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Newly discovered Ca II absorbers in the early universe: statistics and system properties

Presentation #141.09 in the session Intergalactic Medium, QSO Absorption Line Systems — iPoster Session.

Published onJun 29, 2022
Newly discovered Ca II absorbers in the early universe: statistics and system properties

In the search of CaIIƛƛ3934, 3969 quasar absorbers with redshifts up to z = 1.4, we have discovered 334 unique new CaIIƛƛ3934, 3969 absorber doublets in quasar spectra from the Sloan Digital Sky Survey (SDSS) Data Release (DR) 7 and 12. With the use of Mg II absorbers as the redshift indicators, the sensitivity for detecting CaIIƛƛ3934, 3969 quasar absorbers has been improved, allowing us to detect a majority of weak absorbers (79% of our catalog has equivalent width (EW) < 0.7Å). We evaluate the physical differences between strong and weak subpopulations through measurements of metallicity and depletion to draw further conclusions about their environments. Comparison of dust depletion supports the indication that weak Ca II absorbers have environments consistent with halo-type gas while strong Ca II absorbers have environments consistent with halo- and disc-type gas. Spanning redshifts 0.4 < z < 1.4, we could probe 60% of our catalog (z ≥ 0.8) for the 2175 Å dust extinction bumps. Dust extinction curves derived from all quasar spectra with the 2175 Å dust absorbers are all consistent with the Large Magellanic Cloud dust extinction law. The 2175 Å dust bumps were detected ≈ 2.4 times more within the strong subpopulation than the weak subpopulation. Reddening measurements show the strong subpopulation to have stronger dust extinction than the weak population. A composite spectrum of the Ca II absorbers from the strong subpopulations clearly shows O II emission, indicating on-going star-formation associated with host galaxies of these strong absorbers. Detailed analysis results will be reported.

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