Astron. Astrophys. 362, 27-41 (2000)

6. Concluding remarks

We have determined the small-scale structure of samples of CSS, GPS and larger sources at 327 MHz using the technique of IPS with the Ooty Radio Telescope. We have also compiled the information on the structure of these sources and summarise the conclusions based on both our IPS and interferometric measurements.

1. The prominence of the hotspots shows very little dependence on the luminosity of the radio source over few decades of luminosity from about to 10²⁸ W Hz^-1 sr^-1. The prominence of the hotspots also shows no significant dependence on the linear size over about two decades in linear size. These are based on both the IPS observations as well as interferometric observations from the literature.

2. The size of the hotspots were shown earlier to increase linearly with the projected linear size for the CSS and GPS sources upto about 20 kpc, and then flattens at larger distances by considering objects observed with a similar number of resolution elements (Jeyakumar & Saikia 2000a,b). The sizes of the hotspots estimated from the IPS observations as well as the interferometric observations of hotspots with resolutions comparable to the IPS cut-off size are consistent with this flattening.

3. We identify candidates for milliarcsec `halos' at 327 MHz in 8 CSS and GPS objects. These could be due to earlier periods of activity or diffusion of relativistic electrons from the jets and lobes. VLBI imaging at low-frequencies of these sources would be useful to clarify the situation.

4. We have determined the spectra of the dominant component in five GPS objects from both IPS and VLBI observations in order to distinguish between free-free and synchrotron self absorption. The turnover in their spectra is consistent with synchrotron self absorption although models involving free-free absorption are viable.

© European Southern Observatory (ESO) 2000

Online publication: October 30, 19100
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