Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Multicolor photometry of 145 of the HII regions in M33   This paper is the first in a series presenting CCD multicolor photometry for
145 HII regions, selected from 369 candidate regions from Boulesteix et al.
(1974), in the nearby spiral galaxy M33. The observations, which covered the
whole area of M33, were carried out by the Beijing Astronomical Observatory
60/90 cm Schmidt Telescope, in 13 intermediate-band filters, covering a range
of wavelength from 3800 to 10000 A. This provides a series of maps which can be
converted to a multicolor map of M33, in pixels of 1.7''*1.7''. Using aperture
photometry we obtain the spectral energy distributions (SEDs) for these HII
regions. We also give their identification charts. Using the relationship
between the BATC intermediate-band system used for the observations and the
UBVRI broad-band system, the magnitudes in the B and V bands are then derived.
Histograms of the magnitudes in V and in B-V are plotted, and the
color-magnitude diagram is also given. The distribution of magnitudes in the V
band shows that the apparent magnitude of almost all the regions is brighter
than 18, corresponding to an absolute magnitude of -6.62 for an assumed
distance modulus of 24.62, which corresponds to a single main sequence O5 star,
while the distribution of color shows that the sample is blue, with a mode
close to -0.05 as would be expected from a range of typical young clusters.

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The categories of this paper are: dg-ga
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The categories of this paper are: acc-phys
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The categories of this paper are: ao-sci
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The categories of this paper are: cmp-lg
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The categories of this paper are: cond-mat
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The categories of this paper are: patt-sol
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The categories of this paper are: hep-lat
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The categories of this paper are: math
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The categories of this paper are: atom-ph
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The categories of this paper are: hep-th
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The categories of this paper are: funct-an
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The categories of this paper are: q-bio
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The categories of this paper are: physics
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The categories of this paper are: alg-geom
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The categories of this paper are: nlin
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The categories of this paper are: mtrl-th