Millimeter-and submillimeter-wave astronomy
The list of astrophysical problems, which are solved by means of millimeter- and submillimeter-wave astronomy, includes studies of the Sun and the planets, the interstellar medium and star formation, activity of galaxies and quasars, the spectrum of and angular variations in the intensity of the cosmic microwave background, etc. The relevance of these problems stimulates a fast technical advance in this field.
Studies of the star formation regions.
One of the results of these surveys was the discovery of regular chemical differentiation in these regsions, which differs significantly from that taking place in the regions of low mass star formation. An increase in the degree of ionization of dense molecular gas near young stars of high luminosity was detected. This can be the reason of the observed variations in the chemical composition. The detected ''ripples'' of the
J = 1—0 HCN emission lines in the regions of massive-star formation along with the observed features of the hyperfine structure of this line, indicates that the dense gas is characterized by significant small-scale inhomogeneity.
The purpose of multi-frequency observations of several such objects (S76, S255, W40) with the use of interferometers and single-dish antennas on the scales from several thousandths to several parsecs was to gain in-depth understanding of the conditions and processes that take place in the star formation regions. As a result, the data about the distribution and properties of dense molecular and ionized gases, characteristics of high-speed bipolar flows, etc. have been obtained. Great attention is given to the study of so-called infrared dark clouds which are assumed to be the earliest stage of formation of massive stars. Important data about their chemical composition and structure have been obtained.
Precision spectroscopy of molecules.
Galactic dark cold clouds, where low-mass stars are formed, are characterized by extremely narrow molecular emission lines. Observations of different lines allow one to conduct detail studies of relative motions of different components in the star formation regions (e.g., dense clumps in diffuse clouds, ions, neutrals, etc.). This requires knowing the frequencies of the corresponding transitions basing on the laboratory data with sufficient accuracy. Additionally, such observations allow one to check the theories, which predict variations of some fundamental constants (specifically, the ratio µ of the masses of the electron and the proton) as a function of the local barion density, with high accuracy that exceeds the accuracy of optical measurements (A. V. Lapinov). Numerous measurement errors have been found in the results obtained at largest radio telescopes, and the upper limits of possible µ variations have been improved significantly.
Molecules in the early Universe.
Chemistry of the Universe soon after formation of the first stars and galaxies is only starting to be studied now. The number of molecules detected at high redshifts
IAP traditionally is the Russian leader in the field of development of radio astronomical receivers operated in the millimeter and submillimeter wavelength ranges. Notable recent developments include the HEMT-based 3-mm receiver for the 14-meter radiotelescope in Finland (V. F. Vdovin, A. M. Shtanyuk, O. S. Bol'shakov, et al.), the dual band radiometer for monitoring of atmosphere transparency at millimeter waves (V. I. Nosov, et al.). IAP is the leading organization responsible for the receiving equipment of the 70-meter radiotelescope which is currently under construction on the Suffa plateau, Uzbekistan.