C.D.S. - SIMBAD4 rel 1.7 - 2020.07.14CEST18:53:31

2011A&A...529A..28A - Astronomy and Astrophysics, volume 529A, 28-28 (2011/5-1)

First measurement of Mg isotope abundances at high redshifts and accurate estimate of Δα/α.


Abstract (from CDS):

Abundances of the Mg isotopes 24Mg, 25Mg, and 26Mg can be used to test models of chemical enrichment of interstellar/intergalactic gas clouds. Additionally, because the position of the MgII λλ2796, 2803Å lines is often taken as a reference in computations of possible changes of the fine-structure constant α, it should be clarified to which extent these lines are affected by isotopic shifts. We use a high-resolution spectrum (pixel size ≃1.3km/s) of the quasar HE0001-2340 observed with the UVES/VLT to measure Mg isotope abundances in the intervening absorption-line systems at high redshifts. Line profiles are prepared taking into account possible shifts between the individual exposures. In the line-fitting procedure, the lines of each ion are treated independently. Because of the unique composition of the selected systems - the presence of several transitions of the same ion - we can test the local accuracy of the wavelength scale calibration, which is the main source of errors in the sub-pixel line position measurements. In the system at zabs=0.45, which is probably a fragment of the outflow caused by SN Ia explosion of high-metallicity white dwarf(s), we measured velocity shifts of MgII and MgI lines with respect to other lines (FeI, FeII, CaI, CaII): ΔVMgII=-0.44±0.05km/s, and ΔVMgI=-0.17±0.17km/s. This translates into the isotopic ratio 24Mg:25Mg:26Mg=(19±11):(22±13):(59±6) with a strong relative overabundance of heavy Mg isotopes, (25Mg+26Mg)/24Mg=4, as compared to the solar ratio 24Mg:25Mg:26Mg=79:10:11, and (25Mg+26Mg)/24Mg=0.3. In the systems at zabs=1.58 and zabs=1.65 enriched by AGB-stars we find only upper limits on the content of heavy Mg isotopes (25Mg+ 26Mg)/24Mg≲0.7 and (25Mg+26Mg)/24Mg≲2.6, respectively. At zabs=1.58, we also put a strong constraint on a putative variation of α: Δα/α=(-1.5 ±2.6)x10–6, which is one of the most stringent limits obtained from optical spectra of QSOs. We reveal that the wavelength calibration in the range above 7500Å is subject to systematic wavelength-dependent drifts.

Abstract Copyright:

Journal keyword(s): line: profiles - methods: data analysis - galaxies: abundances - quasars: absorption lines - quasars: individual: HE0001-2340

Simbad objects: 2

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Number of rows : 2

N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
1 QSO J0003-2323 QSO 00 03 44.9144470879 -23 23 55.075352888     16.7     ~ 69 0
2 HE 0515-4414 QSO 05 17 07.6239672230 -44 10 55.578294294 14.74 15.49 15.16     ~ 97 0

    Equat.    Gal    SGal    Ecl

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