Mingaliev M.G., Sotnikova Yu.V., Erkenov A.K. Torniainen I., Tornikoski M.
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Transcript of 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
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]
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
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
fluxes and radiospectra
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
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%
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 ???
variability
11.0(±1.4)% QSO8.4 (±3.2)% G
QSO, z=2.37 G, z=0.08
QSO, z=0.68 QSO, z=1.13, var = 70%
QSO, z= 1.45, c n, c
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? …
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)
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.
Thank you for attention!
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)