SHALON observations of Active Galactic Nuclei

at red shift from z=0.0179 to z=1.375

V.G. SINITSYNA, A.Y. ALAVERDYAN, M.S. ANDREEVA, K.A. BALYGIN, S.S. BORISOV, I.A. IVANOV,

A.M. KIRICHENKO, A.I. KLIMOV, I.P. KOZHUKHOVA,Yu.B. MAMAEVA, R.M. MIRZAFATIKHOV, N.I. MOSEIKO,

A.I. PALAMARCHUK, S.I. NIKOLSKY, V.Y. SINITSYNA, I.G. VOLOKH

P. N. Lebedev Physical Institute, Leninsky prospect 53, Moscow, 119991 Russia

Very high energy gamma-ray emission ofmetagalactic sources

The radio-loud active galactic nuclei having the radio emission arising from a core region rather than from lobes are often referred to as ”blazars” and include Flat Spectrum Radio Quasars (FSRQ) and BL Lacertae (BL Lac) objects. We present results of long term observations of FSRQ: among them are known object 3c454.3 (z=0.859), high-red shifted quasar 1739+522 (4c+51.37) (z=1.375) and 4c+31.63 (z=0.295), 4c+55.17 (z=0.896) as well as BL Lac type object OJ 287 (z=0.306) which was recently detected by SHALON Cherenkov telescopic system. Also we present the observation results of known BL Lacs Mkn 421 (z=0.031), Mkn 501 (z=0.034) and Mkn 180 (z=0.046). A number of variability periods in different wavelengths including VHE gamma rays were found.

SHALON sky-map catalogue of γ -quantum sources 800 GeV – 100TeV (2013)

A ROSAT HRI image of the region around the galaxyNGC 1275 at the centre of the Perseus galaxy cluster. The contour lines show the radio structure as given byVLA observations. The maxima of the X-ray andradio emission coincide with the active nucleus ofNGC 1275. In contrast, the X-ray emission disappearsalmost completely in the vicinity of the radio lobes.

A Chandra X-ray image of NGC 1275 at the centre of the Perseus galaxycluster. The contour lines show the TeV -structure by SHALON observations.

NGC 1275

NGC 1275In 1996 year a new metagalactic source are detected bySHALON in TeV energies. This object was identified withSeyfert galaxy NGC 1275 (z=0.0179). The γ-ray emissionfrom the position of NGC 1275 was detected above 800 GeV with a statistical significance of 31.4σ (for 271.2hours). The integral γ-ray flux for this source is found tobe (0.78±0.05)×10-12 cm-2s-1 at energies of > 800 GeV . The energy spectrum of NGC 1275 at 0.8 to 20 TeV can beapproximated by the power law F(>EO)∝ E kγ, withkγ= -2.24 ± 0.09. The variations of the γ-ray flux on theyear scale are no more than 20% of average value.

The Seyfert galaxy NGC 1275 has been also observed with Tibet Array(>5TeV) and Veritas telescope at energies about 300 GeV at 2009. The radio-galaxy NGC 1275 has been recently detected by Fermi as a source of high-energy γ-rays. NGC 1275 was recently detected at energies >100 GeVwith MAGIC in observations of 2010 – 2011yy.

The available high and very high energy data for NGC 1275 are well fittedin CM model with three components (Colafrancesco S et al. 2010), inwhich the most energetic and smaller blob produces a synchrotron self-Compton emission observed at γ-ray energies red curve).

Overall spectral energy distribution of NGC 1275. The TeV energy spectrum of NGC 1275 from SHALON,

15 year observations in comparison with other experiments: Fermi LAT’09-11, MAGIC’10-11 and upper limits: EGRET’95, Whipple’06, Veritas’09 and models

Markarian 421The Bl Lac Mkn 421 was detected as the first and the nearest(z = 0.031) metagalactic source of blazar type of TeV energyγ-quanta in 1992 year using Whipple telescope. Presentlythis source is systematic studied by different experiments: VERITAS, SHALON, TACTIC, HESS, MAGIC. Mkn 421 is being intensively studied since 1994 by SHALON. As isseen from figure the SHALON results for this known γ-source are consistent with the data by best world telescopes. An image of γ-ray emission from Mkn 421 is also shown. The integral averaged for the period 1994 to 2011 γ-ray fluxabove 0.8 TeV was estimated as (0.63 ± 0.05) ×10-12 cm-2s-1. Within the range 1 - 10 TeV, the integral energy spectrum iswell described by the power law F( >EO) ∝ Ekγ , withkγ=-1.87 ± 0.11. Extreme variability in different wavelengthsincluding VHE γ-rays on the time-scales from minutes toyears is the most distinctive feature of BL Lac objects.

