Measurements of Quasar Proximity Zones with the Lyα Forest of DESI Y1 Quasars

Journal Article · Mon May 18 00:00:00 UTC 2026 · Astrophys.J.

DOI: https://doi.org/10.3847/1538-4357/ae644b · OSTI ID:3018457

Hada, Ryuichiro  ^[1]; Martini, Paul  ^[2]; Weinberg, David H.  ^[3]; Zheng, Zheng  ^[4]; Aguilar, J.  ^[5]; Ahlen, S.  ^[6]; Bianchi, D.  ^[7]; Brooks, D.  ^[8]; Claybaugh, T. ^[5]; Cuceu, A.  ^[5]; de la Macorra, A.  ^[9]; Ferraro, S.  ^[10]; Font-Ribera, A.  ^[11]; Forero-Romero, J. E.  ^[12]; Gaztañaga, E.  ^[13]; Gutierrez, G.  ^[14]; Guy, J.  ^[5]; Herrera-Alcantar, H. K.  ^[15]; Honscheid, K.  ^[16]; Ishak, M.  ^[17] ; Joyce, R.  ^[18]; Kirkby, D.  ^[19]; Kisner, T.  ^[5]; Kremin, A.  ^[5]; Lamman, C.  ^[20]; Landriau, M.  ^[5]; Le Guillou, L.  ^[21]; Meisner, A.  ^[18]; Miquel, R.  ^[22]; Muñoz-Gutiérrez, A. ^[9]; Palanque-Delabrouille, N.  ^[23]; Percival, W. J.  ^[24]; Poppett, C.  ^[25]; Prada, F.  ^[26]; Pérez-Ràfols, I.  ^[27]; Rossi, G. ^[28]; Sanchez, E.  ^[29]; Schlegel, D.  ^[5]; Schubnell, M. ^[30]; Silber, J.  ^[5]; Sprayberry, D.  ^[18]; Tarlé, G.  ^[31]; Weaver, B. A. ^[18]; Zou, H.  ^[32]

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1. Ohio State U., Dept. Astron.; Chicago U., KICP; ASIAA, Taipei
2. Ohio State U., Dept. Astron.; Chicago U., KICP; Ohio State U.
3. Ohio State U., Dept. Astron.; Chicago U., KICP
4. Utah U.
5. LBL, Berkeley
6. Boston U.
7. Milan U.; Brera Observ.
8. University Coll. London
9. UNAM, Mexico
10. LBL, Berkeley; UC, Berkeley, Math. Dept.
11. Barcelona, IFAE
12. Andes U., Bogota
13. Barcelona, IEEC; Portsmouth U., ICG; ICE, Bellaterra
14. Fermilab
15. Paris, Inst. Astrophys.; IRFU, Saclay
16. Chicago U., KICP; Ohio State U.
17. U. Texas, Dallas
18. Natl. Solar Observ., Tucson
19. UC, Irvine
20. Ohio State U.
21. LPNHE, Paris
22. ICREA, Barcelona; Barcelona, IFAE
23. IRFU, Saclay; LBL, Berkeley
24. Waterloo U.; Perimeter Inst. Theor. Phys.
25. LBL, Berkeley; UC, Berkeley (main); UC, Berkeley, Math. Dept.
26. Granada U., Theor. Phys. Astrophys.
27. Barcelona, Polytechnic U.
28. Sejong U.
29. Madrid, CIEMAT
30. Michigan U., MCTP; Syracuse U.; Michigan U.; KEK, Tsukuba; Hiroshima Shudo U.
31. Michigan U.; KEK, Tsukuba; Hiroshima Shudo U.
32. Beijing Observ.

The intergalactic medium (IGM) around a quasar is shaped by its dense environment and by its excess ionizing radiation, which form 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$$_{⊥}$$ < 2h$$^{−1}$$ Mpc, we investigate how the proximity zone of foreground quasars at z ∼ 2–3.5 affects Lyα 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 Δ ∼ 10 at comoving distance ∼1h$$^{−1}$$ 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.

• Research Organization: ASIAA, Taipei; Andes U., Bogota; Barcelona, IEEC; Barcelona, IFAE; Barcelona, Polytechnic U.; Beijing Observ.; Boston U.; Brera Observ.; Chicago U., KICP; Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Granada U., Theor. Phys. Astrophys.; Hiroshima Shudo U.; ICE, Bellaterra; ICREA, Barcelona; IRFU, Saclay; KEK, Tsukuba; LPNHE, Paris; Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); Madrid, CIEMAT; Michigan U.; Michigan U., MCTP; Milan U.; Natl. Solar Observ., Tucson; Ohio State U.; Ohio State U., Dept. Astron.; Paris, Inst. Astrophys.; Perimeter Inst. Theor. Phys.; Portsmouth U., ICG; Sejong U.; Syracuse U.; U. Texas, Dallas; UC, Berkeley (main); UC, Berkeley, Math. Dept.; UC, Irvine; UNAM, Mexico; University Coll. London; Utah U.; Waterloo U.
• Sponsoring Organization: US Department of Energy
• Grant/Contract Number: 89243024CSC000002
• OSTI ID: 3018457
• Report Number(s): FERMILAB-PUB-25-0966-PPD; oai:inspirehep.net:3095019; arXiv:2512.18281
• Journal Information: Astrophys.J., Journal Name: Astrophys.J. Journal Issue: 1 Vol. 1003
• Country of Publication: United States
• Language: English