Evidence of Increased UV FeII Emission in Quasars in Candidate Overdense Regions

TL;DR

This study finds that quasars in candidate overdense regions at redshifts 1.11 to 1.67 exhibit increased UV FeII emission, likely due to higher iron abundance and star formation rates compared to field quasars.

Contribution

It provides the first evidence linking increased UV FeII emission in quasars to their environment, specifically overdense regions, suggesting environmental effects on quasar properties.

Findings

Overdense regions have more high equivalent width FeII quasars.

Overdense regions show a scarcity of low equivalent width FeII quasars.

Enhanced iron abundance likely causes increased FeII emission in overdense regions.

Abstract

We present evidence for a skewed distribution of UV FeII emission in quasars within candidate overdense regions spanning spatial scales of ~ 50 Mpc at 1.11 < z < 1.67, compared to quasars in field environments at comparable redshifts. The overdense regions have an excess of high equivalent width sources (W2400 > 42 \AA), and a dearth of low equivalent width sources. There are various possible explanations for this effect, including dust, Ly\alpha fluorescence, microturbulence, and iron abundance. We find that the most plausible of these is enhanced iron abundance in the overdense regions, consistent with an enhanced star formation rate in the overdense regions compared to the field.