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Register a new userX-ray obscuration from a variable ionized absorber in PG 1114+445
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Added by
Roberto Serafinelli
Publication date
2021
fields
Physics
and research's language is
English
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Photoionized absorbers of outflowing gas are commonly found in the X-ray spectra of active galactic nuclei (AGN). While most of these absorbers are seldom significantly variable, some ionized obscurers have been increasingly found to substantially change their column density on a wide range of time scales. These $N_text{H}$ variations are often considered as the signature of the clumpy nature of the absorbers. Here we present the analysis of a new Neil Gehrels Swift Observatory campaign of the type-1 quasar PG 1114+445, which was observed to investigate the time evolution of the multiphase outflowing absorbers previously detected in its spectra. The analyzed dataset consists of 22 observations, with a total exposure of $sim90$ ks, spanning about $20$ months. During the whole campaign, we report an unusually low flux state with respect to all previous X-ray observations of this quasar. From the analysis of the stacked spectra we find a fully covering absorber with a column density $log(N_text{H}/text{cm}^{-2})=22.9^{+0.3}_{-0.1}$. This is an order of magnitude higher than the column density measured in the previous observations. This is either due to a variation of the known absorbers, or by a new one, eclipsing the X-ray emitting source. We also find a ionization parameter of $log(xi/text{erg cm s}^{-1})=1.4^{+0.6}_{-0.2}$. Assuming that the obscuration lasts for the whole duration of the campaign, i.e. more than $20$ months, we estimate the minimum distance of the ionized clump, which is located at $rgtrsim0.5$ pc.
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Substantial evidence in the last few decades suggests that outflows from supermassive black holes (SMBH) may play a significant role in the evolution of galaxies.Large-scale outflows known as warm absorbers (WA) and fast disk winds known as ultra-fast outflows (UFO) are commonly found in the spectra of many Seyfert galaxies and quasars, and a correlation has been suggested between them. Recent detections of low ionization and low column density outflows, but with a high velocity comparable to UFOs, challenge such initial possible correlations. Observations of UFOs in AGN indicate that their energetics may be enough to have an impact on the interstellar medium (ISM). However, observational evidence of the interaction between the inner high-ionization outflow and the ISM is still missing. We present here the spectral analysis of 12 XMM-Newton/EPIC archival observations of the quasar PG 1114+445, aimed at studying the complex outflowing nature of its absorbers. Our analysis revealed the presence of three absorbing structures. We find a WA with velocity $vsim530$ km s$^{-1}$, ionization $logxi/text{erg cm s}^{-1}sim0.35,$ and column density $log N_text{H}/text{cm}^{-2}sim22$, and a UFO with $v_text{out}sim0.145c$, $logxi/text{erg cm s}^{-1}sim4$, and $log N_text{H}/text{cm}^{-2}sim23$. We also find an additional absorber in the soft X-rays ($E<2$ keV) with velocity comparable to that of the UFO ($v_text{out}sim0.120c$), but ionization ($logxi/text{erg cm s}^{-1}sim0.5$) and column density ($log N_text{H}/text{cm}^{-2}sim21.5$) comparable with those of the WA. The ionization, velocity, and variability of the three absorbers indicate an origin in a multiphase and multiscale outflow, consistent with entrainment of the clumpy ISM by an inner UFO moving at $sim15%$ the speed of light, producing an entrained ultra-fast outflow (E-UFO).
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We present the first analysis of the X-ray warm absorber and nuclear obscuration in the Seyfert 1.8 galaxy ESO 113-G010. We used archival data from a 100 ks XMM-Newton observation made in 2005. From high resolution spectroscopy analysis of the RGS data, we detect absorption lines originating from a warm absorber consisting of two distinct phases of ionisation, with log xi ~ 3.2 and 2.3 respectively. The higher-ionised component has a larger column density and outflow velocity (N_H ~ 1.6 x 10^22 cm^-2, v ~ -1100 km/s) than the lower-ionised component (N_H ~ 0.5 x 10^22 cm^-2, v ~ -700 km/s). The shape of the optical-UV continuum and the large Balmer decrement (H_alpha/H_beta ~ 8) indicate significant amount of reddening is taking place in our line of sight in the host galaxy of the AGN; however, the X-ray spectrum is not absorbed by cold neutral gas intrinsic to the source. We discuss different explanations for this discrepancy between the reddening and the X-ray absorption, and suggest that the most likely solution is a dusty warm absorber. We show that dust can exist in the lower-ionised phase of the warm absorber, which causes the observed reddening of the optical-UV emission, whereas the X-rays remain unabsorbed due to lack of cold neutral gas in the ionised warm absorber. Furthermore, we have investigated the uncertainties in the construction of the Spectral Energy Distribution (SED) of this object due to obscuration of the nuclear source and the effects this has on the photoionisation modelling of the warm absorber. We show how the assumed SEDs influence the thermal stability of each phase and whether or not the two absorber phases in ESO 113-G010 can co-exist in pressure equilibrium.
The analysis of a series of seven observations of the nearby ($z=0.0809$) QSO, PG 1211+143, taken with the Reflection Grating Spectrometer (RGS) on-board XMM-Newton in 2014, are presented. The high resolution soft X-ray spectrum, with a total exposure exceeding 600 ks, shows a series of blue-shifted absorption lines, from the He and H-like transitions of N, O and Ne, as well as from L-shell Fe. The strongest absorption lines are all systematically blue-shifted by $-0.06c$, originating in two absorption zones, from low and high ionization gas. Both zones are variable on timescales of days, with the variations in absorber opacity effectively explained by either column density changes or by the absorber ionization responding directly to the continuum flux. We find that the soft X-ray absorbers probably exist in a two-phase wind, at a radial distance of $10^{17}-10^{18}$ cm from the black hole, with the lower ionization gas as denser clumps embedded within a higher ionization outflow. The overall mass outflow rate of the soft X-ray wind may be as high as $2{rm M}_{odot}$ yr$^{-1}$, close to the Eddington rate for PG 1211+143 and similar to that previously deduced from the Fe K absorption.
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