1245+676 - a CSO/GPS source being an extreme case of a double-double structure

AGN with the so-called `double-double' radio structure have been interpreted as restarted AGN where the inner structure is a manifestation of a new phase of activity which happened to begin before the outer radio lobes resulting from the previous one had faded completely. The radio galaxy 1245+676 is an extreme example of such a double-double object - its outer structure, measuring 970 h^{-1} kpc, is five orders of magnitude larger than the 9.6 h^{-1} pc inner one. We present a series of VLBI observations of the core of 1245+676 which appears to be a compact symmetric object (CSO). We have detected the motion of the CSO's lobes, measured its velocity, and inferred the kinematic age of that structure.Comment: A contribution to The Third Workshop on Compact Steep Spectrum and GHz-Peaked Spectrum Radio Sources, Kerastari, Greece May 28-31, 2002. Refereed and accepted by Publications of the Astronomical Society of Australia. 4 pages. Final version copyedited by PASA Edito

FIRST-based survey of Compact Steep Spectrum sources, IV. Multifrequency VLBA observations of very compact objects

Evidence has been mounting recently that activity in some radio-loud AGNs (RLAGNs) can cease shortly after ignition and that perhaps even a majority of very compact sources may be short-lived phenomena because of a lack of stable fuelling from the black hole. Thus, they can fade out before having evolved to large, extended objects. Re-ignition of the activity in such objects is not ruled out. With the aim of finding more examples of these objects and to investigate if they could be RLAGNs switched off at very early stages of their evolution, multifrequency VLBA observations of six sources with angular sizes significantly less than an arcsecond, yet having steep spectra, have been made. Observations were initially made at 1.65 GHz using the VLBA with the inclusion of Effelsberg telescope. The sources were then re-observed with the VLBA at 5, 8.4 and 15.4 GHz. All the observations were carried out in a snapshot mode with phase referencing. One of the sources studied, 0809+404, is dominated by a compact component but also has diffuse, arcsecond-scale emission visible in VLA images. The VLBI observations of the "core" structure have revealed that this is also diffuse and fading away at higher frequencies. Thus, the inner component of 0809+404 could be a compact fading object. The remaining five sources presented here show either core-jet or edge-brightened double-lobed structures indicating that they are in an active phase. The above result is an indication that the activity of the host galaxy of 0809+404 may be intermittent. Previous observations obtained from the literature and those presented here indicate that activity had ceased once in the past, then restarted, and has recently switched off again.Comment: 15 pages, 7 figures, matches the version printed in Astronomy & Astrophysic

