697 research outputs found
An extended XMM-Newton observation of the Seyfert galaxy NGC 4051. I. Evidence for a shocked outflow
An extended XMM-Newton observation of the Seyfert 1 galaxy NGC 4051 has
revealed a rich absorption line spectrum indicating the presence of a
photoionized outflow with a wide range of velocities and ionization parameter.
At low continuum fluxes an emission line spectrum is well defined with both
narrow and broad components of several abundant metal ions. The absorption line
velocity structure and a broad correlation of velocity and ionization parameter
are consistent with an outflow scenario where a highly ionized, high velocity
wind, perhaps launched during intermittent super-Eddington accretion, runs into
the interstellar medium or previous ejecta, losing much of its kinetic energy
in the resultant strong shock. We explore the possibility that a quasi-constant
soft X-ray emission component may be evidence of this post-shock cooling. This
revised view of AGN outflows is consistent with multiple minor Eddington
accretion episodes creating a momentum-driven feedback linking black hole and
host galaxy growth.Comment: accepted for publication in Monthly Notices of the Royal Astronomical
Societ
Black Hole Winds
We show that black holes accreting at or above the Eddington rate probably
produce winds which are optically thick in the continuum, whether in quasars or
X-ray binaries. The photospheric radius and outflow speed are proportional to
\mo^2 and \mo^-1 respectively, where \mo is the mass outflow rate. The outflow
momentum rate is always of order L_Edd/c. Blackbody emission from these winds
may provide the big blue bump in some quasars and AGN, as well as ultrasoft
X-ray components in ULXs.Comment: 3 pages, no figures; MNRAS, in press (with minor corrections applied
An extended XMM-Newton observation of the Seyfert galaxy NGC 4051. II. Soft X-ray emission from a limb-brightened shell of post-shock gas
An extended XMM-Newton observation of the Seyfert I galaxy NGC 4051 in 2009
revealed a complex absorption spectrum, with a wide range of outflow velocities
and ionisation states.The main velocity and ionisation structure was
interpreted in Paper I in terms of a decelerating, recombining flow resulting
from the shocking of a still higher velocity wind colliding with the ISM or
slower moving ejecta. The high sensitivity of the XMM-Newton observation also
revealed a number of broad emission lines, all showing evidence of
self-absorption near the line cores. The line profiles are found here to be
consistent with emission from a limb-brightened shell of post-shock gas
building up ahead of the contact discontinuity. While the broad emission lines
remain quasi-constant as the continuum flux changes by an order of magnitude,
recombination continua of several H- and He-like ions are found to vary in
response to the continuum, providing an important key to scaling the ionised
flow.Comment: Accepted for publication in MNRA
The Locus of Highly Accreting AGNs on the M_BH--sigma Plane: Selections, Limitations, and Implications
We re-examine the locus of narrow line Seyfert 1 galaxies on the M_BH--sigma
(black hole mass--bulge velocity dispersion) plane in the light of the results
from large new optically selected samples. We find that (1) soft X-ray selected
NLS1s have a lower ratio of BH mass to \sigma^{4}_{[OIII]} than broad line
Seyfert 1 galaxies; this remains a robust statistical result contrary to recent
claims otherwise; (2) optically selected NLS1s have systematically lower
Eddington luminosity ratio compared to X-ray selected NLS1s; and (3) as a
result, the locus of NLS1s on the M_BH--sigma plane is affected by selection
effects. We argue that there is no single explanation for the origin of the
M_BH--sigma relation; instead tracks of galaxies on the M_BH--sigma plane
differ with redshift, consistent with the downsizing of AGN activity. If these
results at face value are incorrect, then the data imply that AGNs with high
Eddington accretion reside preferentially in relatively late type galaxies at
the present epoch, perhaps a more interesting result and a challenge to
theoretical models.Comment: To appear in Ap
Quantifying the fast outflow in the luminous Seyfert galaxy PG1211+143
We report two new XMM-Newton observations of PG1211+143 in December 2007,
again finding evidence of the fast outflow of highly ionised gas first detected
in 2001. Stacking the new spectra with those from two earlier XMM-Newton
observations reveals strong and broad emission lines of FeXXV and OVIII,
indicating the fast outflow to be persistent and to have a large covering
factor. This finding confirms a high mass rate for the ionised ouflow in
PG1211+143 and provides the first direct measurement of a wide angle,
sub-relativistic outflow from an AGN transporting mechanical energy with the
potential to disrupt the growth of the host galaxy. We suggest PG1211+143 may
be typical of an AGN in a rapid super-Eddington growth phase.Comment: Accepted for publication in MNRAS. Extended version with new figures
and table
Resolving the large scale spectral variability of the luminous Seyfert 1 galaxy 1H 0419-577: Evidence for a new emission component and absorption by cold dense matter
An XMM-Newton observation of the luminous Seyfert 1 galaxy 1H 0419-577 in
September 2002, when the source was in an extreme low-flux state, found a very
hard X-ray spectrum at 1-10 keV with a strong soft excess below ~1 keV.
Comparison with an earlier XMM-Newton observation when 1H 0419-577 was `X-ray
bright' indicated the dominant spectral variability was due to a steep power
law or cool Comptonised thermal emission. Four further XMM-Newton observations,
with 1H 0419-577 in intermediate flux states, now support that conclusion,
while we also find the variable emission component in intermediate state
difference spectra to be strongly modified by absorption in low ionisation
matter. The variable `soft excess' then appears to be an artefact of absorption
of the underlying continuum while the `core' soft emission can be attributed to
recombination in an extended region of more highly ionised gas. We note the
wider implications of finding substantial cold dense matter overlying (or
embedded in) the X-ray continuum source in a luminous Seyfert 1 galaxy.Comment: 34 pages, 15 figures, submitted to Ap
An XMM-Newton observation of Mrk 3 - a Seyfert galaxy just over the edge
A 100ks XMM-Newton observation of the nearby Seyfert 2 galaxy Mrk 3 offers a
unique opportunity to explore the complexity of its X-ray spectrum. We find the
\~3-8 keV continuum to be dominated by reflection from cold matter, with
fluorescent K-shell lines detected from Ni, Fe, Ca, Ar, S, Si and Mg. At higher
energies an intrinsic power law continuum, with canonical Seyfert 1 photon
index, is seen through a near-Compton-thick cold absorber. A soft excess below
\~3 keV is found to be dominated by line emission from an outflow of `warm'
gas, photo-ionised and photo-excited by the intrinsically strong X-ray
continuum. Measured blue-shifts in the strong Fe K-alpha and OVII and VIII
emission lines are discussed in terms of the properties of the putative
molecular torus and ionised outflow.Comment: 16 figures; accepted for publication in MNRA
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