The circumgalactic medium in Lyman-alpha: a new constraint on galactic outflow models

Abstract

Galactic outflows are critical to our understanding of galaxy formation and evolution. However the details of the underlying feedback process remain unclear. We compare Ly$\alpha$ observations of the circumgalactic medium (CGM) of Lyman Break Galaxies (LBGs) with mock observations of their simulated CGM. We use cosmological hydrodynamical `zoom-in' simulations of an LBG which contains strong, momentum-driven galactic outflows. Simulation snapshots at $z=2.2$ and $z=2.65$ are used, corresponding to the available observational data. The simulation is post-processed with the radiative transfer code \textsc{crash} to account for the impact of ionising photons on hydrogen gas surrounding the simulated LBG. We generate mock absorption line maps for comparison with data derived from observed close galaxy-galaxy pairs. We perform calculations of Ly$\alpha$ photons scattering through the CGM with our newly developed Monte-Carlo code \textsc{slaf}, and compare to observations of diffuse Ly$\alpha$ halos around LBGs. Our fiducial galactic outflow model comes closer to reproducing currently observed characteristics of the CGM in Ly$\alpha$ than a reference inefficient feedback model used for comparison. Nevertheless, our fiducial model still struggles to reproduce the observed data of the inner CGM (at impact parameter $b<30$kpc). Our results suggest that galactic outflows affect Ly$\alpha$ absorption and emission around galaxies mostly at impact parameters $b<50$ kpc, while cold accretion flows dominate at larger distances. We discuss the implications of this result, and underline the potential constraining power of CGM observations - in emission and absorption - on galactic outflow models.

14 pages, 12 figures

References in corpus (15)

• Wilkinson Microwave Anisotropy Probe (WMAP) Three Year Results: Implications for Cosmology
• Cold streams in early massive hot haloes as the main mode of galaxy formation
• Cosmological Simulations of Intergalactic Medium Enrichment from Galactic Outflows
• The COS-Halos Survey: Physical Conditions and Baryonic Mass in the Low-Redshift Circumgalactic Medium
• Mass, Metal, and Energy Feedback in Cosmological Simulations
• 3D Lyman-alpha radiation transfer. I. Understanding Lyman-alpha line profile morphologies
• The COS-Halos Survey: Metallicities in the Low-Redshift Circumgalactic Medium
• Quasar Quartet Embedded in Giant Nebula Reveals Rare Massive Structure in Distant Universe
• Diffuse Lyman-alpha Halos around Galaxies at z=2.2-6.6: Implications for Galaxy Formation and Cosmic Reionization
• The Lyman alpha Reference Sample: Extended Lyman alpha Halos Produced at Low Dust Content
• Lyman alpha Radiative Transfer in Cosmological Simulations using Adaptive Mesh Refinement
• The MUSE Hubble Ultra Deep Field Survey VIII : Extended Lyman-alpha haloes around high-redshift star-forming galaxies
• Directional Lya equivalent boosting I. Spherically symmetric distributions of clumps
• CRASH2: colored packets and other updates
• The Diversity of Diffuse Ly$\alpha$ Nebulae around Star-Forming Galaxies at High Redshift