scholarly journals TeV Gamma–Ray Absorption and the Intergalactic Infrared Background

2001 ◽  
Vol 204 ◽  
pp. 135-149 ◽  
Author(s):  
F. W. Stecker
Keyword(s):  
Gamma Ray ◽  
Lorentz Invariance ◽  
Spectral Energy Distribution ◽  
Far Infrared ◽  
High Energy ◽  
Spectral Energy ◽  
Empirical Modelling ◽  
Infrared Spectral ◽  
Infrared Background ◽  
Γ Ray

In this paper, I will take a synoptic approach to determining the intergalactic infrared radiation field (IIRF). This approach draws on both the multi-TeV γ-ray observations and the infrared background observations and relates them via the semi-empirical modelling method of Malkan & Stecker. I discuss the evidence for an intergalactic infrared background obtained by an analysis of the HEGRA observations of the high energy γ-ray spectrum of Mrk 501 and from constraints from Mrk 421 deduced from the Whipple air Cherenkov telescope results. I will show that this evidence is in accord with the predictions made by Malkan & Stecker (1998) for the intergalactic infrared spectral energy distribution produced by galaxies. The Malkan-Stecker predictions are also in excellent agreement with mid-infrared galaxy counts. However, there may be potential problems relating these predictions with the results of the analysis of COBE–DIRBE far infrared data. The γ-ray and COBE–DIRBE observations may also need to be reconciled. I will discuss possible ways to resolve this situation including a partial nullification of the γ-ray absorption process which can hypothetically occur if Lorentz invariance is broken.

scholarly journals Extreme and high synchrotron peak blazars beyond 4FGL: The 2BIGB γ-ray catalogue

2020 ◽  
Vol 493 (2) ◽  
pp. 2438-2451
Author(s):  
B Arsioli ◽  
Y-L Chang ◽  
B Musiimenta
Keyword(s):  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
High Energy ◽  
Spectral Energy ◽  
Large Area ◽  
Data Repositories ◽  
Total Contribution ◽  
Public Data ◽  
Γ Ray

ABSTRACT This paper presents the results of a γ-ray likelihood analysis over all the extreme and high synchrotron peak blazars (EHSP and HSP) from the 3HSP catalogue. We investigate 2013 multifrequency positions under the eyes of Fermi Large Area Telescope, considering 11 yr of observations in the energy range between 500 MeV and 500 GeV, which results in 1160 γ-ray signatures detected down to the TS=9 threshold. The detections include 235 additional sources concerning the Fermi Large Area Telescope Fourth Source Catalog (4FGL), all confirmed via high-energy TS (Test Statistic) maps, and represent an improvement of ∼25 per cent for the number of EHSP and HSP currently described in γ-rays. We build the γ-ray spectral energy distribution (SED) for all the 1160 2BIGB sources, plot the corresponding γ-ray logN−logS, and measure their total contribution to the extragalactic gamma-ray background, which reaches up to ∼33 per cent at 100 GeV. Also, we show that the γ-ray detectability improves according to the synchrotron peak flux as represented by the figure of merit parameter, and note that the search for TeV peaked blazars may benefit from considering HSP and EHSP as a whole, instead of EHSPs only. The 2BIGB acronym stands for ‘Second Brazil-ICRANet Gamma-ray Blazars’ catalogue, and all the broad-band models and SED data points will be available on public data repositories (OpenUniverse, GitHub, and Brazilian Science Data Center-BSDC).

MODELING THE MULTIWAVELENGTH SPECTRA AND VARIABILITY OF 3C 66A IN 2003–2004

2007 ◽  
Vol 22 (19) ◽  
pp. 3147-3154
Author(s):  
M. JOSHI ◽  
M. BÖTTCHER
Keyword(s):  
Background Radiation ◽  
Spectral Energy Distribution ◽  
High Energy ◽  
Spectral Energy ◽  
Emission Region ◽  
X Ray ◽  
Central Engine ◽  
Infrared Background ◽  
Very High Energy ◽  
Γ Ray

