Shadow of a colossus: A z = 2.44 galaxy protocluster detected in 3D Lyα forest tomographic mapping of the cosmos field
- Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, West Germany (Germany)
- Department of Astronomy, University of California at Berkeley, B-20 Hearst Field Annex # 3411, Berkeley, CA 94720 (United States)
- Department of Astronomy and Astrophysics, University of California at Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States)
- Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, CA 94720 (United States)
- Department of Physics and Astronomy, University of California at Los Angeles, Los Angeles, CA 90095-1562 (United States)
- Kavli Institute for the Physics and Mathematics of the Universe (IPMU), The University of Tokyo, Kashiwano-ha 5-1-5, Kashiwa-shi, Chiba (Japan)
- Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, F-13388, Marseille (France)
- Max Planck Institute for Extraterrestrial Physics, Gießenbachstrae 1, D-85741 Garching bei München (Germany)
- INAF—Osservatorio Astronomico di Bologna, via Ranzani,1, I-40127, Bologna (Italy)
Using moderate-resolution optical spectra from 58 background Lyman-break galaxies and quasars at z∼2.3--3 within a 11.′5 × 13.′5 area of the COSMOS field (∼1200 deg{sup −2} projected area density or ∼2.4 h{sup −1} Mpc mean transverse separation), we reconstruct a 3D tomographic map of the foreground Lyα forest absorption at 2.2 < z < 2.5 with an effective smoothing scale of ϵ{sub 3D}≈2.5 h{sup −1} Mpc comoving. Comparing with 61 coeval galaxies with spectroscopic redshifts in the same volume, we find that the galaxy positions are clearly biased toward regions with enhanced intergalactic medium (IGM) absorption in the tomographic map. We find an extended IGM overdensity with deep absorption troughs at z = 2.45 associated with a recently discovered galaxy protocluster at the same redshift. Based on simulations matched to our data, we estimate the enclosed dark matter mass within this IGM overdensity to be M{sub dm}(z=2.45)=(1.1±0.6)×10{sup 14} h{sup −1}M{sub ⊙}, and argue based on this mass and absorption strength that it will form at least one z ∼ 0 galaxy cluster with M(z=0)=(3±1.5)×10{sup 14} h{sup −1}M{sub ⊙}, although its elongated nature suggests that it will likely collapse into two separate clusters. We also point out a compact overdensity of six MOSDEF galaxies at z = 2.30 within a r∼1 h{sup −1} Mpc radius and Δz ∼ 0.006, which does not appear to have a large associated IGM overdensity. These results demonstrate the potential of Lyα forest tomography on larger volumes to study galaxy properties as a function of environment, as well as revealing the large-scale IGM overdensities associated with protoclusters or other features of large-scale structure.
- OSTI ID:
- 22887080
- Journal Information:
- Astrophysical Journal, Vol. 817, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Since 2009, the country of publication for this journal is the UK.; ISSN 0004-637X
- Country of Publication:
- United Kingdom
- Language:
- English
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