A Review on the Quantum Mechanical Calculation of Rotational Constants for Interstellar Organic Molecules

Interstellar medium consists of gas and dust, even no part of galaxy is completely empty and interstellar dust is most crucial constituent of our Galaxy. ISM has extremely low density, 90% of it contains gas mainly atomic or molecular hydrogen, 9% is helium, and the remaining 1% consists of heavier elements. The spectroscopic observations both in absorption and emission in ISM, along with laboratory studies of sample materials, have increased interest in the study of organic molecules in ISM. Dust grains in ISM absorb and emit energy in the microwave and far-IR part of the spectrum. Here we are presenting the comparison between computed and observed rotational constant for interstellar organic molecules like CN, CO, HCN, OCS and so many other identified interstellar molecules.

Experiments on molecular hydrogen formation on cold ISM dust

We investigate the formation of molecular hydrogen on ISM dust grains at T < 10 K. We use laboratory methods to detect newly formed D2 that is rovibrationally excited at v” = 4, J” = 2. We discover that recombination is catalyzed by pre-existing molecules on the dust surface and present this an important process in the coldest regions of the ISM.

The Spitzer Survey of the Large Magellanic Cloud: SAGE, A Review of Initial Results

We have performed a uniform and unbiased imaging survey of the Large Magellanic Cloud, using the IRAC and MIPS instruments on board the Spitzer Space Telescope. This Spitzer survey of the Large Magellanic Cloud is surveying the agents of a galaxy's evolution (SAGE), the interstellar medium and stars. The SAGE data are nonproprietary and the team has been creating catalogs and improved images for use by the astronomical community. This paper highlights some of the initial results being published by the SAGE team covering the topics of evolved stars and their mass-loss return to the ISM, young stellar objects and the properties of the ISM dust.

Metallicity Evolution of Damped Lyman-α Systems

According to Pei, Fall, & Hauser (1999), the global metallicity evolution of the Universe can be represented by the ratio of the total metal content to the total gas content measured in damped Lyman–α (DLA) systems (the “column density weighted metallicity” à la Pettini). To minimize dust obscuration effects, a DLA sample with negligible dust content is considered, namely, 50 DLAs with log NHI < 20.8. The global metallicity found shows clear evidence of redshift evolution that goes from ~ 1/30 solar at z ~ 4.1 to solar at z ~ 0.4. More generally, DLAs with measured heavy elements probe the ISM of high redshift galaxies. The whole sample collected from the literature contains 75 DLAs. The metallicity is calculated adopting for the dust correction the most general method used so far, based on models of the ISM dust depletions in the Galaxy. The intrinsic metallicity evolution of DLA galaxies is d log ZDLA/dz = −0.33 ± 0.06.