The Lyman alpha forest towards B2 1225 + 317

Pushpa Khare; R. Srianand; D. G. York; R. Green; D. Welty; Ke Liang Huang; J. Bechtold

doi:10.1093/mnras/285.1.167

The Lyman alpha forest towards B2 1225 + 317

Pushpa Khare, R. Srianand, D. G. York, R. Green, D. Welty, Ke Liang Huang, J. Bechtold

Steward Observatory

Research output: Contribution to journal › Article › peer-review

24 Scopus citations

Abstract

We present observations of the Lyman alpha (Ly α) forest towards B2 1225 + 317 taken at a resolution of 18 km s^-1. A clean sample of Ly α forest lines is extracted after a careful profile-fitting analysis and the removal of the absorption lines of heavy elements. The sample is analysed for statistical properties. Eighty per cent of the column densities are < 10¹⁴ cm^-2. A single power law is inconsistent with the column density distribution and a steepening/break in the distribution is indicated. The average velocity dispersion parameter is 29.4 km s^-1. We find 3σ evidence for a correlation between column density and the velocity dispersion parameter. The correlation, however, is mainly the result of narrow lines and weakens to 1.2σ if lines with a velocity dispersion parameter smaller than 20 km s^-1 are excluded. An excess of line pairs with velocity separation ≤ 100 km s^-1 over the expected number is found.

Original language	English (US)
Pages (from-to)	167-180
Number of pages	14
Journal	Monthly Notices of the Royal Astronomical Society
Volume	285
Issue number	1
DOIs	https://doi.org/10.1093/mnras/285.1.167
State	Published - 1997

Keywords

Intergalactic medium
Quasars: absorption lines

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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10.1093/mnras/285.1.167

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title = "The Lyman alpha forest towards B2 1225 + 317",

abstract = "We present observations of the Lyman alpha (Ly α) forest towards B2 1225 + 317 taken at a resolution of 18 km s-1. A clean sample of Ly α forest lines is extracted after a careful profile-fitting analysis and the removal of the absorption lines of heavy elements. The sample is analysed for statistical properties. Eighty per cent of the column densities are < 1014 cm-2. A single power law is inconsistent with the column density distribution and a steepening/break in the distribution is indicated. The average velocity dispersion parameter is 29.4 km s-1. We find 3σ evidence for a correlation between column density and the velocity dispersion parameter. The correlation, however, is mainly the result of narrow lines and weakens to 1.2σ if lines with a velocity dispersion parameter smaller than 20 km s-1 are excluded. An excess of line pairs with velocity separation ≤ 100 km s-1 over the expected number is found.",

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AU - Khare, Pushpa

AU - Srianand, R.

AU - York, D. G.

AU - Green, R.

AU - Welty, D.

AU - Huang, Ke Liang

AU - Bechtold, J.

PY - 1997

Y1 - 1997

N2 - We present observations of the Lyman alpha (Ly α) forest towards B2 1225 + 317 taken at a resolution of 18 km s-1. A clean sample of Ly α forest lines is extracted after a careful profile-fitting analysis and the removal of the absorption lines of heavy elements. The sample is analysed for statistical properties. Eighty per cent of the column densities are < 1014 cm-2. A single power law is inconsistent with the column density distribution and a steepening/break in the distribution is indicated. The average velocity dispersion parameter is 29.4 km s-1. We find 3σ evidence for a correlation between column density and the velocity dispersion parameter. The correlation, however, is mainly the result of narrow lines and weakens to 1.2σ if lines with a velocity dispersion parameter smaller than 20 km s-1 are excluded. An excess of line pairs with velocity separation ≤ 100 km s-1 over the expected number is found.

AB - We present observations of the Lyman alpha (Ly α) forest towards B2 1225 + 317 taken at a resolution of 18 km s-1. A clean sample of Ly α forest lines is extracted after a careful profile-fitting analysis and the removal of the absorption lines of heavy elements. The sample is analysed for statistical properties. Eighty per cent of the column densities are < 1014 cm-2. A single power law is inconsistent with the column density distribution and a steepening/break in the distribution is indicated. The average velocity dispersion parameter is 29.4 km s-1. We find 3σ evidence for a correlation between column density and the velocity dispersion parameter. The correlation, however, is mainly the result of narrow lines and weakens to 1.2σ if lines with a velocity dispersion parameter smaller than 20 km s-1 are excluded. An excess of line pairs with velocity separation ≤ 100 km s-1 over the expected number is found.

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KW - Quasars: absorption lines

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The Lyman alpha forest towards B2 1225 + 317

Abstract

Keywords

ASJC Scopus subject areas

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