Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Near-infrared imaging of 222 nearby Hdelta-strong galaxies from the SDSS   We present UFTI K-band imaging observations of 222 galaxies that are selected
from the Sloan Digital Sky Survey to have unusually strong Hdelta absorption
equivalent widths, W(Hd)>4A. Using GIM2D, the images are fit with
two-dimensional surface brightness models consisting of a simple disk and bulge
component to derive B/T, the fraction of luminosity in the bulge. We find that
the galaxies with weak or absent Halpha or [OII] emission (known as k+a
galaxies) are predominantly bulge-dominated (with a mode of B/T~0.6), while
galaxies with nebular emission (known as e[a] galaxies) are mostly
disk-dominated (B/T~0.1). The morphologies and (r-k) colours of most k+a
galaxies are inconsistent with the hypothesis that they result from the
truncation of star formation in normal, spiral galaxies. However, their (u-g)
and (r-k) colours, as well as their Hdelta line strengths, form a sequence that
is well matched by a model in which >5 per cent of the stellar mass has been
produced in a recent starburst. The lack of scatter in the dust-sensitive (r-k)
colours suggests that the unusual spectra of k+a galaxies are not due to the
effects of dust. The e(a) galaxies, on the other hand, have a colour
distribution that is distinct from the k+a population, and typical of normal or
dusty (tauV~2) spiral galaxies. We conclude that many e(a) galaxies are not
progenitors of k+a galaxies, but are a separate phenomenon. Both k+a and e(a)
galaxies reside in environments (characterized by the local density of galaxies
brighter than Mr=-20) that are typical of normal galaxies and that are
inconsistent with overdense regions like rich galaxy clusters.

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The categories of this paper are: nucl-th
11
The categories of this paper are: hep-lat
17
The categories of this paper are: q-fin
34
The categories of this paper are: chem-ph
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The categories of this paper are: nlin
4
The categories of this paper are: cond-mat
25
The categories of this paper are: patt-sol
0
The categories of this paper are: hep-ph
30
The categories of this paper are: q-alg
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The categories of this paper are: stat
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The categories of this paper are: chao-dyn
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The categories of this paper are: cs
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The categories of this paper are: supr-con
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The categories of this paper are: quant-ph
35
The categories of this paper are: mtrl-th
32
The categories of this paper are: atom-ph