The Very Large Telescope Ultraviolet and Visible Echelle Spectrograph survey for molecular hydrogen in high‐redshift damped Lyman α systems

By C. Ledoux, P. Petitjean, R. Observatory, Iap, París, France., Iucaa, Pune, India.. 2003

223 citations recorded by the source corpus.

We have searched for molecular hydrogen in damped Lyman α (DLA) and sub-DLA systems at high redshift (z abs > 1.8) using the Ultraviolet and Visible Echelle Spectrograph (UVES) at the Very Large Telescope (VLT) down to a detection limit of typically N(H 2 ) = 2 × 10 14 cm -2 . Out of the 33 systems in our sample, eight have firm and two have tentative detections of associated H 2 absorption lines. Considering that three detections were already known from past searches, molecular hydrogen is detected in 13-20 per cent of the newly surveyed systems. We report new detections of molecular hydrogen at z abs = 2.087 and 2.595 toward, respectively, Q 1444+014 and Q 0405-443, and also reanalyse the system at z abs = 3.025 toward Q 0347-383. In all of the systems, we measure metallicities relative to solar, [X/H] (with either X = Zn, S or Si), and depletion factors of Fe, [X/Fe], supposedly on to dust grains, and compare the characteristics of our sample with those of the global population of DLA systems (60 systems in total). We find that there is a correlation between the metallicity and the depletion factor in both our sample and also the global population of DLA systems. Although H 2 molecules are detected in systems with [Zn/Fe] as small as 0.3, the DLA and sub-DLA systems where H 2 is detected are usually amongst those having the highest metallicities and the largest depletion factors. In particular, H 2 is detected in the five systems having the largest depletion factors. Moreover, the individual components where H 2 is detected have depletion factors systematically larger than other components in the profiles. In two different systems, one of the H 2 -detected components even has [Zn/Fe]≥1.4. These are the largest depletion factors ever seen in DLA systems. All of this clearly demonstrates the presence of dust in a large fraction of the DLA systems. The mean H 2 molecular fraction, f= 2N (H 2 )/[2N(H 2 ) +N(H i)], is generally small in DLA systems (typically log f 2 and the H i column density. In fact, two systems where H 2 is detected have log N(H i) 2 on to dust grains is reduced in those systems, probably because the gas is warm (T > 1000 Κ) and/or the ionizing flux is enhanced relative to what is observed in our Galaxy.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/502080f06da83c6d040c2947674c5f0da3e57887

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In Astronomy and Astrophysics

1. P. Noterdaeme
2. P. Petitjean
3. R. Srianand
4. C. Ledoux
5. A. Meiksin
6. D. Turnshek
7. S. Rao
8. D. Nestor

Citations in the corpus

• Molecular hydrogen in high-redshift Damped Lyman-alpha systems: The VLT/UVES database (2008, methodology): “Because DLAs contain most of the neutral hydrogen available for star formation in the Universe (Wolfe et al. 1986; Lanzetta et al. 1991) and are associated with numerous metal absorption lines, they probably arise in the interstellar medium of protogalaxies, progenitors of present-day Based on data ”
• Damped Lyα Systems at z < 1.65: The Expanded Sloan Digital Sky Survey Hubble Space Telescope Sample (2006, background): “Ledoux et al. (2003) find that the DLAs in which H2 is detected have among the highest metallicities and the highest depletion factors, hinting at the possibility of much higher depletions in much higher column density molecular gas clouds.”
• The VLT-UVES survey for molecular hydrogen in high-redshift damped Lyman α systems: physical conditions in the neutral gas (2005, methodology): “Ledoux et al. (2003) found that approximately 13–20 per cent of DLAs show H2 absorption lines with most of the H2 components having column densities in the range 16.0 log N (H2) (cm−2) 19.0.”
• Damped Lyman α systems in galaxy formation simulations (2008, unknown): “In DLAs with detectable molecular hydrogen (H2), the local UV can be estimated from pumping into high energy rotational levels ( .g. Srianand et al. 2005), results suggesting star formation rates comparable to the present day Milky Way (∼ 1M⊙ yr−1).”
• The physics of the intergalactic medium (2007, background): “Molecular hydrogen is present in about 15–20% of the systems (Ledoux et al., 2006b), with the metallicity and depletion factor increasing with the amount of H2 (Ledoux et al., 2003).”
• First detection of CO in a high-redshift damped Lyman-α system (2008, background): “We noticed a strong preference for H2-bearing DLAs being associated with C i absorption (Srianand et al. 2005) and having high metallicities and large depletion factors (Petitjean et al. 2006; Noterdaeme et al. 2008).”
• The ESO UVES advanced data products quasar sample: II. Cosmological evolution of the neutral gas mass density (2013, background): “The redshift path and an additional sub-DLA reported by Ledoux et al. (2003) were included in our statistical sample.”
• Velocity-metallicity correlation for high-z DLA galaxies: evidence of a mass-metallicity relation? (2006, methodology): “Most of the systems in our sample were selected from the follow-up of the Large Bright QSO Survey (LBQS; Wolfe et al. 1995) and observed at the ESO VLT with UVES between 2000 and 2004 in the course of a systematic search for molecular hydrogen atzabs> 1.8 (Petitjean et al. 2000; Ledoux et al. 2003).”
• Evolution of the cosmological mass density of neutral gas from Sloan Digital Sky Survey II - Data Release 7 (2009, background): “In addition, there is only a small tendency for increasing H2 molecular fraction with larger Hi column density (Ledoux et al. 2003; Noterdaeme et al. 2008a).”