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The X-ray background during the epoch of reionization is currently poorly constrained. We demonstrate that it is possible to use first generation 21 cm experiments to calibrate it. Using the semi-numerical simulation, 21cmFAST, we calculate…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-16 Pierre Christian , Abraham Loeb

We report on the polarization measure, obtained with IBIS on board INTEGRAL, of the prompt emission of GRB 061122. Over an 8 s interval containing the brightest part of the Gamma-Ray Burst we put a lower limit on its polarization fraction…

High Energy Astrophysical Phenomena · Physics 2015-06-15 D. Gotz , S. Covino , A. Fernandez-Soto , P. Laurent , Z . Bosnjak

The cosmic far infrared background detected recently by the COBE-DIRBE team is presumably due, in large part, to the far infrared (FIR) emission from all galaxies. We take the well-established correlation between FIR and radio luminosity…

Astrophysics · Physics 2009-10-30 D. B. Haarsma , R. B. Partridge

Recent suggestions of a "photon underproduction crisis" (Kollmeier \etal\ 2014) have generated concern over the intensity and spectrum of ionizing photons in the metagalactic ultraviolet background (UVB). The balance of hydrogen…

Cosmology and Nongalactic Astrophysics · Physics 2015-09-23 J. Michael Shull , Joshua Moloney , Charles W. Danforth , Evan M. Tilton

We analyze the gamma-ray emission from 9 high latitude, translucent molecular clouds taken with the Fermi Large Area Telescope (LAT) between 250 MeV and 10 GeV. Observations of gamma-rays allow us to probe the density and spectrum of cosmic…

High Energy Astrophysical Phenomena · Physics 2015-05-27 R. D. Abrahams , T. A. D. Paglione

We present an upper limit for the relative escape fraction (f_{esc}^{rel}) of ionizing radiation at z~3.3 using a sample of 11 Lyman Break Galaxies (LBGs) with deep imaging in the U band obtained with the Large Binocular Camera, mounted on…

We use new studies of the cosmic evolution of star-forming galaxies to estimate the production rate of ionizing photons from hot, massive stars at low and intermediate redshifts. The luminosity function of blue galaxies in the Canada-France…

Astrophysics · Physics 2015-06-24 E. Giallongo , A. Fontana , P. Madau

This paper presents infrared spectra taken with the newly commissioned NIRSPEC spectrograph on the Keck Telescope of the High Redshift Radio Galaxy MRC 2025-218 (z=2.630) and an extremely red galaxy (R-K > 6 mag) 9'' away. These…

We use the measured scattering timescales of Fast Radio Bursts (FRBs) from the CHIME catalog to derive an upper limit on the magnetic field on sub-kpc scales in the intergalactic medium (IGM). A nonmagnetized, photoionized IGM is…

High Energy Astrophysical Phenomena · Physics 2023-04-05 Hamsa Padmanabhan , Abraham Loeb

Spatial fluctuations in ultraviolet backgrounds can subtly modulate the distribution of extragalactic sources, a potential signal and systematic for large-scale structure surveys. While this modulation has been shown to be significant for…

Cosmology and Nongalactic Astrophysics · Physics 2019-10-16 Phoebe Upton Sanderbeck , Vid Irsic , Matthew McQuinn , Avery Meiksin

The average rate of emission of ionizing radiation per unit volume (or emissivity) in the universe can be calculated as the ratio of the intensity of the ionizing background to the mean free path of ionizing photons. The intensity of the…

Astrophysics · Physics 2009-11-07 Jordi Miralda-Escude

The star-forming activity in the HII region RCW 42 is investigated using multiple wavebands, from near-infrared to radio wavelengths. Located at a distance of 5.8 kpc, this southern region has a bolometric luminosity of 1.8 $\times$ 10$^6$…

Astrophysics of Galaxies · Physics 2022-08-17 Vipin Kumar , S. Vig , V. S. Veena , S. Mohan , S. K. Ghosh , A. Tej , D. K. Ojha

The conditions within the ionization front of a quasar during reionization (T ~ 30,000 K, neutral hydrogen fraction ~ 0.5) are ideal for producing Lyman-alpha emission via collisional excitation of hydrogen atoms. Observations of this…

Cosmology and Nongalactic Astrophysics · Physics 2017-02-15 Frederick B. Davies , Steven R. Furlanetto , Matthew McQuinn

We present the first limits on the Epoch of Reionization (EoR) 21-cm HI power spectra, in the redshift range $z=7.9-10.6$, using the Low-Frequency Array (LOFAR) High-Band Antenna (HBA). In total 13\,h of data were used from observations…

Following our previously proposed technique, we have used the recent gamma-ray observations of Mrk 421 to place theoretically significant constraints on and possible estimates of the intergalactic infrared radiation field (IIRF) which are…

Astrophysics · Physics 2011-04-15 F. W. Stecker , O. C. De Jager

Low mass, low metallicity galaxies at low to moderate ($z\lesssim3$) redshifts offer the best opportunity for detailed examination of the interplay between massive stars, ionizing radiation and gas in sources similar to those that likely…

Astrophysics of Galaxies · Physics 2019-10-16 Dawn K. Erb , Danielle A. Berg , Matthew W. Auger , David L. Kaplan , Gabriel Brammer , Max Pettini

The recently published GALFA-HI Compact Cloud Catalogue lists 20 neutral hydrogen clouds that might pinpoint previously undiscovered high-latitude dwarf galaxies. Detection of an associated gamma-ray dark matter signal could provide a route…

High Energy Astrophysical Phenomena · Physics 2015-06-15 N. Mirabal

The density of the far infrared / submillimeter (FIR/SMM) diffuse extragalactic radiation field has recently been determined from COBE data. Nearly simultaneously, deep FIR/SMM surveys have detected substantial numbers of optically…

Astrophysics · Physics 2009-10-31 Martin Harwit

... A strict lower-limit flux for the evolving extragalactic background light (and in particular the cosmic infrared background) has been calculated up to redshift of 5. The computed flux is below the existing upper limits from direct…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-14 Tanja M. Kneiske , Herve Dole

We used New Horizons LORRI images to measure the optical-band ($0.4\lesssim\lambda\lesssim0.9{\rm\mu m}$) sky brightness within a high galactic-latitude field selected to have reduced diffuse scattered light from the Milky Way galaxy (DGL),…