The BL Lac object 3C 66A was the target of an intensive multiwavelength monitoring campaign organized in 2003–2004. During the campaign, its spectral energy distribution (SED) was measured and flux measurements from radio to X-ray frequencies as well as upper limits in the very high energy (VHE) γ-ray regime were obtained. Here, we reproduce the SED and optical spectral variability pattern observed during our multiwavelength campaign using a time-dependent leptonic jet model. Our model could successfully simulate the observed SED and optical light curves and predict an intrinsic cutoff value for the VHE γ-ray emission at ~4 GeV implying the effect of the optical depth due to the intergalactic infrared background radiation (IIBR) to be negligible. Also, the contribution of external Comptonization (EIC), due to the presence of a broad-line region (BLR), in the emission of γ-ray photons could be significant early-on when the emission region is very close to the central engine but as it travels farther out, the production mechanism of hard X-ray and γ-ray photons becomes dominated by synchrotron self-Compton mechanism (SSC).

scholarly journals Fundamental physics with blazar spectra: a critical appraisal

2019 ◽  
Vol 491 (4) ◽  
pp. 5268-5276 ◽  
Author(s):  
Giorgio Galanti ◽  
Fabrizio Tavecchio ◽  
Marco Landoni
Keyword(s):  
Gamma Ray ◽  
Lorentz Invariance ◽  
Spectral Energy Distribution ◽  
High Energy ◽  
New Physics ◽  
Spectral Energy ◽  
Bl Lac ◽  
Very High Energy ◽  
Emission Models ◽  
Hadron Beam

ABSTRACT Very-high-energy (VHE) BL Lacertae (BL Lac) spectra extending above $10 \, \rm TeV$ provide a unique opportunity for testing physics beyond the standard model of elementary particle and alternative blazar emission models. We consider the hadron beam scenario, the conversion of photons to axion-like particles (ALPs) and the Lorentz invariance violation (LIV) by analysing their consequences and induced modifications to BL Lac spectra. In particular, we consider how different processes can provide similar spectral features (e.g. hard tails) and we discuss the ways they can be disentangled. We use data from High-Energy Gamma-Ray Astronomy (HEGRA) of a high state of Markarian 501 and the High-Energy Stereoscopic System (H.E.S.S.) spectrum of the extreme BL Lac (EHBL) 1ES 0229+200. In addition, we consider two hypothetical EHBLs similar to 1ES 0229+200 located at redshifts z = 0.3 and z = 0.5. We observe that both the hadron beam and the photon–ALP oscillations predict a hard tail extending to energies larger than those possible in the standard scenario. Photon–ALP interaction predicts a peak in the spectra of distant BL Lacs at about $20\rm {-}30 \, \rm TeV$, while LIV produces a strong peak in all BL Lac spectra around $\sim 100 \, \rm TeV$. The peculiar feature of the photon–ALP conversion model is the production of oscillations in the spectral energy distribution, so that its detection/absence can be exploited to distinguish between the considered models. The above-mentioned features of the three models might be detected by the upcoming Cherenkov Telescope Array. Thus, future observations of BL Lac spectra could eventually shed light on new physics and alternative blazar emission models, driving fundamental research towards a specific direction.

scholarly journals Fermi LAT detection of the supernova remnant SN 1006 revisited: The southwest limb

2019 ◽  
Vol 71 (4) ◽  
Author(s):  
Yi Xing ◽  
Zhongxiang Wang ◽  
Xiao Zhang ◽  
Yang Chen
Keyword(s):  
Supernova Remnant ◽  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
High Energy ◽  
Spectral Energy ◽  
Large Area ◽  
Significance Level ◽  
Very High Energy ◽  
Γ Ray ◽  
Energy Emissions

Abstract The data from the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope have recently been updated. Thus we re-analyze the LAT data for the supernova remnant (SNR) SN 1006. Two parts of γ-ray emission from the region are clearly resolved, which correspond to the northeast (NE) and southwest (SW) limbs of the SNR. The former has been detected in the previous LAT data (Xing et al. 2016, ApJ, 823, 44), but the latter is newly detected in this work. The detections of the two limbs are at a ∼4σ significance level, and the spectral results for the NE limb are consistent with those obtained in previous detection analyses. We construct the broadband spectral energy distribution (SED) for the SW limb. Different scenarios are considered for its SED in γ-ray energies. We conclude that, very similarly in the case of the NE limb, the high-energy and very high-energy emissions from the SW limb is likely dominated by the leptonic process, in which high-energy electrons accelerated from the shell region of the SNR inverse-Compton scatter background photons to γ-rays.

scholarly journals Limits on quantum gravity effects from Swift short gamma-ray bursts

