Updates from the Astrophysics Group



Alma observatory results of the Cartwheel ring galaxy by Drs. James & Sarah Higdon of the COSM Physics Department. The distribution of gas is shown using the yellow contour lines.

To the right are the results of observations taken with the Atacama Large Millimeter Array (ALMA) high in the Chilean Andes by Drs. James & Sarah Higdon of the COSM Physics Department to measure the distribution and motions of cold molecular gas in the Cartwheel ring galaxy. Ring galaxies are created when a small neighbor galaxy crashes through the center of a large spiral galaxy. Such a collision creates a series of rings that move outward at speeds in excess of 150,000 mph. The Cartwheel’s ring appears bright blue in the optical photograph due to the presence of large numbers of young massive stars. These stars form out of giant clouds of cold gas and the ALMA observations will shed light on how stars form. Surprisingly cold gas was only found in the galaxy’s small nucleus and inner ring, which are forming stars slowly. The distribution of gas is shown using yellow contour lines. Additional analysis of the ALMA data have uncovered very small amounts of cold molecular gas in the blue outer ring, which tells us that the rings of these systems form stars very efficiently and have nearly exhausted their gas reservoirs. These results will appear in the Astrophysical Journal Letters.

In addition to observing with ALMA remotely, Georgia Southern Physics Department Professor James Higdon traveled to the high Atacama Plain (3.2-miles above sea level) in September and November 2014 to study star formation in extremely distant galaxies using Zeus-2, a sensitive spectrograph operating at sub-millimeter wavelengths. This project, in collaboration with Cornell University, is intended to better understand the history of star formation in the universe. The September trip was funded by a COSM travel grant.  Dr. Higdon also traveled to the National Radio Astronomy Observatory’s headquarters in Charlottesville, Virginia to conduct the initial analysis of the ALMA observations of the Cartwheel galaxy. This work of Drs. Sarah and James Higdon was funded by an NSF grant to study star formation and the interstellar medium of nuclear starburst rings using observations over a wide range of wavelengths, including ALMA.


Professor Monique Aller took a group of  physics department majors (Will LePain, DJ Cistola, Julian Hershey, and Billy Brewer) to the 2014 Georgia Regional Astronomers Meeting (GRAM) held at the Tellus Museum in Cartersville on Saturday, October 25, 2014, where she presented a talk on “Interstellar Silicate Dust Properties in Quasar Absorption Systems at Redshifts z<1.4”. This annual meeting of astronomers, astrophysicists, and planetary scientists of all backgrounds and expertise featured planetarium demonstrations, scientific posters, talks on topics ranging from cutting-edge research to programs for students, and sunspot viewing through the Tellus Observatory 20″ telescope.

Professor Aller has also begun working on a project to study the co-evolution of dust and gas in distant galaxies, as part of a 3 year (mid 2014-mid 2016) NASA Astrophysics Data Analysis Program grant ($313k) entitled “Connecting the Interstellar Gas and Dust Properties of Distant Galaxies”. Dr. Aller is the science-PI of this project and is leading the study of dust grain properties in distant galaxies over the past 10 billion years, in collaboration with Dr. V.P. Kulkarni (University of South Carolina, PI), who is leading the associated study of the galaxy gas properties, and Dr. E. Dwek (NASA-GSFC, co-I), who will be developing models to explain the observed gas-dust connections in the context of galaxy evolution.

Professor Aller presented her lasted results at the 225th Meeting of the American Astronomical Society held January 4-8, 2015 in Seattle, WA where she presented a poster on “Interstellar Silicate Dust Grain Properties in Distant Galaxies Probed by Quasar Absorption Systems”.

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