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Mingaliev M.G., Sotnikova Yu.V., Erkenov A.K. Torniainen I., Tornikoski M.

Special Astrophysical Observatory of RAS, Nizhnij Arkhyz. Multifrequency study of Gigahertz Peaked Spectrum (GPS) sources and candidates with RATAN-600. Mingaliev M.G., Sotnikova Yu.V., Erkenov A.K. Torniainen I., Tornikoski M. what is GPS (Gigahertz Peaked Spectrum)?.

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Mingaliev M.G., Sotnikova Yu.V., Erkenov A.K. Torniainen I., Tornikoski M.

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  1. Special Astrophysical Observatory of RAS, NizhnijArkhyz Multifrequency study of Gigahertz Peaked Spectrum (GPS) sources and candidates with RATAN-600 Mingaliev M.G., Sotnikova Yu.V., Erkenov A.K. Torniainen I., Tornikoski M.

  2. what is GPS (Gigahertz Peaked Spectrum)? spectral peak (500 MHz - 10 GHz in observer’s frame); homogeneous self-absorbed synchrotron source; powerful (log P1.4 ≥ 25 WHz-1); compact (≤1 kpc); bright radio source population (~10%); ● young radio sources (< 104 yr) [Fanti 1995; Readhead 1996; O’Dea & Baum 1997] ● dense environment [O'Dea 1991, Gopal-Krishna 1991] ● recurrent activity [Baum 1991]

  3. why GPS? • contaminated GPS-sources sample • galaxy type 0.1≤ z ≤1;quasar type 1≤ z ≤4 • different properties but similar spectrum’s shape • GPS quasars are considerably “contaminated” by variable sources • variable or not? • long-term multifrequency monitoring

  4. goals, tools, sample, observations 2006-2010 simultaneousradiospectra variability spectralproperties countof sources RATAN-600: 1.1, 2.3, 4.8, 7.7, 11.2 and 21.7 GHz 12 observing campaigns (5 years of monitoring): 76 quasar-type and 29 galaxy-type; 17 – unidentified; total number - 122 sources 2) complete sample (1999-2010): 75° ≤ δ ≤ 88°, S1.4GHz ≥ 200mJy: 4-5 candidates

  5. fluxes and radiospectra

  6. fluxes and radiospectra

  7. candidates in GPS only 25% candidates in GPS (using parameters of spectrum for homogeneous self-absorbed synchrotron source with a power law electron energy distribution: α1≥ 0.5 and α2 ≤-0.7 (below and above spectral peak) FWHM ≤ 1.2 frequency decades (full width at half maximum) Var ≤ 25%

  8. spectral properties The average spectral index of the optically thin part: -0.90(0.07) - galaxies, -0.75 (0.04) – quasars, -0.7(0.11) – unidentified the difference is about 0.15electron energy distribution* for GPS galaxies is steeper than for GPS quasars; index (γ) for GPS galaxies differs by 0.3 *dN(E) = kE-γdE α1= (γ1 - 1) /2; α2 = (γ2 - 1)/2 Δα = (α1 - α2)= 0.15; Δγ = 0.3 selection effect ???

  9. variability 11.0(±1.4)% QSO 8.4 (±3.2)%G

  10. QSO, z=2.37 G, z=0.08 QSO, z=0.68 QSO, z=1.13,var = 70%

  11. QSO, z= 1.45, c n, c

  12. width of the spectra (FWHM) there are sufficiently few sources with narrow spectra narrowest reasonable spectrum, assuming homogeneous self-absorbed synchrotron source with a power law electron energy distribution = 0.77 (+0.8) using observational data FWHM = 1.2 Is the lack of sources with narrower spectra a real effect? …

  13. statistics 4-5 candidates selected; 3 of them for the first time (S1.4GHz ≥ 200 mJy, Dec 75º - 88º) The percentage of sources (AGNs) with identical and increasing spectra is about 25% at the studied flux level. This means that GPS sources are about 40% of the total number of AGNs or about 10% of all bright sources [0.25*0.4=0.1]. 0.8 Jy at 1.4 GHz – 450 0.8 Jy at 4 GHz – 225 10% sources, 0.2 sterad [(225/10)*0.2]=4.5 sources

  14. conclusions • The 5-year monitoring of 122 GPS source and candidates revealed a small number of such sources - 25% of the initial sample. Only about 45% of candidates to GPSs remained as early as in the first RATAN-600 observational set (2006). Averaged instantaneous spectra at several epochs were obtained at frequencies 1.1, 2.3, 4.8, 7.7, 11.2 and 21.7 GHz • The shape of the spectra remained clearly convex for only a fraction of sources of the sample. Most of the sources are variable flat-spectrum sources with inverted spectral shape only during flares (most of them - quasars). According to various study the genuine quasar-type GPS sources seem to be very rare. Spectral properties of galaxies and quasars differ: in optically thin part the average spectral index of galaxies is less than for quasars (~0.15 ???). There is a correlation between the high-frequency variability index and the high-frequency spectral index (99.5%). There are sufficiently few sources with narrower spectra in our sample (25%). Studying spectral properties of complete sample in the polar region 4-5 candidates to GPSs were selected (full sample of objects of this class in this area); 3 of them are considered as GPSs for the first time.

  15. Thank you for attention!

  16. G QSO only 20% QSO 50% G α2= -0.90(0.07) α2= -0.75 (0.04) 50% galaxies and 20% quasars (from the sample)

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