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Q 1622+235
V = 18.3; z = 0.927; exp = 19,240 s; coverage = 3726.9-6191.0
This QSO field has been exhaustively studied by Steidel et al. (1997), who built upon the work of Steidel & Dickinson (1992) and SS92. Steidel et al. reported six definite absorbing systems (with associated galaxies) at z = 0.3181, 0.3675, 0.4721, 0.6563, 0.7973, and 0.8912, and three potential absorbing galaxies at z = 0.5652, 0.6352, and 0.7016. The HIRES spectrum of this QSO ranges in signal to noise from 2-20 per resolution element. Thus, the absorption profiles are not without their ambiguity. Four of the six definite systems have been detected in the HIRES spectrum, z = 0.4721, 0.6563, 0.7973, and 0.8912. The spectrum was searched for the potential absorbers (upon request of C. Steidel), and only the 0.7016 system turned up a tentative detection using a 5-sigma EW(rest) limit (see Steidel et al. for details). The z = 0.4721 Mg II profiles, though clearly detected because they are broad and fully saturated, are not included in this work because of the very low signal to noise. Three systems are included in this work. The VP decomposition for only the 0.7971 system is robust.
z=0.656114 |DATA & VOIGT PROFILES| |EWs & AOD COLUMNS| |VP PARAMETERS|
This system is a damped Ly-alpha system (Steidel et al.). The Mg II profiles have full widths ~150 km/s and are fully saturated with some component structure in both wings. Fe II 2587 is blended with Fe II 2383 at z = 0.7971. It is likely that the Fe II from the 0.7971 system is negligible, given the null detection of all other observed Fe II transitions in that system. The Fe II 2587 transition may exhibit a double "horn" shape, but the signal to noise is poor and the elevated flux in the profile may be nothing but noise fluctuations. The VP profile fits are shown with the spectrum (three VP components were fit), but they are not to be believed. Damped systems usually exhibit Mn II absorption (Lu et al. 1996). but none is seen to 5-sigma EW(rest) = 0.18 A, though higher signal to noise may reveal absorption, especially in the 2594 transition. The Ca II 3934, 3969 doublet was not covered by the HIRES format. It is interesting to note that SS92 and Steidel & Dickinson (1992) both reported an unphysical Mg II doublet ratio and suggested the presence of a second Mg II absorber at ~+800 km/s from which the 2796 transition is blended with the 2803 transition of this system. In the HIRES spectrum the doublet ratio of this system was measured to be 1.10+/-0.03.
z=0.797107 |DATA & VOIGT PROFILES| |EWs & AOD COLUMNS| |VP PARAMETERS|This system, at first, was an unidentified triple-component absorption profile in the HIRES spectrum. C. Steidel (private communication) suggested a search for the Mg II doublet at this redshift based upon a C IV detection in his FOS/HST spectrum. The unidentified profile was then determined to be the 2803 tranistion of the Mg II doublet, the 2796 transition having been lost due to the ink mark on the HIRES Tektronics CCD. The profile is comprised of three subsystems evenly split by ~75 k/ms to which a total of four VP components were fit. The total velocity spread is ~140 km/s. The Mn II 2576 transition and the Ca II 3934, 3969 doublet were not covered by the HIRES format. The other two Mn II tranistions showed no absorption to the EW(rest) limits given in Table~\ref{tab:q1622z0.7}. Note that Fe II 2382 is blended with the Fe II 2587 transition at z = 0.6561. Given the null detection of all other observed Fe II transitions in the 0.7971 system, it is likely that the Fe II 2382 transition is also a null detection.
z=0.891253 |DATA & VOIGT PROFILES| |EWs & AOD COLUMNS| |VP PARAMETERS|This is a highly saturated system with a full velocity spread of ~200 km/s. The blue wing shows some component structure, and, interestingly, the Mg I absorption is not observed over the same velocity where this structure in the Mg II is seen. The Fe II transitions are saturated as well, but with some structure in the 2587 transition. An attempt at VP decomposition was deemed a failure, but the "best" fit is presented with the absorption profiles. The only real constraint for the component velocities was the Mg I profile. Steidel et al. report a possible high gas phase iron abundance in this system and a relatively small H I column density [17.9 < N(HI) < 19.4 cm^-2]. They suggest that the absorption in this system may arise in H II regions. Based upon the integrated apparent column densities, N_a, the lower limit for log N(MgII) - log N(MgI) is 1.67, which implies a lower limit to the collisionally ionized gas temperature of 3 x 10^-4 K (see Tytler et al. 1987). This in turn implies a negative log N(MgII) - log N(FeII). Unfortunately, the measured column densities of both the Mg II and the Fe II ions are poorly determined, and so the supposition that the gas arises in H II regions cannot be addressed with confidence.
Post Thesis WorkFOS/HST data have been investigated.
See Churchill et al. (2000a)
See Churchill et al. (2000b)
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