scholarly journals Very high-energy constraints on the infrared extragalactic background light

2019 ◽  
Vol 629 ◽  
pp. A2 ◽  
Author(s):  
A. Franceschini ◽  
L. Foffano ◽  
E. Prandini ◽  
F. Tavecchio
Keyword(s):  
Dust Emission ◽  
High Energy ◽  
Interplanetary Dust ◽  
Extragalactic Background Light ◽  
Background Light ◽  
Very High Energy ◽  
Infrared Wavelengths ◽  
Favorable Conditions ◽  
High Energy Emission ◽  
Very High

Context. Measurements of the extragalactic background light (EBL) are a fundamental source of information on the collective emission of cosmic sources. Aims. At infrared wavelengths, however, these measurements are precluded by the overwhelming dominance from interplanetary dust emission and the Galactic infrared foreground. Only at λ >  300 μm, where the foregrounds are minimal, has the infrared EBL (IR EBL) been inferred from analysis of the COBE maps. The present paper aims to assess the possibility of evaluating the IR EBL from a few micrometers up to the peak of the emission at > 100 μm using an indirect method that avoids the foreground problem. Methods. To this purpose we exploit the effect of pair-production from gamma-gamma interaction by considering the highest-energy photons emitted by extragalactic sources and their interaction with the IR EBL photons. We simulate observations of a variety of low-redshift emitters with the forthcoming Imaging Atmospheric Cherenkov Telescope (IACT) arrays (CTA in particular) and water Cherenkov observatories (LHAASO, HAWC, SWGO) to assess their suitability to constrain the EBL at such long wavelengths. Results. We find that even under the most extremely favorable conditions of huge emission flares, extremely high-energy emitting blazars are not very useful for our purpose because they are much too distant (> 100 Mpc the nearest ones, MKN 501 and MKN 421). Observations of more local AGNs displaying very high-energy emission, like low-redshift radio galaxies (M 87, IC 310, Centaurus A), are better suited and will potentially allow us to constrain the EBL up to λ ≃ 100 μm.

scholarly journals GAMMA-RAYS FROM BLAZARS AND THE EXTRAGALACTIC BACKGROUND LIGHT

2013 ◽  
Vol 22 (13) ◽  
pp. 1330025 ◽  
Author(s):  
LUIGI COSTAMANTE
Keyword(s):  
Gamma Rays ◽  
Far Infrared ◽  
High Energy ◽  
Extragalactic Background Light ◽  
Background Light ◽  
Theoretical Progress ◽  
Very High Energy ◽  
Very High

Recent observations of blazars at high energy (0.1–100 GeV) and very high energy (> 0.1 TeV) have provided important constraints on the intensity and spectrum of the diffuse extragalactic background light (EBL), shedding light on its main origin. Several issues remain open, however, in particular in the mid- and far-infrared bands and in the blazar emission at multi-TeV energies. This review summarizes the observational and theoretical progress in the study of the EBL with gamma-rays and the most promising future improvements, which are mainly expected from spectra in the multi-TeV range.

scholarly journals Effect of axion-like particles on the spectrum of the extragalactic gamma-ray background

2021 ◽  
Vol 2021 (11) ◽  
pp. 030
Author(s):  
Yun-Feng Liang ◽  
Xing-Fu Zhang ◽  
Ji-Gui Cheng ◽  
Hou-Dun Zeng ◽  
Yi-Zhong Fan ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Small Region ◽  
High Energy ◽  
Extragalactic Background Light ◽  
Background Light ◽  
Very High Energy ◽  
The Universe ◽  
Very High

