New perspectives on strong z ≃ 0.5 Mg II absorbers

Are halo mass and equivalent width anticorrelated?

Nicolas Bouché, Michael T. Murphy, Céline Péroux, I. Csabai, Vivienne Wild

Research output: Contribution to journalArticle

96 Citations (Scopus)

Abstract

We measure the mean halo mass of z ≃ 0.5 Mg II absorbers using the cross-correlation (over comoving scales 0.05-13 h -1 Mpc) between 1806 Mg II quasar absorption systems and ∼250 000 luminous red galaxies (LRGs), both selected from the Sloan Digital Sky Survey Data Release 3. The Mg II systems have λ2796 rest-frame equivalent widths W r λ2796 ≳ 0.3 Å. From the ratio of the Mg II-LRG cross-correlation to the LRG-LRG auto-correlation, we find that the bias ratio between Mg II absorbers and LRGs is b̄ Mg II/b̄ LRG = 0.65 ± 0.08, which implies that the absorber host galaxies have a mean halo mass ∼20-40 times smaller than that of the LRGs; the Mg II absorbers have haloes of mean mass (log M h(M )) = 11.94 ± 0.31 (stat) -0.25 +0.24 (sys). We demonstrate that this statistical technique, which does not require any spectroscopic follow-up, does not suffer from contaminants such as stars or foreground and background galaxies. Finally, we find that the absorber halo mass is anticorrelated with the equivalent width. If Mg II absorbers were virialized in galaxy haloes, a positive M h -W r λ2796 correlation would have been observed since W r λ2796 is a direct measure of the velocity spread of the Mg II subcomponents. Thus, our results demonstrate that the individual clouds of a Mg II system are not virialized in the gaseous haloes of the host galaxies. We review past results in the literature on the statistics of Mg II absorbers and find that they too require a M h, -W r λ2796 anticorrelation. When combined with measurements of the equivalent width distribution (d 2N/dz/dW r), the M h -W r λ2796 anti-correlation naturally explains why absorbers with W r λ2796 ≳ 2 Å are not seen at large impact parameters. We interpret the M h -W r λ2796 anticorrelation within the starburst scenario where strong Mg II absorbers are produced by supemovae-driven winds.

Original languageEnglish
Pages (from-to)495-512
Number of pages18
JournalMonthly Notices of the Royal Astronomical Society
Volume371
Issue number1
DOIs
Publication statusPublished - Sep 2006

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halos
absorbers
galaxies
autocorrelation
cross correlation
pollutant
quasars
contaminants
statistics
stars

Keywords

  • Cosmology: observations
  • Galaxies: evolution
  • Galaxies: haloes
  • Quasars: absorption lines

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

New perspectives on strong z ≃ 0.5 Mg II absorbers : Are halo mass and equivalent width anticorrelated? / Bouché, Nicolas; Murphy, Michael T.; Péroux, Céline; Csabai, I.; Wild, Vivienne.

In: Monthly Notices of the Royal Astronomical Society, Vol. 371, No. 1, 09.2006, p. 495-512.

Research output: Contribution to journalArticle

Bouché, Nicolas ; Murphy, Michael T. ; Péroux, Céline ; Csabai, I. ; Wild, Vivienne. / New perspectives on strong z ≃ 0.5 Mg II absorbers : Are halo mass and equivalent width anticorrelated?. In: Monthly Notices of the Royal Astronomical Society. 2006 ; Vol. 371, No. 1. pp. 495-512.
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T2 - Are halo mass and equivalent width anticorrelated?

AU - Bouché, Nicolas

AU - Murphy, Michael T.

AU - Péroux, Céline

AU - Csabai, I.

AU - Wild, Vivienne

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N2 - We measure the mean halo mass of z ≃ 0.5 Mg II absorbers using the cross-correlation (over comoving scales 0.05-13 h -1 Mpc) between 1806 Mg II quasar absorption systems and ∼250 000 luminous red galaxies (LRGs), both selected from the Sloan Digital Sky Survey Data Release 3. The Mg II systems have λ2796 rest-frame equivalent widths W r λ2796 ≳ 0.3 Å. From the ratio of the Mg II-LRG cross-correlation to the LRG-LRG auto-correlation, we find that the bias ratio between Mg II absorbers and LRGs is b̄ Mg II/b̄ LRG = 0.65 ± 0.08, which implies that the absorber host galaxies have a mean halo mass ∼20-40 times smaller than that of the LRGs; the Mg II absorbers have haloes of mean mass (log M h(M ⊙)) = 11.94 ± 0.31 (stat) -0.25 +0.24 (sys). We demonstrate that this statistical technique, which does not require any spectroscopic follow-up, does not suffer from contaminants such as stars or foreground and background galaxies. Finally, we find that the absorber halo mass is anticorrelated with the equivalent width. If Mg II absorbers were virialized in galaxy haloes, a positive M h -W r λ2796 correlation would have been observed since W r λ2796 is a direct measure of the velocity spread of the Mg II subcomponents. Thus, our results demonstrate that the individual clouds of a Mg II system are not virialized in the gaseous haloes of the host galaxies. We review past results in the literature on the statistics of Mg II absorbers and find that they too require a M h, -W r λ2796 anticorrelation. When combined with measurements of the equivalent width distribution (d 2N/dz/dW r), the M h -W r λ2796 anti-correlation naturally explains why absorbers with W r λ2796 ≳ 2 Å are not seen at large impact parameters. We interpret the M h -W r λ2796 anticorrelation within the starburst scenario where strong Mg II absorbers are produced by supemovae-driven winds.

AB - We measure the mean halo mass of z ≃ 0.5 Mg II absorbers using the cross-correlation (over comoving scales 0.05-13 h -1 Mpc) between 1806 Mg II quasar absorption systems and ∼250 000 luminous red galaxies (LRGs), both selected from the Sloan Digital Sky Survey Data Release 3. The Mg II systems have λ2796 rest-frame equivalent widths W r λ2796 ≳ 0.3 Å. From the ratio of the Mg II-LRG cross-correlation to the LRG-LRG auto-correlation, we find that the bias ratio between Mg II absorbers and LRGs is b̄ Mg II/b̄ LRG = 0.65 ± 0.08, which implies that the absorber host galaxies have a mean halo mass ∼20-40 times smaller than that of the LRGs; the Mg II absorbers have haloes of mean mass (log M h(M ⊙)) = 11.94 ± 0.31 (stat) -0.25 +0.24 (sys). We demonstrate that this statistical technique, which does not require any spectroscopic follow-up, does not suffer from contaminants such as stars or foreground and background galaxies. Finally, we find that the absorber halo mass is anticorrelated with the equivalent width. If Mg II absorbers were virialized in galaxy haloes, a positive M h -W r λ2796 correlation would have been observed since W r λ2796 is a direct measure of the velocity spread of the Mg II subcomponents. Thus, our results demonstrate that the individual clouds of a Mg II system are not virialized in the gaseous haloes of the host galaxies. We review past results in the literature on the statistics of Mg II absorbers and find that they too require a M h, -W r λ2796 anticorrelation. When combined with measurements of the equivalent width distribution (d 2N/dz/dW r), the M h -W r λ2796 anti-correlation naturally explains why absorbers with W r λ2796 ≳ 2 Å are not seen at large impact parameters. We interpret the M h -W r λ2796 anticorrelation within the starburst scenario where strong Mg II absorbers are produced by supemovae-driven winds.

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KW - Galaxies: evolution

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KW - Quasars: absorption lines

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