Abstract
Since the development of radio aperture synthesis techniques, the HI gas has proved ideal to probe the gravitational potential in the outer parts of spiral and dwarf irregular galaxies. The great advantage of the 21 cm observations over optical techniques, such as long-slit spectroscopy and Fabry-Pérot interferometry, is that the HI gas extends to much larger galactocentric distances; in some cases, as much as 5 times the optical diameter (Bothun et al. 1987, Carignan & Freeman 1988, Hoffman et al. 1993). While most optical rotation curves can well be explained only by the luminous matter component, one cannot escape the necessity to postulate the existence of an unseen dark halo component to explain the fact that the HI rotation curves stay flat even at several optical radii.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
