A local, topology-independent parameterization of quasar IGM damping wings

Abstract

Lyman-$\alpha$ damping wings towards quasars provide a unique probe of reionization because their strength correlates strongly with the global volume-averaged neutral hydrogen (HI) fraction of the intergalactic medium (IGM). Cosmic variance in the IGM, however, is a major source of stochasticity since the local neutral environment around a quasar varies significantly even at fixed global neutral fraction. We show that the IGM damping wing carries additional information about this local ionization topology, unexploited by current analysis frameworks. We introduce a set of two new physically motivated summary statistics encoding the local information about the HI distribution in the IGM before it is altered by ionization radiation from the quasar, encompassing 1) the HI column density, weighted by a Lorentzian profile mimicking the frequency dependence of the Lyman-$\alpha$ cross section, and 2) the distance from the quasar to the first neutral patch. This description, when combined with the quasar's lifetime as a third parameter, reduces the IGM transmission scatter in the damping wing region of the spectrum to $\lesssim 1\%$ across the full range of physical parameter space. We introduce a simple procedure for generating synthetic HI sightlines around quasars and demonstrate that the resulting damping wing profiles are statistically indistinguishable from a realistic reionization topology. This opens the door for optimally extracting the salient local information encoded in the imprint in a model-independent fashion. In the context of a specific reionization model, measurements of these local parameters can be translated into constraints on the global timing of reionization, but in addition, they provide information about the reionization topology, hitherto unused. A marginally modified version of our framework can also be employed in the context of damping wings towards galaxies.

Submitted to MNRAS

References in corpus (15)

• Array Programming with NumPy
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• Model-independent evidence in favor of an end to reionization by z~6
• The JWST-PRIMAL Legacy Survey. A JWST/NIRSpec reference sample for the physical properties and Lyman-$\alpha$ absorption and emission of $\sim 500$ galaxies at $z=5.5-13.4$
• (Nearly) Model-Independent Constraints on the Neutral Hydrogen Fraction in the Intergalactic Medium at $z\sim 5-7$ Using Dark Pixel Fractions in Ly$\alpha$ and Ly$\beta$ Forests
• XQR-30: the ultimate XSHOOTER quasar sample at the reionization epoch
• The Sherwood-Relics simulations: overview and impact of patchy reionization and pressure smoothing on the intergalactic medium
• Chronicling the reionization history at $6\lesssim z\lesssim 7$ with emergent quasar damping wings
• Estimating the effective lifetime of the $z\sim 6$ quasar population from the composite proximity zone profile
• On the sizes of ionized bubbles around the highest redshift galaxies. Spectral shapes of the Lyman-alpha emission from galaxies
• Anatomy of an ionized bubble: NIRCam grism spectroscopy of the $z=6.6$ double-peaked Lyman-$\alpha$ emitter COLA1 and its environment
• Mapping reionization bubbles in the JWST era I: empirical edge detection with Lyman alpha emission from galaxies
• Mapping reionization bubbles in the JWST era II: inferring the position and characteristic size of individual bubbles
• Optical and near-infrared spectroscopy of quasars at $z>6.5$: public data release and composite spectrum
• Signatures of Small-scale Structure of the Pre-reionization Intergalactic Medium in $z\gtrsim 7$ Quasar Proximity Zones

Cited by in corpus (1)

• First constraints on the local ionization topology in front of two quasars at z ~ 7.5