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IPM
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“School of Astronomy”

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Paper   IPM / Astronomy / 15222
School of Astronomy
  Title:   Eclipsing damped Lyα systems in the Sloan Digital Sky Survey Data Release 12
  Author(s): 
1.  H. Fathivavsari
2.  P. Petitjean
3.  N. Jamialahmadi
4.  H. G Khosroshahi
5.  H. Rahmani
6.  H. Finley
7.  P. Noterdaeme
8.  I. Pâris
9.  R. Srianand
  Status:   Published
  Journal: MNRAS
  Year:  2018
  Supported by:            ipm IPM
  Abstract:
We present the results of our automatic search for proximate damped Lyα absorption (PDLA) systems in the quasar spectra from the Sloan Digital Sky Survey Data Release 12. We constrain our search to those PDLAs lying within 1500 km s−1 from the quasar to make sure that the broad DLA absorption trough masks most of the strong Lyα emission from the broad line region (BLR) of the quasar. When the Lyα emission from the BLR is blocked by these so-called eclipsing DLAs, narrow Lyα emission from the host galaxy could be revealed as a narrow emission line (NEL) in the DLA trough. We define a statistical sample of 399 eclipsing DLAs with log N(H I) ≥ 21.10. We divide our statistical sample into three subsamples based on the strength of the NEL detected in the DLA trough. By studying the stacked spectra of these subsamples, we found that absorption from high ionization species are stronger in DLAs with stronger NEL in their absorption core. Moreover, absorption from the excited states of species like Si II are also stronger in DLAs with stronger NEL. We also found no correlation between the luminosity of the Lyα NEL and the quasar luminosity. These observations are consistent with a scenario in which the DLAs with stronger NEL are denser and physically closer to the quasar. We propose that these eclipsing DLAs could be the product of the interaction between infalling and outflowing gas. High resolution spectroscopic observation would be needed to shed some light on the nature of these eclipsing DLAs.

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