Ghostly strong Lya absorbers in SDSS DR12 Virtual Observatory Resource

Authors
  1. Fathivavsari H.
  2. Published by
    CDS
Abstract

We have searched the Sloan Digital Sky Survey Data Release 12 for ghostly strong Ly{alpha} (DLA) systems. These systems, located at the redshift of the quasars, show strong absorption from low-ionization atomic species but reveal no HI Ly{alpha} absorption. Our search has, for the first time, resulted in a sample of 30 homogeneously selected ghostly absorbers with z_QSO_>2.0. Thirteen of the ghostly absorbers exhibit absorption from other HI Lyman series lines. The lack of Ly{alpha} absorption in these absorbers is consistent with them being dense and compact with projected sizes smaller than the broad-line region of the background quasar. Although uncertain, the estimated median HI column density of these absorbers is logN(HI)~21.0. We compare the properties of ghostly absorbers with those of eclipsing DLAs that are high-column-density absorbers, located within 1500km/s of the quasar emission redshift and showing strong Ly{alpha} emission in their DLA trough. We discover an apparent sequence in the observed properties of these DLAs, with ghostly absorbers showing wider HI kinematics, stronger absorptions from high-ionization species, CII and SiII excited states, and a higher level of dust extinction. Since we estimate that all these absorbers have similar metallicities, logZ/Z_{sun}_~-1.0, we conclude that ghostly absorbers are part of the same population as eclipsing DLAs, except that they are denser and located closer to the central active galactic nuclei.

Keywords
  1. quasars
  2. visible-astronomy
  3. spectroscopy
  4. intergalactic-medium
  5. redshifted
Bibliographic source Bibcode
2020ApJ...888...85F
See also HTML
https://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/888/85
IVOA Identifier IVOID
ivo://CDS.VizieR/J/ApJ/888/85
Document Object Identifer DOI
doi:10.26093/cds/vizier.18880085

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History

2021-07-19T08:38:07Z
Resource record created
2021-07-19T08:38:07Z
Created
2021-10-25T10:15:53Z
Updated

Contact

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