scholarly journals An empirical approach to the extragalactic background light from AEGIS galaxy SED-type fractions

2011 ◽  
Vol 7 (S284) ◽  
pp. 442-445
Author(s):  
Alberto Domínguez
Keyword(s):  
Galaxy Evolution ◽  
Direct Measurement ◽  
Spectral Energy ◽  
Intensity Level ◽  
Energy Distributions ◽  
Extragalactic Background Light ◽  
Background Light ◽  
Luminosity Functions ◽  
Novel Method ◽  
Γ Ray

AbstractThe extragalactic background light (EBL) is of fundamental importance both for understanding the entire process of galaxy evolution and for γ-ray astronomy. However, the overall spectrum of the EBL between 0.1 and 1000 μm has never been determined directly, neither from observed luminosity functions (LFs), over a wide redshift range, nor from any multiwavelength observation of galaxy spectral energy distributions (SEDs). The evolving overall spectrum of the EBL is derived here utilizing a novel method based on observations only. It is emphasized that the local EBL seems already well constrained from the UV up to the mid-IR. Different independent methodologies such as direct measurement, galaxy counts, γ-ray attenuation and realistic EBL modelings point towards the same EBL intensity level. Therefore, a relevant contribution from Pop III stars to the local EBL seems unlikely.

scholarly journals Overdensity of SMGs in fields containing z ∼ 0.3 galaxies: magnification bias and the implications for studies of galaxy evolution

2020 ◽  
Vol 498 (4) ◽  
pp. 4635-4649
Author(s):  
L Dunne ◽  
L Bonavera ◽  
J Gonzalez-Nuevo ◽  
S J Maddox ◽  
C Vlahakis
Keyword(s):  
Galaxy Evolution ◽  
Cross Correlation ◽  
High Redshift ◽  
Spectral Energy ◽  
Complete Sample ◽  
Energy Distributions ◽  
Statistical Measures ◽  
Luminosity Functions ◽  
Significant Contamination ◽  
The Impact

ABSTRACT We report a remarkable overdensity of high-redshift submillimetre galaxies (SMG), 4–7 times the background, around a statistically complete sample of twelve 250 μm selected galaxies at z = 0.35, which were targeted by ALMA in a study of gas tracers. This overdensity is consistent with the effect of lensing by the haloes hosting the target z = 0.35 galaxies. The angular cross-correlation in this sample is consistent with statistical measures of this effect made using larger sub-mm samples. The magnitude of the overdensity as a function of radial separation is consistent with intermediate scale lensing by haloes of the order of $7\times 10^{13}\mbox{ $\rm M_{\odot }$ }$, which should host one or possibly two bright galaxies and several smaller satellites. This is supported by observational evidence of interaction with satellites in four out of the six fields with SMG, and membership of a spectroscopically defined group for a fifth. We also investigate the impact of these SMG on the reported Herschel fluxes of the z = 0.35 galaxies, as they produce significant contamination in the 350 and 500 μm Herschel bands. The higher than random incidence of these boosting events implies a significantly larger bias in the sub-mm colours of Herschel sources associated with z < 0.7 galaxies than has previously been assumed, with fboost = 1.13, 1.26, 1.44 at 250, 350, and 500 μm . This could have implications for studies of spectral energy distributions, source counts, and luminosity functions based on Herschel samples at z = 0.2–0.7.

scholarly journals Nonthermal Radiation of the Extreme TeV Blazar 1ES 0229+200 from Electromagnetic Cascades on Infrared Photon Field

Universe ◽  
2021 ◽  
Vol 7 (12) ◽  
pp. 494
Author(s):  
Timur Dzhatdoev ◽  
Vladimir Galkin ◽  
Egor Podlesnyi
Keyword(s):  
Galactic Nuclei ◽  
Spectral Energy ◽  
Emission Model ◽  
Energy Distributions ◽  
Extragalactic Background Light ◽  
Nonthermal Radiation ◽  
Photon Field ◽  
Emission Models ◽  
Infrared Photon ◽  
Γ Ray

