Current Research Interests Chris Churchill Assistant Professor of Astronomy Overview GOAL I study the role of gas in the evolution of galaxies. My goal is to obtain definitive observational data to constrain our models and scenarios of galaxy evolution within the current paradigm of structure growth in the cosmic web. TOOLS I use the spectra of quasars to study absorption lines in the quasar spectra (a field called "quasar absorption lines"). The facilities mostly used are the HIRES on the Keck I telescope, the UVES on The Very Large Telescope, the STIS on the Hubble Space Telescope, and the IRCS on the Subaru telescope. Images of the quasar fields are also utilized in order to measure the properties of the galaxies. the facilities mostly used are the WFPC and ACS on Hubble and more recently SPIcam on the apache Point 3.5 meter telescope. EXPERIMENTAL DESIGN Quasars are very distant highly luminous objects. Their light travels from the farthest reaches of the cosmos, throughout which gas and galaxies are peppered in a giant cosmic web structure. On its path to Earth, the quasar light probes the universe like a geological core sample of space and time. With each interaction with a cloud of gas, the dynamical motion of the gas and the chemical and ionization condistions are recorded in the patterns in the light. By obtaining the spectrum of the quasar, we can chart these patterns and study the conditions of the gas. Since the location of the pattern in the spectrum depends upon the distance (or redshift) of the gas, and since the distance is also a measure of the cosmic moment in which the cloud was probed, this technique allows the gaseous properties to be charted over all cosmic time. (Like a core sample, where the deeper layers are older layers). Some of the gas arises very near galaxies. Figure 1 (above) is an example of the imaging data I use to obtain the properties of the galaxies. Fig. 1 --- This is an HST image of the galaxy field around the quasar 3C 336, which is the bright object in the middle of the image labeled "QSO: 0.927". The redshift of this quasar is z = 0.927. There are many galaxies with lower redshifts, i.e., they are between us and the quasar. Four galaxies and their redshifts are labeled. These galaxies have a large exteneded halo of gas surrounding them and some of the gas actually subtends in directly out in front of the quasar. The properties of the gas can be studeid in the spectrum of the quasar and the properties of the galaxies can be measured in the image and then compared to the gas. In the process, I compare the detailed gas properties to the detailed galaxy properties. and determine in their is any cause and effect processes between the two. These absorption lines provide direct probes of the kinematic, chemical, and ionization conditions in gas surrounding the galaxies. In particular, I study the absorption lines from the strong, resonant MgII 2796, 2803 doublet, which arises in the interstellar medium and halos of galaxies. I am researching how large these halos are (how far from the galaxies they extend), and their geometric shapes around the galaxies. Since my research is focused on the evolution of gas in galaxies with the goal of obtaining observational data that are necessary for placing constraints on models and scenarios of the role of gas in galaxy formation and evolution, I also study the detailed properties of the galaxies. These properties include their morphologies, orientations, and their environments (do they belong to a group or are they isolated in the field?). Fig2. --- The light of the quasar (upper left) passes through the gas in a galaxy (green). The gas comprises several gas clouds, each with its own velocity (speed and direction, shown as blue arrows). The gas absorbs the quasar light which is observed in the spectrum (lower right). Each cloud absorbs light at different velocities. In Figure 2 (above) a schematic of how the light is absorbed by the gas clouds in an intervening galaxy and then recorded in the spectrum is shown. One important observational quantity is the "impact parameter", which is the projected separation between the quasar and the galaxy in the images. This is basically the distance out from the center of the galaxy that the gas is being sampled by the quasar light beam. Figure 3, below, is a diagram showing the galaxy-absorption pairs as a function of impact parameter. Fig 3. --- Each panel is a a galaxy-absorprion pair. The images of the galaxies were obtained with the Hubble Space Telescope. The spectra of the quasars were obtained with HIRES/Keck and UVES/VLT. The transition of the absorption is the MgII 2796 trasition presented in velocity spread. The line down the center provided the impact parameter where the absorption arises (where the quasar sighline samples the halo of gas surrounding the galaxy. (Note: in the images at small impact parameter, the quasar acan be seen.) Getting Detailed: Galaxy--Absorber Kinematic Connections The focus of the project is to observationally quantify the kinematic properties of galaxies that are selected by the presence of absorption lines in quasar spectra. The absorption line arise in the extended gaseous halos of the galaxies, which lie between us and the quasars. These gaseous halos often extend to ten times the diameter of the stellar component of the galaxies; how their dynamical properties relate to the galaxies themselves remains unknown; it is our goal to establish the specifics of these connections. This will involve observations at the Keck, Gemini, and