2WHSP: A multi-frequency selected catalogue of high energy and very high energy<i>γ</i>-ray blazars and blazar candidates

Chang, Y. L.; Arsioli, B.; Giommi, P.; Padovani, P.

doi:10.1051/0004-6361/201629487

Cited by 78 publications

(88 citation statements)

References 58 publications

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“…We have used all the high energy catalogs presently available including the 2FHL, the 2WHSP [35], and the 3LAC [36], as detailed in [29] and Tab. I, focusing on HBL blazars.…”

Section: Discussionmentioning

confidence: 99%

A Novel Study Connecting Ultra-High Energy Cosmic Rays, Neutrinos, and Gamma-Rays

Coenders

Resconi

Padovani

et al. 2018

Proceedings of 2016 International Conference on Ultra-High Energy Cosmic Rays (UHECR2016)

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We present a novel study connecting ultra-high energy cosmic rays, neutrinos, and gamma-rays with the objective to identify common counterparts of the three astrophysical messengers. In the test presented here, we first identify potential hadronic sources by filtering gamma-ray emitters that are in spatial coincidence with IceCube neutrinos. Subsequently, these objects are correlated against ultra-high energy cosmic rays detected by the Pierre Auger Observatory and the Telescope Array, scanning in gamma-ray flux and angular separation between sources and cosmic rays. A maximal excess of 80 cosmic rays (41.9 expected) is observed for the second catalog of hard Fermi-LAT objects of blazars of the high synchrotron peak type. This corresponds to a deviation from the nullhypothesis of 2.94σ. No excess is observed for objects not in spatial connection with neutrinos. The gamma-ray sources that make up the excess are blazars of the high synchrotron peak type.

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“…We have used all the high energy catalogs presently available including the 2FHL, the 2WHSP [35], and the 3LAC [36], as detailed in [29] and Tab. I, focusing on HBL blazars.…”

Section: Discussionmentioning

confidence: 99%

A Novel Study Connecting Ultra-High Energy Cosmic Rays, Neutrinos, and Gamma-Rays

Coenders

Resconi

Padovani

et al. 2018

Proceedings of 2016 International Conference on Ultra-High Energy Cosmic Rays (UHECR2016)

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“…They applied two different SSC models Fossati et al 1998) to calculate the level of TeV emission. Arsioli et al (2015); Chang et al (2017) (hereafter,1WHSP and 2WHSP) introduced 76 and 136 promising high synchrotron peak (HSP) blazars by applying the figure of merit (FOM) criterion, which is defined as the ratio between the synchrotron peak flux (ν peak F ν peak ) of a source and the faintest TeV blazars. These sources were selected from a list of 992 and 1691 infrared colour-colour selected sources restricted by IR-radio and IR-X-ray flux ratios.…”

Section: Discussionmentioning

confidence: 99%

Empirical multi-wavelength prediction method for Very High Energy Gamma-ray emitting BL Lacs

2016

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Aim:We have collected the most complete multi-wavelength (6.0 − 6.0 × 10 −18 cm) dataset of very high energy (VHE) γ-ray emitting (TeV) BL Lacs, which are the most numerous extragalactic VHE sources. Using significant correlations between different bands, we aim to identify the best TeV BL Lac candidates that can be discovered by the current and next generation of imaging air Cherenkov telescopes. Methods: We formed five datasets from lower energy data, i.e. radio, mid-infrared, optical, X-rays, and GeV γ-ray, and five VHE γ-ray datasets to perform a correlation study between different bands and to construct the prediction method. The low energy datasets were averaged for individual sources, while the VHE γ-ray data were divided into subsets according to the flux state of the source. We then looked for significant correlations and determined their best-fit parameters. Using the best-fit parameters we predicted the level of VHE γ-ray flux for a sample of 182 BL Lacs, which have not been detected at TeV energies. We identified the most promising TeV BL Lac candidates based on the predicted VHE γ-ray flux for each source. Results: We found 14 significant correlations between radio, mid-infrared, optical, γ-ray, and VHE γ-ray bands. The correlation between optical and VHE γ-ray luminosity is established for the first time. We attribute this to the more complete sample and more accurate handling of host galaxy flux in our work. We found nine BL Lac candidates whose predicted VHE γ-ray flux is high enough for detection in less than 25 hours with current imaging air Cherenkov telescopes.

