Examining the Radio-Loud/Radio-Quiet dichotomy with new Chandra and VLA observations of 13 UGC galaxies

Abstract

(Abridged) We present the results from new 15 ks Chandra-ACIS and 4.9 GHz Very Large Array observations of 13 galaxies hosting low luminosity AGN. This completes the multiwavelength study of a sample of 51 nearby early-type galaxies described in Capetti & Balmaverde (2005, 2006); Balmaverde & Capetti (2006). The aim of the three previous papers was to explore the connection between the host galaxies and AGN activity in a radio-selected sample. We detect nuclear X-ray emission in eight sources and radio emission in all but one (viz., UGC6985). The new VLA observations improve the spatial resolution by a factor of ten: the presence of nuclear radio sources in 12 of the 13 galaxies confirms their AGN nature. As previously indicated, the behavior of the X-ray and radio emission in these sources depends strongly on the form of their optical surface brightness profiles derived from Hubble Space Telescope imaging, i.e., on their classification as "core", "power-law" or "intermediate" galaxies. With more than twice the number of "power-law" and "intermediate" galaxies compared to previous work, we confirm with a much higher statistical significance that these galaxies lie well above the radio-X-ray correlation established in FRI radio galaxies and the low-luminosity "core" galaxies. This result highlights the fact that the "radio-loud/radio-quiet" dichotomy is a function of the host galaxy's optical surface brightness profile. We present radio-optical-X-ray spectral indices for all 51 sample galaxies. Survival statistics point to significant differences in the radio-to-optical and radio-to-X-ray spectral indices between the "core" and "power-law" galaxies (Gehan's Generalized Wilcoxon test probability "p" for the two classes being statistically similar is <10^-5), but not in the optical-to-X-ray spectral indices (p=0.25).

40 pages, Accepted for publication in AJ

References in corpus (5)

• Radio-Loudness of Active Galactic Nuclei: Observational Facts and Theoretical Implications
• On the origin of radio-loudness in AGNs and its relationship with the properties of the central supermassive black hole
• The host galaxy/AGN connection in nearby early-type galaxies. A new view of the origin of the radio-quiet/radio-loud dichotomy?
• The connection between radio-loudness and central surface brightness profiles in optically-selected low-luminosity active galaxies
• Revisiting the census of low-luminosity AGN

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• The Atlas3D project -- XXXI. Nuclear radio emission in nearby early-type galaxies
• What sparks the radio-loud phase of nearby quasars?
• LeMMINGs. III. The e-MERLIN Legacy Survey of the Palomar sample. Exploring the origin of nuclear radio emission in active and inactive galaxies through the [O III] -- radio connection
• Binary black holes in nuclei of extragalactic radio sources
• Early-type galaxies in the Antlia Cluster: A deep look into scaling relations
• The LOFAR view of NGC 3998, a sputtering AGN
• The distribution and lifetime of powerful radio galaxies as a function of environment and redshift
• Molecular gas and nuclear activity in early-type galaxies: any link with radio-loudness?
• Unveiling the 100 pc scale nuclear radio structure of NGC 6217 with e-MERLIN and the VLA
• The eMERLIN and EVN view of FR0 radio galaxies