  I got the position after giving a talk at ETH in the summer of 2013. At the end of grad school I had the urge to go somewhere very, very different, and this job was perfect—it’s foreign enough, yet academically well-connected to the US. Plus, Switzerland is beautiful! (Laughs.) The nominal contract is for three years, but I think there’s flexibility on both sides. 

The main theme of my current research is still gravitational lensing, but I’m now using the data coming out of the Dark Energy Survey (DES), in which KIPAC is also heavily involved. It’s exciting because I actually have very little experience from grad school in working with real data, so I’m learning a lot. (You can find an engaging public blog of things DES is steadily discovering here.)  In fact, I recently participated in one of the first major gravitational lensing results to come out of DES, a big map showing where we believe the dark matter to be distributed, seen through its gravitational effects.

Above: Chihway Chang standing under the Victor M. Blanco Telescope, site of the Dark Energy Survey Camera, located at Cerro Tololo Inter-American Observatory in Chile. (Courtesy Chihway Chang.) 

I’m also starting to learn about radio astronomy, which is one of the areas in the group that is developing recently. The science goal here is to map out neutral hydrogen emissions (sometimes called "HI intensity mapping") in the Universe, which is a new way to look at the matter distribution in the Universe at a very early stage and constrain cosmological models. I’m still learning about this so I'm not going to try to say anything intelligent here. (Laughs.)

LW:  Tell us about your life as a postdoc. 

CC:  I’m very much enjoying my postdoc life at Zürich now. It’s in many ways similar to being a senior grad student, but there’s much more excitement and distraction at the same time. There’s now plenty of meetings and I need to learn a lot of new things, from mentoring students and teaching, new science areas that I’ve not touched before, to living in a foreign country. I have a cool group and it’s fun working with a bunch of smart people. 

Of course there are always frustrations and days when nothing works. And also moments where I just miss the understandable, friendly American English in the bus. But all in all I’m pretty happy with my job. One big plus is that I get to travel a lot due to collaborations. This is very important for me—I get bored staying at the same place for too long, which is why I decided to pick up and leave for Europe in the first place!

LW:  How do you think KIPAC helped you in preparing for your career? 

CC:  KIPAC was a great place to get a PhD. I realized how lucky I was only after the fact (yes, we always take it for granted when we’re in the situation…). Needless to say, the resources—computational, technical and intellectual—were bountiful and people were, and still are, always on top of the newest, hottest astrophysics developments. 

One important aspect of life at KIPAC for me is that I learned to work in a big collaboration. During my PhD research, I had to work with various LSST scientists and engineers at different levels on different things. I learned the importance of communication, and to respect expertise in all areas. KIPAC sets up such an environment that all these areas of expertise merge easily and, even for a grad student, huge collaborations become less intimidating. Now that I’m working with DES, a somewhat smaller collaboration than LSST, I find that what I learned at LSST/KIPAC really helped.

Above: Chihway Chang (third from left) as part of an all-women observing team in the control room of the Victor M. Blanco Telescope, site of the Dark Energy Survey Camera, located at Cerro Tololo Inter-American Observatory in Chile. (Credit: Dark Energy Detectives.)

LW:  What do you miss, if anything, from your days here?

CC:  I miss the outreach activities at KIPAC and SLAC—being a SLAC tour guide was probably one of my best decisions ever in grad school. I learned that the best way to explain science, even to scientists, is to make things simple. Now that the general public around me all speaks Swiss German, it’s hard to do outreach even if I wanted to.

The other thing I miss is the broader physics community at SLAC and Stanford. The ETH astronomy institute I am now in is pretty heavy in observational astronomy. From time to time, I miss being around high-energy and AMO physicists. Nothing against astronomers, it just provides a little more variety in the discussions. (Laughs.)

LW:  Do you have any advice for current grad students at KIPAC?

CC:  To those of you getting your PhD’s—congratulations! It feels pretty cool to be called a Doctor. (Laughs.) 

I don't really feel like I can give much advice going forward. I can just let you know what my humble post-PhD life is like. Different people seek different things in life, and I can’t say that my case is typical. So what you do after graduation—whether you stay in research or not—is really your own decision. 

I like academics, mostly because I enjoy the day-to-day challenges and the people around me. Science people have a certain attitude and simplicity that I really like, or maybe I've just grown so used to it that it feels very comfortable. On the other hand, I’ve never tried working outside academics, so I don’t know, maybe it’s not that different. 

But that's my choice. Remember, whatever you decide, it’ll be fine. You’ve thought it through, you balanced the pros and cons, and it can only be the best decision because you’ll never know what the alternative choices might lead to. So just have fun!   

------ FURTHER LINKS (some included in the body above):

Dark Energy Detectives

The LSST:  Knowing the Telescope Before It is Built

Shear Analysis for LSST Cuts to the Chase

An Interpolation Sensation for Image Relations