Query : 2014A&A...572A.102F

2014A&A...572A.102F - Astronomy and Astrophysics, volume 572A, 102-102 (2014/12-1)

VLT/UVES observations of peculiar α abundances in a sub-DLA at z ≃ 1.8 towards the quasar B1101-26.


Abstract (from CDS):

We present a detailed analysis of chemical abundances in a sub-damped Lyman α absorber at z=1.839 towards the quasar B1101-26, based on a very-high-resolution (R∼75000) and high-signal-to-noise (S/N>100) spectrum observed with the UV Visual Echelle spectrograph (UVES) installed on the ESO Very Large Telescope (VLT). The absorption line profiles are resolved into a maximum of eleven velocity components spanning a rest-frame velocity range of ≃200km/s. Detected ions include CII, CIV, NII, OI, MgI, MgII, AlII, AlIII, SiII, SiIII, SiIV, FeII, and possibly SII. The total neutral hydrogen column density is logN(HI)=19.48±0.01. From measurements of column densities and Doppler parameters we estimate element abundances of the above-given elements. The overall metallicity, as traced by [OI/HI], is -1.56±0.01. For the nitrogen-to-oxygen ratio we derive an upper limit of [NI/OI]≤-0.65, which suggests a chemically young absorption line system. This is supported by a supersolar α/Fe ratio of [SiII/FeII]≃0.5. The most striking feature in the observed abundance pattern is an unusually high sulphur-to-oxygen ratio of 0.69≤[SII/OI]≤1.26. We calculate detailed photoionisation models for two subcomponents with Cloudy, and can rule out that ionisation effects alone are responsible for the high S/O ratio. We instead speculate that the high S/O ratio is caused by the combination of several effects, such as specific ionisation conditions in multi-phase gas, unusual relative abundances of heavy elements, and/or dust depletion in a local gas environment that is not well mixed and/or that might be related to star-formation activity in the host galaxy. We discuss the implications of our findings for the interpretation of α-element abundances in metal absorbers at high redshift.

Abstract Copyright:

Journal keyword(s): galaxies: abundances - intergalactic medium - quasars: absorption lines - cosmology: observations

Simbad objects: 4

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Number of rows : 4
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
1 NAME Magellanic Stream HVC 00 32 -30.0           ~ 942 1
2 ESO 113-45 Sy1 01 23 45.7631533440 -58 48 20.808928944   14.08 13.83 13.34   ~ 855 0
3 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 6827 1
4 PG 1101-264 QSO 11 03 25.2993421704 -26 45 15.808554720   16.08 16.02     ~ 246 0

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