1,771 research outputs found
Optimal Fourier filtering of a function that is strictly confined within a sphere
We present an alternative method to filter a distribution, that is strictly
confined within a sphere of given radius , so that its Fourier transform
is optimally confined within another sphere of radius .
In electronic structure methods, it can be used to generate optimized
pseudopotentials, pseudocore charge distributions, and pseudo atomic orbital
basis sets.Comment: 3 pages, 2 figure
Two triangulations methods based on edge refinement
In this paper two curvature adaptive methods of surface triangulation
are presented. Both methods are based on edge refinement to obtain a
triangulation compatible with the curvature requirements. The first
method applies an incremental and constrained Delaunay triangulation
and uses curvature bounds to determine if an edge of the triangulation
is admissible. The second method uses this function also in the edge
refinement process, i.e. in the computation of the location of a
refining point, and in the re-triangulation needed after the insertion
of this refining point. Results are presented, comparing both
approachesPostprint (published version
Analysis and test of the central-blue-spot infall hallmark
The infall of material onto a protostar, in the case of optically thick line
emission, produces an asymmetry in the blue- and red-wing line emission. For an
angularly resolved emission, this translates in a blue central spot in the
first-order moment (intensity weighted velocity) map. An analytical expression
for the first-order moment intensity as a function of the projected distance
was derived, for the cases of infinite and finite infall radius. The effect of
a finite angular resolution, which requires the numerical convolution with the
beam, was also studied. This method was applied to existing data of several
star-forming regions, namely G31.41+0.31 HMC, B335, and LDN 1287, obtaining
good fits to the first-order moment intensity maps, and deriving values of the
central masses onto which the infall is taking place (G31.41+0.31 HMC: 70-120
; B335: 0.1 ; Guitar Core of LDN 1287: 4.8 ). The
central-blue-spot infall hallmark appears to be a robust and reliable indicator
of infall.Comment: Accepted for publication in A&
The L723 low mass star forming protostellar system: resolving a double core
We present 1.35 mm SMA observations around the low-mass Class 0 source IRAS
19156+1906, at the the center of the L723 dark cloud. We detected emission from
dust as well as emission from H2CO, DCN and CN, which arise from two cores, SMA
1 and SMA 2, separated by 2.9" (880 AU). SMA 2 is associated with VLA 2. SiO
5-4 emission is detected, possibly tracing a region of interaction between the
dense envelope and the outflow. We modeled the dust and the H2CO emission from
the two cores: they have similar physical properties but SMA 2 has a larger
p-H2CO abundance than SMA 1. The p-H2CO abundances found are compatible with
the value of the outer part of the circumstellar envelopes associated with
Class 0 sources. SMA 2 is likely more evolved than SMA 1. The kinematics of the
two sources show marginal evidence of infall and rotation motions. The mass
detected by the SMA observation, which trace scales of ~1000 AU, is only a
small fraction of the mass contained in the large scale molecular envelope,
which suggests that L723 is still in a very early phase of star formation.
Despite the apparent quiescent nature of the L723, fragmentation is occurring
at the center of the cloud at different scales. Thus, at 1000 AU the cloud has
fragmented in two cores, SMA 1 and SMA 2. At the same time, at least one of
these cores, SMA 2, has undergone additional fragmentation at scales of 150 AU,
forming a multiple stellar system.Comment: 35 pages, 15 figures. Accepted to the Astrophysical Journa
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