Two-point velocity and spatial correlation functions of the C IV absorption systems toward the tololo quasar group: Evidence for superclustering at z ≃ 21

Nadine Dinshaw, Chris D. Impey

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31 Scopus citations


The large number of apparently correlated C IV absorption systems observed in the lines of sight to the wide QSO pair Tol 1037-2704 (zcm = 2.193) and Tol 1038-2712 (zcm = 2.331) between the redshifts 1.88 ≤ z ≤ 2.15 is thought to be produced by an intervening supercluster. We present high-resolution echelle spectra of Tol 1037-2704 and Toi 1038-2712, as well as two neighboring QSOs with the aim of searching for absorption associated with the putative supercluster. The lines of sight toward the original pair are separated by 17′.9 corresponding to a proper separation of D ≃ 4.4 h-1 Mpc (h = Ho/100 km s-1 Mpc-1; qo = 0.5) at z = 2. We confirm the existence of the C IV absorption complexes already reported, and find additional complexes. At a resolution of ∼30 km s-1 FWHM, many of the C IV complexes break up into multiple discrete components with a velocity spread of Δv ≃ 50-1000 km s-1. This brings the total number of C IV absorption systems with secure identifications to 22 in Tol 1037 - 2704 and 11 in Toi 1038 - 2712 in the redshift range 1.48 ≤ z ≤ 2.15, well above the expectation from Poisson statistics. The two neighboring QSOs, Tol 1035-2737 (zcm = 2.159) and Tol 1029-2654 (zcm = 2.586), are located roughly 40′ (D⊥. ≃ 10 h-1 Mpc) southwest and 115′ (D ≃ 30 h-1 Mpc) northwest of the Tololo pair, respectively. We found five C IV systems in the line of sight to Tol 1035-2737, and six toward Toi 1029-2654. Most of these systems appear to match systems in the original QSO pair within a velocity separation of less than 5000 km s-1, though the significance of the matches is not strong. We find a marginal excess of C IV absorption systems in the line of sight to Tol 1029-2654, whereas the number of systems in the line of sight to Tol 1035 -2737 agrees with expectation. The inferred proper dimensions of the proposed supercluster are at least 30 h-1 Mpc on the plane of the sky and approximately 80 h-1 Mpc along the line of sight. We examined the clustering properties of the absorbers toward the Tololo QSOs using the two-point velocity and spatial correlation functions. The velocity correlation function of the complete sample of 44 C IV systems shows strong clustering for velocity separations less than 1000 km s-1, which probe clouds in galactic halos as well as individual galaxies in clusters, and significant clustering signal out to scales of 7000 km s-1. In a subsample of 16 systems (Wo ≥ 0.15 Å), where the power associated with virialized clusters on scales less than 1000 km s-1 has been removed, significant correlation signal persists for velocity separations of 4000-7000 km s-1, which correspond to comoving spatial scales of ∼30-40 h-1 Mpc. The spatial correlation function of the same subsample, derived by pairing absorbers between different lines of sight, shows a marginally significant peak on comoving scales of less than 18 Mpc. The clustering amplitude on these scales is larger than predicted by current theories of the formation of large-scale structure.

Original languageEnglish (US)
Pages (from-to)73-99
Number of pages27
JournalAstrophysical Journal
Issue number1 PART I
StatePublished - 1996


  • Absorption lines
  • Clusters
  • Galaxies
  • General - Quasars

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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