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Narrow-line Region (narrow-line + region)

Distribution by Scientific Domains
Physics and Astronomy100%

Selected Abstracts

Gemini near-infrared integral field spectroscopy of the narrow-line region of ESO 428,G14: kinematics, excitation and the role of the radio jet

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2006
Rogemar A. Riffel
ABSTRACT We present two-dimensional (2D) gas kinematics and excitation of the inner 300 pc of the Seyfert galaxy ESO 428,G14 at a sampling of 14 pc2, from near-infrared spectroscopic observations at R, 6000 obtained with the Integral Field Unit (IFU) of the Gemini Near-Infrared Spectrograph. From measurements of fluxes and profiles of the emission lines [Fe ii],1.257 ,m, Pa,, H2, 2.121 ,m and Br,, we construct 2D maps of line intensities and ratios, radial velocities and velocity dispersions. Emission line ,tomography' is provided by velocity slices obtained across the line profiles, a unique capability of IFUs, which allows the mapping of not only the peak velocities but including also the wings. We compare these maps with a previously published high spatial resolution radio map and find a tight relation between the radio structure and the emission-line flux distributions and kinematics, revealing that the radio jet plays a fundamental role not only in shaping the narrow-line region but also in the imprint of its kinematics. Blueshifts of up to 400 km s,1 and velocity dispersions of up to 150 km s,1 are observed in association with the radio jet at a position angle (PA) = 129°, which is also the PA of the photometric major axis of the galaxy. We conclude that the radio jet is launched at a small angle relative to the galactic plane, with the north-western side slightly oriented towards us. This angle is small enough for the radio jet to shock and compress the gas in the plane of the galaxy, and for the nuclear continuum to ionize and heat it. The distinct kinematics and flux distributions observed for the different emission lines suggest different origins for their emission. The [Fe ii] shows the largest blueshifts and velocity dispersions and its flux distribution is concentrated along the jet, while the H2 shows the lowest velocity dispersions and has additional flux contribution from regions beyond the jet. Both X-rays emitted by the active galactic nucleus and shocks produced by the radio jet can excite the H2 and [Fe ii] emission lines. We use the 2D velocity dispersion maps to estimate upper limits to the contribution of the radio jet to the excitation of [Fe ii] and H2 which may reach 90 per cent for [Fe ii] and 80 per cent for H2 in the jet region. The [Fe ii]/Pa, emission-line ratios and the association of the [Fe ii] flux distribution and kinematics with the radio structure support a stronger contribution of the radio jet to the [Fe ii] excitation than that of H2. In the regions beyond the jet, the observations favour X-ray excitation. [source]

Emission-line outflows in PKS1549,79: the effects of the early stages of radio-source evolution?

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2001
C. Tadhunter
We present new spectroscopic observations of the southern radio galaxy . Despite the flat-spectrum character of the radio emission from this source, our optical spectra show no sign of the broad permitted lines and non-stellar continuum characteristic of quasar nuclei and broad-line radio galaxies. However, the high-ionization forbidden lines, including [O iii],,5007, 4959, are unusually broad for a narrow-line radio galaxy , and are blueshifted by 600 km s,1 relative to the low-ionization lines such as [O ii],,3726,3729. The [O ii] lines are also considerably narrower than the [O iii] lines, and have a redshift consistent with that of the recently detected H i 21-cm absorption-line system. Whereas the kinematics of the [O iii] emission lines are consistent with outflow in an inner narrow-line region, the properties of the [O ii] emission lines suggest that they are emitted by a more extended and quiescent gaseous component. We argue that, given the radio properties of the source, our line of sight is likely to be lying close to the direction of bulk outflow of the radio jets. In this case it is probable that the quasar nucleus is entirely obscured at optical wavelengths by the material responsible for the H i absorption-line system. The unusually broad [O iii] emission lines suggest that the radio source is intrinsically compact. Overall, our data are consistent the idea that is a radio source in an early stage of evolution. [source]

A model for the infrared emission of FSC 10214+4724

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY: LETTERS (ELECTRONIC), Issue 1 2006
Andreas Efstathiou
ABSTRACT A model for the infrared emission of the high-redshift ultraluminous infrared galaxy FSC 10214+4724 is presented. The model assumes three components of emission: a dusty torus viewed edge-on, clouds that are associated with the narrow-line region and a highly obscured starburst. It is demonstrated that the presence of clouds in the narrow-line region, with a covering factor of 17 per cent, can explain why the mid-infrared spectrum of FSC 10214+4724 shows a silicate feature in emission despite the fact that its torus is viewed edge-on. It is also shown that the same model, but with the torus viewed face-on, predicts a spectrum with silicate emission features that is characteristic of the spectra of quasars recently observed with Spitzer. [source]