5,876 research outputs found
Transient Relativistically-Shifted Lines as a Probe of Black Hole Systems
X-ray spectra of Seyfert galaxies have revealed a new type of X-ray spectral
feature, one which appears to offer important new insight into the black hole
system. XMM/Chandra revealed several narrow emission lines redward of Fe Kalpha
in NGC 3516. Since that discovery the phenomenon has been observed in other
Seyfert galaxies, e.g. NGC 7314 and ESO 198-G24. We present new evidence for a
redshifted Fe line in XMM spectra of Mrk 766. These data reveal the first
evidence for a significant shift in the energy of such a line, occurring over a
few tens of kiloseconds. This shift may be interpreted as deceleration of an
ejected blob of gas traveling close to the escape velocity.Comment: 13 pages, 5 figures (4 color) accepted by Ap
Resolved Spectroscopy of the Narrow-Line Region in NGC 1068: Kinematics of the Ionized Gas
We have determined the radial velocities of the [O III] emitting gas in the
inner narrow-line region (NLR) of the Seyfert 2 galaxy NGC 1068, along a slit
at position angle of 202 degrees, from STIS observations at a spatial
resolution of 0.1 arcsec and a spectral resolving power of approximately 1000.
We use these data to investigate the kinematics of the NLR within 6 arcsec (430
pc) of the nucleus. The emission-line knots show evidence for radial
acceleration, to a projected angular distance of 1.7 arcsec in most cases,
followed by deceleration that approaches the systemic velocity at a projected
distance of about 4 arcsec. We find that a simple kinematic model of biconical
radial outflow can match the general trend of observed radial velocities. In
this model, the emitting material is evacuated along the bicone axis, and the
axis is inclined 5 degrees out of the plane of the sky. The acceleration of the
emission-line clouds provides support for dynamical models that invoke
radiation and/or wind pressure. We suggest that the deceleration of the clouds
is due to their collision with a patchy and anistropically distributed ambient
medium.Comment: 18 pages, Latex, includes 3 figures in postscript, to appear in the
Astrophysical Journal Letter
Observations of Outflowing UV Absorbers in NGC 4051 with the Cosmic Origins Spectrograph
We present new Hubble Space Telescope (HST)/Cosmic Origins Spectrograph
observations of the Narrow-Line Seyfert 1 galaxy NGC 4051. These data were
obtained as part of a coordinated observing program including X-ray
observations with the Chandra/High Energy Transmission Grating (HETG)
Spectrometer and Suzaku. We detected nine kinematic components of UV
absorption, which were previously identified using the HST/Space Telescope
Imaging Spectrograph. None of the absorption components showed evidence for
changes in column density or profile within the \sim 10 yr between the STIS and
COS observations, which we interpret as evidence of 1) saturation, for the
stronger components, or 2) very low densities, i.e., n_H < 1 cm^-3, for the
weaker components. After applying a +200 km s^-1 offset to the HETG spectrum,
we found that the radial velocities of the UV absorbers lay within the O VII
profile. Based on photoionization models, we suggest that, while UV components
2, 5 and 7 produce significant O VII absorption, the bulk of the X-ray
absorption detected in the HETG analysis occurs in more highly ionized gas.
Moreover, the mass loss rate is dominated by high ionization gas which lacks a
significant UV footprint.Comment: 41 pages, 10 Figures; accepted for publication in the Astrophysical
Journa
The Variable X-ray Spectrum of Markarian 766 - II. Time-Resolved Spectroscopy
CONTEXT: The variable X-ray spectra of AGN systematically show steep
power-law high states and hard-spectrum low states. The hard low state has
previously been found to be a component with only weak variability. The origin
of this component and the relative importance of effects such as absorption and
relativistic blurring are currently not clear. AIMS: In a follow-up of previous
principal components analysis, we aim to determine the relative importance of
scattering and absorption effects on the time-varying X-ray spectrum of the
narrow-line Seyfert 1 galaxy Mrk~766. METHODS: Time-resolved spectroscopy,
slicing XMM and Suzaku data down to 25 ks elements, is used to investigate
whether absorption or scattering components dominate the spectral variations in
Mrk 766.Time-resolved spectroscopy confirms that spectral variability in Mrk
766 can be explained by either of two interpretations of principal components
analysis. Detailed investigation confirm rapid changes in the relative
strengths of scattered and direct emission or rapid changes in absorber
covering fraction provide good explanations of most of the spectral
variability. However, a strong correlation between the 6.97 keV absorption line
and the primary continuum together with rapid opacity changes show that
variations in a complex and multi-layered absorber, most likely a disk wind,
are the dominant source of spectral variability in Mrk 76
Dynamics of the Narrow-Line Region in the Seyfert 2 Galaxy NGC 1068
We present dynamical models based on a study of high-resolution long-slit
spectra of the narrow-line region (NLR) in NGC 1068 obtained with the Space
Telescope Imaging Spectrograph (STIS) aboard The Hubble Space Telescope (HST).
The dynamical models consider the radiative force due to the active galactic
nucleus (AGN), gravitational forces from the supermassive black hole (SMBH),
nuclear stellar cluster, and galactic bulge, and a drag force due to the NLR
clouds interacting with a hot ambient medium. The derived velocity profile of
the NLR gas is compared to that obtained from our previous kinematic models of
the NLR using a simple biconical geometry for the outflowing NLR clouds. The
results show that the acceleration profile due to radiative line driving is too
steep to fit the data and that gravitational forces along cannot slow the
clouds down, but with drag forces included, the clouds can slow down to the
systemic velocity over the range 100--400 pc, as observed. However, we are not
able to match the gradual acceleration of the NLR clouds from ~0 to ~100 pc,
indicating the need for additional dynamical studies.Comment: Paper prepared by emulateapj version 10/09/06 and accepted for print
in Ap
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