The Mean Metal-line Absorption Spectrum of Damped Lyα Systems in BOSS

Lluís Mas-Ribas, Jordi Miralda-Escudé, Ignasi Pérez-Ràfols, Andreu Arinyo-I-Prats, Pasquier Noterdaeme, Patrick Petitjean, Donald P. Schneider, Donald G. York, Jian Ge

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Abstract

We study the mean absorption spectrum of the Damped Lyα (DLA)opulation 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 H 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.

Original languageEnglish (US)
Article number4
JournalAstrophysical Journal
Volume846
Issue number1
DOIs
StatePublished - Sep 1 2017

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absorption spectrum
line spectra
baryons
ionization
oscillation
absorption spectra
oscillations
metal
metals
stacking
intervals
signal-to-noise ratio
high resolution
hydrogen
signal to noise ratios
derivation

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Mas-Ribas, L., Miralda-Escudé, J., Pérez-Ràfols, I., Arinyo-I-Prats, A., Noterdaeme, P., Petitjean, P., ... Ge, J. (2017). The Mean Metal-line Absorption Spectrum of Damped Lyα Systems in BOSS. Astrophysical Journal, 846(1), [4]. https://doi.org/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. / The Mean Metal-line Absorption Spectrum of Damped Lyα Systems in BOSS. In: Astrophysical Journal. 2017 ; Vol. 846, No. 1.
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abstract = "We study the mean absorption spectrum of the Damped Lyα (DLA)opulation 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 H 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.",
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Mas-Ribas, L, Miralda-Escudé, J, Pérez-Ràfols, I, Arinyo-I-Prats, A, Noterdaeme, P, Petitjean, P, Schneider, DP, York, DG & Ge, J 2017, 'The Mean Metal-line Absorption Spectrum of Damped Lyα Systems in BOSS', Astrophysical Journal, vol. 846, no. 1, 4. https://doi.org/10.3847/1538-4357/aa81cf

The Mean Metal-line Absorption Spectrum of Damped Lyα Systems in BOSS. / 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.

In: Astrophysical Journal, Vol. 846, No. 1, 4, 01.09.2017.

Research output: Contribution to journalArticle

TY - JOUR

T1 - The Mean Metal-line Absorption Spectrum of Damped Lyα Systems in BOSS

AU - Mas-Ribas, Lluís

AU - Miralda-Escudé, Jordi

AU - Pérez-Ràfols, Ignasi

AU - Arinyo-I-Prats, Andreu

AU - Noterdaeme, Pasquier

AU - Petitjean, Patrick

AU - Schneider, Donald P.

AU - York, Donald G.

AU - Ge, Jian

PY - 2017/9/1

Y1 - 2017/9/1

N2 - We study the mean absorption spectrum of the Damped Lyα (DLA)opulation 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 H 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.

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Mas-Ribas L, Miralda-Escudé J, Pérez-Ràfols I, Arinyo-I-Prats A, Noterdaeme P, Petitjean P et al. The Mean Metal-line Absorption Spectrum of Damped Lyα Systems in BOSS. Astrophysical Journal. 2017 Sep 1;846(1). 4. https://doi.org/10.3847/1538-4357/aa81cf