149 research outputs found
High-resolution radio observations of Seyfert galaxies in the extended 12-micron sample - II. The properties of compact radio components
We discuss the properties of compact nuclear radio components in Seyfert
galaxies from the extended 12-micron AGN sample of Rush et al.(1993). Our main
results can be summarised as follows. Type 1 and type 2 Seyferts produce
compact radio components which are indistinguishable in strength and aspect,
indicating that their central engines are alike as proposed by the unification
model. Infrared IRAS fluxes are more closely correlated with low-resolution
radio fluxes than high-resolution radio fluxes, suggesting that they are
dominated by kiloparsec-scale, extra-nuclear emission regions; extra-nuclear
emission may be stronger in type 2 Seyferts. Early-type Seyfert galaxies tend
to have stronger nuclear radio emission than late-type Seyfert galaxies.
V-shaped extended emission-line regions, indicative of `ionisation cones', are
usually found in sources with large, collimated radio outflows. Hidden broad
lines are most likely to be found in sources with powerful nuclear radio
sources. Type 1 and type 2 Seyferts selected by their IRAS 12-micron flux
densities have well matched properties
The Relationship Between Beam Power and Radio Power for Classical Double Radio Sources
Beam power is a fundamental parameter that describes, in part, the state of a
supermassive black hole system. Determining the beam powers of powerful
classical double radio sources requires substantial observing time, so it would
be useful to determine the relationship between beam power and radio power so
that radio power could be used as a proxy for beam power. A sample of 31
powerful classical double radio sources with previously determined beam and
radio powers are studied; the sources have redshifts between about 0.056 and
1.8. It is found that the relationship between beam power, Lj, and radio power,
P, is well described by Log(Lj) = 0.84 Log(P) + 2.15, where both L_j and P are
in units of 10^(44) erg/s. This indicates that beam power is converted to radio
power with an efficiency of about 0.7%. The ratio of beam power to radio power
is studied as a function of redshift; there is no significant evidence for
redshift evolution of this ratio over the redshift range studied. The
relationship is consistent with empirical results obtained by Cavagnolo et al.
(2010) for radio sources in gas rich environments, which are primarily FRI
sources, and with the theoretical predictions of Willott et al. (1999).Comment: 6 pages, 2 figures, 2 tables; accepted for publication in MNRA
Star formation and gas inflows in the OH Megamaser galaxy IRAS03056+2034
We have obtained observations of the OH Megamaser galaxy IRAS03056+0234 using
Gemini Multi-Object Spectrograph (GMOS) Integral Field Unit (IFU), Very Large
Array (VLA) and Hubble Space Telescope (HST). The HST data reveals spiral arms
containing knots of emission associated to star forming regions. The GMOS-IFU
data cover the spectral range of 4500 to 7500 \AA\ at a velocity resolution of
90 km s and spatial resolution of 506 pc. The emission-line flux
distributions reveal a ring of star forming regions with radius of 786 pc
centred at the nucleus of the galaxy, with an ionized gas mass of 1.2
10M, an ionizing photon luminosity of log Q[H]=53.8 and a
star formation rate of 4.9 M yr. The emission-line ratios and
radio emission suggest that the gas at the nuclear region is excited by both
starburst activity and an active galactic nucleus. The gas velocity fields are
partially reproduced by rotation in the galactic plane, but show, in addition,
excess redshifts to the east of the nucleus, consistent with gas inflows
towards the nucleus, with velocity of 45 km s and a mass inflow
rate of 7.710 M yr.Comment: To be published in MNRA
Hubble Space Telescope Near-infrared Snapshot Survey of 3CR Radio Source Counterparts. II. An Atlas and Inventory of the Host Galaxies, Mergers, and Companions
We present the second part of an H-band (1.6 μm) “atlas” of z \u3c 0.3 3CR radio galaxies, using the Hubble Space Telescope Near Infrared Camera and Multi- Object Spectrometer (HST NICMOS2). We present new imaging for 21 recently acquired sources, and host galaxy modeling for the full sample of 101 (including 11 archival) – an 87% completion rate. Two different modeling techniques are applied, following those adopted by the galaxy morphology and the quasar host galaxy communities. Results are compared, and found to be in excellent agreement, although the former breaks down in the case of strongly nucleated sources
- …