Monday, June 18, 2012

Astronomy in the Last Frontier

What better place to hear about the current frontiers of astronomy and astrophysics than the Last Frontier? That's what hundreds of astronomers from all over the world were thinking as they arrived in Anchorage, Alaska for the 220th meeting of the American Astronomical Society (AAS). Alaska truly is a land of astronomical marvels. It is known for the Aurora Borealis, caused by ejections of charged particles from the sun, as they follow the magnetic field lines of the Earth and crash down on the polar regions. And today, one week away from the summer solstice, Alaska earns its name as the land of the midnight sun. The sun circles overhead for 20 hours before briefly dipping below the horizon in four hour long twilight.

CANDELS scientists Tommy Wiklind, Tomas Dahlen,
and Ray Lucas discuss redshift measurements
in Anchorage, Credit: Christina Williams
The frontiers of astronomy are vast indeed. There have been presentations all week about cutting edge research, from the formation of the first galaxies in the universe to exoplanets in our own galaxy, from star-formation to cosmology. The CANDELS collaboration has been making waves here as well. Many members are here presenting their work using CANDELS data. Some highlights: Norman Grogin is studying distant galaxies whose central black holes are actively accreting matter, mysteriously varying the luminosity of their nuclei. New breakthroughs are being made in astronomical image construction by Ray Lucas. Tomas Dahlen showed how CANDELS data are helping us learn better ways to estimate the redshifts of galaxies, and how massive they are. And Viviana Aquaviva is showing what the colors of galaxies can tell us, for example, about the age of their stars. Among the CANDELS results being presented at the AAS meeting were mine. I'm a graduate student studying galaxy evolution, and this is an amazing opportunity to share my dissertation research on high-redshift galaxies, and why some of them stop forming stars only three billion years after the big bang. One of my favorite parts of science is finding out what other scientists think about new results, so the poster sessions at the AAS meetings are the perfect venue. People come to see the presentation, which is displayed in a large hall with other presentations organized by astronomical topic, and there are many hours for great discussions, and meeting new scientists.

Sandy Faber receives the Henry Russell Norris Lectureship
Credit: Christina Williams
Here in Anchorage, CANDELS Principle Investigator Sandy Faber was awarded the Henry Norris Russell Lectureship of the American Astronomical Society, for her lifetime of contributions to the field of Astronomy. These include breakthroughs in galaxy evolution and the distribution of dark matter, astronomical instrumentation and her dedication to mentoring the world's future leaders in Astronomy. Her Russell Lecture Tuesday morning was a status report of the cold dark matter theory of galaxy evolution. Generally, we think that the universe is made of up of mostly cold dark matter and dark energy. All we can see and interact with is the icing on the cake: ordinary matter and the light it emits. Where the ordinary matter ends up (in stars and galaxies) and how the galaxies cluster together in a cosmic web of structure is largely dependent on the properties of the dark matter and its gravitational attraction.

So, what was Sandy's conclusion about galaxy evolution and our understanding of it? While we appear to have some things remarkably right in terms of the theory of how dark matter behaves, even though we can't directly observe it, there is still much work to do to understand how the universe makes real galaxies. For example, the theory of cold dark matter predicts a large number of tiny galaxies, "satellites", which orbit larger more massive galaxies, and we only find a fraction of them. Another example, in simulations of galaxy evolution, we don't understand how galaxies receive new gas from the intergalactic medium. As we look farther back in time, galaxies form stars at remarkably higher rates than today, and we don't understand why the star formation in galaxies suddenly stopped. This is an area where CANDELS data will be indispensable to fill in the blanks, and help us solve some of the still outstanding mysteries of how galaxies evolve through cosmic time. Stay tuned for new results, the next AAS meeting is in January 2013 in Long Beach, California. What new breakthroughs will we be presenting there?

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