40 research outputs found
Preliminary results from the COLA N sample
We present preliminary radio imaging results for the northern COLA (Compact Objects in Low power AGN) sample. COLA is a large sample of moderate luminosity 10 †log(L_(FIR)/L_â) †12 infra-red selected galaxies. Our primary aim is to investigate possible connections between starburst activity and AGN. The sample has been observed in a variety of wavebands searching for correlations between AGN presence, galactic structure, gas content or degree of interaction. VLA A-array observations of half of the Northern sample are presented. From this data we find, consistent with previous studies, an anti-correlation between FIR luminosity and radio size. Unexpectedly we find that amongst sources which lie slightly above the radio-IR correlation, the excess radio emission is mostly in large scale structure (â„ 1kpc). Studies of the southern COLA sample suggest a strong correlation between having a radio excess and the presence of a compact AGN core, even though the core itself only accounts for small fraction of the excess. We speculate that either the bulk of AGN radio emission is on unexpectedly large scales or that AGN presence is correlated with old starbursts; a result consistent with proposed evolutionary models
HI Absorption in GPS/CSS Sources
Combining our own observations with data from the literature, we consider the
incidence of HI absorption in Gigahertz Peaked Spectrum (GPS) and Compact Steep
Spectrum (CSS) sources. Here we present our preliminary results, where we find
that the smaller GPS sources (<1 kpc) on average have larger HI column
densities than the larger CSS sources (>1 kpc). Both a spherical and an
axi-symmetric gas distribution, with a radial power law density profile, can be
used to explain this anti-correlation between projected linear size and HI
column density. Since most detections occur in galaxy classified objects, we
argue that if the unified schemes apply to the GPS/CSSs, a disk distribution
for the HI is more likely.Comment: 6 pages, 3 figures, LaTeX. Accepted by Publications of the
Astronomical Society of Australia, as a contribution to The 3rd GPS/CSS
Workshop, ed. T. Tzioumis, W. de Vries, I. Snellen, A. Koekemoe