A search for galaxies in and around an HI overdense region at z=5 - Astrophysics > Cosmology and Nongalactic AstrophysicsReport as inadecuate

A search for galaxies in and around an HI overdense region at z=5 - Astrophysics > Cosmology and Nongalactic Astrophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: We present the discovery of a large-scale structure of emission-line galaxiesat redshift z=4.86 behind a massive cluster of galaxies, A1689. Previousspectroscopic observations of a galaxy, A1689-7.1 at z=4.87, near thisstructure, revealed a possible overdense region of inter-galactic medium IGMaround the galaxy, which extends at least ~80 comoving Mpc along the line ofsight. In order to investigate whether this z~5 IGM overdense region contains agalaxy overdensity, we undertook narrow- and broad-band imaging observationsaround A1689-7.1 with Subaru-Suprime-Cam. We detected 51 candidate Ly-alphaemitters at redshift z=4.86+-0.03 in the 32 x 24 arcmin^2 field of view. Aftercorrection for lensing by the foreground cluster, we found a large-scale ~20 x60 comoving Mpc overdense region of galaxies around A1689-7.1 in the sourceplane at z=4.86. The densest peak in this region has an overdensity of delta~4,suggesting that this structure is probably a good candidate for a protocluster.A1689-7.1 is located at the edge of this region, where the local galaxy densityis ~1.6 times the mean density and is close to the density contrast in the IGMalong the line of sight to A1689-7.1 estimated from the optical depth. Theoverdensities of galaxies we have found may suggest that at least some parts ofthe IGM overdense region have already started to form galaxies and moreoverthey relate to the formation of a protocluster. Although we lack information onthe three dimensional distributions of both IGM and galaxy overdense regions,the similarity of the scales of both regions may suggest that the two are partsof a single large-scale structure, which would be an large edge-on sheet alongthe line of sight with a size of ~20 x 60 x 80 comoving Mpc.

Author: Y. Matsuda 1, J. Richard 1, Ian Smail 1, N. Kashikawa 2, K. Shimasaku 3, B. L. Frye 4, T. Yamada 5, Y. Nakamura 5, T. Hayashino 5

Source: https://arxiv.org/

Related documents