MAPPING the MOST MASSIVE OVERDENSITY THROUGH HYDROGEN (MAMMOTH). I. METHODOLOGY

Zheng Cai, Xiaohui Fan, Sebastien Peirani, Fuyan Bian, Brenda Frye, Ian McGreer, J. Xavier Prochaska, Marie Wingyee Lau, Nicolas Tejos, Shirley Ho, Donald P. Schneider

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Abstract

Modern cosmology predicts that a galaxy overdensity (e.g., protocluster) will be associated with a large intergalactic medium gas reservoir, which can be traced by Lyα forest absorption. We have undertaken a systematic study of the relation between Coherently Strong intergalactic Lyα Absorption systems (CoSLAs), which have the highest optical depth (τ) in the τ distribution, and mass overdensities on the scales of ∼10-20 h -1 comoving Mpc. On such large scales, our cosmological simulations show a strong correlation between the effective optical depth (τ eff) of the CoSLAs and the three-dimensional mass overdensity. In spectra with moderate signal-to-noise ratio, however, the profiles of CoSLAs can be confused with individual high column density absorbers. For z > 2.6, where the corresponding Lyβ is redshifted to the optical, we have developed a selection technique to distinguish between these two alternatives. We have applied this technique to ∼6000 sight lines provided by Sloan Digital Sky Survey III quasar survey at z = 2.6-3.3 with a continuum-to-noise ratio greater than 8, and we present a sample of five CoSLA candidates with τ eff on 15 h -1 Mpc greater than 4.5× the mean optical depth. At lower redshifts of z < 2.6, where the background quasar density is higher, the overdensity can be traced by intergalactic absorption groups using multiple sight lines with small angular separations. Our overdensity searches fully use the current and next generation of Lyα forest surveys, which cover a survey volume of >1 (h -1 Gpc)3. Systems traced by CoSLAs will yield a uniform sample of the most massive overdensities at z > 2 to provide stringent constraints to models of structure formation.

Original languageEnglish (US)
Article number135
JournalAstrophysical Journal
Volume833
Issue number2
DOIs
StatePublished - Dec 20 2016

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optical thickness
optical depth
hydrogen
methodology
intergalactic media
visual perception
cosmology
signal-to-noise ratio
quasars
absorbers
signal to noise ratios
galaxies
continuums
profiles
gases
simulation
gas reservoir
distribution

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Cai, Zheng ; Fan, Xiaohui ; Peirani, Sebastien ; Bian, Fuyan ; Frye, Brenda ; McGreer, Ian ; Prochaska, J. Xavier ; Lau, Marie Wingyee ; Tejos, Nicolas ; Ho, Shirley ; Schneider, Donald P. / MAPPING the MOST MASSIVE OVERDENSITY THROUGH HYDROGEN (MAMMOTH). I. METHODOLOGY. In: Astrophysical Journal. 2016 ; Vol. 833, No. 2.
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abstract = "Modern cosmology predicts that a galaxy overdensity (e.g., protocluster) will be associated with a large intergalactic medium gas reservoir, which can be traced by Lyα forest absorption. We have undertaken a systematic study of the relation between Coherently Strong intergalactic Lyα Absorption systems (CoSLAs), which have the highest optical depth (τ) in the τ distribution, and mass overdensities on the scales of ∼10-20 h -1 comoving Mpc. On such large scales, our cosmological simulations show a strong correlation between the effective optical depth (τ eff) of the CoSLAs and the three-dimensional mass overdensity. In spectra with moderate signal-to-noise ratio, however, the profiles of CoSLAs can be confused with individual high column density absorbers. For z > 2.6, where the corresponding Lyβ is redshifted to the optical, we have developed a selection technique to distinguish between these two alternatives. We have applied this technique to ∼6000 sight lines provided by Sloan Digital Sky Survey III quasar survey at z = 2.6-3.3 with a continuum-to-noise ratio greater than 8, and we present a sample of five CoSLA candidates with τ eff on 15 h -1 Mpc greater than 4.5× the mean optical depth. At lower redshifts of z < 2.6, where the background quasar density is higher, the overdensity can be traced by intergalactic absorption groups using multiple sight lines with small angular separations. Our overdensity searches fully use the current and next generation of Lyα forest surveys, which cover a survey volume of >1 (h -1 Gpc)3. Systems traced by CoSLAs will yield a uniform sample of the most massive overdensities at z > 2 to provide stringent constraints to models of structure formation.",
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Cai, Z, Fan, X, Peirani, S, Bian, F, Frye, B, McGreer, I, Prochaska, JX, Lau, MW, Tejos, N, Ho, S & Schneider, DP 2016, 'MAPPING the MOST MASSIVE OVERDENSITY THROUGH HYDROGEN (MAMMOTH). I. METHODOLOGY', Astrophysical Journal, vol. 833, no. 2, 135. https://doi.org/10.3847/1538-4357/833/2/135

MAPPING the MOST MASSIVE OVERDENSITY THROUGH HYDROGEN (MAMMOTH). I. METHODOLOGY. / Cai, Zheng; Fan, Xiaohui; Peirani, Sebastien; Bian, Fuyan; Frye, Brenda; McGreer, Ian; Prochaska, J. Xavier; Lau, Marie Wingyee; Tejos, Nicolas; Ho, Shirley; Schneider, Donald P.

In: Astrophysical Journal, Vol. 833, No. 2, 135, 20.12.2016.

Research output: Contribution to journalArticle

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AU - Cai, Zheng

AU - Fan, Xiaohui

AU - Peirani, Sebastien

AU - Bian, Fuyan

AU - Frye, Brenda

AU - McGreer, Ian

AU - Prochaska, J. Xavier

AU - Lau, Marie Wingyee

AU - Tejos, Nicolas

AU - Ho, Shirley

AU - Schneider, Donald P.

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