Searching for new very high energy emitting AGN among the unclassifed and unassociated Fermi-LAT sources
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Date
2019-01
Authors
Marais, Johannes Petrus
Journal Title
Journal ISSN
Volume Title
Publisher
University of the Free State
Abstract
English: Jet dominated Active Galactic Nuclei (AGN) are the most energetic persistent sources of emission
in the universe, emitting radiation across the entire electromagnetic spectrum. When these jets
are pointed towards the observer, they become known as blazars. Blazar emission is dominated
by the beamed non-thermal emission from the relativistic jet and are the brightest sources in the
extragalactic sky. Blazars, sub-categorized into BL Lacertae objects (BL Lacs) and Flat Spectrum
Radio Quasars (FSRQs) exhibit variability at all wavelengths on diverse timescales, high
polarization and weak or featureless optical spectra. These extreme sources provide a laboratory
to test some of the most energetic physical processes in the known universe. In order to study the
processes responsible for the highest energy emission originating from blazar jets, more Very High
Energy (VHE) emitting blazars must be found and studied with Imaging Air Cherenkov Telescopes
(IACTs). The small sample of currently known VHE emitting blazars, studied for many years,
has not yet provided a complete understanding of blazar physics. A study to monitor 17 VHE
blazars detected by the High Energy Stereoscopic System (H.E.S.S.) with the Watcher Robotic
Telescope has been underway since May 2015. A fast reduction and analysis pipeline, written in
python and using PyRAF to interface with IRAF, was developed to perform aperture photometry
on 14 of these sources and search for long-term variability (LTV). In addition, to search for new
VHE emitting blazars observable with IACTs, a sample of 11 Blazar Candidates of Uncertain
Type (BCUs) listed in the Third Fermi Large Area Telescope Source Catalog (3FGL), 11 BCUs
and an unassociated source listed in the Third Catalogue of Hard Large Area Telescope sources
(3FHL), selected based on hard
-ray spectra and lack of redshift measurements were identi ed
for spectroscopic follow-up with the aim of classifying them. The selected sources were observed
with the SpUpNIC grating spectrograph mounted on the SAAO 1.9-m telescope. A selection of
6 3FHL sources identi ed for spectroscopic study were also observed with the Sutherland Highspeed
Optical Camera (SHOC) mounted on the SAAO 1.0-m telescope to search for intra-day
variability (IDV). All 22 of the BCUs were classi ed as BL Lac objects based on the absence of
strong emission lines and a diluted Ca break (less than 40%). Further, redshifts were calculated
for 11 BCUs and potential redshifts for 4 BCUs. Further searches for photometry variability were
undertaken for all sources. Spectral Energy Distributions (SEDs) were constructed to determine
which of the observed BCUs were good candidates to be observed with IACTs. The 50h H.E.S.S.
and Cherenkov Telescope Array (CTA) South sensitivity curves were overlayed on the SEDs. Of
the BCUs observed, 8 of the sources have
-ray emission above the CTA detection threshold and
are good candidates for VHE observation.
Afrikaans: Spuitstraal gedomineerde Aktiewe Galaktiese Kerne (AGN) is die mees energieke permanente stralingsbronne in die heelal en produseer straling wat strek oor meeste van die elektromagnetiese spectrum. Wanneer die spuitstraal in die rigting van die waarnemer geori enteer is, staan die AGN as blazars bekend. Blazar straling word gedomineer deur nie-termiese straling vanaf die relativistiese spuitstraal en is die helderste voorwerpe in in die buitegalaktiese hemelruim. Blazars, verdeel in BL Lacertae voorwerpe (BL Lacs) en Plat Spectrum Radio Kwasars (FSRQ), varieer op diverse tydskale, het ho e polarisasie en swak of afwesige optiese emissielyne. Hierdie eksotiese voorwerpe verskaf `n laboratorium om die mees energieke siese prosesse in die heelal te toets. Om die prosesse verandwoordelik vir die hoogste energie uitstraling van die spuitstraal te toets, moet meer Baie Ho e Energie (VHE) bronne ondek word en met Beelding Atmosferiese Cherenkov Teleskope (IACT) bestudeer word. Die klein populasie reeds bekende VHE blazars wat al vir baie jare bestudeer word het nog nie `n volledige begrip van blazar Fisika openbaar nie. `n Studie om 17 VHE blazars wat voorheen deur die Ho e Energie Stereoskopiese Sisteem (H.E.S.S.) waargeneem is te monitor met die Watcher robotiese teleskoop is al besig vanaf Mei 2015. `n Vinnige analiese pyplyn, ontwikkel in python, wat gebruik maak van PyRAF om met IRAF te kommunikeer, was gebruik om die lang-termyn variasie van 14 van die blazars gemonitor deur Watcher te ondersoek. `n Soektog na nuwe blazars wat deur IACTs waargeneem kan word is ook begin. 11 blazars van onbekende tipe (BCU) gelys in die \Third Fermi Large Area Telescope Source Catalog" (3FGL), 11 BCUs gelys in die \Third Catalogue of Hard Large Area Telescope sources" (3FHL) en `n 3FHL voorwerp sonder enige genootskap met bronne by ander gol engtes wat gekies is gebaseer op hulle harde -straal emissie en afwesige rooiverskuiwing is waargeneem met die SAAO 1.9-m SpUpNIC spektrograaf met die doel om hulle te klasi seer. `n Groep van 6 3FHL bronne was ook waargeneem met die SAAO 1.0-m Ho e Spoed Optiese Kamera (SHOC) om hulle intra-dag variasie (IDV) te ondersoek. Al 22 van die BCUs is as BL Lac voorwerpe geklasi seer, gebaseer op die afwesigheid van sterk emissie lyne en `n swak Ca breuk. Rooiverskuiwings was vir 11 BCUs bepaal en potensiale rooiverskuiwings vir 4 BCUs. Spectraal Energie Verspreidings was gebou vir die BCUs om te bepaal of hulle sigbaar mag wees met IACTs. Die 50 uur instrument sensitiwiteit kurwes van die Cherenkov Teleskoop Opstelling (CTA) is op die SEDs gepas om te bepaal watter BCUs helder genoeg is om sigbaar te wees. Net 8 van die BCUs se -straal emissie is helder genoeg om deur CTA waargeneem te word.
