Abstract
The distribution and motions of the neutral gas layer in the inner few kpc of the Galaxy, corresponding roughly to the radial extent encompassing the bulge, show properties which distinguish the gas layer in this region from that at larger radii. The inner region is pervaded by a combination of circular and noncircular motions of approximately the same amplitude. This combination is recognized most easily near b = 0° when adequate account is taken of contamination of the HI data by absorption against continuum radiation associated with the Sagittarius source complex in the galactic core. The abrupt kinematic shift in the HI velocities centered on l = 0° is a consequence of distortion of the HI pattern by effects of absorption against sources of continuum radiation confined to the galactic nucleus. This is demonstrated by considering tracers largely unaffected by absorption, like CO, and by considering tracers which follow the absorption directly, like OH and H2CO. The envelope of HI emission around the galactic core is thus not a reliable guide to the run of rotation velocity within the bulge. The noncircular component disqualifies use of the terminal-velocity method to derive the circular-velocity rotation curve for gas lying within the bulge region. The inner-Galaxy gas layer is both tilted, or warped, and flared. The fundamental plane of kinematic symmetry is tilted some 20° with respect to the plane defined by b = 0°. This tilt is revealed by the atomic and by the molecular gas, as well as by the distribution of infrared emission from stars. Lines of sight through the tilted and flared gas layer sample a much more complicated structural and kinematic geometry than prevails in the Galaxy at large. This complicated sampling geometry can, however, be held responsible for a number of characteristics of the observations, including the large line widths observed for the spectral-line tracers and the isolated, but only apparently anomalous, structures occurring in position, velocity maps of the region.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Preview
Unable to display preview. Download preview PDF.
References
Allen, D.A., Hyland, A.R., Jones, T.W. 1983, Monthly Notices Roy. Astron. Soc. 204, 1145
Bahcall, J.N., Schmidt, M., Soneira, R. 1982, Astrophys. J. 258, L23
Bertola, F., Vietri, M., Zeilinger, W.W. 1991, Astrophys. J. 374, L13
Binney, J.J., Gerhard, O.E., Stark, A.A., Bally, J., Uchida, K.I. 1991, Monthly Notices Roy. Astron. Soc. 252, 210
Blitz, L., Spergel, D.N. 1991, Astrophys. J. 379, 631
Burstein, D., Rubin, V.C. 1985, Astrophys. J. 297, 423
Burton, W.B. 1988, in Galactic and Extragalactic Radio Astronomy, G.L. Verschuur, K.I. Kellermann, eds., Springer-Verlag, New York, p. 295
Burton, W.B., Gordon, M.A. 1978, Astron. Astrophys. 63, 7
Burton, W.B., Liszt, H.S. 1978, Astrophys. J. 225, 815
Burton, W.B., Liszt, H.S. 1983, Astron. Astrophys. Suppl. Ser. 52, 63
Burton, W.B., Liszt, H.S. 1992, Astron. Astrophys. Suppl. Ser. in press
Casertano, S., van Gorkom, J.H. 1991, Astron. J. 101, 1234
Ciardullo, R., Rubin, V.C., Jacoby, G.H., Ford, H.C., Ford Jr., W.K. 1988, Astron. J. 95, 438
Clemens, D.P. 1985, Astrophys. J. 295, 422
Cohen, R.J. 1975, Monthly Notices Roy. Astron. Soc. 171, 659
Cohen, R.J., Few, R.W. 1976, Monthly Notices Roy. Astron. Soc. 176, 495
Cohen, R.J., Few, R.W. 1981, Monthly Notices Roy. Astron. Soc. 194, 711
de Zeeuw, P.T. 1992, in Proceedings of IAU Symp. 149 “The Stellar Populations of Galaxies”, in press
Gerhard, O.E., Vietri, M. 1986, Monthly Notices Roy. Astron. Soc. 223, 337
Johnson, H.M. 1961, Astrophys. J. 133, 309
