ISSN:0094-243X    

DOI:10.1063/1.43959

出版商:AIP    

年代:1992

数据来源: AIP

ISSN:0094-243X    

DOI:10.1063/1.43923

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Many kinds of activity are in evidence in the Galactic center, and there are different kinds on different scales from several A. U. to a few hundred parsecs, although some of them might be related to a common cause. This review provides a brief summary of the various known forms of non‐standard activity there, and of the structures which accompany them. It then examines the question of the identity of the central engine; is it a single massive black hole, a cluster of stellar‐mass black holes, or something else? The total mass of the underluminous matter in the inner few tenths of a parsec is consistent with either of these hypotheses. Finally, the nature of the luminous objects in the central parsec is considered. The pros and cons of the hypotheses that they are massive young stars, collisionally merged stars, or stellar remnants with new atmospheres are discussed.

ISSN:0094-243X    

DOI:10.1063/1.44027

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Near‐infrared imaging and spectroscopy have revealed a rich collection of stars whose character are now being understood as the result of several epochs of star formation. The collection of objects known as IRS16 may be intermediate temperature supergiants which need not contribute significantly to the ionizing radiation present in the central few parsecs.

ISSN:0094-243X    

DOI:10.1063/1.43954

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

When Shapley moved us out of the center of the galaxy, he did so with excessive vigor, to a distance of 20 kpc or more. Since then, published values ofRohave oscillated between large and small, with only marginal evidence for convergence.

ISSN:0094-243X    

DOI:10.1063/1.43966

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We have mapped the CO emission inJ=2→1 andJ=1→0 in a 140‘by 100‘region around Sgr A West at radial velocities from −250 to −170 km s−1with a resolution of 11‘. Our maps reveal that the −190 km s−1molecular feature reported by Liszt (1991) appears to end at the brightest clump in the circum‐nuclear molecular ring (Gu¨stenetal. 1987) and makes a sharp bend about a point 50‘due West of the southern end of the ring. Additionally, the blueshift increases with increasing distance from the ring and Galactic center.

ISSN:0094-243X    

DOI:10.1063/1.43971

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We report a large scale mapping observation of the Galactic center region in the CO (J=2−1) line using the Tokyo‐NRO 60 cm survey telescope. Distribution of the CO (J=2−1) emission in theI‐Vplane suggests that molecular clouds forms a huge complex (NuclearMolecularcloudComplex,NMC). Tracers of star formation activities in the last 106–108years show that star formation has occurred in a ring ∼100 pc in radius. Relative to thisStarFormingRing, the molecular gas is distributed mainly on the positive longitude side. This may indicate that much of the gas in NMC is in transient orbit to fall into the star forming ring or to the nucleus in the near future.

ISSN:0094-243X    

DOI:10.1063/1.43927

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We conducted a survey of the 800 &mgr;m continuum emission from ∼15°×0.2° area around the Galactic center. The 800 &mgr;m continuum emission, which traces temperature weighted column density of dust, shows a strong asymmetry between the positive and negative galactic longitudes, similar to that seen in the molecular data; the bulk of the emission occurs at the positive galactic longitudes. One of the most interesting features in the 800 &mgr;m map is a clumpy ridge of emission apparently connecting Sgr B2 and the Radio Continuum Arc. A molecular counterpart of this ridge can be seen in the CSJ=2→1 data. The ridge contains a number of dust cores without identified far–infrared sources or compact H II regions. These dust cores may be unusually cold.

ISSN:0094-243X    

DOI:10.1063/1.43931

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The excitation of oscillation in the rotating disk of the Galactic center is considered. HII regions are usually thermally stable, because of the heating due to photoelectrons produced by ionizations of the UV radiation from central OB stars. The different point from the usual HII regions is that the Galactic center is the rotational HII region. The coupling between the rotational and non‐adiabatic effects brings the instabilities of nonradial oscillations in the HII region of the Galactic center. Hence, it is possible to say that the spiral and bar‐like structure is the trapped nonradial oscillations of gravity mode, excited by the heating of photoelectrons. Furthermore, the oscillation in the outer region surrounding the HII region is generated by the nonadiabatic resonance, where the epicyclic frequency is near to the Lamb frequency. This oscillation is expected to be the warp motion of the molecular ring.

ISSN:0094-243X    

DOI:10.1063/1.43940

出版商:AIP    

年代:1992

数据来源: AIP

ISSN:0094-243X    

DOI:10.1063/1.43947

出版商:AIP    

年代:1992

数据来源: AIP