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“…increases with increasing FOM, and there is a considerable increment in the fraction of sources detected for each FOMbin when accounting for the 150 sources listed in Table A.1. Therefore, the 2WHSP sample shows its potential for unveiling high/lower-significance γ-ray sources, emphasising the power of considering multifrequency information to select VHE γ-ray targets for CTAs, as discussed in Arsioli et al (2015) and Chang et al (2017). In addition, given that γ-ray detected HSP blazars have been suggested as counterparts of IceCube astrophysical neutrinos (Padovani et al 2016), our present work may contribute to discussions in the realm of multi-messenger astrophysics, especially when studying cross-correlations between extreme γ-ray blazars and astro-particles.…”

Section: Detection Efficiency According To Fom Parametermentioning

confidence: 99%

“…Given the importance of finding new HSP blazars, an extension of the 1WHSP sample (the 2WHSP, Chang et al 2017) has ben assembled. It considers sources located at latitudes as low as |b| = 10…”

Section: Introductionmentioning

confidence: 99%

“…Compared to the 1WHSP, the 2WHSP sample incorporates extra X-ray catalogs like Einstein IPC, IPC slew and Chandra (Harris et al 1993;Elvis et al 1992;Evans et al 2010) as well as updated versions from 3XMM-DR5 and XMM-slew catalogs (Rosen et al 2016;Saxton et al 2008). In addition, Swift-XRT alone performed a series of ∼160 new X-ray observation of WHSP sources (enabling us to better estimate synchrotron peak parameters) and an extensive study of X-ray extended sources helped to avoid contamination with spurious objects (more details are given by Chang et al 2017) 4 . Since the 2WHSP catalog supersedes the 1WHSP (with improved selection and better estimate of synchrotron peak parameters), from now on we only refer to the 2WHSP sample.…”

Section: Introductionmentioning

confidence: 99%

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Searching forγ-ray signature in WHSP blazars

Arsioli

Chang

2017

A&A

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Aims. A direct search of γ-ray emission centered on multifrequency selected candidates is a valuable complementary approach to the standard search adopted in current γ-ray Fermi-LAT catalogs. Our sources are part of the 2WHSP sample that was assembled with the aim of providing targets for Imaging Atmospheric Cherenkov Telescopes (IACT). A likelihood analysis based on their known position enabled us to detect 150 γ-ray excess signals that have not yet been reported in previous γ-ray catalogs (1FGL, 2FGL, 3FGL). By identifying new sources, we solve a fraction of the extragalactic isotropic γ-ray background (IGRB) composition, improving the description of the γ-ray sky. Methods. We perform data reduction with the Fermi Science Tools using positions from 400 high synchrotron peaked (HSP) blazars as seeds of tentative γ-ray sources; none of them have counterparts from previous 1FGL, 2FGL and 3FGL catalogs. Our candidates are part of the 2WHSP sample (currently the largest set of HSP blazars). We focus on HSPs characterized by bright synchrotron component with peak flux ν f (ν) ≥ 10 −12.1 erg/cm 2 /s, testing the hypothesis of having a γ-ray source in correspondence to the WHSP positions. Our likelihood analysis considers the 0.3−500 GeV energy band, integrating over 7.2 yr of Fermi-LAT observation and making use of the Pass 8 data release. Results. From the 400 candidates tested, a total of 150 2WHSPs showed excess γ-ray signature: 85 high-significance detections with test statistic (TS) > 25, and 65 lower-significance detections with TS between 10 to 25. We assume a power law spectrum in the 0.3−500 GeV band and list the spectrum parameters describing all 150 new γ-ray sources. We study the γ-ray photon spectral index distribution, the likelihood of detection according to the synchrotron peak brightness (figure of merit parameter), and plot the measured γ-ray LogN-LogS of HSP blazars, also discussing the portion of the IGRB that has been resolved by the present work. We also report on four cases where we could resolve source confusion and find counterparts for unassociated 3FGL sources with the help of high-energy TS maps together with multifrequency data. The 150 new γ-ray sources are named with the acronym 1BIGB for the first version of the Brazil ICRANet Gamma-ray Blazar catalog, in reference to the cooperation agreement supporting this work.

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2WHSP: A multi-frequency selected catalogue of high energy and very high energyγ-ray blazars and blazar candidates

Cited by 78 publications

References 58 publications

A Novel Study Connecting Ultra-High Energy Cosmic Rays, Neutrinos, and Gamma-Rays

A Novel Study Connecting Ultra-High Energy Cosmic Rays, Neutrinos, and Gamma-Rays

Empirical multi-wavelength prediction method for Very High Energy Gamma-ray emitting BL Lacs

Searching forγ-ray signature in WHSP blazars

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