Related papers: GeV Gamma-Ray Attenuation and the High-Redshift UV…
We analyze the distribution of rest-frame U-V and V-J colors for star-forming galaxies at 0.5 < z < 2.5. Using stellar population synthesis, stochastic star formation histories, and a simple prescription for the dust attenuation that…
The cosmic ultraviolet (UV) ionizing background impacts the formation of dwarf galaxies in the low-redshift universe (z=3) by suppressing gas infall into galactic halos with circular velocities up to v(circ)=75 km/s. Using a…
Gamma-ray bursts are produced by the dissipation of the kinetic energy of a highly relativistic fireball, via the formation of a collisionless shock. When this happens, Ultra High Energy Cosmic Rays up to 10^20 eV are produced. I show in…
We discuss the determination of the intergalactic pair-production absorption coefficient (Stecker & De Jager 1998) making use of an empirically based calculation of the IR background spectrum (Malkan & Stecker 1998) which agrees well with…
A numerical calculation of properties of finite absorbers and of intergalactic medium based on photoionization equilibrium is performed to confront alternative UV sources in addition to quasars. It is seen that a spectrum including a large…
The origin of ultra high energy cosmic rays (UHECR) is still unknown. However, great progress has been achieved in past years due to the good quality and large statistics in experimental data collected by the current observatories. The data…
Nearby sources of cosmic rays up to a ZeV(=10^21 eV) could be observed with a multi-messenger approach including secondary gamma-rays and neutrinos. If cosmic rays above ~10^18 eV are produced in magnetized environments such as galaxy…
Observations of very-high-energy (VHE, E > 250 GeV) gamma-ray emission from several blazars at z > 0.1 have placed stringent constraints on the elusive spectrum and intensity of the intergalactic infrared background radiation (IIBR).…
The Galactic gamma-ray diffuse emission is currently observed in the GeV-TeV energy range with unprecedented accuracy by the Fermi satellite. Understanding this component is crucial as it provides a background to many different signals such…
We consider the evolution of the sky-averaged 21 cm background during the early phases of structure formation. Using simple analytic models, we calculate the thermal and ionization histories, assuming that stellar photons dominate the…
We present the first results of an ongoing spectroscopic survey of galaxies selected in the rest-frame ultraviolet (UV). The redshift distribution extends over 0<z<0.5 and a high fraction of the sources show intense nebular emission lines…
The pair-production absorption of high-energy gamma-rays by intergalactic low-energy photons is expected to produce a high-energy cutoff in the spectra of extragalactic sources which is a sensitive function of redshift. We first discuss the…
We discuss the problem of the absorption of very high-energy gamma-rays by pair production interactions with extragalactic photons which originate from stellar emission in the near IR-UV and reradiation of starlight in the mid- and far-IR.…
A computational procedure is presented to estimate the spectral shape of the ionizing background between 1 and 10 Ryd by analyzing optically thin absorption systems in the spectra of high redshift quasars. The procedure is based on the…
Interpretation of the \ion{Fe}{2}(UV)/\ion{Mg}{2} emission ratios from quasars has a major cosmological motivation. Both Fe and Mg are produced by short-lived massive stars. In addition, Fe is produced by accreting white dwarf supernovae…
I discuss how measurements of the absorption of $\gamma$-rays from GeV to TeV energies via pair production on the extragalactic background light (EBL) can probe important issues in galaxy formation. We use semi-analytic models (SAMs) of…
The cosmic gamma-ray background radiation is one of the most fundamental observables in the gamma-ray band. Although the origin of the cosmic gamma-ray background radiation has been a mystery for a long time, the Fermi gamma-ray space…
Blazars with redshifts z<0.1 are likely candidates for detection at energies in the range 300 GeV - 50 TeV with Cerenkov telescopes and scintillator arrays. We present gamma-ray flux predictions for a sample of 15 nearby flat-spectrum radio…
We study the ultraviolet to far-infrared (hereafter UV-to-IR) SEDs of a sample of intermediate redshift (0.2 < z < 0.7) UV-selected galaxies from the ELAIS-N1 and ELAIS-N2 fields by fitting a multi-wavelength dataset to a library of GRASIL…
Connecting the observed rest-ultraviolet (UV) luminosities of high-$z$ galaxies to their intrinsic luminosities (and thus star formation rates) requires correcting for the presence of dust. We bypass a common dust-correction approach that…