ABRIDGED: We use deep optical, IR and radio observations to explore the symbiosis between the nuclear activity and galaxy evolution in the southern compact radio source PKS1549-79 (z=0.1523). The ...optical imaging observations reveal the presence of tidal tail features which provide strong evidence that the host galaxy has undergone a major merger in the recent past. This is further supported by the detection of a young stellar population which was formed 50-250Myr ago and makes up 1-30% of the total stellar mass. Despite the core-jet structure of the radio source we detect HI absorption associated with both the core and the jet. The luminous, quasar-like AGN (M_V < -23.5) is highly extinguished (A_v > 4.9) at optical wavelengths and shows many properties in common with narrow line Seyfert 1 galaxies (NLS1), including relatively narrow permitted lines (FWHM ~ 1940 km/s), highly blueshifted OIII lines (~680 km/s), and evidence that the putative supermassive black hole is accreting at a high Eddington ratio. This suggests that accretion at high Eddington ratio does not prevent the formation of powerful jets. Our observations lend strong support to the predictions of some recent numerical simulations of galaxy mergers in which the black hole grows rapidly through merger-induced accretion following the coalescence of the nuclei of two merging galaxies; the major growth phase largely hidden by the natal gas and dust. Although the models predict that AGN-driven outflows will eventually remove the gas from the bulge of the host galaxy, the visible warm outflow in PKS1549-79 is not currently capable of doing so. ABRIDGED
We report multifrequency radio observations of XTE J1550-564 obtained with
the Molonglo Observatory Synthesis Telescope and the Australia Telescope
Compact Array at the time of its discovery and ...subsequent hard and soft X-ray
outburst in 1998 September. A large radio flare was observed, peaking about 1.8
days after the X-ray flare. In addition, we present Australian Long Baseline
Array images obtained shortly after the maximum of the radio flare which show
evolving structure. The apparent separation velocity of the two outermost
components is v>2c.
Astrophys.SpaceSci.276:45-48,2001 In 1998 September, the X-ray transient XTE J1550-564 underwent a major
outburst in soft and hard X-rays, followed by a radio flare. Australian Long
Baseline Array ...images obtained shortly after the peak in the radio flare showed
evolving structure. The components observed have an apparent separation
velocity of >2c.
The study of both neutral and ionized gas in young radio sources is providing key information on the effect the radio plasma has on the ISM of these objects. We present results obtained for the ...compact radio sources PKS1549-79, 4C12.50 and PKS1814-63 and for the intermediate-size radio galaxy 3C459. At least in the first two, low ionisation optical emission lines and HI absorption appear to be associated with the extended, but relatively quiescent, dusty cocoon surrounding the nucleus. The OIII lines are, on the other hand, mostly associated with the region of interaction between the radio plasma and the ISM, indicating a fast outflow from the canter. A case of fast outflow (up to ~1000 km/s) is also observed in HI in the radio source 4C12.50. As the radio source evolves, any obscuring material along the radio axis is swept aside until, eventually, cavities (of the same kind as observed e.g. in Cygnus A) are hollowed out on either side of the nucleus. We may witness this phase in the evolution of a radio source in the radio galaxy 3C459.
The Radio Astronomy Frequency Committee in the Asia-Pacific region (RAFCAP) was established during the last AP-RASC meeting. Compared to activities in European and American regions, we did not have a ...body to manage radio frequency issues for radio astronomy in the Asia-Pacific region, and the requirement for such a body had been discussed for a long time. Because of the extremely high sensitivity of radio telescopes while the dense usage of frequencies in active services, the interference from active services has been becoming more and more serious for radio astronomy. A brief summary of the situation and activity is given.
We report multifrequency radio observations of XTE J1550-564 obtained with the Molonglo Observatory Synthesis Telescope and the Australia Telescope Compact Array at the time of its discovery and ...subsequent hard and soft X-ray outburst in 1998 September. A large radio flare was observed, peaking about 1.8 days after the X-ray flare. In addition, we present Australian Long Baseline Array images obtained shortly after the maximum of the radio flare which show evolving structure. The apparent separation velocity of the two outermost components is v>2c.
In 1998 September, the X-ray transient XTE J1550-564 underwent a major outburst in soft and hard X-rays, followed by a radio flare. Australian Long Baseline Array images obtained shortly after the ...peak in the radio flare showed evolving structure. The components observed have an apparent separation velocity of >2c.
PDF