Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Colors and color gradients in bulges of galaxies   We have obtained surface photometry in U, B, R and I for a complete optically
selected sample of 45 early-type spiral galaxies, to investigate the colors and
color gradients of spiral bulges. Color profiles in U-R, B-R, U-B and R-I have
been determined in wedges opening on the minor axes. Based on several criteria,
we have defined a subsample of 18 objects whose colors are largely unaffected
by dust. We find that the colors of bulges are predominantly bluer than those
of ellipticals. This result holds even when bulges are compared to ellipticals
of the same luminosity, and indicates that bulges are younger and/or more
metal-poor than elliptical galaxies. Most bulges do not reach solar
metallicities. Bulges show predominantly negative color gradients (bluer
outward) that increases with bulge luminosity. The similarity with ellipticals
suggests that the formation of the disk did not affect the stellar populations
of the bulge in a major way.

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The categories of this paper are: dg-ga
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The categories of this paper are: math-ph
0
The categories of this paper are: hep-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: adap-org
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The categories of this paper are: atom-ph
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The categories of this paper are: q-bio
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The categories of this paper are: mtrl-th
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The categories of this paper are: ao-sci
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The categories of this paper are: alg-geom
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The categories of this paper are: quant-ph
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The categories of this paper are: cs
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The categories of this paper are: q-fin
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The categories of this paper are: patt-sol
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The categories of this paper are: solv-int
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The categories of this paper are: math