We analyze Chandra observations of diffuse soft X-ray emission associated with a complete sample of 3CR radio galaxies at z < 0.3. We focus on the properties of the spectroscopic sub-classes of high excitation galaxies (HEGs) and broad line objects (BLOs). Among the 33 HEGs we detect extended (or possibly extended) emission in about 40% of the sources; the fraction is even higher (8/10) when restricting the analysis to the objects with exposure times larger than 10 ks. In the 18 BLOs, extended emission is seen only in two objects; this lower detection rate can be ascribed to the presence of their bright X-ray nuclei that easily outshine any genuine diffuse emission. A very close correspondence between the soft X-ray and optical line morphology emerges. We also find that the ratio between [O III] and extended soft X-ray luminosity is confined within a factor of 2 around a median value of 5. Both results are similar to what is seen in Seyfert galaxies. We discuss different processes that could explain the soft X-ray emission and conclude that the photoionization of extended gas, coincident with the narrow line region, is the favored mechanism.
Balmaverde B., Capetti A., Grandi P., Torresi E., Chiaberge M., Rodriguez Zaurin J., et al. (2012). Extended soft X-ray emission in 3CR radio galaxies at z < 0.3: high excitation and broad line galaxies. ASTRONOMY & ASTROPHYSICS, 545, 143-157 [10.1051/0004-6361/201219561].
Extended soft X-ray emission in 3CR radio galaxies at z < 0.3: high excitation and broad line galaxies
TORRESI, ELEONORA;GIOVANNINI, GABRIELE;
2012
Abstract
We analyze Chandra observations of diffuse soft X-ray emission associated with a complete sample of 3CR radio galaxies at z < 0.3. We focus on the properties of the spectroscopic sub-classes of high excitation galaxies (HEGs) and broad line objects (BLOs). Among the 33 HEGs we detect extended (or possibly extended) emission in about 40% of the sources; the fraction is even higher (8/10) when restricting the analysis to the objects with exposure times larger than 10 ks. In the 18 BLOs, extended emission is seen only in two objects; this lower detection rate can be ascribed to the presence of their bright X-ray nuclei that easily outshine any genuine diffuse emission. A very close correspondence between the soft X-ray and optical line morphology emerges. We also find that the ratio between [O III] and extended soft X-ray luminosity is confined within a factor of 2 around a median value of 5. Both results are similar to what is seen in Seyfert galaxies. We discuss different processes that could explain the soft X-ray emission and conclude that the photoionization of extended gas, coincident with the narrow line region, is the favored mechanism.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
