We present here the results from dual-frequency phase-referenced VLBI observations of the Seyfert galaxy KISSR1494, which exhibits double peaked emission lines in its SDSS spectrum. We detect a single radio component at 1.6 GHz, but not at 5 GHz impl
ying a spectral index steeper than $-1.5pm0.5$ ($S_ upropto u^alpha$). The high brightness temperature of the radio component ($sim1.4times10^7$ K) and the steep radio spectrum support a non-thermal synchrotron origin. A crude estimate of the black hole mass derived from the $M_{BH}-sigma_{star}$ relation is $sim1.4pm1.0times10^8$ Msun; it is accreting at an Eddington rate of $sim0.02$. The radio data are consistent with either the radio emission coming from the parsec-scale base of a synchrotron wind originating in the magnetised corona above the accretion disk, or from the inner ionised edge of the accretion disk or torus. In the former case, the narrow line region (NLR) clouds may form a part of the broad outflow, while in the latter, the NLR clouds may form a part of an extended disk beyond the torus. The radio and NLR emission may also be decoupled so that the radio emission originates in an outflow while the NLR is in a disk, and vice versa. While with the present data, it is not possible to clearly distinguish between these scenarios, there appears to be greater circumstantial evidence supporting the coronal wind picture in KISSR1494. From the kiloparsec-scale radio emission, the time-averaged kinetic power of this outflow is estimated to be $Qapprox1.5times10^{42}$ erg s$^{-1}$, which is typical of radio outflows in low-luminosity AGN. This supports the idea that radio jets and outflowing coronal winds are indistinguishable in Seyfert galaxies.
We present results from deep (70 ks) Chandra ACIS observations and Hubble Space Telescope ACS F475W observations of two highly optically polarized quasars belonging to the MOJAVE blazar sample, viz., PKS B0106+013 and 1641+399 (3C345). These observat
ions reveal X-ray and optical emission from the jets in both sources. X-ray emission is detected from the entire length of the 0106+013 radio jet, which shows clear bends or wiggles - the X-ray emission is brightest at the first prominent kpc jet bend. A picture of a helical kpc jet with the first kpc-scale bend representing a jet segment moving close(r) to our line of sight, and getting Doppler boosted at both radio and X-ray frequencies, is consistent with these observations. The X-ray emission from the jet end however peaks at about 0.4 (~3.4 kpc) upstream of the radio hot spot. Optical emission is detected both at the X-ray jet termination peak and at the radio hot spot. The X-ray jet termination peak is found upstream of the radio hot spot by around 0.2 (~1.3 kpc) in the short projected jet of 3C345. HST optical emission is seen in an arc-like structure coincident with the bright radio hot spot, which we propose is a sharp (apparent) jet bend instead of a terminal point, that crosses our line of sight and consequently has a higher Doppler beaming factor. A weak radio hot spot is indeed observed less than 1 downstream of the bright radio hot spot, but has no optical or X-ray counterpart. By making use of the pc-scale radio and the kpc-scale radio/X-ray data, we derive constraints on the jet Lorentz factors (Gamma_jet) and inclination angles (theta): for a constant jet speed from pc- to kpc-scales, we obtain a Gamma_jet of ~70 for 0106+013, and ~40 for 3C345. On relaxing this assumption, we derive a Gamma_jet of ~2.5 for both the sources. Upper limits on theta of ~13 degrees are obtained for the two quasars. (ABRIDGED)
(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 Cape
tti & 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 galaxys 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 (Gehans 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).
We present the results of a 8.4 GHz Very Large Array radio survey of early-type galaxies extracted from the ACS Virgo Cluster Survey. The aim of this survey is to investigate the origin of radio emission in early-type galaxies and its link with the h
ost properties in an unexplored territory toward the lowest levels of both radio and optical luminosities. Radio images, available for all 63 galaxies with BT < 14.4, show the presence of a compact radio source in 12 objects, with fluxes spanning from 0.13 to 2700 mJy. The remaining 51 galaxies, undetected at a flux limit of ~0.1 mJy, have radio luminosities L < 4 10E18 W/Hz . The fraction of radio-detected galaxies are a strong function of stellar mass, in agreement with previous results: none of the 30 galaxies with stellar mass M(star) < 1.7 10E10 M(sun) is detected, while 8 of the 11 most massive galaxies have radio cores. There appears to be no simple relation between the presence of a stellar nucleus and radio emission. A multiwavelength analysis of the active galactic nucleus (AGN) emission, combining radio and X-ray data, confirms the link between optical surface brightness profile and radio loudness in the sense that the bright core galaxies are associated with radio-loud AGNs, while non-core galaxies host radio-quiet AGNs. Not all radio-detected galaxies have a X-ray nuclear counter part (and vice-versa). A complete census of AGNs (and supermassive black holes, SMBHs) thus requires observations, at least, in both bands. Nonetheless, there are massive galaxies in the sample, expected to host a large SMBH (M(BH) ~ 10E8 M(sun)), whose nuclear emission eludes detection despite their proximity and the depth and the spatial resolution of the available observations. Most likely this is due to an extremely low level of accretion onto the central SMBH.
