Studying the small scale ISM structure with supernovae
European Organization for Astronomical Research in the
Southern Hemisphere (ESO), K. Schwarzschild-str. 2,
85748 Garching b. München, Germany e-mail: email@example.com
2 Herschel Science Centre, European Space Astronomy Centre, ESA, PO Box 78, 28691 Madrid, Spain
3 Institute of Astronomy, K.U. Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
4 Department of Physics and Astronomy. University of Oklahoma, Norman, OK 73019, USA
5 Department of Physics and Astronomy, Dartmouth College, Hanover, NH 03755-3528, Germany
Accepted: 25 February 2010
Aims. In this work we explore the possibility of using the fast expansion of a type Ia supernova photosphere to detect extra-galactic ISM column density variations on spatial scales of ~100 AU on time scales of a few months.
Methods. We constructed a simple model which describes the expansion of the photodisk and the effects of a patchy interstellar cloud on the observed equivalent width of D lines. Using this model we derived the behavior of the equivalent width as a function of time, spatial scale and amplitude of the column density fluctuations.
Results. The calculations show that isolated, small (≤100 AU) clouds with column densities exceeding a few 1011 cm-2 would be easily detected. In contrast, the effects of a more realistic, patchy ISM become measurable in a fraction of cases, and for peak-to-peak variations larger than ~1012 cm-2 on a scale of 1000 AU.
Conclusions. The proposed technique provides a unique way to probe the extra-galactic small scale structure, which is out of reach for any of the methods used so far. The same tool can also be applied to study the sub-AU Galactic ISM structure.
Key words: supernovae: general / ISM: clouds / ISM: structure / ISM: general
© ESO, 2010