Detection of HI filament: Pair Stacking vs. Filament Stacking

Abstract

The faint 21 cm signal emitted by neutral hydrogen in cosmic filaments is expected to be detectable. However, due to its weakness, stacking techniques are required. We assessed two stacking methods--pair stacking and filament stacking--using the EAGLE and IllustrisTNG simulations. Pair stacking leverages the fact that cosmic filaments connect massive structures (i.e., knots) in the cosmic web, while filament stacking directly aggregates filaments identified from galaxy distributions. Our analysis indicates that, although pair stacking is convenient, it faces contamination from massive structures; after removing this contamination, the filament signal is significantly reduced. In contrast, HI detection via filament stacking appears more promising. The column density in filament stacking reaches $\sim 10^{16}$--$10^{17}{\mathrm{cm}}^{-2}$ even when all haloes are masked, whereas pair stacking does not reach this level even without masking, and is further suppressed by several orders of magnitude once masking is applied. The effectiveness of filament stacking can be further improved with higher galaxy number density and better spatial resolution in radio intensity mapping observations. With the advent of upcoming optical and radio data, the detection of HI in cosmic filaments remains promising.

12 pages, 7 figures; accepted for publication in ApJ

References in corpus (26)

• 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 EAGLE project: Simulating the evolution and assembly of galaxies and their environments
• The EAGLE simulations of galaxy formation: calibration of subgrid physics and model variations
• 21-cm cosmology
• The persistent cosmic web and its filamentary structure I: Theory and implementation
• On the evolution of the HI column density distribution in cosmological simulations
• The EAGLE simulations of galaxy formation: public release of halo and galaxy catalogues
• The persistent cosmic web and its filamentary structure II: Illustrations
• DESI Bright Galaxy Survey: Final Target Selection, Design, and Validation
• Probing the missing baryons with the Sunyaev-Zel'dovich effect from filaments
• The Tianlai project: a 21cm cosmology experiment
• A Wide-field High Resolution HI Mosaic of Messier 31: I. Opaque Atomic Gas and Star Formation Rate Density
• Discovery of Magnetic Fields Along Stacked Cosmic Filaments as Revealed by Radio and X-Ray Emission
• First detection of stacked X-ray emission from cosmic web filaments
• Density and temperature of cosmic-web filaments on scales of tens of megaparsecs
• Detection of Stacked Filament Lensing Between SDSS Luminous Red Galaxies
• Stacking the Cosmic Web in Fluorescent Lyman alpha Emission with MUSE
• X-ray emission from cosmic web filaments in SRG/eROSITA data
• Polarized accretion shocks from the cosmic web
• Searching for HI imprints in cosmic web filaments with 21-cm intensity mapping
• How dark are filaments in the cosmic web?
• Optical Thickness, Spin Temperature, and Correction Factor for Density of the Galactic HI Gas
• FAST drift scan survey for HI intensity mapping: simulation on hunting HI filament with pairwise stacking