2000/08/17 by C. De Breuck, Carlos De Breuck, H. J. A. Röttgering +11
Physics and Astronomy · #Astronomy and Astrophysical Research #Galaxies: Formation, Evolution, Phenomena #Radio Astronomy Observations and Technology #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0008264
28 Pages, including 22 PostScript figures. Accepted for publication in Astronomy & Astrophysics
arxiv created 2000/08/17 · arxiv updated 2009/12/01
We have compiled a sample of 165 radio galaxies from the literature to study the properties of the extended emission line regions and their interaction with the radio source over a large range of redshift 0<z<5.2. For each source, we have collected radio (size, lobe distance ratio and power) and spectroscopic parameters (luminosity, line width and equivalent width) for the four brightest UV lines. We also introduce a parameter ALy-alpha measuring the asymmetry of the Ly-alpha line. Using these 18 parameters, we examine the statistical significance of all 153 mutual correlations, and find the following significant correlations: (i) Ly-alpha asymmetry ALy-alpha with radio size and redshift, (ii) line luminosity with radio power, (iii) line luminosities of UV lines with each other, and (iv) equivalent widths of UV lines with each other. Using line-ratio diagnostic diagrams, we examine the ionization mechanism of the extended emission line regions in HzRGs. The high ionization lines seem to confirm previous results showing that AGN photo-ionization provides the best fit to the data, but are inconsitent with the CII/CIII ratio, which favour the highest velocity shock ionization models. We note that the CII line is 5 times more sensitive to shock ionization than the high ionization UV lines, and show that a combination of shock and photo-ionization provides a better overall fit to the integrated spectra of HzRGs. Because most HzRGs have radio sizes <~150 kpc, their integrated spectra might well contain a significant contribution from shock ionized emission. [abridged]