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Compact Symmetric Objects (compact + symmetric_object)

Distribution by Scientific Domains
Physics and Astronomy100%

Selected Abstracts

Expansion velocities and kinematic ages of Compact Symmetric Objects

ASTRONOMISCHE NACHRICHTEN, Issue 2-3 2009
A.G. Polatidis
Abstract The measurement of expansion velocities in Compact Symmetric Objects, and the calculation of their kinematic ages, showed that the age of these radio sources was of the order of a few hundred to a few thousand years. Further monitoring has proven this trait, but there are also indications of recurrent activity in some CSOs. However, there are many cases where accurate kinematic measurements are not easy to obtain (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

A complete sample of low polarization CSO/MSO

ASTRONOMISCHE NACHRICHTEN, Issue 2-3 2009
P. Cassaro
Abstract The selection of a complete sample of Compact Symmetric Objects (CSOs) is in progress. The sample of candidates has been obtained on the basis of the low fractional polarization of the CSOs. About 60 % of the candidates has been identified as CSO/MSO, and observations are in progress to determine the radio morphology of the sources with unknown structure (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Identifying Compact Symmetric Objects from the VLBA Imaging and Polarization Survey

ASTRONOMISCHE NACHRICHTEN, Issue 2-3 2009
S.E. Tremblay
Abstract Compact Symmetric Objects (CSOs) are small (less than 1 kpc) radio sources which have symmetric double lobes or jets. The dominant theory for the small size of these objects is that they are young radio sources which could grow into larger radio galaxies, but the currently small population of known CSOs makes it difficult to definitively determine whether or not this is the case. While a greater number of Gigahertz peaked sources can be identified by sifting through spectral surveys, this yields none of the dynamics of the sources, and also brings Quasars into the sample, which although interesting are peaked around 1 Gigahertz for very different reasons. We have used the 5 GHz VLBA Imaging and Polarization Survey (VIPS) to identify 103 CSO candidates morphologically, and are following up on these sources with multifrequency VLBA observations to confirm CSO identifications and to study their dynamics. The identification of candidates from within the survey will be discussed, as well as preliminary results from the follow-up observations (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Interferometer observations of molecular gas in radio galaxies

ASTRONOMISCHE NACHRICHTEN, Issue 2-3 2009
S. García-Burillo
Abstract We present the first results of a high-resolution study of the distribution and kinematics of molecular gas in two nearby radio galaxies, 4C 31.04 and 3C 293, representative of two different stages of evolution in radio-loud active galactic nuclei (AGN). These observations, conducted with the IRAM Plateau de Bure Interferometer (PdBI), map with unprecedented spatial resolution (,0.5,,1,) and sensitivity the emission and absorption of key molecular species such as CO, HCN and HCO+. We report on the detection of a kinematically disturbed and massive (Mgas , 1010 M,) molecular/dusty disk of ,1.4 kpc-size fueling the central engine of the compact symmetric object (CSO) 4C 31.04. We also report on the detection of a massive (Mgas , 1010 M,) regularly rotating ,7 kpc-size disk in the FR II radio galaxy 3C 293. A complex system of molecular line absorptions is detected against the mm-continuum source of this galaxy (AGN and jet). We compare the properties of the molecular disks in the two sources and discuss them in the light of the different theories describing the evolution of radio galaxies (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Multifrequency VLBI observations of faint gigahertz peaked spectrum sources

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2000
I. A. G. Snellen
We present the data and analysis of VLBI observations at 1.6, 5 and 15 GHz of a sample of faint gigahertz peaked spectrum (GPS) sources selected from the Westerbork Northern Sky Survey. The 5-GHz observations involved a global array of 16 stations and yielded data on the total sample of 47 sources. A subsample of 26 GPS sources with peak frequencies and/or peak flux densities was observed with the VLBA at 15 GHz. A second subsample of 29 sources, with was observed at 1.6 GHz using a 14-station global VLBI array. In this way, 44 of the 47 sources (94 per cent) in the sample were observed above and at or below their spectral peak. Spectral decomposition allowed us to identify three, 11, seven and two objects as compact symmetric objects, compact doubles, core,jet and complex sources, respectively. However, many of the sources classified as compact double or core,jet sources show only two components making their classification rather tentative. This may explain why the strong morphological dichotomy of GPS quasars and galaxies found for radio-bright GPS sources is not as clear in this faint sample. [source]

The lack of large compact symmetric objects

ASTRONOMISCHE NACHRICHTEN, Issue 2-3 2009
P. Augusto
Abstract In recent years, ,baby' (<103 yr) and ,young' (103,105 yr) radio galaxies have been found and classified, although their numbers are still small (tens). Also, they have many different names, depending on the type of survey and scientific context in which they were found: compact steep spectrum sources (CSS), giga-Hertz peaked spectrum sources (GPS) and compact-medium symmetric objects (C-MSO). The latter have the radio galaxy structure more obvious and correspond to the ,babies' (CSOs; < 1 kpc) and ,young' (MSOs; 1,15 kpc) radio galaxies. The log-size distribution of CSOs shows a sharp drop at 0.3 kpc. This trend continues through flat-spectrum MSOs (over the full 1,15 kpc size range). In order to find out if this lack of large CSOs and flat-spectrum MSOs is due to poor sampling (lack of surveys that probe efficiently the 0.3,15 kpc size range) and/or has physical meaning (e.g. if the lobes of CSOs expand as they grow and age, they might become CSSs, ,disappearing' from the flat-spectrum MSO statistics), we have built a sample of 157 flat-spectrum radio sources with structure on ,0.3,15 kpc scales. We are using new, archived and published data to produce and inspect hundreds of multi-frequency multi-instrument maps and models. We have already found 13 new secure CSO/MSOs. We expect to uncover ,30,40 new CSOs and MSOs, most on the 0.3,15 kpc size range, when our project is complete (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Fate of baby radio galaxies: Dead or alive?

ASTRONOMISCHE NACHRICHTEN, Issue 2-3 2009
N. Kawakatu
Abstract In order to reveal the long-term evolution of relativistic jets in active galactic nuclei (AGNs), we examine the dynamical evolution of variously-sized radio galaxies [i.e., compact symmetric objects (CSOs), medium-size symmetric objects (MSOs), Fanaroff-Riley type II radio galaxies (FRIIs)]. By comparing the observed relation between the hot spot size and the linear size of radio source with a coevolution model of hot spot and cocoon, we find that the advance speed of hot spots and lobes inevitably show the deceleration phase (CSO-MSO phase) and the acceleration phase (MSO-FRII phase). The deceleration is caused by the growth of the cross-sectional area of the cocoon head. Moreover, by comparing the hot spot speed with the sound speed of the ambient medium, we predict that only CSOs whose initial advance speed is higher than 0.3,0.5 c can evolve into FRIIs (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]