CENTENNIAL HONORS COLLEGE
Western Illinois University
Undergraduate Research Day 2015
Poster Presentation
Filaments in Galactic Molecular Clouds or Changes in a Distant Quasar?
Alexander Kacija
Faculty Mentors: Esteban Araya and Natalia Andreev
Physics
Recent infrared observations of molecular clouds in the Galaxy have shown the ubiquitous presence of
filamentary structures, from regions of star formation to diffuse interstellar clouds. The filamentary
structure of molecular clouds in our Galaxy can be investigated by absorption studies against quasars.
Araya and collaborators recently reported variability of formaldehyde lines from galactic molecular
clouds observed in absorption towards the quasar NRAO 150 over the period of 1992 to 2009. The
variability was explained by the relative displacement of a filamentary structure with respect to the
background quasar due to the revolution of the Solar System and the molecular cloud around the Galaxy.
However, a different interpretation is possible: changes in the background quasar could have resulted in
the observed variability. In this project, we studied the effect of changes in the structure of NRAO 150 on
the observed variability of the formaldehyde absorption lines. A literature review of scientific
publications reporting high angular resolution observations of NRAO 150 was done. We determined the
rate-of-change of the expansion of the quasar projected at the distance of the foreground molecular cloud,
the projected separation of the two main radio components of the quasar, and their relative intensity. We
conclude that changes in the quasar are unlikely to explain the observed variability of the formaldehyde
lines.