Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Arcfinder: An algorithm for the automatic detection of gravitational
  arcs   We present an efficient algorithm designed for and capable of detecting
elongated, thin features such as lines and curves in astronomical images, and
its application to the automatic detection of gravitational arcs. The algorithm
is sufficiently robust to detect such features even if their surface brightness
is near the pixel noise in the image, yet the amount of spurious detections is
low. The algorithm subdivides the image into a grid of overlapping cells which
are iteratively shifted towards a local centre of brightness in their immediate
neighbourhood. It then computes the ellipticity for each cell, and combines
cells with correlated ellipticities into objects. These are combined to graphs
in a next step, which are then further processed to determine properties of the
detected objects. We demonstrate the operation and the efficiency of the
algorithm applying it to HST images of galaxy clusters known to contain
gravitational arcs. The algorithm completes the analysis of an image with
3000x3000 pixels in about 4 seconds on an ordinary desktop PC. We discuss
further applications, the method's remaining problems and possible approaches
to their solution.

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The categories of this paper are: hep-ph
10
The categories of this paper are: q-bio
5
The categories of this paper are: gr-qc
35
The categories of this paper are: mtrl-th
13
The categories of this paper are: quant-ph
25
The categories of this paper are: patt-sol
32
The categories of this paper are: atom-ph
37
The categories of this paper are: supr-con
28
The categories of this paper are: alg-geom
36
The categories of this paper are: cmp-lg
4
The categories of this paper are: cond-mat
14
The categories of this paper are: math-ph
8
The categories of this paper are: hep-ex
1
The categories of this paper are: cs
9
The categories of this paper are: nlin
15
The categories of this paper are: nucl-ex