Abstract Axion-like particles (ALPs) provide a feasible explanation for the observed lower TeV opacity of the Universe. If the anomaly TeV transparency is caused by ALPs, then the fluxes of distant extragalactic sources will be enhanced at photon energies beyond TeV, resulting in an enhancement of the observed extragalactic gamma-ray background (EGB) spectrum. In this work, we have investigated the ALP modulation on the EGB spectrum at TeV energies. Our results show that in the most optimistic case, the existence of ALPs can cause the EGB spectrum to greatly deviate from the prediction of a pure extragalactic-background-light (EBL) absorption scenario. The deviation occurs at approximately ≳1 TeV, and the current EGB measurements by Fermi-LAT cannot identify such an effect. We also find that most of the sensitive ALP parameters have been ruled out by existing constraints, leaving only a small region of unrestricted parameters that can be probed using the EGB effect investigated in this work. Observations from forthcoming very-high-energy instruments like LHAASO and CTA may be beneficial for the study of this effect.

THE EXTRAGALACTIC BACKGROUND LIGHT: LOWER VERSUS UPPER LIMITS

2009 ◽  
Vol 18 (10) ◽  
pp. 1633-1637 ◽  
Author(s):  
MARTIN RAUE
Keyword(s):  
High Energy ◽  
Energy Spectra ◽  
Extragalactic Background Light ◽  
Background Light ◽  
Upper Limits ◽  
Very High Energy ◽  
Γ Rays ◽  
Deep Source ◽  
Lower Limits ◽  
Very High

The discovery of distant sources of very high energy (VHE) γ-rays with hard energy spectra enabled to derive strong upper limits on the density of the extragalactic background light (EBL). These limits are close to the lower limits derived from deep source counts. A recent re-dertemination of the EBL contribution from resolved sources at 3.6 μm finds a higher EBL density, which is claimed to be in conflict with the assumptions utilized to derive the EBL upper limits from VHE spectra. Here, it is shown that is possible to recover the canonical Γ ~ 1.5 intrinsic spectra for such a higher EBL density.

RESULTS FROM GALACTIC OBSERVATIONS WITH MAGIC

2010 ◽  
Vol 19 (06) ◽  
pp. 1023-1029
Author(s):  
◽  
JAVIER RICO
Keyword(s):  
Gamma Rays ◽  
Energy Band ◽  
Binary Systems ◽  
High Energy ◽  
Cherenkov Telescope ◽  
La Palma ◽  
Very High Energy ◽  
Energy Gamma ◽  
High Energy Emission ◽  
Very High

MAGIC is a single-dish Cherenkov telescope located on La Palma (Spain), hence with an optimal view on the Northern sky. Sensitive to the 30 GeV–30 TeV energy band, it is nowadays the only ground-based instrument being able to measure high-energy gamma-rays below 100 GeV. With the operation in coincidence with MACIC-II, starting in Fall 2009, the sensitivity will be improved by a factor ~ 2. We review the results obtained by MAGIC on the very-high energy emission from pulsars, binary systems and microquasars.

scholarly journals A New Chapter in Hard X-rays of the M87 AGN

Proceedings ◽  
2019 ◽  
Vol 17 (1) ◽  
pp. 9
Author(s):  
Ka-Wah Wong ◽  
Rodrigo S. Nemmen ◽  
Jimmy A. Irwin ◽  
Dacheng Lin
Keyword(s):  
High Energy ◽  
X Rays ◽  
X Ray ◽  
Accretion Flow ◽  
Relativistic Jet ◽  
Very High Energy ◽  
Γ Ray ◽  
High Energy Emission ◽  
First Time ◽  
Very High

The nearby M87 hosts an exceptional relativistic jet. It has been regularly monitored in radio to TeV bands, but little has been done in hard X-rays ≳10 keV. For the first time, we have successfully detected hard X-rays up to 40 keV from its X-ray core with joint Chandra and NuSTAR observations, providing important insights to the X-ray origins: from the unresolved jet or the accretion flow. We found that the hard X-ray emission is significantly lower than that predicted by synchrotron self-Compton models introduced to explain very-high-energy γ -ray emission above a GeV. We discuss recent models to understand these high energy emission processes.

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