A bird’s eye view of the universe
Telescopes have come a long way since William Herschel invented the first reflecting telescope in 1789. The latest adaptation of his telescope for space astronomy, launched in 2009, has the largest mirror of its kind with a diameter of 3.5 metres and operates at infrared wavelengths of 60 to 600 microns.
“It takes pictures and measures spectra of planets in our solar system like Neptune and Jupiter as well as distant galaxies and everything in between,” said Christine Wilson, professor in the Department of Physics and Astronomy at McMaster University. “Herschel is good at seeing dust emission from galaxies and emission lines in spectra from gas in galaxies.”
Wilson has used the telescope to survey 13 nearby galaxies. “We use high resolution images to see what’s going on with those galaxies and interpret what’s happening in galaxies that are much farther away,” said Wilson. The Herschel mission ran for about four years. When the telescope ran out of liquid helium, a cooling agent, it stoppped working.
Wilson is part of a team that built SPIRE, one of Herschel’s three instruments. SPIRE collected data in the form of images and spectra. Atoms and molecules can be identified by the frequency they emit while the intensity of the lines they produce indicates their quantity. “Carbon monoxide emits very characteristic lines,” Wilson explained. “It’s a very regular pattern that’s easy to recognize.”
Initial spectral data from two galaxies showed strong lines, but the type of molecule producing some of the strongest lines was a mystery. “We didn’t know what it was,” said Wilson. “We didn’t know if it was this molecule or that molecule. If it was methanol, for example, we would have seen more lines.” After consulting with colleagues and the spectral line catalogue, the team concluded that they were looking at water.
“It was a bit of a eureka moment,” said Wilson. “The galaxy is the remnant of a merger between two galaxies. Two nuclei that came together can still be seen separately. It looked like water was coming from one nucleus and not the other. Why does one nucleus have water and the other doesn’t?” Although water is expected to be found in clouds, it’s usually absent when it freezes to dust particles and vapourizes when the dust is heated or shocked.
Wilson is currently focusing more of her research efforts on data from ALMA, the world’s most sophisticated ground-based radio telescope located in the Chilean Andes. “ALMA can see really fine detail of star formation and galaxies,” said Wilson. Astronomers from around the world, including Canada, the United States, Europe, Japan, Taiwan, Korea, and Chile, use ALMA for a wide variety of research.
Research Interests
My work involves all aspects of observational star formation and the molecular interstellar medium, both in our own Galaxy and in other galaxies. I am particularly interested in the properties of giant molecular clouds, the nature of the interstellar medium in dwarf galaxies, the mechanisms regulating star formation rates and efficiencies in galaxies, and the properties of low-mass protostars in nearby molecular clouds. A large part of my observational work is concentrated in the regime of millimeter-wave radio interferometry, where high-resolution images of the emission from molecules in the interstellar medium can be obtained. However, many of these problems require a multi-wavelenght approach and so I have used a variety of optical and radio telescopes, including the Submillimeter Array (SMA), the James Clerk Maxwell Telescope (JCMT), and the Herschel Space Observatory . In 2013-2014 I was on research leave at the Atacama Large Millimeter Array (ALMA) and the North American ALMA Science Center .
Here are some of the projects that my group is currently working on:
- JINGLE, a survey of ~200 nearby galaxies in CO and dust emission using the JCMT
- a large survey of HI-selected galaxies within 25 Mpc to study the dense molecular gas associated with star formation, the gas-to-dust mass ratio, and to look for variations and correlations with galaxy type, mass, star formation rate, metallicity, etc. (The JCMT Nearby Galaxy Legacy Survey, with former graduate student Angus Mok, and roughly 50 collaborators).
- a detailed study of the dense gas in the nearest interacting galaxy system known as "the Antennae" using ALMA and Herschel (involving graduate student Ashley Bemis and former graduate student Max Schirm)
- a major survey of 14 nearby luminous infrared galaxies to determine the distribution, kinematics, and physical conditions of the gas and dust, to compare with simulations of galaxy mergers to understand how the gas and star formation rates evolve during the merger process, and as a well-studied local sample to understand high-redshift submillimeter galaxies (with former graduate student Kaz Sliwa and various collaborators)
From 1999-2014 I was the Canadian Project Scientist for the Atacama Large Millimeter Array (ALMA), which was recommended as the highest priority for Canadian participation in a major, new, ground-based observatory in the report of the Long Range Planning Panel, "The Origins of Structure in the Universe" . ALMA began Early Science observations in September 2011. I am an Associate Scientist with the SPIRE instrument for the Herschel Space Observatory , which operated from 2009 to 2013. I am also a member of the Board of Trustess of Associate Universities, Inc.
Here is where you can find my 2013-2014 sabbatical blog which has both science and personal entries.
Star formation and the interstellar medium in galaxies; observational radio and far-infrared astronomy
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