2017 ◽  
Vol 607 ◽  
pp. A121 ◽  
Author(s):  
M. G. Bernardini ◽  
G. Ghirlanda ◽  
S. Campana ◽  
P. D’Avanzo ◽  
J.-L. Atteia ◽  
...  
Keyword(s):  
Quantum Gravity ◽  
Gamma Ray ◽  
Lorentz Invariance ◽  
Spectral Energy Distribution ◽  
Gamma Ray Bursts ◽  
Low Energy ◽  
Energy Separation ◽  
Spectral Energy ◽  
Spectral Evolution ◽  
Short Grbs

The delay in arrival times between high and low energy photons from cosmic sources can be used to test the violation of the Lorentz invariance (LIV), predicted by some quantum gravity theories, and to constrain its characteristic energy scale EQG that is of the order of the Planck energy. Gamma-ray bursts (GRBs) and blazars are ideal for this purpose thanks to their broad spectral energy distribution and cosmological distances: at first order approximation, the constraints on EQG are proportional to the photon energy separation and the distance of the source. However, the LIV tiny contribution to the total time delay can be dominated by intrinsic delays related to the physics of the sources: long GRBs typically show a delay between high and low energy photons related to their spectral evolution (spectral lag). Short GRBs have null intrinsic spectral lags and are therefore an ideal tool to measure any LIV effect. We considered a sample of 15 short GRBs with known redshift observed by Swift and we estimate a limit on EQG ≳ 1.5 × 1016 GeV. Our estimate represents an improvement with respect to the limit obtained with a larger (double) sample of long GRBs and is more robust than the estimates on single events because it accounts for the intrinsic delay in a statistical sense.

scholarly journals Big Three Dragons: A [N ii] 122 μm Constraint and New Dust-continuum Detection of a z = 7.15 Bright Lyman-break Galaxy with ALMA

2021 ◽  
Vol 923 (1) ◽  
pp. 5
Author(s):  
Yuma Sugahara ◽  
Akio K. Inoue ◽  
Takuya Hashimoto ◽  
Satoshi Yamanaka ◽  
Seiji Fujimoto ◽  
...  
Keyword(s):  
Spectral Energy Distribution ◽  
Far Infrared ◽  
Abundance Ratio ◽  
Continuum Emission ◽  
Spectral Energy ◽  
High Ionization ◽  
The Galaxy ◽  
Infrared Spectral ◽  
Best Fit ◽  
Redshift Galaxies

Abstract We present new Atacama Large Millimeter/submillimeter Array Band 7 observational results of a Lyman-break galaxy at z = 7.15, B14-65666 (“Big Three Dragons”), which is an object detected in [O iii] 88 μm, [C ii] 158 μm, and dust continuum emission during the epoch of reionization. Our targets are the [N ii] 122 μm fine-structure emission line and the underlying 120 μm dust continuum. The dust continuum is detected with a ∼19σ significance. From far-infrared spectral energy distribution sampled at 90, 120, and 160 μm, we obtain a best-fit dust temperature of 40 K (79 K) and an infrared luminosity of log 10 ( L IR / L ⊙ ) = 11.6 (12.1) at the emissivity index β = 2.0 (1.0). The [N ii] 122 μm line is not detected. The 3σ upper limit of the [N ii] luminosity is 8.1 × 107 L ⊙. From the [N ii], [O iii], and [C ii] line luminosities, we use the Cloudy photoionization code to estimate nebular parameters as functions of metallicity. If the metallicity of the galaxy is high (Z > 0.4 Z ⊙), the ionization parameter and hydrogen density are log 10 U ≃ − 2.7 ± 0.1 and n H ≃ 50–250 cm−3, respectively, which are comparable to those measured in low-redshift galaxies. The nitrogen-to-oxygen abundance ratio, N/O, is constrained to be subsolar. At Z < 0.4 Z ⊙, the allowed U drastically increases as the assumed metallicity decreases. For high ionization parameters, the N/O constraint becomes weak. Finally, our Cloudy models predict the location of B14-65666 on the BPT diagram, thereby allowing a comparison with low-redshift galaxies.

scholarly journals An intermittent extreme BL Lac: MWL study of 1ES 2344+514 in an enhanced state

2020 ◽  
Vol 496 (3) ◽  
pp. 3912-3928
Author(s):  
MAGIC Collaboration: V A Acciari ◽  
S Ansoldi ◽  
L A Antonelli ◽  
A Arbet Engels ◽  
A Babić ◽  
...  
Keyword(s):  
Crab Nebula ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
High Energy ◽  
Spectral Energy ◽  
Bl Lac ◽  
Very High Energy ◽  
Γ Ray ◽  
Using Data ◽  
The Crab Nebula

