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We present a new halo model of neutral hydrogen (HI) calibrated to galaxy formation simulations at redshifts $z\sim0.1$ and $z\sim1.0$ that we employ to investigate the constraining power of interferometric HI intensity mapping on HI…

Cosmology and Nongalactic Astrophysics · Physics 2021-03-23 Zhaoting Chen , Laura Wolz , Marta Spinelli , Steven G. Murray

We present an extragalactic HI 21-cm absorption lines catalog from a blind search at z $\leqslant$ 0.35, using drift-scan data collected in 1325.6 hours by the ongoing Commensal Radio Astronomy FasT Survey (CRAFTS) and FAST All Sky HI…

We present a measurement of the mean intensity of the hydrogen-ionizing background radiation field at low redshift using 906 Ly-alpha absorption lines in 151 quasar spectra from the archives of the Faint Object Spectrograph on the Hubble…

Astrophysics · Physics 2007-05-23 J. Scott , J. Bechtold , M. Morita , A. Dobrzycki , V. Kulkarni

The bispectrum is a 3-point statistic with the potential to provide additional information beyond power spectra analyses of survey datasets. Radio telescopes which broadly survey the 21cm emission from neutral hydrogen (HI) are a promising…

Cosmology and Nongalactic Astrophysics · Physics 2021-08-11 Steven Cunnington , Catherine Watkinson , Alkistis Pourtsidou

Spectral-line results from a new cryogenic phased array feed (cryoPAF) on the Murriyang telescope at Parkes are presented. This array offers a significant improvement in field of view, aperture efficiency, bandwidth, chromaticity and survey…

The GASS is a survey of Galactic atomic hydrogen (HI) emission in the southern sky observed with the Parkes 64-m Radio Telescope. With a sensitivity of 60 mK for a channel width of 1 km/s the GASS is the most sensitive and most accurate…

Instrumentation and Methods for Astrophysics · Physics 2011-02-25 Peter M. W. Kalberla

Line intensity mapping using atomic hydrogen (HI) has the potential to efficiently map large volumes of the universe if the signal can be successfully separated from overwhelmingly bright radio foreground emission. This motivates…

Neutral hydrogen (HI) will soon be the dark matter tracer observed over the largest volumes of Universe thanks to the 21 cm intensity mapping technique. To unveil cosmological information it is indispensable to understand the HI…

Cosmology and Nongalactic Astrophysics · Physics 2017-12-06 Aurélie Pénin , Obinna Umeh , Mario Santos

Phased array feeds (PAFs) for reflector antennas offer the potential for increased reflector field of view and faster survey speeds. To address some of the development challenges that remain for scientifically useful PAFs, including…

Instrumentation and Methods for Astrophysics · Physics 2015-05-14 Jonathan Landon , Michael Elmer , Jacob Waldron , David Jones , Alan Stemmons , Brian D. Jeffs , Karl F. Warnick , J. Richard Fisher , Roger D. Norrod

After reionization, neutral hydrogen (HI) traces the large-scale structure (LSS) of the Universe, enabling HI intensity mapping (IM) to capture the LSS in 3D and constrain key cosmological parameters. We present a new framework utilizing…

Cosmology and Nongalactic Astrophysics · Physics 2025-06-10 Eishica Chand , Arka Banerjee , Simon Foreman , Francisco Villaescusa-Navarro

HI intensity mapping is a new observational technique to map fluctuations in the large-scale structure of matter using the 21 cm emission line of atomic hydrogen (HI). Sensitive radio surveys have the potential to detect Baryon Acoustic…

Cosmology and Nongalactic Astrophysics · Physics 2017-11-22 L. C. Olivari , M. Remazeilles , C. Dickinson

We construct a simple but self-consistent analytic ionization model for rapid exploration of 21cm power spectrum observables in redshift space. It is fully described by the average ionization fraction $x_e(z)$ and HII patch size $R(z)$ and…

Astrophysics · Physics 2009-11-13 Xiaomin Wang , Wayne Hu

We have used the Five-hundred-meter Aperture Spherical radio Telescope (FAST) to make a blind ultra-deep survey for neutral hydrogen (HI). We present the complete results from the first of six fields (FUDS0). This observation of 95 hours…

Astrophysics of Galaxies · Physics 2024-09-11 Hongwei Xi , Bo Peng , Lister Staveley-Smith , Bi-Qing For , Bin Liu , Dejian Ding

The post-reionization $(z \le 6)$ neutral hydrogen (HI) 21-cm intensity mapping signal holds the potential to probe the large scale structures, study the expansion history and constrain various cosmological parameters. Here we apply the…

The neutral hydrogen 21-cm spectral line (1420.4 MHz) and the four 18-cm lines of the hydroxyl molecule (1612-1720 MHz) are observable at redshifts which put their measured line frequencies well below their protected frequency bands. Part…

Astrophysics · Physics 2009-11-10 J. R. Fisher , Q. Zhang , Y. Zheng , S. G. Wilson , R. F. Bradley

The neutral hydrogen (HI) power spectrum, measured from intensity fluctuations in the 21-cm background, offers insights into the large-scale structures (LSS) of our Universe in the post-reionization era (redshift $z<6$). A significant…

Cosmology and Nongalactic Astrophysics · Physics 2024-09-10 Mohd Kamran , Martin Sahlén , Debanjan Sarkar , Suman Majumdar

HI Intensity Mapping (IM) will be used to do precision cosmology using many existing and upcoming radio observatories. The signal will be contaminated due to absorption, the largest component of which will be the flux absorbed by the HI…

Cosmology and Nongalactic Astrophysics · Physics 2019-11-06 Sambit Roychowdhury , Clive Dickinson , Ian W. A. Browne

HI intensity mapping is a promising technique to probe large-scale structure, traditionally analyzed via two-point statistics such as the angular power spectrum. This technique has proven very powerful but may miss key non-Gaussian…

Cosmology and Nongalactic Astrophysics · Physics 2026-05-12 Pauline Gorbatchev , Jean-Luc Starck , Stefano Camera , Marta Spinelli

We present the first installation and characterization of a phased array feed (PAF) on the 64 m Parkes radio telescope. The combined system operates best between 0.8 GHz and 1.74 GHz where the beamformed noise temperature is between 45 K…

Instrumentation and Methods for Astrophysics · Physics 2017-03-08 A. P. Chippendale , R. J. Beresford , X. Deng , M. Leach , J. E. Reynolds , M. Kramer , T. Tzioumis

An anisotropic power spectrum will have a clear signature in the 21cm radiation from high-redshift hydrogen. We calculate the expected power spectrum of the intensity fluctuations in neutral hydrogen from before the epoch of reionization,…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-28 Oscar F. Hernandez , Gilbert P. Holder