Ms. Erika T. Hamden is awarded an NSF Astronomy and Astrophysics Postdoctoral Fellowship to carry out a program of research and education at the California Institute of Technology. Our current understanding the formation of galaxies has thus far relied on our ability to directly detect light from the stars of those galaxies. But directly observing galaxies isn't enough to tell us exactly how a particular galaxy has formed or why one galaxy differs from another. According to high-resolution computer simulations, there should be large reservoirs of gas and dust outside of galaxies, providing new inflowing material and feeding star formation. This inflowing material is combined with hot gas blown off by explosive events in the galaxy itself, such as exploding stars. This gas, surrounding and feeding the galaxy, is known as the Circumgalactic Medium (CGM), and is extremely dim. The CGM has only been observed indirectly, by looking at what the gas does to light from a more distant object, which cannot create a full picture of the gas. The PI will observe this gas directly for the first time by taking advantage of new instruments. Direct detection of the CGM gas will help determine how the types of galaxies observed today were formed. The PI will also work within the community of public schools around Caltech to create a program that teaches public school science teachers about astronomy and telescope use and that gives them the tools to start astronomy classes and clubs at their schools. These classes will then work on a small project building their own instrumentation that can be used to take data.
This project will directly detect the CGM for the first time using newly built and proposed IFUs to observe x, y, velocity, temperature, and metallicity information. The observing program will incorporate existing absorption line studies to select galaxies with known MgII absorption. The outer regions and halos of these galaxies should have bright metal emission lines in the Keck Cosmic Web Imager (KCWI) redshift range. Hamden will also use KCWI, and the Cosmic Web Imager (CWI) on Palomar, to detect redshifted emission lines from galaxies observed by the Faint Intergalactic Redshifted Balloon (FIREBall, a forthcoming UV multi-object spectrograph, attempting to detect the CGM at UV wavelengths). Maps of UV emission from FIREBall can be paired with maps of other metal lines from KCWI and CWI to provide temperature diagnostics, density measurements, and velocity information for a galaxy halo. Accurate sky background subtraction is the key to observing the CGM in emission and determining the conditions and history of galaxy growth.