Kerr, F.J. 1967, in Proceedings of IAU Symp. 31 “Radio Astronomy and the Galactic System”, H. van Woerden, (ed.), Academic Press, London, p. 239
Light, E.S., Danielson, R.E., Schwarzschild, M. 1974, Astrophys. J. 194, 257
Lindqvist, M., Winnberg, A., Habing, H.J., Matthews, H.E. 1992, preprint. (See also Lindqvist’s Ph.D. Thesis, Chalmers Institute of Technology 1992)
Liszt, H.S. 1988, in Galactic and Extragalactic Radio Astronomy, G.L. Verschuur, K.I. Kellermann, eds., Springer-Verlag, New York, p. 359
Liszt, H.S., Burton, W.B. 1978, Astrophys. J. 226, 790
Liszt, H.S., Burton, W.B. 1980, Astrophys. J. 236, 779
Liszt, H.S., Burton, W.B., van der Hulst, J.M. 1985, Astron. Astrophys. 142, 245
Matusumoto, T., Hayakawa, S., Koizumi, H., Murakawa, H. 1982, in AIP Conf. No. 83 “The Galactic Center”, G. Riegler, R. Blandford, (eds.), American Institute of Physics, New York, p. 48
Mizutani, K., et al. 1991, preprint
Mulder, W.A., Liem, B.T. 1986, Astron. Astrophys. 157, 148
Okuda, H., Shibai, H., Nakagawa, T., Matsuhara, T., Maihara, T., Mizutani, K., Kobayashi, Y., Hiromoto, N., Low, F.J., Nishimura, T. 1989, in Proceedings of IAU Symp. 136 “The Center of the Galaxy”, M. Morris, (ed.), Kluwer Academic Pub. Co., Dordrecht, p. 145
Oort, J.H. 1977, Ann. Rev. Astron. Astrophys. 15, 295
Peters, W.L. 1975, Astrophys. J. 196, 617
Reich, W., Fürst, E., Steffen, P., Reif, K., Haslem, C.G.T. 1984, Astron. Astrophys. Suppl. Ser. 58, 197
Roberts, W.W. 1979, in Proceedings of IAU Symp. 84 “The Large-Scale Characteristics of the Galaxy”, W.B. Burton, (ed.), Reidel Pub. Co., Dordrecht, p. 175
Rougoor, G.W., Oort, J.H. 1960, Proc. Nat. Acad. Sci., U.S.A. 46, 1
Rubin, V. C. 1983, in Kinematics, Structure, and Dynamics of the Milky Way, W.L.H. Shuter, (ed.), Reidel Pub. Co., Dordrecht, p. 379
Rubin, V.C., Thonnard, N., Ford, W.K., Jr. 1977, Astrophys. J. 217, L1
Sanders, D.B., Solomon, P.M., Scoville, N.Z. 1984, Astrophys. J. 276, 182
Sanders, R.H., Lowinger, T. 1972, Astron. J. 77, 292
Sanders, R.H., Wrixon, G.T. 1972, Astron. Astrophys. 18, 467
Sanders, R.H., Wrixon, G.T. 1973, Astron. Astrophys. 26, 365
Schmidt, M. 1985, in Proceedings of IAU Symp. 106 “The Milky Way Galaxy”, H. van Woerden, R.J. Allen, W.B. Burton, (eds.), Reidel Pub. Co., Dordrecht, p. 75
Shane, W.W. 1972, Astron. Astrophys. 16, 118
Shibai, H., et al. 1991, Astrophys. J. 374, 522
Simonson III, S.C. 1976, Astron. Astrophys. 46, 261
Simonson III, S.C., Mader, G.L. 1973, Astron. Astrophys. 27, 337
Sinha, R.P. 1978, Astron. Astrophys. 69, 227
Sinha, R.P. 1979, in Proceedings of IAU Symp. 84 “The Large-Scale Characteristics of the Galaxy”, W.B. Burton, (ed.), Reidel Pub. Co., Dordrecht, p. 341
Spergel, D.N., Blitz, L. 1992, Nature, submitted
van Albada, G.D. 1985, in Proceedings of IAU Symp. 106 “The Milky Way Galaxy”, H. van Woerden, R.J. Allen, W.B. Burton, (eds.), Reidel Pub. Co., Dordrecht, p. 547
van der Kruit, P.C. 1970, Astron. Astrophys. 4, 462
van Woerden, H., Rougoor, G.W., Oort, J.H. 1957, Compt. Rend. Acad. Sci., Paris 244 1961
Weinberg, M.D. 1991, Astrophys. J. 384, 81
Yuan, C. 1984, Astrophys. J. 281, 600
Author information
Authors and Affiliations
Rights and permissions
Copyright information
© 1992 Springer-Verlag Berlin Heidelberg
About this chapter
Cite this chapter
Burton, W., Liszt, H. (1992). Kinematics and Distribution of Neutral Interstellar Gas in the Galactic Bulge Region. In: The Galactic Interstellar Medium. Saas-Fee Advanced Courses, vol 21. Springer, Berlin, Heidelberg. https://doi.org/10.1007/3-540-31629-9_6
Download citation
DOI: https://doi.org/10.1007/3-540-31629-9_6
Publisher Name: Springer, Berlin, Heidelberg
Print ISBN: 978-3-540-55805-7
Online ISBN: 978-3-540-31629-9
eBook Packages: Springer Book Archive