skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: The Mean Metal-line Absorption Spectrum of Damped Ly α Systems in BOSS

Abstract

We study the mean absorption spectrum of the Damped Ly α (DLA) population at z ∼ 2.6 by stacking normalized, rest-frame-shifted spectra of ∼27,000 DLA systems from the DR12 of the Baryon Oscillation Spectroscopic Survey (BOSS)/SDSS-III. We measure the equivalent widths of 50 individual metal absorption lines in five intervals of DLA hydrogen column density, five intervals of DLA redshift, and overall mean equivalent widths for an additional 13 absorption features from groups of strongly blended lines. The mean equivalent width of low-ionization lines increases with N {sub H} {sub i}, whereas for high-ionization lines the increase is much weaker. The mean metal line equivalent widths decrease by a factor ∼1.1–1.5 from z ∼ 2.1 to z ∼ 3.5, with small or no differences between low- and high-ionization species. We develop a theoretical model, inspired by the presence of multiple absorption components observed in high-resolution spectra, to infer mean metal column densities from the equivalent widths of partially saturated metal lines. We apply this model to 14 low-ionization species and to Al iii, S iii, Si iii, C iv, Si iv, N v, and O vi. We use an approximate derivation for separating the equivalent width contributions of several linesmore » to blended absorption features, and infer mean equivalent widths and column densities from lines of the additional species N i, Zn ii, C ii*, Fe iii, and S iv. Several of these mean column densities of metal lines in DLAs are obtained for the first time; their values generally agree with measurements of individual DLAs from high-resolution, high signal-to-noise ratio spectra when they are available.« less

Authors:
 [1]; ; ;  [2]; ;  [3];  [4];  [5];  [6]
  1. Institute of Theoretical Astrophysics, University of Oslo, Postboks 1029, NO-0315 Oslo (Norway)
  2. Institut de Ciències del Cosmos, Universitat de Barcelona (UB-IEEC), Barcelona E-08028, Catalonia (Spain)
  3. Institut d’Astrophysique de Paris, UPMC and CNRS, UMR7095 98bis Boulevard Arago, F-75014—Paris (France)
  4. Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States)
  5. Department of Astronomy and Astrophysics and the Enrico Fermi Institute, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States)
  6. Department of Astronomy, University of Florida, Bryant Space Science Center, Gainesville, FL 32611-2055 (United States)
Publication Date:
OSTI Identifier:
22679888
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 846; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION SPECTRA; APPROXIMATIONS; BARYONS; COSMOLOGY; DENSITY; ELEMENT ABUNDANCE; GALAXIES; HYDROGEN; IONIZATION; LYMAN LINES; METALS; NOISE; OSCILLATIONS; QUASARS; RED SHIFT; RESOLUTION; SIGNAL-TO-NOISE RATIO; SIMULATION

Citation Formats

Mas-Ribas, Lluís, Miralda-Escudé, Jordi, Pérez-Ràfols, Ignasi, Arinyo-i-Prats, Andreu, Noterdaeme, Pasquier, Petitjean, Patrick, Schneider, Donald P., York, Donald G., and Ge, Jian, E-mail: l.m.ribas@astro.uio.no. The Mean Metal-line Absorption Spectrum of Damped Ly α Systems in BOSS. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA81CF.
Mas-Ribas, Lluís, Miralda-Escudé, Jordi, Pérez-Ràfols, Ignasi, Arinyo-i-Prats, Andreu, Noterdaeme, Pasquier, Petitjean, Patrick, Schneider, Donald P., York, Donald G., & Ge, Jian, E-mail: l.m.ribas@astro.uio.no. The Mean Metal-line Absorption Spectrum of Damped Ly α Systems in BOSS. United States. doi:10.3847/1538-4357/AA81CF.
Mas-Ribas, Lluís, Miralda-Escudé, Jordi, Pérez-Ràfols, Ignasi, Arinyo-i-Prats, Andreu, Noterdaeme, Pasquier, Petitjean, Patrick, Schneider, Donald P., York, Donald G., and Ge, Jian, E-mail: l.m.ribas@astro.uio.no. Fri . "The Mean Metal-line Absorption Spectrum of Damped Ly α Systems in BOSS". United States. doi:10.3847/1538-4357/AA81CF.
@article{osti_22679888,
title = {The Mean Metal-line Absorption Spectrum of Damped Ly α Systems in BOSS},
author = {Mas-Ribas, Lluís and Miralda-Escudé, Jordi and Pérez-Ràfols, Ignasi and Arinyo-i-Prats, Andreu and Noterdaeme, Pasquier and Petitjean, Patrick and Schneider, Donald P. and York, Donald G. and Ge, Jian, E-mail: l.m.ribas@astro.uio.no},
abstractNote = {We study the mean absorption spectrum of the Damped Ly α (DLA) population at z ∼ 2.6 by stacking normalized, rest-frame-shifted spectra of ∼27,000 DLA systems from the DR12 of the Baryon Oscillation Spectroscopic Survey (BOSS)/SDSS-III. We measure the equivalent widths of 50 individual metal absorption lines in five intervals of DLA hydrogen column density, five intervals of DLA redshift, and overall mean equivalent widths for an additional 13 absorption features from groups of strongly blended lines. The mean equivalent width of low-ionization lines increases with N {sub H} {sub i}, whereas for high-ionization lines the increase is much weaker. The mean metal line equivalent widths decrease by a factor ∼1.1–1.5 from z ∼ 2.1 to z ∼ 3.5, with small or no differences between low- and high-ionization species. We develop a theoretical model, inspired by the presence of multiple absorption components observed in high-resolution spectra, to infer mean metal column densities from the equivalent widths of partially saturated metal lines. We apply this model to 14 low-ionization species and to Al iii, S iii, Si iii, C iv, Si iv, N v, and O vi. We use an approximate derivation for separating the equivalent width contributions of several lines to blended absorption features, and infer mean equivalent widths and column densities from lines of the additional species N i, Zn ii, C ii*, Fe iii, and S iv. Several of these mean column densities of metal lines in DLAs are obtained for the first time; their values generally agree with measurements of individual DLAs from high-resolution, high signal-to-noise ratio spectra when they are available.},
doi = {10.3847/1538-4357/AA81CF},
journal = {Astrophysical Journal},
number = 1,
volume = 846,
place = {United States},
year = {Fri Sep 01 00:00:00 EDT 2017},
month = {Fri Sep 01 00:00:00 EDT 2017}
}