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Mapping the unresolved intensity of the 21-cm emission of neutral hydrogen (HI) is now regarded as one the most promising tools for cosmological investigation in the coming decades. Here, we investigate, for the first time, extensions of…

Cosmology and Nongalactic Astrophysics · Physics 2021-02-05 Stefano Camera , Hamsa Padmanabhan

Due to the fact that HI mass measurements are not available for large galaxy samples at high redshifts, we apply a photometric estimator of the HI-to-stellar mass ratio (M_HI/M_*) calibrated using a local Universe sample of galaxies to a…

Astrophysics of Galaxies · Physics 2021-04-07 Wei Zhang , Guinevere Kauffmann , Jing Wang , Yanmei Chen , Jian Fu , Hong Wu

Intensity mapping surveys will provide access to a coarse view of the cosmic large-scale structure in unprecedented large volumes at high redshifts. Given the large fractions of the sky that can be efficiently scanned using emission from…

Cosmology and Nongalactic Astrophysics · Physics 2019-01-09 Oliver Leicht , Cora Uhlemann , Francisco Villaescusa-Navarro , Sandrine Codis , Lars Hernquist , Shy Genel

This study investigates the estimation of the neutral hydrogen (HI) mass function (HIMF) using a Bayesian stacking approach with simulated data for the Five-hundred-meter Aperture Spherical radio Telescope (FAST) HI intensity mapping (HIIM)…

Cosmology and Nongalactic Astrophysics · Physics 2025-01-22 Jiaxin Wang , Yichao Li , Hengxing Pan , Furen Deng , Diyang Liu , Wenxiu Yang , Wenkai Hu , Yougang Wang , Xin Zhang , Xuelei Chen

[Abridged] We study the abundance and clustering properties of HI at redshifts $z\leqslant5$ using TNG100, a large state-of-the-art magneto-hydrodynamic simulation of a 75 Mpc/h box size. We show that most of the HI lies within dark matter…

We describe a combined halo model to constrain the distribution of neutral hydrogen (HI) in the post-reionization universe. We combine constraints from the various probes of HI at different redshifts: the low-redshift 21-cm emission line…

Cosmology and Nongalactic Astrophysics · Physics 2017-08-23 Hamsa Padmanabhan , Alexandre Refregier

One of the most promising probes to complement current standard cosmological surveys is the HI intensity map, i.e. the distribution of temperature fluctuations in neutral hydrogen. In this paper we present calculations of the 2-point…

Cosmology and Nongalactic Astrophysics · Physics 2024-06-24 Anut Sangka , David Bacon

Intensity mapping (IM) of spectral lines has the potential to revolutionize cosmology by increasing the total number of observed modes by several orders of magnitude compared to the cosmic microwave background (CMB) anisotropies. In this…

Cosmology and Nongalactic Astrophysics · Physics 2020-12-22 Jurek B. Bauer , David J. E. Marsh , Renée Hložek , Hamsa Padmanabhan , Alex Laguë

Modified gravity theories offer a well-motivated extension of General Relativity and provide a possible explanation for the late-time accelerated expansion of the Universe. Among them, $f(R)$ gravity represents a minimal and theoretically…

Cosmology and Nongalactic Astrophysics · Physics 2026-02-06 Yanling Song , Yu Sang , Linfeng Xiao , Boyu Zhang , Bin Wang

Line intensity mapping provides a statistical approach to tracing the large-scale distribution of matter in the Universe. We apply the HI intensity mapping technique to interferometric data from the MeerKAT International GHz-Tiered…

The 21cm emission line from neutral hydrogen (HI) contained within galaxies provides a way to make accurate spectroscopic redshift determinations in the radio part of the spectrum. Large radio arrays such as SKA-MID are coming online that…

Cosmology and Nongalactic Astrophysics · Physics 2026-04-30 Ainulnabilah Nasirudin , Philip Bull , Isabelle Ye

The Square Kilometre Array (SKA) will be a formidable instrument for the detailed study of neutral hydrogen (HI) in external galaxies and in our own Galaxy and Local Group. The sensitivity of the SKA, its wide receiver bands, and the…

Astrophysics of Galaxies · Physics 2015-06-16 Lister Staveley-Smith , Tom Oosterloo

This paper introduces the Hidden Valley simulations, a set of trillion-particle N-body simulations in gigaparsec volumes aimed at intensity mapping science. We present details of the simulations and their convergence, then specialize to the…

Cosmology and Nongalactic Astrophysics · Physics 2019-11-19 Chirag Modi , Emanuele Castorina , Yu Feng , Martin White

Observations of intergalactic neutral hydrogen can provide a wealth of information about structure and galaxy formation, potentially tracing accretion and feedback processes on Mpc scales. Below a column density of NHI ~ 10^19 cm-2, the…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-13 Attila Popping , Romeel Dave , Robert Braun , Benjamin D. Oppenheimer

We combine information from the clustering of HI galaxies in the 100% data release of the Arecibo Legacy Fast ALFA survey (ALFALFA), and from the HI content of optically-selected galaxy groups found in the Sloan Digital Sky Survey (SDSS) to…

Cosmology and Nongalactic Astrophysics · Physics 2019-05-01 Andrej Obuljen , David Alonso , Francisco Villaescusa-Navarro , Ilsang Yoon , Michael Jones

It is shown that 21 cm intensity mapping could be used in the near term to make cosmologically useful measurements. Large scale structure could be detected using existing radio telescopes, or using prototypes for dedicated redshift survey…

Cosmology and Nongalactic Astrophysics · Physics 2010-10-13 Kiyoshi Wesley Masui , Patrick McDonald , Ue-Li Pen

The HI mass function is a crucial tool to understand the evolution of the HI content in galaxies over cosmic times. We aim to derive semi-empirical constraints at $z\sim 0.37$ by combining literature results on the $M_\star$ function from…

We introduce a new Bayesian HI spectral line fitting technique capable of obtaining spectroscopic redshifts for millions of galaxies in radio surveys with the Square Kilometere Array (SKA). This technique is especially well-suited to the…

Cosmology and Nongalactic Astrophysics · Physics 2017-04-28 Ian Harrison , Michelle Lochner , Michael L. Brown

Imaging surveys of galaxies will have a high number density and angular resolution yet a poor redshift precision. Intensity maps of neutral hydrogen (HI) will have accurate redshift resolution yet will not resolve individual sources. Using…

Cosmology and Nongalactic Astrophysics · Physics 2017-08-23 David Alonso , Pedro G. Ferreira , Matt J. Jarvis , Kavilan Moodley

The Square Kilometre Array (SKA) will conduct the biggest spectroscopic galaxy survey ever, by detecting the 21cm emission line of neutral hydrogen (HI) from around a billion galaxies over 3/4 of the sky, out to a redshift of z~2. This will…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-08 S. Yahya , P. Bull , M. G. Santos , M. Silva , R. Maartens , P. Okouma , B. Bassett