Extreme TeV blazars (ETBs) are active galactic nuclei with jets presumably pointing towards the observer having their intrinsic (compensated for the effect of γ-ray absorption on extragalactic background light photons) spectral energy distributions (SEDs) peaked at an energy in excess of 1 TeV. These sources typically reveal relatively weak and slow variability as well as higher frequency of the low-energy SED peak compared to other classes of blazars. It proved to be exceedingly hard to incorporate all these peculiar properties of ETBs into the framework of conventional γ-ray emission models. ETB physics have recently attracted great attention in the astrophysical community, underlying the importance of the development of self-consistent ETB emission model(s). We propose a new scenario for the formation of X-ray and γ-ray spectra of ETBs assuming that electromagnetic cascades develop in the infrared photon field surrounding the central blazar engine. This scenario does not invoke compact fast-moving sources of radiation (so-called “blobs”), in agreement with the apparent absence of fast and strong variability of ETBs. For the case of the extreme TeV blazar 1ES 0229+200 we propose a specific emission model in the framework of the considered scenario. We demonstrate that this model allows to obtain a good fit to the measured SED of 1ES 0229+200.

scholarly journals Far Infrared Extragalactic Background Radiation: Source Counts with ISOPHOT

2001 ◽  
Vol 204 ◽  
pp. 261-261
Author(s):  
M. Juvela ◽  
K. Mattila ◽  
D. Lemke
Keyword(s):  
Galaxy Evolution ◽  
Background Radiation ◽  
Far Infrared ◽  
Spectral Energy ◽  
Number Density ◽  
High Confidence ◽  
Energy Distributions ◽  
Extragalactic Background Light ◽  
Distant Galaxies ◽  
High Confidence Level

We have searched for point-like sources in eight fields mapped at two or three wavelengths between 90 μm and 180 μm with the ISOPHOT instrument aboard the ISO satellite. Most of the 55 sources detected are suspected to be extragalactic and cannot be associated with previously known objects. It is probable, also from the far-infrared (FIR) spectral energy distributions, that dust-enshrouded, distant galaxies form a significant fraction of the sources.We present a tentative list of the detected extragalactic FIR-sources. Based on the analyzed data we estimate the number density of extragalactic sources at wavelengths 90 μm, 150 μm and 180 μm and at flux density levels down to 100 mJy to be 1 x 105 sr−1, 2x105 sr−1, and 3xl05 sr−1, respectively.Models of strong galaxy evolution are in best agreement with our results, although the number of detections exceeds predictions of most models. No-evolution models can be rejected at a high confidence level. Comparison with COBE results indicates that at 90 μm the detected sources correspond to >20% of the extragalactic background light. At longer wavelengths the corresponding fraction is ~ 10%.

scholarly journals Studies of extragalactic background light with TeV BL Lacertae objects

2020 ◽  
Vol 499 (2) ◽  
pp. 2662-2671
Author(s):  
Qin Longhua ◽  
Wang Jiancheng ◽  
Gao Quangui ◽  
Na Weiwei ◽  
Li Huaizhen ◽  
...  
Keyword(s):  
Power Law ◽  
High Energy ◽  
Spectral Energy ◽  
Photon Density ◽  
Energy Distributions ◽  
Bl Lacertae Objects ◽  
Extragalactic Background Light ◽  
Background Light ◽  
Bl Lacertae ◽  
Bl Lacs

