Galactic Centre

Fig. 3.43. Variation of CNO isotopic ratios with Galactocentric distance, deduced from mm wave measurements of molecules in molecular clouds, (a) 12C/13C from CO (triangles) and formaldehyde CH2O (circles). (b)14N/15N from HCN (circles) and NH3 (triangles). (c)160/180 from formaldehyde. Solar-System values are indicated by the O sign and Galactic centre values (or a lower limit in the case of 14N/15N) by a filled circle. Adapted from Wilson and Rood (1994).

H. Shapley locates Galactic centre at centre of system of globular clusters, now thought to be 8.5 kpc away. 

The flattening of the Galaxy suggests that it is rotating about an axis perpendicular to the disk, and this is indeed confirmed by direct observation of the large-scale motions of the stars. In fact, they orbit about the galactic centre, making a complete revolution every 200 million years. 

HOC+, the metastable isomer to the well-known HCO+ molecule, has probably been detected in the galactic centre source Sgr B2 (Woods et al. 1983). This identification rests on only the J = 1 - 0 transition, which has been measured in the laboratory by Gudeman and Woods (1982). Since this line lies in the galactic centre near several rotational transitions of HCOOH, there remains some doubt as to the proper identification. An unambiguous interstellar identification of HOC + would therefore have to await the detection of higher rotational transitions, which have been measured in the laboratory by Blake et al. (1983), or isotopically substituted species. In addition, the HCO+/HCO+ abundance ratio of 330 obtained from the observation is at odds witt theoretical determinations (De Frees et al. 1984 Jarrold et al. 1986). 

The Galactic Centre could provide a smoking gun" with radio synchrotron, 7-ray and v data annihilations measure cold dark matter where Milky Way formation began inside-out", some 12 Gyr ago. Accretion models onto the central black hole fail to give sufficient low frequency radio or gamma ray emission to account for the observed fluxes from SagA, and it is tempting to invoke a more exotic alternative. For example, the low frequency radio emission can be explained by spike-enhanced self-absorbed synchrotron emission,... 

D., Aschenbach, B. 2003b. Near-infrared flares from accreting gas around the supermassive black hole at the Galactic Centre, Nature425, 934... 

The principal constituents of interstellar matter are fine dust particles (with a diameter of several pro) and gas. One therefore believes that the dust-to-gas ratio is about constant throughout the galaxy with the possible exception of the galactic centre. Table 1 which is adopted from Winnewisser et al. (1979) summarizes... 

The contemporary observation of the full sky with at least two neutrino telescopes in opposite Earth Hemispheres is an important issue for the study of transient phenomena. Moreover v events detection from the Northern Hemisphere is required to observe the Galactic Centre region (not seen by ICECUBE), already observed by HESS as an intense TeV gamma source. In the Norther Hemisphere a favourable region is offered by the Mediterranean Sea, where several abyssal sites (> 3000 m) close to the coast are present and where it is possible to install the detector near scientific and industrial infrastructures. 

The kinematics of the R CrB, cool HdC and EHe stars are all similar, being those of an old stellar population strongly concentrated towards the Galactic Centre. They do not share the galactic rotation [136,137]. UW Cen and U Aqr may be in halo orbits. Such a distribution is consistent with a wide range of metallicity. 

A real advantage of working in the FIR is that both polar and non-polar chains may be searched for. Indeed, the lowest bending frequency of C3 has been studied in the laboratory [69], and tentatively detected toward the galactic centre source Sgr B2 [70]. Other large molecules such as polycyclic aromatic hydrocarbons (anthracene, pyrene, perylene, etc) or biomolecules such as glycine or uracil also possess low-frequency FIR vibrations, and can be produced in sizable quantities in supersonic expansions through heated planar nozzles... 

Fig. 1. Reconstruction of a simulated coded mask observation of the galactic centre region...

The Galactic Centre currently poses the most severe problems from a... 

In talking about infrared emission from HII regions, I ain supposed to review the observational results and discuss possible theoretical interpretation. Recent reviews on the observational aspects are available in the literature (Wynn-Williams and Becklin, 1974 Olthof, 1975 see also the Proceedings of the 8th ESLAB Symposium on "HII Regions and the Galactic Centre", ed. by A.F.M. Moorwood,... 

Molecular clouds. HII and HI regions. Galactic centre. Nature and distribu-. tion of dust. Protostars. Stellar evolution. Development of HII regions. Multiband photometry (X/AX 1-20). XX 20 ym - 1 mm. High spatial resolution mapping. Polarimetry. 

I demonstTate with examples om the Galactic centre the astronomical potency of imaging spectroscopy, derived by scanning a slit across a portion of sky to produce a data cube with one spectral and two spatial dimensions. 

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