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Molecular hydrogen absorption systems in sloan digital sky survey

Monthly Notices of the Royal Astronomical Society, ISSN: 1365-2966, Vol: 440, Issue: 1, Page: 225-239
2014
  • 39
    Citations
  • 0
    Usage
  • 8
    Captures
  • 0
    Mentions
  • 0
    Social Media
Metric Options:   Counts1 Year3 Year

Metrics Details

  • Citations
    39
    • Citation Indexes
      39
  • Captures
    8

Article Description

We present a systematic search for molecular hydrogen absorption systems at high redshift in quasar spectra from the Sloan Digital Sky Survey (SDSS)-II Data Release 7 and SDSS-III Data Release 9. We have selected candidates using a modified profile fitting technique taking into account that the Lyα forest can effectively mimic H absorption systems at the resolution of SDSS data. To estimate the confidence level of the detections, we use two methods: a Monte Carlo sampling and an analysis of control samples. The analysis of control samples allows us to define regions of the spectral quality parameter space where H absorption systems can be confidently identified.We find that H absorption systems with column densities logNH > 19 can be detected in only less than 3 per cent of SDSS quasar spectra.We estimate the upper limit on the detection rate of saturated H absorption systems (logNH > 19) in damped Lya (DLA) systems to be about 7 per cent. We provide a sample of 23 confident H absorption system candidates that would be interesting to follow up with high-resolution spectrographs. There is a 1σ r - i colour excess and non-significant A extinction excess in quasar spectra with an H candidate compared to standard DLA-bearing quasar spectra. The equivalent widths of C II, Si II and Al III (but not Fe II) absorptions associated with H candidate DLAs are larger compared to standard DLAs. This is probably related to a larger spread in velocity of the absorption lines in the H-bearing sample. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

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