ABSTRACT Very high energy (VHE; E ≥ 100 GeV) gamma-rays from cosmological distances are attenuated by the extragalactic background light (EBL) in the infrared to ultraviolet bands. By contrasting measured versus intrinsic emission,we can derive the EBL photon density. However, we do not know the intrinsic spectra and the EBL separately, only their combined effect. Here we first present a flexible model-dependent optical depth method to study the EBL by fitting the emission spectra of TeV BL Lacertae objects (BL Lacs) via a one-zone leptonic synchrotron self-Compton model (SSC). We have little information about electron energy distributions (EEDs) in the jet, which is critically important to build spectral energy distributions (SEDs) in the SSC scenario. Based on current particle acceleration models, we use two types of EEDs to fit the observed spectra: a power-law log-parabola (PLLP) EED and a broken power-law (BPL) EED. We find that the upper limit of the EBL density is about 30 n W m−2 sr−1, which is similar to the published measurement. Furthermore, we propose an unprecedented method to test the radiation mechanisms involved in TeV objects, by simply comparing the reduced EBL density with the limit obtained by galaxy counts. We demonstrate that for some BL Lacs, at least, the one-zone SSC model should be reconsidered.

scholarly journals Identifications of Faint IRAS Sources

1996 ◽  
Vol 171 ◽  
pp. 402-402
Author(s):  
M.W. Kümmel ◽  
S.J. Wagner
Keyword(s):  
Broad Band ◽  
Far Infrared ◽  
Power Laws ◽  
Point Sources ◽  
Spectral Energy ◽  
Energy Distributions ◽  
The North ◽  
Luminosity Functions ◽  
Error Circle ◽  
Radio Band

From overlapping scans in the IRAS all-sky survey and additional pointed observations the deepest far infrared survey before ISO exists in the region around the North Ecliptic Pole (NEP) (Hacking P. and Houck J.R., ApJS 63 p. 311). This survey contains detections up to 10 and fluxes up to 100 times fainter than the IRAS survey. In the central square degree around the NEP we combine the far IR-survey with deep radio data at 151 MHz and 1.5 GHz (Visser, A.E. et al., A&AS 110 p. 419, Kollgaard, R.I. et al., ApJS 93 p. 145) and own observation at 2.2μm (K′) and 435nm (B). The error circle around the IRAS source was chosen to include the true source with 85% probability (1.4 sigma). For 29 of the 32 IRAS sources we found at least one possible counterpart. Ten of the objects have multiple (up to four) counterparts in K′. Four of the IRAS sources have counterparts in the 1.5 GHz survey. The higher accuracy of the radio position (∼ 1″) allowed an unambiguous identification of the K′ counterpart. None of the IRAS sources could be found in the 151 MHz survey. The broad band spectra of the three galaxies with measured radio flux exhibit maximum emission between the radio band and 100μm which corresponds to emission by cool dust (< 50 K). Contrary to the infrared luminosity functions at 12μm and 60μm which show power laws, the K′ luminosity function is bimodal. The brightest K′ objects are all point sources. Due to the small number statistics the power law indices of the luminosity functions can not be distinguished. We find a linear relationship between the K′ flux and the flux at 60μm and 12μm over at least one decade. The large deviations by individual sources make an identification of the correct counterpart through this relation impossible. The spectral energy distributions of unambiguously identified sources span only one decade in energy (vSv), i.e. they have flat energy distributions. This suggests an identification of K′ objects with flat energy distribution in case of multiple counterparts.

scholarly journals Counts and Colors of Faint Galaxies

1980 ◽  
Vol 92 ◽  
pp. 9-15
Author(s):  
Richard G. Kron
Keyword(s):  
Galaxy Evolution ◽  
Rest Frame ◽  
Spectral Energy ◽  
Measured Quantity ◽  
Energy Distributions ◽  
Color Distribution ◽  
Number Magnitude ◽  
Redshift Galaxy ◽  
Wide Range ◽  
Apparent Color