The increase of the flux over theaverage value was detected in1997 and 2004 observations ofMkn 421 by SHALON andestimated to be(1.01 ± 0.25)×10-12 cm-2s-1 and(0.96±0.2)×10-12cm-2s-1, respectively. The similar variations of the fluxover the average value was alsoobserved with the telescopes ofWhipple, HEGRA, TACTIC, HESS (60O – 67O), MAGIC (45O).

Markarian 501The detection of Mkn 421 as metagalactic VHE γ-ray sourceinitiated a search for VHE emission from several other activegalactic nuclear of blazar type. This led to the detection of BL Lac object Mkn 501 (z = 0.034) by Whipple in 1995. Incontrast to Mkn 421, EGRET had not detected this source, assi\gnificant source of γ-rays. So Mkn 501 was the first object tobe discovered by as γ-ray source from the ground. An image ofγ-ray emission from Mkn 501 by SHALON telescope is alsoshown. The integral average γ-ray flux above 0.8 TeV wasestimated as (0.86±0.06)×10-12 cm-2s-1 and the power index ofthe integral spectrum is kγ=-1.87±0.13. The significant increaseof Mkn 501 flux was detected in 1997 with the VHE groundtelescopes all over the world. The integral γ-ray flux in 1997 and 2006 by by SHALON telescope was estimated as(1.21±0.13)×10-12 cm-2s-1 and (2.05±0.23)×10-12 cm-2s-1, respectively that is comparable with flux of powerful galacticsource Crab Nebula by SHALON.

The last flaring state of Mkn 501 at thevery high energies was detected in theSHALON observational period betweenMarch and June 2009. The flux increasewas detected at 23-24 April and 23-25 May with average flaring flux of(3.41±0.70)×10-12cm-2s-1. This increaseis correlated with the flaring activity atlower energy range in observations ofFermi LAT and VERITAS, MAGIC, Whipple.

Mkn 180 is a known extragalactic source of highfrequency peaked BL Lac type (z = 0.045). As theVHE γ-ray emitting AGNi are variable in flux in allwavebands the correlations between low energyemission (for example X-ray) and γ -ray emission havebeen found. Recently, optical - TeV/GeV correlationwas also found. Mkn 180 was detected in TeV γ-raysby MAGIC during an optical high state [35] .

Earlier, Mkn 180 had been observed byHEGRA [36] and Whipple [37] but were only able toderive flux upper limits, and EGRET did not detect thesource [38, 39]).

The spectral energy distribution of Mrk 180 from modern andarchival observations [3, 35].

Mkn 180

Mkn 180 was observed by SHALON in2007, 2009, 2010, 2011 and 2012, for a total of 71.0 hours, at zenith angles rangingfrom 25o to 34o. After the standardanalysis, a clear excess corresponding to a 14.5σ [40] was determined. No evidencefor flux variability was found. Themeasured integral energy spectrum of Mkn180 can be well described by a power lawwith the index -2.16±0.15. The observedintegral flux above 0.8TeV is

F(E > 0.8TeV ) = (0.65±0.09)×10-12cm-2s-1.

3c 382

3c 382 has been detected by SHALON at TeVenergies (in observations of 2009 - 2012 years)with a statistical significance of 7.8σ. The integral γ-ray flux above 0.8 TeV wasestimated as (0.95±0.20)×10-12 cm-2s-1. Theenergy spectrum of γ-rays in the observedenergy region from 800 GeV is described bythe power law with the index kγ=-1.08± 0.11.The observations of 3c 382 at the high energieswith FermiLAT have gave only the upper limitin the range 0.1-100 GeV.

The 3c 382 observational data bySHALON: Left: The γ-ray integral spectrum;

Right: 3c 382 image at energyrange of > 800 GeV by SHALON;

The spectral energy distribution of 3c 382 by SHALON (open triangles) in comparison with other experiments.

Spectral energy distribution of the gamma-ray emissionfrom 4C+31.63 by SHALON (open triangles) incomparison with thr experimental data at high enrgiesby Fermi LAT (2011).

In observations of 2012 year a new metagalacticsource are detected by SHALON in TeVenergies. This object was identified with FSRQtype source 4с+31.63, previously detected at high energies with Fermi LAT.