SPECYFIKA REALIZACJI LINIOWYCH INWESTYCJI W PASIE DROGOWYM W AGLOMERACJI MIEJSKIEJ Z UWZGLĘDNIENIEM OBSZARÓW ZABYTKOWYCH

Treścią referatu jest problematyka budowlanego procesu inwestycyjnego w pasie drogowym na terenie miast. W aglomeracjach miejskich realizacja zadań związanych z budową, przebudową lub modernizacją ciągów drogowych lub sieci infrastruktury liniowej związana jest z pokonaniem szczególnych utrudnień. Wynika to nie tylko ze specyfiki technologicznej ale również z szeroko pojętej interakcji społecznych. Inwestorzy realizujący zadania w miastach muszą szukać nie tylko innowacyjnych rozwiązań technicznych ale również muszą spełniać, często - „wygórowane” oczekiwania społeczne. W referacie omówione zostaną typowe zagrożenia procesu inwestycyjnego na etapach koncepcji, projektowania, realizacji i eksploatacji - ze szczególnym uwzględnieniem aspektów dotyczących realizacji liniowych robót budowlanych na obszarach objętych warunkami ochrony, wynikającymi z zapisów ustawy o ochronie zabytków[1]. Należy podkreślić, że ochrona ta zgodnie z Art. 4 przedmiotowej Ustawy polega, na podejmowaniu przez organy administracji publicznej działań mających między innymi na celu: zapewnienie warunków prawnych, organizacyjnych i finansowych, umożliwiających trwałe zachowanie zabytków oraz ich zagospodarowanie i utrzymanie. Przekłada się to na obligatoryjny warunek prowadzenia prac konserwatorskich, restauratorskich i oczywiście robót budowlanych za pozwoleniem właściwego konserwatora zabytków i pod jego nadzorem. Realizacja liniowych zadań inwestycyjnych z natury rzeczy odbywa się nie tylko w obszarze wpływu zabytków nieruchomych ale także w bezpośrednim kontakcie z zabytkami archeologicznymi tj. – zabytkami nieruchomymi, będącymi powierzchniową, podziemną lub podwodną pozostałością egzystencji i działalności człowieka, złożoną z nawarstwień kulturowych i znajdujących się w nich wytworów bądź ich śladów. Warunkiem pogodzenia interesów stron tego skomplikowanego procesu budowlanego oraz spełnienie ustawowych wymagań formalno-prawnych jest sprawna koordynacja projektowania i realizacji oraz akceptacja społeczna zamierzenia inwestycyjnego

Weak CSS Sources from FIRST Survey

We report early results of an observational campaign targeted on a sample of compact steep spectrum sources selected from the FIRST survey which are significantly weaker than those investigated before. The selection criteria and procedure are given in detail. We present here an assortment of MERLIN and VLBI observations and make some general comments based on the morphologies of the sources presented.Comment: A contribution to The Third Workshop on GHz-Peaked Spectrum and Compact Steep Spectrum Radio Sources, Kerastari, Greece, May 28-31, 2002. Refereed and accepted by Publications of the Astronomical Society of Australia. Final version copyedited by PASA Edito

Activity restart - a key to explaining the morphology of J1211+743

J1211+743 is a giant radio galaxy with a one-sided jet and two asymmetric lobes, one of which is of Fanaroff-Riley (FR) type II with a hotspot and the other is a diffuse relic devoid of a hotspot. The jet points towards the latter lobe, which is difficult to explain in a standard way within the double-lobed radio source paradigm. Here, I propose to assume that the nucleus of J1211+743 has undergone a re-ignition of activity and its lobes, presumably both originally of FR II type, represent an earlier active phase, while the jet represents the current one. The asymmetry of the lobes is a consequence of the orientation of the source combined with an activity switch-off that occurred between two active periods. The relic lobe is on the near side with regard to the observer, whereas the radiation from the far-side lobe arrives significantly later owing to its longer distance to the observer. The far-side lobe is thus perceived to have not yet decayed. On the other hand, the jet behaves in a standard way, i.e. its projected orientation reflects the near side of the source. Hence, we are able to explain why the location of the relic lobe correlates with the direction of the jet.Comment: 4 pages, 1 figure, accepted as a Letter to A&

Multi-epoch VLBA observations of radio galaxy 0932+075: is this a compact symmetric object?

A part of the radio structure of the galaxy 0932+075 emerged as a possible compact symmetric object (CSO) after the observation with the Very Long Baseline Array (VLBA) at 5 GHz in 1997. More than a decade later, we carried out observations at 5, 15.4, and 22.2 GHz using the VLBA to test this possibility. We report here that we have found a component whose spectrum is inverted in the whole range from 5 GHz to 22 GHz and we label it a high-frequency peaker (HFP). Using a set of 5 GHz images from two epochs separated by 11.8 years and a set of 15.4 GHz images separated by 8.2 years, we were able to examine the proper motions of the three components of the CSO candidate with respect to the HFP. We found that their displacements cannot be reconciled with the CSO paradigm. This has led to the rejection of the hypothesis that the western part of the arcsecond-scale radio structure of 0932+075 is a CSO anchored at the HFP. Consequently, the HFP cannot be labelled a core and its role in this system is unclear