The color distribution of faint galaxies is an observational dimension which has not yet been fully exploited, despite the important constraints obtainable for galaxy evolution and cosmology. Number-magnitude counts alone contain very diluted information about the state of things because galaxies from a wide range in redshift contribute to the counts at each magnitude. The most-frequently-seen type of galaxy depends on the luminosity function and the relative proportions of galaxies of different spectral classes. The addition of color as a measured quantity can thus considerably sharpen the interpretation of galaxy counts since the apparent color depends on the redshift and rest-frame spectrum. To a first approximation two colors for a galaxy can determine a redshift and a spectral class, because redshift loci in a color-color diagram run roughly parallel to each other, and roughly perpendicular to the zero-redshift galaxy “main sequence” (Tinsley 1977a, Pence 1976) for small redshift. This game becomes more and more uncertain at higher redshift, because the systematics of galaxy UV spectral energy distributions are not well known, and what is known is not well understood (Code and Welch 1979). Redshifts for some random sample of faint galaxies is required to pin down the color-redshift relations; steps in this direction have already been taken by E. Turner. The reason for stressing colors, as opposed to redshifts, is that colors can be obtained relatively easily for large samples of faint galaxies if panoramic detectors are used: indeed, colors are not much more difficult to obtain than magnitudes.

scholarly journals The intrinsic gamma-ray spectrum of TXS 0506+056: intergalactic propagation effects

2020 ◽  
Vol 500 (2) ◽  
pp. 2188-2195
Author(s):  
Andrey Saveliev ◽  
Rafael Alves Batista
Keyword(s):  
Gamma Ray ◽  
Recent Observation ◽  
High Energy ◽  
Spectral Energy ◽  
Electromagnetic Spectrum ◽  
Extragalactic Background Light ◽  
Background Light ◽  
Propagation Effects ◽  
Very High Energy ◽  
Energy Gamma

ABSTRACT The recent observation of high-energy neutrinos from the 2017 flare of the blazar TXS 0506+056, together with counterparts across the whole electromagnetic spectrum, opens up new possibilities for investigating the properties of this class of objects as well as the traversed medium. Propagation effects such as the attenuation of the very-high-energy gamma-ray component by the extragalactic background light are well known, and usually taken into account when fitting spectral energy distributions of objects. Other effects such as those of intergalactic magnetic fields are, however, often neglected. In this work, we present a comprehensive study of the influence of these fields and the extragalactic background light on the determination of the intrinsic gamma-ray spectrum of this blazar.

scholarly journals Recent star formation in intermediate redshift (0.35< z <1.5) early–type galaxies

2012 ◽  
Vol 10 (H16) ◽  
pp. 132-132
Author(s):  
M. J. Rutkowski ◽  
H. Jeong ◽  
S. Yi ◽  
S. Kaviraj ◽  
S. H. Cohen ◽  
...  
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Hubble Space Telescope ◽  
Spectral Energy ◽  
Observational Constraints ◽  
Wide Field ◽  
Early Type ◽  
Energy Distributions ◽  
Near Ir ◽  
Intermediate Redshift

AbstractWe measured the UV-optical-near-IR spectral energy distributions (SEDs) of redshift z ~ 0.3-1.5 early-type galaxies (ETGs) with the Hubble Space Telescope (HST) Wide Field Camera 3 (Rutkowski et al.2012). We searched for young stellar populations and morphological signatures of the mechanisms driving recent star formation (RSF) in these ETGs in order to provide observational constraints on models of galaxy evolution.

A COMPREHENSIVE STATISTICAL DESCRIPTION OF RADIO-THROUGH- γ -RAY SPECTRAL ENERGY DISTRIBUTIONS OF ALL KNOWN BLAZARS

2016 ◽  
Vol 224 (2) ◽  
pp. 26 ◽  
Author(s):  
Peiyuan Mao ◽  
C. Megan Urry ◽  
Francesco Massaro ◽  
Alessandro Paggi ◽  
Joe Cauteruccio ◽  
...  
Keyword(s):  
Spectral Energy ◽  
Spectral Energy Distributions ◽  
Energy Distributions ◽  
Γ Ray
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