Projects at Harvard

Interstellar Medium and Formation of Stars

Members of the Department use a wide variety of instruments to study
molecular clouds, star formation, and the interstellar medium. They have
special access to the 1.2-m diameter

millimeter-wavelength telescope on
the roof of the Observatory; the 37-m centimeter- and millimeter- wavelength
telescope of
Haystack Observatory in Westford, Massachusetts; the optical
and infrared telescope of the Multiple Mirror Telescope Observatory
(MMT), and
the 1.2-m optical and infrared telescope of the

Whipple Observatory, both
on Mount Hopkins, Arizona. Other facilities operated by SAO are the
NASA Submillimeter Wavelength Astronomical Satellite
(SWAS)
and the
SAO Submillimeter Wavelength Telescope Array
(SMA)
in Hawaii. In addition, members of
the Department use many other telescopes around the world, including those of
the 27-antenna
Very Large Array in New Mexico, the
Very Long Baseline Array,
and the 30-m telescope of the
Institute de Radio Astronomie Millimetrique
in Spain.

Among the topics pursued by members of the Department in this area are
theoretical calculations of the heating, cooling, ionization, and chemical
reactions among atoms and molecules in molecular clouds; observations and
analysis of the structure, motions, and energy balance of molecular clouds
and their condensations; the structure and strength of the interstellar
magnetic field and its role in cloud evolution; initial conditions for
star formation and the collapse of cloud cores to form stars; very young
stars and their circumstellar environs, including interstellar masers;
physical conditions and processes in circumstellar disks and in the
protosolar nebula; the structure and development of multiple star systems;
and the origin of stellar populations.

Magnetic Fields and Turbulence: Magnetism plays a critical
role in many areas of astrophysics, because it controls both
the bulk flow properties of interstellar gas as well as the
motion of individual charged particles. However, we know
surprisingly little about the properties of the Galactic
magnetic field. Harvard researchers are making a concerted
effort to redress this situation, using the Faraday rotation
of the diffuse polarized radio background as a new way to
study structure and turbulence in magnetized gas. Some of
our current projects include using the power spectra of
rotation measures to map the turbulent cascade of ionized
gas in the Galactic plane, using the Faraday rotation of
background point sources to map out the large-scale magnetic
structure of the inner Galaxy, and analyzing polarization
data on the Large Magellanic Cloud in order to carry out the
most detailed study yet of the magnetic field of an external
galaxy. Such data represent a whole new way of studying the
ISM, and can allow a comprehensive study of interstellar
magnetic fields on scales ranging from sub-parsec turbulence
up to global galactic structure.