The Interstellar Medium of Dwarf Galaxies
In this project we study
properties of the ISM in
galaxies that have low masses. With their shallow potentials, they lack
density waves or stellar bars which in massive galaxies permanently
stir up the
gas. In dwarf galaxies, star formation is patchy and hence allows to
properties of the ISM under strongly varying conditions. Such
may help to understand and properly interpret observations of galaxies
distances or redshifts. While galaxies in the early universe are
similar to low-mass galaxies in the local universe, observations of
galaxies will not be carried out in any detail for a long time to come.
stars form out of molecular material, we are primarily interested in
distribution and properties of the molecular gas, best traced by the
monoxide. In regions with intense UV radiation fields, the CO molecule
on the surfaces of clouds, and atomic carbon can be traced in its
Observations of CO, [CI] and [CII] therefore deliver the best picture
state of the ISM in the vicinity of star-forming regions, which are
as photon-dominated regions (PDRs). Another important issue is the
conversion factor XCO = N(H2)/ICO,
permits to estimate the abundance of molecular gas consisting mainly of
In spite of the debate, its value for the interpretation of high-z
beyond any doubt. Studying it in environments of varying physical
(metallicity, radiation field) is therefore a prime task of Galactic
extragalactic mm astronomy.
We therefore focus our studies on dwarf galaxies with strong to intense star formation, such as for instance NGC 1569, a prototypical object. One may consider its centre as a huge PDR region, heated by the intense starburst. The images below show the Hα (left) and CO (right) emission. The CO emission, mapped with the IRAM 30-m telescope on Pico Veleta, encompasses the innermost brightest portion of NGC 1569. The blow-up contains a map obtained with the IRAM interferometer on Plateau de Bure.
Since a number of powerful
telescopes are being deployed
We map the PDR regions of southern galaxies in the CO(4→3) line and in the carbon fine structure, or [CI] lines, 3P1→3P0 at 490 GHz and 3P2→3P1 at 810 GHz, using the newly deployed NANTEN2 telescope. These observations will provide a beam that nicely matches the measurements with MOPRA. The project will be conducted in collaboration with Yasuo Fukui and Norikazu Mizuno (University of Nagoya), and Carsten Kramer and Jürgen Stutzki (University of Cologne). Summaries of our project goals may be found in two posters, one devoted dwarf galaxies, one dealing with the LMC.