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Q 1101-264
V = 16.1; z = 2.140; exp = 100,200 s; coverage = 3791.8-3847.8 A (one echelle order)
The absorption lines in this QSO spectrum have been the subject of several studies, but those relevant to the Mg II absorbing systems are Carswell et al. (1984) and ("Again") Carswell et al.(1991). The fully reduced and continuum normalized spectra studied in this work were kindly provided by Max Pettini (Pettini & Hunstead, unpublished). The spectra were obtained with the UCL echelle spectrograph on the AAT, with the IPCS as the detector. The resolution is 6 km/s FWHM (or approximately 0.07-0.08 A at the wavelengths covered here); the signal to noise ratio in the region of the Mg II absorbing systems studied in this work is roughly 30.
z=0.356286 |DATA & VOIGT PROFILES| |EWs & AOD COLUMNS| |VP PARAMETERS|
Carswell et al. (1984) claim that this system is not well fit by a single VP component, and in fact they fit six VP components in their high resolution ( ~9 km/s) spectrum (Carswell et al. 1991). Actually, it is likely that the Mg II 2803 transition is blended with a Ly-alpha line, since this system lies just blueward of the Ly-alpha emission line of the QSO. The Mg II 2796 profile has a weak blueward asymmetry (eta(v)/omega(v) = -0.58), and has been well fit by a single VP component. The Mg II 2803 profile shows a strong redward asymmetry and exhibits absorption that is too strong relative to the Mg II 2803 profile (also see Figure 3.13). Note that this shape is counter to the blue-wing asymmetry of the doublet discussed by Carswell et al. (1991), who used it to justify their multicomponent VP decomposition. A naive measurement of the doublet ratio yields 1.13, when in fact the measured column density [log N(MgII) = 12.8 cm^-2] is consistent with the linear part of the curve of growth. All things considered, it is unlikely that unresolved saturation of several optically thick narrow components is giving rise to the peculiar aspects of this absorption profile.
z=0.359153 |DATA & VOIGT PROFILES| |EWs & AOD COLUMNS| |VP PARAMETERS|This system was also first reported by Carswell et al. (1984), who fit the complex profiles with seven VP components. A fit to the UCL/AAT spectra yields six components. The latter fit is virtually identical but for the fit to the saturated portion of the profile (VP component No.2), where the two components found by Carswell et al. (1991) have been consolidated into a single component. However, they simultaneously fit Fe II 2600 and Mg I, which both show strong absorption aligned with this velocity region of the profile. On the other hand, the shapes of these latter transitions in the Carswell et al. (1990) spectra are not suggestive of multiple components. Other ion transitions were not available for the work presented here.
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