Multi-Filament Inflows Fueling Young Star Forming Galaxies

TL;DR

This study uses high-resolution observations and modeling to detect and analyze cold gas inflows along cosmic web filaments fueling star formation in young galaxies at high redshift.

Contribution

It introduces a new suite of kinematic models that successfully identify and characterize filamentary inflows in galaxy gas accretion, supported by high-resolution KCWI data.

Findings

Detection of radial inflows consistent with cold filamentary accretion

Gas flux and inflow paths match galaxy star formation needs

Strong evidence for cosmic web feeding galaxy growth

Abstract

Theory suggests that there are two primary modes of accretion through which dark matter halos acquire the gas to form and fuel galaxies, hot and cold mode accretion. In cold mode accretion, gas streams along cosmic web filaments to the center of the halo, allowing for the efficient delivery of star-forming fuel. Recently, two QSO-illuminated HI Lyman alpha (Ly{\alpha}) emitting objects were reported to have properties of cold, rotating structures (Martin et al. 2015, Martin et al. 2016). However, the spatial and spectral resolution available was insufficient to constrain radial flows associated with connecting filaments. With the Keck Cosmic Web Imager (KCWI) we now have eight times the spatial resolution, permitting the detection of these in-spiraling flows. In order to detect these inflows, we introduce a suite of models which incorporate zonal radial flows, demonstrate their performance on a numerical simulation that exhibits coldflow accretion, and show that they are an excellent match to KCWI velocity maps of two Ly{\alpha} emitters observed around high-redshift quasars. These Multi-Filament Inflow models kinematically isolate zones of radial inflow that correspond to extended filamentary emission. The derived gas flux and inflow path is sufficient to fuel the inferred central galaxy star formation rate and angular momentum. Thus, our kinematic emission maps provide strong evidence for the inflow of gas from the cosmic web building galaxies at the peak of star formation.