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Register a new userA high velocity ionised outflow and XUV photosphere in the narrow emission line quasar PG1211+143
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Authors
K.A. Pounds
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We report on the analysis of a ~60 ksec XMM observation of the bright, narrow emission line quasar PG 1211+143. Absorption lines are seen in both EPIC and RGS spectra corresponding to H- and He-like ions of Fe, S, Mg, Ne, O, N and C. The observed line energies indicate an ionised outflow velocity of ~24000 km s^-1. The highest energy lines require a column density of N_H ~ 5 x 10^23 cm^-2, at an ionisation parameter of log(xi) ~ 3.4. If the origin of this high velocity outflow lies in matter being driven from the inner disc, then the flow is likely to be optically thick within a radius ~130 Schwarzschild radii, providing a natural explanation for the Big Blue Bump (and strong soft X-ray) emission in PG 1211+143.
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We analyze the X-ray spectrum of the quasar PG1211+143 observed with the CCD and grating spectrometers on board XMM-Newton. Using an ion by ion fitting model we find an outflow component of about 3000 km/s that includes absorption lines of K-shell and L-shell ions of the astrophysically abundant elements. We also identify and include in our model broad (FWHM = 6000 km/s) emission lines from H-like ions of C, N, O, and Ne, and He-like ions of O, Ne, and Mg. The outflow velocity we find is an alternative interpretation of the data and is in contrast with the ultra high velocity of ~24000 km/s reported previously for this object. Nevertheless, we can not completely rule out the presence of a high velocity component due to the poor signal-to-noise ratio of the data.
We observed the quasar PG1211+143 using the Cosmic Origins Spectrograph on the Hubble Space Telescope in April 2015 as part of a joint campaign with the Chandra X-ray Observatory and the Jansky Very Large Array. Our ultraviolet spectra cover the wavelength range 912-2100 A. We find a broad absorption feature (~1080 km/s) at an observed wavelength of 1240 A. Interpreting this as HI Ly alpha, in the rest frame of PG1211+143 (z=0.0809), this corresponds to an outflow velocity of -16,980 km/s (outflow redshift z_out ~ -0.0551), matching the moderate ionization X-ray absorption system detected in our Chandra observation and reported previously by Pounds et al. (2016). With a minimum HI column density of log N_HI > 14.5, and no absorption in other UV resonance lines, this Ly alpha absorber is consistent with arising in the same ultra-fast outflow as the X-ray absorbing gas. The Ly alpha feature is weak or absent in archival ultraviolet spectra of PG1211+143, strongly suggesting that this absorption is transient, and intrinsic to PG1211+143. Such a simultaneous detection in two independent wavebands for the first time gives strong confirmation of the reality of an ultra-fast outflow in an active galactic nucleus.
Blueshifted absorption lines in the X-ray spectra of AGN show that ultra-fast outflows with typical velocities $v sim 0.1c$ are a common feature of these luminous objects. Such powerful AGN winds offer an explanation of the observed M-$sigma$ relation linking the mass of the supermassive black hole and the velocity dispersion in the galaxys stellar bulge. An extended XMM-Newton study of the luminous Seyfert galaxy PG1211+143 recently revealed a variable multi-velocity wind. Here we report the detection of a short-lived, ultra-fast inflow during the same observation. Previous reports of inflows used single absorption lines with uncertain identifications, but this new result identifies an array of resonance absorption lines of highly ionised Fe, Ca, Ar, S and Si, sharing a common redshift when compared with a grid of realistic photoionization spectra. The redshifted absorption arises in a column of highly ionized matter close to the black hole, with a line-of-sight velocity, $v sim 0.3c$, inconsistent with the standard picture of a plane circular accretion disc. This may represent the first direct evidence for chaotic accretion in AGN, where accretion discs are generally misaligned to the black hole spin. For sufficient inclinations, the Lense-Thirring effect can break the discs into discrete rings, which then precess, collide and shock, causing near free-fall of gas towards the black hole. The observed accretion rate for the reported infall is comparable to the hard X-ray luminosity in PG1211+143, suggesting that direct infall may be a significant contributor to inner disc accretion.
The current paradigm for the AGN phenomenon is a central engine that consists of an inflow of material accreting in the form of a disk onto a supermassive black hole. Observations in the UV and optical find high velocity ionized material outflowing from the black hole. We present results from Suzaku and XMM-Newton observations of a sample of intrinsic NAL quasars with high velocity outflows. Our derived values of the intrinsic column densities of the X-ray absorbers are consistent with an outflow scenario in which NAL quasars are viewed at smaller inclination angles than BAL quasars. We find that the distributions of alpha_ox and Dalpha_ox of the NAL quasars of our sample differ significantly from those of BAL quasars and SDSS radio-quiet quasars. The NAL quasars are not significantly absorbed in the X-ray band and the positive values of Dalpha_ox suggest absorption in the UV band. The positive values of Dalpha_ox of the intrinsic NAL quasars can be explained in a geometric scenario where our lines of sight towards the compact X-ray hot coronae of NAL quasars do not traverse the absorbing wind whereas lines of sight towards their UV emitting accretion disks do intercept the outflowing absorbers.
We present and discuss high-resolution grating spectra of the quasar PG1211+143 obtained over three years. Based on an early observation from 2001, we find an outflow component of about 3000 km/s in contrast with the much higher velocity of about 24000 km/s reported earlier for this source, and based on the same data set. Subsequent grating spectra obtained for PG1211+143 are consistent with the first observation in the broad-band sense, but not all narrow features used to identify the outflow are reproduced. We demonstrate that the poor S/N and time variability seen during all existing observations of PG1211+143 make any claims about the outflow precariously inconclusive.
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