9 research outputs found
A New Model for the Spiral Structure of the Galaxy. Superposition of 2+4-armed patterns
We investigate the possibility of describing the spiral pattern of the Milky
Way in terms of a model of superposition 2- and 4-armed wave harmonics (the
simplest description, besides pure modes). Two complementary methods are used:
a study of stellar kinematics, and direct tracing of positions of spiral arms.
In the first method, the parameters of the galactic rotation curve and the free
parameters of the spiral density waves were obtained from Cepheid kinematics,
under different assumptions. To turn visible the structure corresponding to
these models, we computed the evolution of an ensemble of N-particles,
simulating the ISM clouds, in the perturbed galactic gravitational field. In
the second method, we present a new analysis of the longitude-velocity (l-v)
diagram of the sample of galactic HII regions, converting positions of spiral
arms in the galactic plane into locii of these arms in the l-v diagram. Both
methods indicate that the ``self-sustained'' model, in which the 2-armed and
4-armed mode have different pitch angles (6 arcdeg and 12 arcdeg, respectively)
is a good description of the disk structure. An important conclusion is that
the Sun happens to be practically at the corotation circle. As an additional
result of our study, we propose an independent test for localization of the
corotation circle in a spiral galaxy: a gap in the radial distribution of
interstellar gas has to be observed in the corotation region.Comment: 17 pages, 9 figures, Latex, uses aas2pp4.st
CCT-K2.1: NRC/VNIIFTRI bilateral comparison of capsule-type standard platinum resistance thermometers from 13.8 K to 273.16 K
NRC publication: Ye
Final Report on CCT-K1: realizations of the ITS-90, 0.65 K to 24.5561 K, using rhodium?iron resistance thermometers
NRC publication: Ye