This week’s Hubble fix to give UCI ‘huge lift’

The Orange County Register

May 10th, 2009

By Gary Robbins

Astronauts aboard the shuttle Atlantis will travel about 350 miles above Earth this to service the Hubble Space Telescope, a tricky high wire act that benefit UC Irvine, among scores of other research schools. UCI has about a half-dozen scientists who use Hubble. The researchers include Elizabeth Barton, who recently put the mission into perspective.

Q: How will the upgrade benefit UCI — you and other researchers? What will you be able to do or see that’s been difficult or impossible in the past?

A: Many of us at Irvine use HST for various purposes. Aaron Barth’s research has involved Hubble a lot. In the past he has used the Space Telescope Imaging Spectrograph (STIS) to measure the masses of black holes in nearby galaxies, so I know he is hoping STIS will get fixed. Currently, HST has extremely limited spectroscopic capabilities, so fixing STIS and adding the Cosmic Origins Spectrographs will be huge for UCI.

Astronomer Betsy Barton. Image courtesy of UCI.

Right now, the big problem is that to measure a galaxy-scale black hole mass, you need a spectrum from the very center of the galaxy, which means you need extremely good spatial resolution. HST was the best way to do it for a long time. Now that we have adaptive optics (AO) and AO-related instrumentation at Keck, Aaron and his team can sometimes do it from the ground … but there are times when HST is much better.

(Astronomer) Tammy Smecker-Hane has historically done a lot of wider-field imaging observations of the stellar populations of nearby galaxies, an extremely “hot” field right now. Again, I’m not sure what her current plans are but I bet she’ll be excited if they fix the Advanced Camera for Surveys (ACS).

A postdoctoral researcher here named Misty Bentz, who works with Aaron Barth, was the Principle Investigator on two (!!) successful HST proposals during the last major round of proposals. This feat was amazing in and of itself because the over-subscription rate on HST was huge.

A postdoctoral researcher here named Jeff Cooke, who works with me, recently used HST to take UV spectra of nearby Type IIn supernovae; I was a collaborator on that proposal. I think we used the only spectroscopic capabilities HST currently has, so that project isn’t directly affected by the servicing mission. The supernovae are really exciting, however, because they are the only ones that are really bright in the ultraviolet, which means that you can find them in redshifted objects in the distant universe. Jeff is learning about local examples using the HST data and he recently used a survey from the Canada France Hawaii telescope in conjunction with Keck to discover them at really high redshift.

Nebula M1-67 around Star WR124. Image by Hubble Space Telescope

Personally, when the upgrade has gone through I will likely want to use both the restored imaging capabilities of HST and the Cosmic Origins Spectrograph (COS). I have been working (with Jeff) on using background quasars that are along nearly the same line-of-sight as nearby galaxies, to find the really rarefied gas in the outer halos of galaxies in absorption in the Keck spectra of the quasars. We see it because Magnesium in this gas absorbs light at specific frequencies with a pattern that is easy to identify in the quasar spectrum. This technique has been used before, but we are doing the most systematic survey to date in the nearby universe. We will most likely propose to use HST’s repaired ACS imager and/or the new WFC3 camera to take pictures of the absorbing galaxies to look for “junk” near the quasar that might be responsible for the absorption. We will also likely try for COS spectra well into the ultraviolet to look for the much more abundant hydrogen associated with the magnesium absorption that we are already seeing. Most of the work on magnesium absorbers has been done in the much more distant universe, so it is good to have this nearby sample constructed with Keck data, where we can really get “up close and personal” with the galaxies and understand the origins of the absorption.

Q: I know this is a broad question. But how deeply has Hubble changed scientist’s thinking of the nature of the universe?

A: This is a broad question. I can really only answer it from my personal perspective. In my own mind, Hubble has changed our view of the universe by giving us an up-close look at the most distant galaxies and earliest epochs in the universe. With the Hubble Deep Fields, and now the Hubble Ultra-deep Field, we have been able to see pictures of galaxies whose light has been traveling to us for nearly 13 billion years. We can see that these galaxies look very different from the ones in the nearby universe. Big galaxies formed stars at much greater rates in the past, and they were much more disturbed looking.

The Sombrero galaxy. Image by Hubble Space Telescope

This direct view of the history of galaxy evolution has, I think, created a revolution in the field. We now have both data and theories that make (almost) detailed predictions about what galaxies have been like during their over 13 billion year lifetimes. Hubble made huge contributions to the discovery of dark energy. I think it’s fair to say that the results from Type Ia supernovae discovered by HST convinced most of us that dark energy is real.

Hubble also gave us an up-close perspective on the processes that shape galaxies, like the huge interactions and mergers that happen on hundred-million-year timescales and that completely change the shapes of galaxies. (This will likely happen to the Milky Way, when we merge with Andromeda in a few billion years; we will probably go from being a spiral to being an elliptical galaxy.) Finally, Hubble has given us the opportunity to map out individual stars in nearby galaxies, allowing us to understand that even the puffy little dwarf galaxies that live near us have complex star formation histories.

In other fields, I attribute lots of the more detailed knowledge about how stars are born to HST. I also have vivid memories of the pictures of Comet Shoemaker-Levy crashing into Jupiter…

In terms of changes in the field, I think Hubble helped to teach us about how much we can learn with higher spatial resolution data. It now seems that every big jump in spatial resolution is accompanied by major discoveries that we may not even be anticipating. I imagine that this knowledge has actually pushed the (now rapid) development of adaptive optics from the ground.

From a more human perspective, I also personally attribute something of a culture change in astronomy to Hubble. I think it was really Hubble, and the related images, that brought the field of astronomy closer to the forefront of public knowledge, because of the incredible images and almost daily (sometimes) press releases related to HST and its science. In my mind, my generation of astronomers is more oriented toward sharing our discoveries with the public, and I attribute a lot of that to Hubble’s legacy.