ABSTRACT Extreme high-frequency BL Lacs (EHBL) feature their synchrotron peak of the broad-band spectral energy distribution (SED) at νs ≥ 1017 Hz. The BL Lac object 1ES 2344+514 was included in the EHBL family because of its impressive shift of the synchrotron peak in 1996. During the following years, the source appeared to be in a low state without showing any extreme behaviours. In 2016 August, 1ES 2344+514 was detected with the ground-based γ-ray telescope FACT during a high γ-ray state, triggering multiwavelength (MWL) observations. We studied the MWL light curves of 1ES 2344+514 during the 2016 flaring state, using data from radio to very-high-energy (VHE) γ-rays taken with OVRO, KAIT, KVA, NOT, some telescopes of the GASP-WEBT collaboration at the Teide, Crimean, and St. Petersburg observatories, Swift-UVOT, Swift-XRT, Fermi-LAT, FACT, and MAGIC. With simultaneous observations of the flare, we built the broad-band SED and studied it in the framework of a leptonic and a hadronic model. The VHE γ-ray observations show a flux level of 55 per cent of the Crab Nebula flux above 300 GeV, similar to the historical maximum of 1995. The combination of MAGIC and Fermi-LAT spectra provides an unprecedented characterization of the inverse-Compton peak for this object during a flaring episode. The Γ index of the intrinsic spectrum in the VHE γ-ray band is 2.04 ± 0.12stat ± 0.15sys. We find the source in an extreme state with a shift of the position of the synchrotron peak to frequencies above or equal to 1018 Hz.

scholarly journals Tracing the high energy emission of γ-ray detected radio loud quasars

2014 ◽  
Vol 10 (S313) ◽  
pp. 225-230
Author(s):  
Giulia Migliori
Keyword(s):  
Spectral Energy Distribution ◽  
High Energy ◽  
Host Galaxy ◽  
Spectral Energy ◽  
X Ray ◽  
Relativistic Jet ◽  
Quasar Jets ◽  
Γ Ray ◽  
High Energy Emission ◽  
Jet Power

AbstractWe present a multiwavelength study of the core and relativistic jet of the radio loud (RL) quasar RGB J1512+020A (z=0.20). We report the discovery of a bright, 13” extended X-ray jet with a short Chandra observation. We discuss the origin of the jet X-ray emission and its properties in comparison with sample of X-ray quasar jets. The broadband core spectrum is contributed by the emission of the central quasar, by a blazar component, responsible for the γ-ray emission detected by Fermi, and by the host galaxy. We model the non-thermal blazar spectral energy distribution (SED) and constrain the total jet power. The jet power inferred from the blazar SED modeling is in agreement with the values obtained from the total radio power, pointing to a jet that efficiently carries its power up to kiloparsec scales. The quasar emission appears intrinsically weak in the optical-UV band. The disk luminosity estimated from the broad emission lines is lower than the jet power, in agreement with recent results from observations and theory.

scholarly journals A NuSTAR view of powerful γ-ray loud blazars

2019 ◽  
Vol 627 ◽  
pp. A72 ◽  
Author(s):  
G. Ghisellini ◽  
M. Perri ◽  
L. Costamante ◽  
G. Tagliaferri ◽  
T. Sbarrato ◽  
...  
Keyword(s):  
Energy Distribution ◽  
Spectral Energy Distribution ◽  
Peak Frequency ◽  
High Energy ◽  
Spectral Energy ◽  
X Rays ◽  
X Ray ◽  
Γ Ray ◽  
The Universe ◽  
Jet Power

We observed three blazars at z >  2 with the NuSTAR satellite. These were detected in the γ-rays by Fermi/LAT and in the soft X-rays, but have not yet been observed above 10 keV. The flux and slope of their X-ray continuum, together with Fermi/LAT data allows us to estimate their total electromagnetic output and peak frequency. For some of them we were able to study the source in different states, and investigate the main cause of the different observed spectral energy distribution. We then collected all blazars at redshifts greater than 2 observed by NuSTAR, and confirm that these hard and luminous X-ray blazars are among the most powerful persistent sources in the Universe. We confirm the relation between the jet power and the disk luminosity, extending it at the high-energy end.

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