4с +31.63

4C+31.63, at redshift z = 0.295, is theexample of blazar class of objects.

4C+31.63 was observed by SHALON in the 2012 at the clear moonless nights, for a total of 13.5 hours, atzenith angles ranging from 12o to 35o

(Li&Ma). After the standard analysis, a clear excess corresponding to a 5.6σwas determined.

I4c+31.63(>0,8ТэВ)=(0.72±0.22)•10-12 см-2 с-1

Spectral energy distribution [53] of the γ-ray emissionfrom OJ 287 by SHALON in comparison with otherexperiment data EGRET [54], Fermi/LAT [55, 56], MAGIC [53] and with theoretical predictions from [55, 56] and also [53]. The open triangles at TeV energies areSHALON spectrum of OJ287; an upper limit at > 0.8 TeVcorresponds to SHALON observations in 1999, 2000; theblack triangles are the gamma-ray spectrum at theincreased flux period of 2010. OJ 287 is the weakestextragalactic source observed by SHALON

OJ 287

In observations of 2008, 2009 and 2010 (31.2 hours in total) the weak γ-ray fluxwas detected. An excess corresponding to a 6.9 σ [40] was determined.The observed integral flux is

F(E > 0.8TeV )=(0.26±0.07)×10-12cm-2s-1. The flux increase over the detected averageflux was found at 14,15 November and 4, 5 December 2010 with value ofF(E > 0.8TeV ) = (0.63±0.15)×10-12cm-2s-1.

(statistical significance of 6.2 σ [40]) withthe softer energy spectrum with a powerlaw with the index -1.96±0.16.

OJ 287 was observed by SHALON in 1999, 2000, 2008,2009 and 2010, for a total of 47.3 hours, at zenith anglesranging from 22o to 34o. The observations of 1999 and2000 years does not reveal a γ-ray flux from the position ofOJ 287, but only an upper limit of < 1.1×10-13cm-2s-1.

3C 454.3, at redshift z = 0.859, is a well-known example of blazar class of objects

Spectral energy distribution of the gamma-rayemission from 3c454.3 by SHALON (open triangles) in comparison with other experimentdata, Fermi/LAT (2009 - 2011); upper limits by MAGIC (2010). In 1998 year a new metagalactic source aredetected by SHALON in TeV energies. Thisobject was identified with FSRQ type source 3c454.3.

3с 454.3

3C 454.3 was observed by SHALON in the period from 1998 to 2012, fora total of 61 hours, at zenith anglesranging from 18o to 35o. After thestandard analysis, a clear excesscorresponding to a 12.2σ wasdetermined.

I3c454.3(>0,8ТэВ)=(0.43±0.07)•10-12cm-2s-1

Spectral energy distribution of the gamma-ray emissionfrom 4C+55.17 by SHALON (open triangles) incomparison with the experiment data by EGRET, FermiLAT (2011).

In 2012 year a new metagalactic source aredetected by SHALON in TeV energies. This objectwas identified with FSRQ type source 4с+55.17, previously detected at high energies with EGRET and Fermi LAT.

4с +55.17

4C+55.17, at redshift z = 0.896, is the radio-loud active galaxy clasified as a FSRQ.

4C+55.17 was observed by SHALON in the period from 2012 and 2013 at the clear moonless nights, for a total of 23hours, at zenith angles ranging from13o to 35o (Li&Ma). After the standardanalysis, a clear excess correspondingto a 7.8σ was determined.

I4c+55.17(>0,8ТэВ)=(0.93±0.23)•10-12 cm-2 s-1

1739+522, at redshift z = 1.375, is a powerful example of blazar class ofobjects.1739+522 was observed by SHALON inthe period from 1999 to 2012, at the clear moonless nights, for a total of 114 hours, atzenith angles ranging from 14o to 35o

(Li&Ma). After the standard analysis, a clear excess corresponding to a 14.2σ wasdetermined.

I1739+522(>0,8ТэВ)=(0.49±0.05)•10-12 cm-2 s-1

1739+522 (4с+51.37)

Spectral energy distribution of the gamma-rayemission from 1739+522 by SHALON (open triangles) in comparison with other experimentdata Fermi/LAT (2009 - 2011).

In 1999 year a new metagalactic source aredetected by SHALON in TeV energies. Thisobject was identified with FSRQ type source 1739+522 (4с+51.37).

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