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

Journal Article · Tue Dec 20 04:00:00 EST 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/833/2/135· OSTI ID:22660903

Cai, Zheng; Prochaska, J. Xavier; Lau, Marie Wingyee; Tejos, Nicolas ^[1]; Fan, Xiaohui; Frye, Brenda; McGreer, Ian ^[2]; Peirani, Sebastien ^[3]; Bian, Fuyan ^[4]; Ho, Shirley ^[5]; Schneider, Donald P. ^[6]

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1. UCO/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)
2. Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)
3. Institut d’Astrophysique de Paris, 98 bis, Boulevard Arago—F-75014 Paris (France)
4. Research School of Astronomy and Astrophysics, Mount Stromlo Observatory, Cotter Road, Weston ACT 2611 (Australia)
5. McWilliams Center for Cosmology, Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213 (United States)
6. Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States)

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 Ly α forest absorption. We have undertaken a systematic study of the relation between Coherently Strong intergalactic Ly α Absorption systems (CoSLAs), which have the highest optical depth ( τ ) in the τ distribution, and mass overdensities on the scales of ∼10–20 h {sup −1} comoving Mpc. On such large scales, our cosmological simulations show a strong correlation between the effective optical depth ( τ {sub 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 Ly β 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 {sub eff} on 15 h {sup −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 Ly α forest surveys, which cover a survey volume of >1 ( h {sup −1} Gpc){sup 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.

• OSTI ID: 22660903
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 833; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABSORPTION
CORRELATIONS
COSMOLOGY
DENSITY
GALAXIES
HYDROGEN
INTERGALACTIC SPACE
LYMAN LINES
MAPPING
MASS
NOISE
QUASARS
RED SHIFT
SIGNAL-TO-NOISE RATIO
THREE-DIMENSIONAL CALCULATIONS