A feature at z ∼ 3.2 in the evolution of the Lyα forest optical depth

Mariangela Bernardi, Ravi K. Sheth, Mark SubbaRao, Gordon T. Richards, Scott Burles, Andrew J. Connolly, Joshua Frieman, Robert Nichol, Joop Schaye, Donald P. Schneider, Daniel E. Vanden Berk, Donald G. York, J. Brinkmann, Don Q. Lamb

Research output: Contribution to journalArticle

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Abstract

The effective optical depth in the Lyα forest region of 1061 low-resolution QSO spectra drawn from the SDSS database decreases with decreasing redshift over the range 2.5 ≤ z ≤ 4. Although the evolution is relatively smooth, τeff ∝ (1 + z)3.8±0.2, at z ∼ 3.2 the effective optical depth decreases suddenly by about 10% with respect to this smoother evolution. It climbs back to the original smooth scaling again by z ∼ 2.9. We describe two techniques, one of which is new, for quantifying this evolution that give consistent results. A variety of tests show that the feature is not likely to be a consequence of how the QSO sample was selected nor the result of flux calibration or other systematic effects. Other authors have argued that, at this same epoch, the temperature of the IGM also shows a departure from an otherwise smooth decrease with time. These features in the evolution of the temperature and the optical depth are signatures of the reionization of Hen.

Original languageEnglish (US)
Pages (from-to)32-52
Number of pages21
JournalAstronomical Journal
Volume125
Issue number1 1765
DOIs
StatePublished - Jan 1 2003

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optical thickness
optical depth
quasars
temperature
time measurement
signatures
calibration
scaling

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Bernardi, M., Sheth, R. K., SubbaRao, M., Richards, G. T., Burles, S., Connolly, A. J., ... Lamb, D. Q. (2003). A feature at z ∼ 3.2 in the evolution of the Lyα forest optical depth. Astronomical Journal, 125(1 1765), 32-52. https://doi.org/10.1086/344945
Bernardi, Mariangela ; Sheth, Ravi K. ; SubbaRao, Mark ; Richards, Gordon T. ; Burles, Scott ; Connolly, Andrew J. ; Frieman, Joshua ; Nichol, Robert ; Schaye, Joop ; Schneider, Donald P. ; Vanden Berk, Daniel E. ; York, Donald G. ; Brinkmann, J. ; Lamb, Don Q. / A feature at z ∼ 3.2 in the evolution of the Lyα forest optical depth. In: Astronomical Journal. 2003 ; Vol. 125, No. 1 1765. pp. 32-52.
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Bernardi, M, Sheth, RK, SubbaRao, M, Richards, GT, Burles, S, Connolly, AJ, Frieman, J, Nichol, R, Schaye, J, Schneider, DP, Vanden Berk, DE, York, DG, Brinkmann, J & Lamb, DQ 2003, 'A feature at z ∼ 3.2 in the evolution of the Lyα forest optical depth', Astronomical Journal, vol. 125, no. 1 1765, pp. 32-52. https://doi.org/10.1086/344945

A feature at z ∼ 3.2 in the evolution of the Lyα forest optical depth. / Bernardi, Mariangela; Sheth, Ravi K.; SubbaRao, Mark; Richards, Gordon T.; Burles, Scott; Connolly, Andrew J.; Frieman, Joshua; Nichol, Robert; Schaye, Joop; Schneider, Donald P.; Vanden Berk, Daniel E.; York, Donald G.; Brinkmann, J.; Lamb, Don Q.

In: Astronomical Journal, Vol. 125, No. 1 1765, 01.01.2003, p. 32-52.

Research output: Contribution to journalArticle

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T1 - A feature at z ∼ 3.2 in the evolution of the Lyα forest optical depth

AU - Bernardi, Mariangela

AU - Sheth, Ravi K.

AU - SubbaRao, Mark

AU - Richards, Gordon T.

AU - Burles, Scott

AU - Connolly, Andrew J.

AU - Frieman, Joshua

AU - Nichol, Robert

AU - Schaye, Joop

AU - Schneider, Donald P.

AU - Vanden Berk, Daniel E.

AU - York, Donald G.

AU - Brinkmann, J.

AU - Lamb, Don Q.

PY - 2003/1/1

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N2 - The effective optical depth in the Lyα forest region of 1061 low-resolution QSO spectra drawn from the SDSS database decreases with decreasing redshift over the range 2.5 ≤ z ≤ 4. Although the evolution is relatively smooth, τeff ∝ (1 + z)3.8±0.2, at z ∼ 3.2 the effective optical depth decreases suddenly by about 10% with respect to this smoother evolution. It climbs back to the original smooth scaling again by z ∼ 2.9. We describe two techniques, one of which is new, for quantifying this evolution that give consistent results. A variety of tests show that the feature is not likely to be a consequence of how the QSO sample was selected nor the result of flux calibration or other systematic effects. Other authors have argued that, at this same epoch, the temperature of the IGM also shows a departure from an otherwise smooth decrease with time. These features in the evolution of the temperature and the optical depth are signatures of the reionization of Hen.

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Bernardi M, Sheth RK, SubbaRao M, Richards GT, Burles S, Connolly AJ et al. A feature at z ∼ 3.2 in the evolution of the Lyα forest optical depth. Astronomical Journal. 2003 Jan 1;125(1 1765):32-52. https://doi.org/10.1086/344945