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

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

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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)?. - PowerPoint PPT Presentation

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Page 1: Mingaliev M.G., Sotnikova Yu.V., Erkenov A.K.  Torniainen I., Tornikoski M

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

Multifrequency study of Gigahertz Peaked Spectrum (GPS) sources and candidates with

RATAN-600

Special Astrophysical Observatory of RAS, Nizhnij Arkhyz

Page 2: Mingaliev M.G., Sotnikova Yu.V., Erkenov A.K.  Torniainen I., Tornikoski M

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]

Page 3: Mingaliev M.G., Sotnikova Yu.V., Erkenov A.K.  Torniainen I., Tornikoski M

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

Page 4: Mingaliev M.G., Sotnikova Yu.V., Erkenov A.K.  Torniainen I., Tornikoski M

goals, tools, sample, observations2006-2010simultaneous radio spectravariabilityspectral propertiescount of sources

RATAN-600: 1.1, 2.3, 4.8, 7.7, 11.2 and 21.7 GHz1) 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 ≥ 200 mJy: 4-5 candidates

Page 5: Mingaliev M.G., Sotnikova Yu.V., Erkenov A.K.  Torniainen I., Tornikoski M

fluxes and radiospectra

Page 6: Mingaliev M.G., Sotnikova Yu.V., Erkenov A.K.  Torniainen I., Tornikoski M

fluxes and radiospectra

proposed class N sources type of spectra

maxmax1

max2

max12

risingflatcomplexsteep

48101111419910

maximum at cm rangeflat plateau at low frequenciesvariable (≥25%)flattering and variable

≥ 0α0 ≥ ≥ -0.5αtwo or more minimum

≤ -0.5α

all 122

Page 7: Mingaliev M.G., Sotnikova Yu.V., Erkenov A.K.  Torniainen I., Tornikoski M

candidates in GPSonly 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%

Page 8: Mingaliev M.G., Sotnikova Yu.V., Erkenov A.K.  Torniainen I., Tornikoski M

spectral propertiesThe 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 0.15 electron 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 ???

Page 9: Mingaliev M.G., Sotnikova Yu.V., Erkenov A.K.  Torniainen I., Tornikoski M

variability

11.0(±1.4)% QSO8.4 (±3.2)% G

Page 10: Mingaliev M.G., Sotnikova Yu.V., Erkenov A.K.  Torniainen I., Tornikoski M

QSO, z=2.37 G, z=0.08

QSO, z=0.68 QSO, z=1.13, var = 70%

Page 11: Mingaliev M.G., Sotnikova Yu.V., Erkenov A.K.  Torniainen I., Tornikoski M

QSO, z= 1.45, c n, c

Page 12: Mingaliev M.G., Sotnikova Yu.V., Erkenov A.K.  Torniainen I., Tornikoski M

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? …

Page 13: Mingaliev M.G., Sotnikova Yu.V., Erkenov A.K.  Torniainen I., Tornikoski M

statistics

0.8 Jy at 1.4 GHz – 4500.8 Jy at 4 GHz – 22510% sources, 0.2 sterad[(225/10)*0.2]=4.5 sources

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].

4-5 candidates selected; 3 of them for the first time (S1.4GHz ≥ 200 mJy, Dec 75º - 88º)

Page 14: Mingaliev M.G., Sotnikova Yu.V., Erkenov A.K.  Torniainen I., Tornikoski M

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.

Page 15: Mingaliev M.G., Sotnikova Yu.V., Erkenov A.K.  Torniainen I., Tornikoski M

Thank you for attention!

Page 16: Mingaliev M.G., Sotnikova Yu.V., Erkenov A.K.  Torniainen I., Tornikoski M
Page 17: Mingaliev M.G., Sotnikova Yu.V., Erkenov A.K.  Torniainen I., Tornikoski M

50% galaxies and 20% quasars (from the sample)

α2= -0.90(0.07)only 20% QSO

QSO G

50% G

α2= -0.75 (0.04)

Page 18: Mingaliev M.G., Sotnikova Yu.V., Erkenov A.K.  Torniainen I., Tornikoski M