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Giant Radio Sources as a Probe of the Cosmological Evolution of the IGM. II. The Observational Constraint on the Model of Radio-Jets Propagation through the X-ray Halo-IGM Interface

Kuligowska E., Jamrozy M., Koziel-Wierzbowska D., Machalski J.

Acta Astronomica

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2009

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Vol. 59, No. 4

431--455

EN

Three limited samples of high-redshift radio sources of FRII-type are used to constrain the dynamical model for the jets' propagation through the two-media environment: the X-ray emitting halo with the power-law density profile surrounding the parent galaxy and the much hotter intergalactic medium (IGM) of a constant density. The model, originally developed by Gopal-Krishna and Wiita, is modified adopting modern values of its free parameters taken from recent X-ray measurements with the XMM-Newton and Chandra Observatories. We find that (i) giant-sized radio sources (≈1 Mpc) exist at redshifts up to z≈2, (ii) all newly identified the largest radio sources with 1

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Giant Radio Galaxies as a Probe of the Cosmological Evolution of the IGM I. Preliminary Deep Detections and Low-Resolution Spectroscopy with SALT

Machalski J., Kozieł-Wierzbowska D., Jamrozy M.

Acta Astronomica

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2007

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Vol. 57, No. 3

227--248

EN

A problem of the cosmological evolution of the intergalactic medium (IGM) is recalled and a necessity to find distant (z>0.5) "giant" radio galaxies (GRGs) with the lobe energy densities lower than about 10-14 J/m3 to solve this problem is emphasized. Therefore we undertake a search for such GRGs on the southern sky hemisphere using SALT. In this paper we present a selected sample of the GRG candidates and the first deep detections of distant host galaxies, as well as the low-resolution spectra of the galaxies identified on the DSS frames. The data collected during the Performance Verification (P-V) phase show that 21 of 35 galaxies with the spectroscopic redshift have the projected linear size greater than 1 Mpc (for H0=71 km/s Mpc). However their redshifts do not exceed the value of 0.4 and the energy density in only two of them is less than 10-14 J/m3. A photometric redshift estimate of one of them (J1420-0545) suggests a linear extent larger than 4.8 Mpc, i.e., larger than that of 3C236, the largest GRG known up to now.

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Giant Radio Sources in View of the Dynamical Evolution of FRII-type Population. I. The Observational Data and Basic Physical Parameters of Sources Derived from the Analytical Model

Machalski J., Chyży K. T., Jamrozy M.

Acta Astronomica

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2004

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Vol. 54, No. 3

249--279

EN

The time evolution of giant lobe-dominated radio galaxies (with projected linear size D>1 Mpc if H0=50 km/s Mpc and q0=0.5) is analyzed on the basis of dynamical evolution of the entire FRII-type population. Two basic physical parameters, namely the jet power Q0 and central density of the galaxy nucleus ρ0 are derived for a sample of giants with synchrotron ages reliably determined, and compared with the relevant parameters in a comparison sample of normal-size sources consisting of 3C, B2, and other sources. Having the apparent radio luminosity P and linear size D of each sample source, Q0 and ρ0 are obtained by fitting the dynamical model of Kaiser et al. We find that: (i) There is no unique factor governing the source size. The sources are old, with temperate jet power (Q0) and are evolved in a relatively low-density environment (ρ0). The size is dependent, in order of decreasing partial correlation coefficients, on age, then on Q0, next on ρ0. (ii) A self-similar expansion of the sources' cocoon seems to be feasible if the power supplied by the jets is a few orders of magnitude above the minimum-energy value. In other cases the expansion can only initially be self-similar, a departure from self-similarity for large and old sources is justified by observational data of giant sources. (iii) An apparent increase of the lowest internal pressure value observed within the largest sources' cocoon with redshift is obscured by the intrinsic dependence of their size on age and the age on redshift, which hinders us from making definite conclusions about a cosmological evolution of intergalactic medium (IGM) pressure.

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Giant Radio Sources in View of the Dynamical Evolution of FRII-Type Population. II. The Evolutionary Tracks on the P-D and uc - Etot Planes

Machalski J., Chyży K. T., Jamrozy M.

Acta Astronomica

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2004

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Vol. 54, No. 4

391--403

EN

The time evolution of "fiducial" radio sources derived from fitting the dynamical model of Kaiser et al. (1997) is compared with the observational data for the "clan" sources found in the sample of giant and normal-size FRII-type sources published in Paper I (Machalski et al. 2004). Each "clan" comprises 3, 4 or 5 sample sources having similar values of the two basic physical parameters: the jet power Q0 and central density of the galaxy nucleus ρ0 (determined in Paper I) but different ages, radio luminosities and axial ratios. These sources are considered as the "same" source observed at different epochs of its lifetime and used to fit the evolutionary luminosity-size (P-D) and energy density-total energy (uc-Etot) tracks derived from the model for a "fiducial" source with Q0 and ρ0 equal to the averages of relevant values obtained for the "clan" members, as well as to constrain the evolutionary model of the source dynamics used. In the result we find that (i) the best fit is achieved when the Kaiser et al.'s model is modified by allowing an evolution of the sources' cocoon axial ratio with time as suggested by Blundell et al. (1999), (ii) a slow acceleration of the average expansion speed of the cocoon along the jet axis is suggested by the "clan" sources. We argue that this acceleration, although minor, may be real and some supporting arguments come from the well known hydrodynamical considerations.

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GB2 0909+353: One of the Largest Double Radio Source

Jamrozy M., Machalski J.

Acta Astronomica

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1999

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Vol. 49, No. 2

181--188

EN

The evidences are given that the radio source GB2 0909+353 (GB2 catalogue: Machalski 1978; ICRS 2000.0 coordinates: 09 12 51.7, +35 10 10) is likely one of the largest classical doubles known, though its optical identification is not certain. Our deep VLA observations at 5 GHz did not reveal a radio core brighter than 0.5 mJy/beam at this frequency. Thus a distance to the source is evaluated using photometric - redshift estimates of the faint galaxies in the optical field. The equipartition magnetic field and energy density in the source is calculated and compared with corresponding parameters of other "giant" radio sources known, showing extremely low values of both physical parameters of the source investigated. On the other hand, the age of relativistic electrons, and the advance speed of the "hot spot" in the source are typical for much smaller and brighter 3CR sources.