The Magellan Uniform Survey of Damped Lyman alpha Systems II: Paucity of Strong Molecular Hydrogen Absorption

Abstract

We present the first large, blind and uniformly selected survey for molecular hydrogen (H_2) in damped Lyman alpha systems (DLAs) with moderate-to-high resolution spectra. 86 DLAs were searched for absorption in the many Lyman and Werner H_2 transitions, with approximately 79% completeness for H_2 column densities above N(H_2)=10^17.5 cm^-2 for an assumed Doppler broadening parameter b=2 km s^-1. Only a single strong H_2 absorber was found -- a system detected previously in VLT/UVES spectra. Given our distribution of N(H_2) upper limits, this ~1% detection rate is smaller than expected from previous surveys at 99.8% confidence. Assuming the N(H_2) distribution shape from previous surveys, our detection rate implies a covering factor of ~1% for N(H_2) >= 10^17.5 cm^-2 gas in DLAs (<6% at 95% confidence). We obtained new Magellan/MagE spectra for 53 DLAs; 8 km s^-1 -resolution spectra were available for 27 DLAs. MagE's moderate resolution (~71 km s^-1) yields weaker N(H_2) upper limits and makes them dependent on the assumed Doppler parameter. For example, half the (relevant) previous H_2 detections have N(H_2) >= 10^18.1 cm^-2, a factor of just 3 higher than our median upper limit. Nevertheless, several tests suggest our upper limits are accurate, and they would need to be increased by 1.8 dex to bring our detection rate within 95% confidence of previous surveys.

arXiv comment21 pages, 20 figures, Accepted by MNRAS

References in corpus (38)

• Star Formation in Galaxies Along the Hubble Sequence
• Spectroscopic Target Selection in the Sloan Digital Sky Survey: The Quasar Sample
• Calibration of X-ray absorption in our Galaxy
• Damped Lyman alpha Systems
• A Universal, Local Star Formation Law in Galactic Clouds, Nearby Galaxies, High-Redshift Disks, and Starbursts
• The SDSS Damped Lya Survey: Data Release 3
• Metallicity Evolution of Damped Lyman-alpha Systems out to z~5
• The Age-Metallicity Relation of the Universe in Neutral Gas: The First 100 Damped Lya Systems
• The VLT-UVES survey for molecular hydrogen in high-redshift damped Lyman-alpha systems
• Cosmic dynamics in the era of Extremely Large Telescopes
• A Direct Precision Measurement of the Intergalactic Lyman-alpha Opacity at 2<z<4.2
• A FUSE Survey of Interstellar Molecular Hydrogen in the Small and Large Magellanic Clouds
• Molecular hydrogen in high-redshift Damped Lyman-alpha systems: The VLT/UVES database
• The CORALS Survey I: New Estimates of the Number Density and Gas Content of Damped Lyman Alpha Systems Free from Dust Bias
• The VLT-UVES survey for molecular hydrogen in high-redshift damped Lyman-alpha systems: Physical conditions in the neutral gas
• The microwave background temperature at the redshift of 2.33771
• CII* Absorption in Damped Lyman Alpha Systems: (I) Star Formation Rates in a Two-Phase Medium
• Molecular hydrogen, deuterium and metal abundances in the damped Ly-alpha system at z = 3.025 toward QSO 0347-3819
• Galaxy Counterparts of metal-rich Damped Lyman-alpha Absorbers - I: The case of the z=2.35 DLA towards Q2222-0946
• Detection of Lyman-alpha emission from a DLA galaxy: Possible implications for a luminosity-metallicity relation at z = 2-3
• Keck telescope constraint on cosmological variation of the proton-to-electron mass ratio
• A SINFONI Integral Field Spectroscopy Survey for Galaxy Counterparts to Damped Lyman-alpha Systems - I. New Detections and Limits for Intervening and Associated Absorbers
• Dust-reddening and gravitational lensing of SDSS QSOs due to foreground damped Lyman-alpha systems
• A FUSE survey of high-latitude Galactic molecular hydrogen
• Molecular Hydrogen in the Damped Ly alpha Absorber of Q1331+170
• Where is the Molecular Hydrogen in Damped Lyman-Alpha Absorbers?
• Metallicity as a criterion to select H2 bearing Damped Lyman-alpha systems
• The UCSD Radio-Selected Quasar Survey for Damped Lyman alpha System
• The Magellan Uniform Survey of Damped Lyman alpha Systems I: Cosmic Metallicity Evolution
• Understanding Physical Conditions in High Redshift Galaxies through C I Fine Structure Lines: Data and Methodology
• Physical conditions in the neutral interstellar medium at z=2.43 toward Q2348-011
• Partial coverage of the Broad Line Region of Q1232+082 by an intervening H2-bearing cloud
• The color excess of quasars with intervening DLA systems- Analysis of the SDSS data release five
• Molecular hydrogen absorption systems in Sloan Digital Sky Survey
• Exploring the dust content of SDSS DR7 damped Lyman alpha systems at 2.15$\le z_{ab}<$5.2
• Spatially Resolved Emission of a High Redshift DLA Galaxy with the Keck/OSIRIS IFU
• A cold component and the complex velocity structure of DLA1331+170
• Searching for Dust Reddening in SDSS Spectra with Damped Lyman $\alpha${} Systems

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