Afrikaans: Spuitstraal gedomineerde Aktiewe Galaktiese Kerne (AGN) is die mees energieke permanente stralingsbronne in die heelal en produseer straling wat strek oor meeste van die elektromagnetiese spectrum. Wanneer die spuitstraal in die rigting van die waarnemer geori enteer is, staan die AGN as blazars bekend. Blazar straling word gedomineer deur nie-termiese straling vanaf die relativistiese spuitstraal en is die helderste voorwerpe in in die buitegalaktiese hemelruim. Blazars, verdeel in BL Lacertae voorwerpe (BL Lacs) en Plat Spectrum Radio Kwasars (FSRQ), varieer op diverse tydskale, het ho e polarisasie en swak of afwesige optiese emissielyne. Hierdie eksotiese voorwerpe verskaf `n laboratorium om die mees energieke siese prosesse in die heelal te toets. Om die prosesse verandwoordelik vir die hoogste energie uitstraling van die spuitstraal te toets, moet meer Baie Ho e Energie (VHE) bronne ondek word en met Beelding Atmosferiese Cherenkov Teleskope (IACT) bestudeer word. Die klein populasie reeds bekende VHE blazars wat al vir baie jare bestudeer word het nog nie `n volledige begrip van blazar Fisika openbaar nie. `n Studie om 17 VHE blazars wat voorheen deur die Ho e Energie Stereoskopiese Sisteem (H.E.S.S.) waargeneem is te monitor met die Watcher robotiese teleskoop is al besig vanaf Mei 2015. `n Vinnige analiese pyplyn, ontwikkel in python, wat gebruik maak van PyRAF om met IRAF te kommunikeer, was gebruik om die lang-termyn variasie van 14 van die blazars gemonitor deur Watcher te ondersoek. `n Soektog na nuwe blazars wat deur IACTs waargeneem kan word is ook begin. 11 blazars van onbekende tipe (BCU) gelys in die \Third Fermi Large Area Telescope Source Catalog" (3FGL), 11 BCUs gelys in die \Third Catalogue of Hard Large Area Telescope sources" (3FHL) en `n 3FHL voorwerp sonder enige genootskap met bronne by ander gol engtes wat gekies is gebaseer op hulle harde -straal emissie en afwesige rooiverskuiwing is waargeneem met die SAAO 1.9-m SpUpNIC spektrograaf met die doel om hulle te klasi seer. `n Groep van 6 3FHL bronne was ook waargeneem met die SAAO 1.0-m Ho e Spoed Optiese Kamera (SHOC) om hulle intra-dag variasie (IDV) te ondersoek. Al 22 van die BCUs is as BL Lac voorwerpe geklasi seer, gebaseer op die afwesigheid van sterk emissie lyne en `n swak Ca breuk. Rooiverskuiwings was vir 11 BCUs bepaal en potensiale rooiverskuiwings vir 4 BCUs. Spectraal Energie Verspreidings was gebou vir die BCUs om te bepaal of hulle sigbaar mag wees met IACTs. Die 50 uur instrument sensitiwiteit kurwes van die Cherenkov Teleskoop Opstelling (CTA) is op die SEDs gepas om te bepaal watter BCUs helder genoeg is om sigbaar te wees. Net 8 van die BCUs se -straal emissie is helder genoeg om deur CTA waargeneem te word.
Description
Keywords
Techniques: photometry, Spectroscopy - active galaxies: BL Lac objects, FSRQ, SpUpNIC, Dissertation (M.Sc. (Physics))--University of the Free State, 2019, Redshift - instruments: Watcher, SHOC