Apache Point Observatory (APO) telescopes. If so, it would imply galaxy halos are coupled to the galaxies both dynamically and geometrically. If not, it would imply, perhaps, that the halos come from the intergalactic medium and are accreted onto the galaxies. The truth probably is a combination of both with varying relative contributions on a galaxy by galaxy basis. This is the figure caption. This is a multi-year project (three years) and is now well established as the Ph.D. thesis for Mr. Glenn Kacprzak, an NMSU astronomy graduate student. Over the 2004-2005 academic period, we accumulated the Hubble Space Telescope images and Keck/HIRES and VLT/UVES quasar spectra for 38 galaxies in collaboration with Dr. Chuck Steidel (Caltech), Dr. Michael Murphy (Cambridge). We will be obtaining spectra of these 38 galaxies at the Apache Point Observatory (APO), Keck, and Gemini telescopes in order to measure the kinematics of the stellar components of the galaxies. These latter data are critical for comparing the galaxy kinematics to the gas kinematics. Going Deeper: The Weakest MgII Absorbers By using the resonant transitions of MgII in absorption in the spectra of quasars as a tracer of the presence of very low column density, low ionization gas, one can explore the distribution of metals in the gaseous medium that is the interface between galaxy halos and intergalactic space. This is important for constraining scenarios of metal production and transport in the early universe. In 1999-2000, I charted the statistical properties of these gas clouds over the redshift regime 0.4 < z < 1.4 (redshift corresponds to cosmic time; z = 0.4 is about 5 billion years ago and z = 1.4 is about 9 billion years ago). Unexplored are the properties of the very weak systems the high redshift regime 1.4 < z < 2.2 (a cosmic time span reaching back to when the universe was 10% of its current age), where active galactic halo formation is expected to be occurring. This is the figure caption. Graduate student Ms. Jessica Evans is analyzing the spectra and finding new systems everyday. With roughly 400 spectra in hand, we anticipate this will require more than a year of effort (1 quasar per day!). Our goal is to then characterize the population of galaxies associated with the population of weak MgII absorbers. Going Further: The Highest Redshift MgII Absorbers Absolutely nothing is known about statistical properties of {\MgII} absorbers for z > 2.2 (actually we have a first result, but I'm not telling yet!). With the recent advent of the sensitive infrared spectrographs, it is now possible to extend our research (described above) all the up to z = 4 (corresponding to when the universe was 5% of its present age. For this very high redshift regime, I am collaborating with Dr. Naoto Kobayashi (Tokyo). We are using the infrared spectrograph (IRCS) on the Subaru telescope; Dr. Kobayashi is the principle scientist of this instrument, which is currently the only facility capable of this research. We have slowly and methodically accumulated 36 infrared quasar spectra since the Fall of 2003. We aim to obtain roughly 100 of these spectra to complete the project. We will be publishing a paper on our first results in the summer of 2006 or (the progress has been slowed by data reduction snags experienced by Dr. Kobayashi). This is the figure caption. The Cosmic Rise of Organic Molecules In the interstellar medium of the Milky Way, organic molecules are seen in abundance in gas clouds. They are observed in the spectra of stars as so--called diffuse interstellar bands (DIBs). It is expected that high redshift damped Ly-aalpha absorbers (DLAs) should also show DIB absorption signatures. Thus, DLAs may provide an astrophysical setting that will allow us to place constraints on the age of the universe when organic molecules first appeared. The goal is to chart the distribution of organic molecules as a function of cosmic time and therefore determine the epoch at which organic molecules first arise in the universe. Since these molecules are the precursors for life on planets, we are aiming to constrain when life could first arise in the universe. Our collaborators are Drs. Ted Snow (Colorado, Boulder), Don York (Chicago), Sara Ellison (Victoria, B.C.), and Naoto Kobayashi (NAOJ/Tokyo). In 2004, we searched six DLAs for DIBs using the APO, Gemini, and VLT. We found that presence of DIBs is far below expectations of those found in the Milky Way. Since the abundance of organic matter is proportional to the chemical enrichment of the gas, it is possible that lower enrichment in DLAs is the culprit, not that the organic molecules are missing altogether. This is the figure caption. We have a new angle that we are noe pursuing that incolves examining the correlations between DIB absorption and PAH emission in ultra-luminous infrared galaxies and starburst galaxies. We are examining if there is evidence that certain DIBs are associated with PAHs. Identifying the carriers of DIBs has been a long standing problem of astrochemstry studies. This work is the Ph.D. thesis of Mr. Brandon Lawton. Text Book on the Subject I am also engaged in the writing of graduate level text book on the topic of Quasar Absorption Lines. I have completed 10 chapters, mostly on review material and spectroscopic techniques. I estimate that I am about half completed with this effort. The book is to be delivered to Cambridge University Press by the summer of 2006 (I'd better get to work!). the book will be part of the Astrophysics Series published by the Press.