AzTEC 1.1 mm observations of high-z protocluster environments: SMG overdensities and misalignment between AGN jets and SMG distribution

TL;DR

This study uses 1.1 mm observations to analyze the distribution of submillimeter galaxies around high-redshift radio galaxies, revealing overdensities and a notable perpendicular alignment with AGN jets, suggesting filamentary structures funneling material into protoclusters.

Contribution

First detailed analysis of SMG spatial distribution around high-z radio galaxies showing overdensities and jet alignment misalignments at millimeter wavelengths.

Findings

Overdensities of SMGs by factor ~2-3 in specific protocluster fields.

SMGs tend to align perpendicularly (~73 degrees) to AGN jets.

SMG surface density decreases to blank field levels beyond 1.5 arcmin radius.

Abstract

We present observations at 1.1 mm towards 16 powerful radio galaxies and a radio-quiet quasar at 0.5<z<6.3 acquired with the AzTEC camera mounted at the JCMT and ASTE to study the spatial distribution of submillimeter galaxies towards possible protocluster regions. The survey covers a total area of 1.01 square degrees with rms depths of 0.52 - 1.44 mJy and detects 728 sources above 3sigma. We find overdensities of a factor of ~2 in the source counts of 3 individual fields (4C+23.56, PKS1138-262 and MRC0355-037) over areas of ~200 sq deg. When combining all fields, the source-count analysis finds an overdensity that reaches a factor $\gtrsim 3$ at S$_{\rm{1.1mm}} \ge 4$ mJy covering a 1.5-arcmin-radius area centred on the AGN. The large size of our maps allows us to establish that beyond a radius of 1.5 arcmin, the radial surface density of SMGs falls to that of a blank field. In addition, we find a trend for SMGs to align closely to a perpendicular direction with respect to the radio jets of the powerful central radio galaxies (73$_{+13}^{-14}$ degrees). This misalignment is found over projected co-moving scales of 4-20 Mpc, departs from perfect alignment (0 deg) by ~5sigma, and apparently has no dependence on SMG luminosity. Under the assumption that the AzTEC sources are at the redshift of the central radio galaxy, the misalignment reported here can be interpreted as SMGs preferentially inhabiting mass-dominant filaments funneling material towards the protoclusters, which are also the parent structures of the radio galaxies.