A BIMA-SONG radio map of the IC 342 central molecular zone; dots indicate locations of SOFIA/GREAT observations.
Credits: Röllig et al.
An international team of researchers used NASA’s Stratospheric
Observatory for Infrared Astronomy, SOFIA, to make maps of the ring of
molecular clouds that encircles the nucleus of galaxy IC 342.
The maps
determined the proportion of hot gas surrounding young stars as well as
cooler gas available for future star formation. The SOFIA maps indicate
that most of the gas in the central zone of IC 342, like the gas in a
similar region of our Milky Way Galaxy, is heated by already-formed
stars, and relatively little is in dormant clouds of raw material.
At a distance of about 13 million light years, galaxy IC 342 is
considered relatively nearby. It is about the same size and type as our
Milky Way Galaxy, and oriented face-on so we can see its entire disk in
an undistorted perspective. Like our galaxy, IC 342 has a ring of dense
molecular gas clouds surrounding its nucleus in which star formation is
occurring. However, IC 342 is located behind dense interstellar dust
clouds in the plane of the Milky Way, making it difficult to study by
optical telescopes.
The team of researchers from Germany and the Netherlands, led by
Markus Röllig of the University of Cologne, Germany, used the German
Receiver for Astronomy at Terahertz frequencies, GREAT, onboard SOFIA to
scan the center of IC 342 at far-infrared wavelengths to penetrate the
intervening dust clouds. Röllig’s group mapped the strengths of two
far-infrared spectral lines – one line, at a wavelength of 158 microns,
is emitted by ionized carbon, and the other, at 205 microns, is emitted
by ionized nitrogen.
The 158-micron line is produced both by cold interstellar gas that is
the raw material for new stars, and also by hot gas illuminated by
stars that have already finished forming. The 205-micron spectral line
is only emitted by the hot gas around already-formed young stars.
Comparison of the strengths of the two spectral lines allows
researchers to determine of the amount of warm gas versus cool gas in
the clouds.
Röllig’s team found that most of the ionized gas in IC 342’s central
molecular zone (CMZ) is in clouds heated by fully formed stars rather
than in cooler gas found farther out in the zone, like the situation in
the Milky Way’s CMZ. The team’s research was published in Astronomy and Astrophysics, volume 591.
“SOFIA and its powerful GREAT instrument allowed us to map star
formation in the center of IC 342 in unprecedented detail,” said Markus
Röllig of the University of Cologne, Germany, “These measurements are
not possible from ground-based telescopes or existing space telescopes.”
Researchers previously used SOFIA’s GREAT spectrometer for a corresponding study of the Milky Way’s CMZ. That research, published in 2015 by principal investigator W.D. Langer, et. al, appeared in the journal Astronomy & Astrophysics 576, A1; an overview of that study can be found here.
SOFIA is a Boeing 747SP jetliner modified to carry a 100-inch diameter
telescope. It is a joint project of NASA and the German Aerospace
Center, DLR. NASA’s Ames Research Center in California’s Silicon Valley
manages the SOFIA program, science and mission operations in cooperation
with the Universities Space Research Association headquartered in
Columbia, Maryland, and the German SOFIA Institute (DSI) at the
University of Stuttgart. The aircraft is based at NASA’s Armstrong
Flight Research Center's Hangar 703, in Palmdale, California.
For More Information
For information about SOFIA's science mission and scientific instruments, visit: http://www.sofia.usra.edu • http://www.dsi.uni-stuttgart.de/index.en.html
Media Point of Contact
Nicholas A. Veronico
NVeronico@sofia.usra.edu • SOFIA Science Center
NASA Ames Research Center, Moffett Field, California
Editor: Kassandra Bell
Source: NASA/Galaxies
