The IUE Survey for Damped Lyman- alpha and Lyman-Limit Absorption Systems: Evolution of the Gaseous Content of the Universe

Lanzetta, Kenneth M.; Wolfe, Arthur M.; Turnshek, David A.

doi:10.1086/175286

Cited by 310 publications

(339 citation statements)

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“…Intriguingly, the median values of abundances in such systems are well reproduced by the current models. This may support the hypothesis, first proposed by Lanzetta, Wolfe & Turnshek (1995), that damped Lyo systems could represent a spheroidal component of galaxies.…”

Section: Two-population Model For Lyo Absorberssupporting

confidence: 89%

On the Origin of Metallicity in Lyman-Alpha Forest Systems

Nath¹

2002

Symp. - Int. Astron. Union

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Several recent observations indicate that even the low H I column density Lyα absorption lines may not be primordial, as they were previously thought to be. High-resolution observations using the Keck telescope (Cowie et al. 1995; Tytler et al 1995.; Songaila & Cowie 1996) have revealed that a large fraction of Lyα absorption lines with H I column density as low as NHI ~ 1014 cm−2 at redshift z ~ 3 are associated with metal lines (C IV). This fraction, hereafter denoted as fm, is estimated as 0.5-0.75. On the other hand, there is an indication that at low z a large fraction of Lyα absorption lines are directly associated with halos of visible galaxies. This fraction is hereafter denoted as fg. Lanzetta et al. (1995, hereafter LBTW) claimed fg ~ 0.6 at z ≲ 1 (see also Bowen, Pettini & Boyle 1997).

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Section: Two-population Model For Lyo Absorberssupporting

confidence: 89%

On the Origin of Metallicity in Lyman-Alpha Forest Systems

Nath¹

2002

Symp. - Int. Astron. Union

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“…Further, as discussed in more detail in Carilli et al (1996), although the covering factor f is sometimes poorly constrained, it is unlikely to Limits are 3σ. a Lanzetta et al (1995), b Rao & Turnshek (1999) lead to a systematic bias for the systems discussed here. We also emphasise that the sample of Table 2 does not contain unpublished non-detections of absorption; since Ts and τ21 are inversely related, the bias in the sample (if it exists) is thus towards lower Ts values.…”

Section: Discussionmentioning

confidence: 82%

“…The current observations used bandwidths of 1 and 2 MHz and no online spectral windowing. 3C446 & PKS 1451-375 : Both PKS 1451-375 and 3C 446 are listed as candidate damped Lyman-α absorbers on the basis of their IUE spectra (Lanzetta et al 1995). The present observations used a total bandwidth of 2 MHz, centred at the frequency of the optically determined redshift (See Table 1 for details).…”

Section: Observations and Resultsmentioning

confidence: 99%

Implications of 21-cm observations for damped Lyalpha systems

Chengalur

Kanekar

2000

Monthly Notices RAS

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We present Giant Metrewave Radio Telescope HI 21cm absorption observations, of candidate and confirmed damped Lyman-α systems. The derived spin temperatures T spin are high, in all cases, ∼ 1000 K or higher. We have also collated from the published literature a list of damped absorbers for which 21cm observations exist, and discuss the implications of the observations for the nature of these systems.A cross-comparison of the HI 21cm profiles (which trace the cold gas) with the low ionization metal profiles (which trace all the neutral HI, both cold and warm) shows that in all cases for which both spectra are available, the 21cm absorption coincides in velocity with the deepest metal line feature. This is consistent with models in which the deep metal line features arise from discrete clouds but not with models where the deepest features are the result of velocity crowding.We also find that the typical derived spin temperatures of damped Lyman-α systems are considerably higher than those in the Milky Way or nearby spiral galaxies. The only exceptions are systems which are known to be associated with the disks of spirals; these do, in fact, show low spin temperature. In a multi-phase medium the derived spin temperature is a weighted average of the temperatures of the individual phases. High apparent T spin values are hence to be expected from small, low metallicity objects since these objects should (as per existing theoretical models of the formation of a multi-phase ISM in the Milky Way and high redshift proto-galaxies) have a lower fraction of the cold phase in their ISM as compared to large galaxies. The high T spin is hence consistent with the observed low metallicities of damped Lyman-α absorbers as well as with recent findings that damped absorption is associated with a variety of galaxy types (as opposed to being confined to the disks of large spirals).Finally, although the number of systems for which observations are available is small, we suggest that the following trend may be identified : at low redshift, damped Lyman-α absorption arises from a range of systems, including spiral galaxy disks, while, at high redshift, absorption occurs predominantly in smaller systems.

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“…Empirical evidence that cold gaseous disks have already condensed at early times comes from the fact that the mass of neutral hydrogen (HI) in damped Ly systems at z 2 3 is comparable to the total mass in stars of local disk galaxies (Lanzetta et al 1995). The detected HI gas has a column density 10 20 22 cm 2 , similar to that found in nearby galactic disks (Broeils & Van Woerden 1994).…”

Section: Discussionmentioning

confidence: 85%