Measurements of quasar proximity zones with the Ly$\alpha$ forest of DESI Y1 quasars

Abstract

The intergalactic medium (IGM) around quasars is shaped by their dense environments and by their excess ionizing radiation, forming a "quasar proximity zone" whose size and anisotropy depend on the quasar's halo mass, luminosity, age, and radiation geometry. Using over 10,000 quasar pairs from the Dark Energy Spectroscopic Instrument (DESI) Year 1 data, with projected comoving separations $r_{\perp }<2h^{-1}\mathrm{Mpc}$, we investigate how the proximity zone of foreground quasars at $z\sim 2-3.5$ affects Lyman-alpha absorption in their background quasars. The large DESI sample enables unprecedented precision in measuring this "transverse proximity" effect, allowing a detailed investigation of the signal's dependence on the projected separation of quasar pairs and the luminosity of the foreground quasar. We find that enhanced gas clustering near quasars dominates over their ionizing effect, leading to stronger absorption on neighboring sightlines. Under the assumption that quasar ionizing luminosity is isotropic and steady, we infer the IGM overdensity profile in the vicinity of quasars, finding overdensities as high as $\Delta \sim 10$ at comoving distance $\sim 1h^{-1}\mathrm{Mpc}$ from the most luminous systems. Surprisingly, however, we find no significant dependence of the proximity profile on the luminosity of the foreground quasar. This lack of luminosity dependence could reflect a cancellation between higher ionizing flux and higher gas overdensity, or it could indicate that quasar emission is highly time variable or anisotropic, so that the observed luminosity does not trace the ionizing flux on nearby sightlines.

arXiv comment22 pages, 7 figures, 1 table; accepted for publication in ApJ

References in corpus (61)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• Astropy: A Community Python Package for Astronomy
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• Efficient Computation of CMB anisotropies in closed FRW models
• Coevolution (Or Not) of Supermassive Black Holes and Host Galaxies
• Composite Quasar Spectra From the Sloan Digital Sky Survey
• Constraining the Evolution of the Ionizing Background and the Epoch of Reionization with z ~ 6 Quasars II: A Sample of 19 Quasars
• Radiative transfer in a clumpy universe: IV. New synthesis models of the cosmic UV/X-ray background
• Revisiting the Unified Model of Active Galactic Nuclei
• Observational constraints on Cosmic Reionization
• DESI DR2 Results II: Measurements of Baryon Acoustic Oscillations and Cosmological Constraints
• Overview of the Instrumentation for the Dark Energy Spectroscopic Instrument
• The Sloan Digital Sky Survey Quasar Catalog: twelfth data release
• The Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Baryon acoustic oscillations with Lyman-$\alpha$ forests
• The Physics of the Intergalactic Medium
• The First Cosmic Structures and their Effects
• The Evolution of the Intergalactic Medium
• Model-independent insights into the nature of the Lyman-alpha forest and the distribution of matter in the universe
• A Systematic Search for Changing-Look Quasars in SDSS
• The first ultraviolet quasar stacked spectrum at z=2.4 from WFC3
• HeII Reionization and its Effect on the IGM
• DESI 2024 IV: Baryon Acoustic Oscillations from the Lyman Alpha Forest
• The Spectroscopic Data Processing Pipeline for the Dark Energy Spectroscopic Instrument
• Target Selection and Validation of DESI Quasars
• The Robotic Multi-Object Focal Plane System of the Dark Energy Spectroscopic Instrument (DESI)
• DESI 2024 VII: Cosmological Constraints from the Full-Shape Modeling of Clustering Measurements
• Clustering of intermediate redshift quasars using the final SDSS III-BOSS sample
• The nature and evolution of the highly ionized near-zones in the absorption spectra of z~6 quasars
• Quasars Probing Quasars VI. Excess HI Absorption Within One Proper Mpc of z~2 Quasars
• Quasars Probing Quasars II: The Anisotropic Clustering of Optically Thick Absorbers around Quasars
• Clustering of quasars in SDSS-IV eBOSS : study of potential systematics and bias determination
• Ionizing radiation fluctuations and large-scale structure in the Lyman-alpha forest
• The large-scale Quasar-Lyman α Forest Cross-Correlation from BOSS
• Cross-Correlation of SDSS DR7 Quasars and DR10 BOSS Galaxies: The Weak Luminosity Dependence of Quasar Clustering at z~0.5
• An unbiased measurement of the UV background and its evolution via the proximity effect in quasar spectra
• DESI DR2 Results I: Baryon Acoustic Oscillations from the Lyman Alpha Forest
• The Temperature-Density Relation in the Intergalactic Medium at Redshift <z>=2.4
• The Luminosity Dependence of Quasar Clustering
• The DESI Survey Validation: Results from Visual Inspection of the Quasar Survey Spectra
• The Lyman-alpha glow of gas falling into the dark matter halo of a z=3 galaxy
• The transverse proximity effect in the z ~ 2 Lyman-alpha forest suggests QSO episodic lifetimes of ~1 Myr
• Detecting and Characterizing Young Quasars II: Four Quasars at $z\sim 6$ with Lifetimes $<10^4$ years
• Performance of the Quasar Spectral Templates for the Dark Energy Spectroscopic Instrument
• Testing AGN outflow and accretion models with CIV and HeII emission line demographics in z=2 quasars
• Statistical Detection of the HeII Transverse Proximity Effect: Evidence for Sustained Quasar Activity for $>$25 Million Years
• The density structure around quasars from optical depth statistics
• The Line-of-Sight Proximity Effect and the Mass of Quasar Host Halos
• Optimal strategies for identifying quasars in DESI
• Measuring the Radiative Histories of QSOs with the Transverse Proximity Effect
• Cosmic Reionization On Computers III. The Clumping Factor
• The apparent shape of the "Strömgren sphere'' around the highest-redshift QSOs with Gunn-Peterson troughs
• Modeling the HeII Transverse Proximity Effect: Constraints on Quasar Lifetime and Obscuration
• Mapping quasar light echoes in 3D with Lyα forest tomography
• Probing the environment of high-z quasars using the proximity effect in projected quasar pairs
• On probing the properties of QSOs through their proximity effects on the intergalactic medium
• Constraining the Temperature-Density Relation of the Inter-Galactic Medium from Analytically Modeling Lyman-alpha Forest Absorbers
• Large-scale surveys of the quasar proximity effect
• Exploratory Study of Transverse Proximity Effect around BAL Quasars
• Prospects for constraining quasar ages with fiber spectrographs: quasar-induced Ly$\alpha$ emission from the intergalactic medium