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The free-free absorption of low frequency radio waves by thermal electrons in the warm ionized medium of our Galaxy becomes very significant at $\lesssim 10$ MHz (ultralong-wavelength), and the absorption strength depends on the radio…

Astrophysics of Galaxies · Physics 2022-12-14 Yanping Cong , Bin Yue , Yidong Xu , Yuan Shi , Xuelei Chen

We present a survey of the radio sky accessible from the first station of the Long Wavelength Array (LWA1). Images are presented at nine frequencies between 35 and 80 MHz with spatial resolutions ranging from $4.7^\circ$ to $2.0^\circ$,…

Instrumentation and Methods for Astrophysics · Physics 2017-07-20 Jayce Dowell , Gregory B. Taylor , Frank K. Schinzel , Namir E. Kassim , Kevin Stovall

The Galactic disc is opaque to radio waves from extragalactic sources with frequencies nu less than ~3 MHz. However, radio waves with kHz, Hz, and even lower frequencies may propagate through the intergalactic medium (IGM). I argue that the…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-18 Brian C. Lacki

The ultra-long wavelength sky ($\nu\lesssim 30$ MHz) is still largely unexplored, as the electromagnetic wave is heavily absorbed and distorted by the ionosphere on Earth. The far-side of the Moon, either in lunar-orbit or on lunar-surface,…

Astrophysics of Galaxies · Physics 2025-11-04 Qige Ao , Furen Deng , Yidong Xu , Bin Yue , Huanyuan Shan , Xuelei Chen

Understanding diffuse Galactic radio emission is interesting both in its own right and for minimizing foreground contamination of cosmological measurements. Cosmic Microwave Background experiments have focused on frequencies > 10 GHz,…

The past decade has seen the rise of various radio astronomy arrays, particularly for low-frequency observations below 100MHz. These developments have been primarily driven by interesting and fundamental scientific questions, such as…

Instrumentation and Methods for Astrophysics · Physics 2016-01-28 Raj Thilak Rajan , Albert-Jan Boonstra , Mark Bentum , Marc Klein-Wolt , Frederik Belien , Michel Arts , Noah Saks , Alle-Jan van der Veen

Radio astronomy has changed. For years it studied relatively rare sources, which emit mostly non-thermal radiation across the entire electromagnetic spectrum, i.e. radio quasars and radio galaxies. Now it is reaching such faint flux…

Astrophysics of Galaxies · Physics 2016-10-19 Paolo Padovani

The Ultra-Long Wavelength (ULW) regime of longer than 10 m (corresponding to frequencies below 30 MHz), remains as the last virtually unexplored window in radio astronomy, and is presently attracting considerable attention as an area of…

Instrumentation and Methods for Astrophysics · Physics 2019-09-04 Linjie Chen , Yihua Yan

A host of new low-frequency radio telescopes seek to measure the 21-cm transition of neutral hydrogen from the early universe. These telescopes have the potential to directly probe star and galaxy formation at redshifts $20 \gtrsim z…

In radio astronomy, the Ultra-Long Wavelengths (ULW) regime of longer than 10 m (frequencies below 30 MHz), remains the last virtually unexplored window of the celestial electromagnetic spectrum. The strength of the science case for…

Instrumentation and Methods for Astrophysics · Physics 2018-02-23 Linjie Chen , Amin Aminaei , Leonid I. Gurvits , Marc Klein Wolt , Hamid Reza Pourshaghaghi , Yihua Yan , Heino Falcke

In the last three decades, about 50 radio supernovae have been detected as a result of targeted searches of optically discovered supernovae in the local universe. Despite this relatively small number some diversity among them has already…

High Energy Astrophysical Phenomena · Physics 2014-01-08 Atish Kamble , Alicia Soderberg , Edo Berger , Ashley Zauderer , Sayan Chakraborti , Peter Williams

The radio sky at lower frequencies, particularly below 20 MHz, is expected to be a combination of increasingly bright non-thermal emission and significant absorption from intervening thermal plasma. The sky maps at these frequencies cannot…

Instrumentation and Methods for Astrophysics · Physics 2021-09-01 Akhil Jaini , Avinash A. Deshpande , Sainath Bitragunta

This white paper emphasizes the potential of QSO absorption lines in the rest-frame far/extreme UV at rest-frame wavelengths from ~500 to 2000 A. In this wavelength range, species such as Ne VIII, Na IX, and Mg X can be detected, providing…

Cosmology and Nongalactic Astrophysics · Physics 2013-03-04 Todd Tripp

Galactic Gamma ray astronomy at very high energy (E > 30 TeV) is a vital tool in the study of the non-thermal universe. The interpretation of the observations in this energy region requires the precise modeling of the attenuation of photons…

High Energy Astrophysical Phenomena · Physics 2016-09-28 Silvia Vernetto , Paolo Lipari

We present intermediate resolution ($\sim3$ \AA ) spectra of the Ly$\alpha$ emission from 15 high redshift radio galaxies ($z>2$). Together with previously published spectra we analyze data for a sample of 18 objects. In 11 of the 18 radio…

Astrophysics · Physics 2007-05-23 R. van Ojik , H. J. A. Röttgering , G. K. Miley , R. W. Hunstead

We have mapped the total sky brightness at 1465 MHz in two adjacent 60-degree declination bands with the portable 5.5-m parabolic reflector of the Galactic Emission Mapping (GEM) project, an on-going international collaboration to survey…

Astrophysics · Physics 2007-05-23 C. Tello , T. Villela , G. F. Smoot , S. Torres , M. Bersanelli

We present a precision measurement of radio sky brightness over 60-350 MHz. Accurate knowledge of the radio sky over these frequencies is essential for modelling foregrounds in experiments targeting cosmic dawn and the epoch of…

Cosmology and Nongalactic Astrophysics · Physics 2026-02-11 Luke McKay , Ravi Subrahmanyan , Aaron Chippendale , Pietro Bolli , Georgios Kyriakou , Alex Dunning , Ronald Ekers

Upcoming radio surveys will probe the sky with unprecedented depth and sky coverage, enabling a broad range of cosmological and astrophysical applications, as well as powerful synergies with experiments at other wavelengths. The preparation…

We investigate the radio properties of a sample of 53 sources selected at 850 $\mu$m from the SCUBA-2 Cosmology Legacy Survey using new deep, low-frequency radio imaging of the Lockman Hole field from the Low Frequency Array. Combining…

Surveys for transient and variable phenomena can be confounded by the presence of extrinsic variability such as refractive interstellar scintillation (RISS). We have developed an all-sky model for RISS which can predict variability on a…

Astrophysics of Galaxies · Physics 2019-07-26 P. J. Hancock , E. G. Charlton , J-P. Macquart , N. Hurley-Walker
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