126 research outputs found
Does the X-ray outflow quasar PDS 456 have a UV outflow at 0.3c?
The quasar PDS 456 (at redshift ~0.184) has a prototype ultra-fast outflow
(UFO) measured in X-rays. This outflow is highly ionized with relativistic
speeds, large total column densities log N_H(cm^-2) > 23, and large kinetic
energies that could be important for feedback to the host galaxy. A UV spectrum
of PDS 456 obtained with the Hubble Space Telescope in 2000 contains one
well-measured broad absorption line (BAL) at ~1346A (observed) that might be
Ly-alpha at v ~ 0.06c or NV 1240 at v ~ 0.08c. However, we use photoionisation
models and comparisons to other outflow quasars to show that these BAL
identifications are problematic because other lines that should accompany them
are not detected. We argue that the UV BAL is probably CIV 1549 at v ~ 0.30c.
This would be the fastest UV outflow ever reported, but its speed is similar to
the X-ray outflow and its appearance overall is similar to relativistic UV BALs
observed in other quasars. The CIV BAL identification is also supported
indirectly by the tentative detection of another broad CIV line at v ~ 0.19c.
The high speeds suggest that the UV outflow originates with the X-ray UFO
crudely 20 to 30 r_g from the central black hole. We speculate that the CIV BAL
might form in dense clumps embedded in the X-ray UFO, requiring density
enhancements of only >0.4 dex compared clumpy structures already inferred for
the soft X-ray absorber in PDS 456. The CIV BAL might therefore be the first
detection of low-ionisation clumps proposed previously to boost the opacities
in UFOs for radiative driving.Comment: in press with MNRA
A Variable PV Broad Absorption Line and Quasar Outflow Energetics
Broad absorption lines (BALs) in quasar spectra identify high velocity
outflows that might exist in all quasars and could play a major role in
feedback to galaxy evolution. The viability of BAL outflows as a feedback
mechanism depends on their kinetic energies, as derived from the outflow
velocities, column densities, and distances from the central quasar. We
estimate these quantities for the quasar, Q1413+1143 (redshift ),
aided by the first detection of PV 1118,1128 BAL variability in
a quasar. In particular, PV absorption at velocities where the CIV trough does
not reach zero intensity implies that the CIV BAL is saturated and the absorber
only partially covers the background continuum source (with characteristic size
<0.01 pc). With the assumption of solar abundances, we estimate that the total
column density in the BAL outflow is log N_H > 22.3 (cm^-2). Variability in the
PV and saturated CIV BALs strongly disfavors changes in the ionization as the
cause of the BAL variability, but supports models with high-column density BAL
clouds moving across our lines of sight. The observed variability time of 1.6
yr in the quasar rest frame indicates crossing speeds >750 km/s and a radial
distance from the central black hole of <3.5 pc, if the crossing speeds are
Keplerian. The total outflow mass is ~4100 M_solar, the kinetic energy ~4x10^54
erg, and the ratio of the outflow kinetic energy luminosity to the quasar
bolometric luminosity is ~0.02 (at the minimum column density and maximum
distance), which might be sufficient for important feedback to the quasar's
host galaxy.Comment: 9 pages, 4 figures, accepted for publication in MNRA
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