Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Proper Motion of Water Masers Near NGC1333-SVS13   VLBA observations of water masers toward the region of NGC1333 near SVS13,
the driving source for the well-known Herbig-Haro objects HH7-11, are reported.
Maser emission was observed over four epochs spaced by three weeks during late
1998. SVS13 is associated with the millimeter continuum SED Class I source
SSV13A1. High resolution CO observations have secured the association of the
flow with the continuum object on arc-second scales. A 1998 Aug 12 VLA
observation places the blueshifted masers within 80 AU (0''.2) of the 2.7 mm
position for A1 reported from BIMA. We report observations of two groups of
masers, one redshifted by about 6 km s-1 and one blueshifted by about 2-3 km
s-1, separated by about 100 AU in projected distance along position angle 21
degrees. Redshifted masers were present only in the latter two epochs. During
all epochs, an arclike structure was present with similar morphology; over time
this structure moved relative to the southernmost blue maser toward the
southeast, roughly along the position angle defined by the Herbig-Haro objects,
with a proper motion of about 13 km s-1. Both redshifted and blueshifted masers
are clearly part of the same lobe of the flow; their observed Doppler shifts
are artifacts of the opening angle of the flow. Our data suggest that the
opening angle is about 10 degrees. We measure lower expansion velocities and a
wider opening angle than has been found in some other flows near Class 0 SED
objects, perhaps indicating that the flows open and slow as they age.

1
The categories of this paper are: cs
34
The categories of this paper are: chem-ph
15
The categories of this paper are: nucl-ex
12
The categories of this paper are: nucl-th
17
The categories of this paper are: q-fin
4
The categories of this paper are: cond-mat
31
The categories of this paper are: ao-sci
27
The categories of this paper are: comp-gas
30
The categories of this paper are: q-alg
19
The categories of this paper are: eess
20
The categories of this paper are: acc-phys
35
The categories of this paper are: mtrl-th
25
The categories of this paper are: patt-sol
26
The categories of this paper are: bayes-an
0
The categories of this paper are: hep-ph
37
The categories of this paper are: supr-con