Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The local stellar velocity field via vector spherical harmonics   We analyze the local field of stellar tangential velocities for a sample of
$42 339$ non-binary Hipparcos stars with accurate parallaxes, using a vector
spherical harmonic formalism. We derive simple relations between the parameters
of the classical linear model (Ogorodnikov-Milne) of the local systemic field
and low-degree terms of the general vector harmonic decomposition. Taking
advantage of these relationships we determine the solar velocity with respect
to the local stars of $(V_X,V_Y,V_Z)=(10.5, 18.5, 7.3)\pm 0.1$ \kms. The Oort's
parameters determined by a straightforward least-squares adjustment in vector
spherical harmonics, are $A=14.0\pm 1.4$, $B=-13.1\pm 1.2$, $K=1.1\pm 1.8$, and
$C=-2.9\pm 1.4$ \kmspc. We find a few statistically significant higher degree
harmonic terms, which do not correspond to any parameters in the classical
linear model. One of them, a third-degree electric harmonic, is tentatively
explained as the response to a negative linear gradient of rotation velocity
with distance from the Galactic plane, which we estimate at $\sim -20$ \kmspc.
The most unexpected and unexplained term within the Ogorodnikov-Milne model is
the first-degree magnetic harmonic representing a rigid rotation of the stellar
field about the axis $-Y$ pointing opposite to the direction of rotation. This
harmonic comes out with a statistically robust coefficient $6.2 \pm 0.9$
\kmspc, and is also present in the velocity field of more distant stars. The
ensuing upward vertical motion of stars in the general direction of the
Galactic center and the downward motion in the anticenter direction are
opposite to the vector field expected from the stationary Galactic warp model.

32
The categories of this paper are: atom-ph
7
The categories of this paper are: hep-th
19
The categories of this paper are: eess
28
The categories of this paper are: alg-geom
5
The categories of this paper are: gr-qc
34
The categories of this paper are: chem-ph
10
The categories of this paper are: q-bio
1
The categories of this paper are: cs
27
The categories of this paper are: comp-gas
4
The categories of this paper are: cond-mat
0
The categories of this paper are: hep-ph
16
The categories of this paper are: stat
23
The categories of this paper are: solv-int
8
The categories of this paper are: hep-ex
26
The categories of this paper are: bayes-an
14
The categories of this paper are: math-ph