Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Hubble Space Telescope Observations of Sub-Damped Lyman-alpha Absorbers
  at z < 0.5, and Implications for Galaxy Chemical Evolution   We report observations of four sub-damped Lyman-alpha (sub-DLA) quasar
absorbers at z<0.5 obtained with the Hubble Space Telescope Cosmic Origins
Spectrograph. We measure the available neutrals or ions of C, N, O, Si, P, S,
Ar, Mn, Fe, and/or Ni. Our data have doubled the sub-DLA metallicity samples at
z<0.5 and improved constraints on sub-DLA chemical evolution. All four of our
sub-DLAs are consistent with near-solar or super-solar metallicities and
relatively modest ionization corrections; observations of more lines and
detailed modeling will help to verify this. Combining our data with
measurements from the literature, we confirm previous suggestions that the
N(HI)-weighted mean metallicity of sub-DLAs exceeds that of DLAs at all
redshifts studied, even after making ionization corrections for sub-DLAs. The
absorber toward PHL 1598 shows significant dust depletion. The absorbers toward
PHL 1226 and PKS 0439-433 show the S/P ratio consistent with solar, i.e., they
lack a profound odd-even effect. The absorber toward Q0439-433 shows
super-solar Mn/Fe. For several sub-DLAs at z<0.5, [N/S] is below the level
expected for secondary N production, suggesting a delay in the release of the
secondary N or a tertiary N production mechanism. We constrain the electron
density using Si II* and C II* absorption. We also report different metallicity
vs. Delta V_90 relations for sub-DLAs and DLAs. For two sub-DLAs with
detections of emission lines from the underlying galaxies, our measurements of
the absorption-line metallicities are consistent with the emission-line
metallicities, suggesting that metallicity gradients are not significant in
these galaxies.

28
The categories of this paper are: alg-geom
33
The categories of this paper are: plasm-ph
20
The categories of this paper are: acc-phys
32
The categories of this paper are: atom-ph
4
The categories of this paper are: cond-mat
1
The categories of this paper are: cs
12
The categories of this paper are: nucl-th
0
The categories of this paper are: hep-ph
16
The categories of this paper are: stat
17
The categories of this paper are: q-fin
10
The categories of this paper are: q-bio
9
The categories of this paper are: nlin
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The categories of this paper are: funct-an
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The categories of this paper are: mtrl-th
5
The categories of this paper are: gr-qc
18
The categories of this paper are: econ