高红移下Mg同位素丰度的首次测量和Delta α/α的精确估计
First measurement of Mg isotope abundances at high redshifts and accurate estimate of Delta alpha/alpha
摘要：
我们利用UVES/VLT观测到的类星体HE 0001 -2340的高分辨率光谱，测量了高红移处中间吸收线系统中的Mg同位素丰度。根据单个暴露之间可能的变化编制线轮廓。由于所选系统的独特组成-存在相同离子的几个跃迁-我们可以测试波长标度校准的局部精度，这是子像素线位置测量中的主要误差来源。在zabs = 0.45的系统中（可能是高金属丰度白矮星（s）的SN Ia爆发引起的外流的碎片），我们测量了MgII和MgI线相对于其他线（FeI，FeII，CaI，CaII）的速度位移：Δ V（MgII）= -0.44 +/- 0.05 km/s和Δ V（MgI）= -0.17 +/- 0.17$ km/s。这转化为同位素比24 Mg：25 Mg：26 Mg =（19 +/- 11）：（22 +/- 13）：（59 +/- 6），与太阳比24 Mg：25 Mg：26 Mg = 79：10：11和（25 Mg +26 Mg）/24 Mg = 0.3相比，重Mg同位素的相对丰度较强，（25 Mg +26 Mg）/24 Mg = 4。在zabs = 1.58时，我们对α的假定变化施加了强约束：Δ α/α =（-1.5 +/- 2.6）x10^{-6}，这是从类星体的光谱中获得的最严格的限制之一。我们发现，在7500 A以上的范围内的波长校准受到系统的波长依赖性漂移。
英文摘要：
(Abridged) We use a high-resolution spectrum 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 accounting for possible shifts between the individual exposures. Due to 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 relative to other lines (FeI, FeII, CaI, CaII): Delta V(MgII) = -0.44 +/- 0.05 km/s and Delta V(MgI) = -0.17 +/- 0.17$ km/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. At zabs = 1.58, we put a strong constraint on a putative variation of alpha: Delta alpha/alpha = (-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 7500 A is subject to systematic wavelength-dependent drifts.
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