Resolving the Multiple Component Outflows in PG 1211+143: II. The Soft X-ray View of the Ultra Fast Outflow

TL;DR

PG 1211+143 hosts a multi-velocity ultra-fast outflow (UFO) whose soft X-ray absorption is mapped at high resolution alongside the Fe K UFO detected by XRISM Resolve. The joint analysis reveals three soft X-ray absorbers with velocities $v/c \approx -0.074$, $-0.120$, and $-0.331$, consistent with their Fe K counterparts, and an Absorption Measure Distribution with slope $a \approx 1.4$ implying a radial density profile $n(r) \propto r^{-5/3}$ and a clumpy wind scenario. The soft X-ray mass outflow rate is about $1\,M_\odot\,\text{yr}^{-1}$, with the fastest component dominating the kinetic power up to a sizable fraction of the Eddington luminosity, while slower zones contribute modestly. These results support a structured, clumpy UFO that challenges purely smooth wind models and point toward a combination of line driving (requiring lower ionization gas) and possible MHD processes in powering AGN winds with implications for feedback at galactic scales.

Abstract

The nearby quasar, PG 1211+143, has one of the prototype examples of an ultra fast outflow (UFO), as seen in several past XMM-Newton and Chandra observations. In December 2024, PG 1211+143 was observed simultaneously with XRISM Resolve and XMM-Newton, allowing both the Fe K and soft X-ray outflows to be examined at high resolution simultaneously. The Resolve spectrum revealed a forest of Fe K band absorption lines from the UFO (Mizumoto et al. 2026), comprising of up to six discrete velocity components ranging from $v/c=-0.074$ to $v/c=-0.40$. Here we present the simultaneous XMM-Newton RGS (Reflection Grating Spectrometer) spectrum, where three lower ionization counterparts of the Fe K velocity zones are observed; at $v/c=-0.074, -0.12$ and $-0.33$. The soft X-ray absorbers tend to be somewhat less ionized than their Fe K counterparts, with their opacity mainly arising from Fe L shell lines and highly ionized Oxygen. From comparing the Resolve and RGS absorbers, we show that the outflow can be parameterized with a density profile varying with radius as $r^{-5/3}$, while the lower ionization zones likely originate from denser clumps of gas. Pure electron scattering appears insufficient to provide enough thrust to power the wind, unless sufficient low ionization gas capable of radiative line driving exists outside of the line of sight. Overall, PG 1211+143 provides further evidence for the clumpy nature of accretion disk winds, as was recently revealed in the quasar PDS 456 with XRISM.

Figures (11)

• Figure 1: The X-ray variability of PG 1211+143. The left panel shows the 2024 RGS spectrum of PG 1211+143 (red points), which is compared to the previous 2014 epoch Reeves18. Here, the mean 2014 spectrum from 7 XMM-Newton orbits is shown in black, the 2014 low flux spectrum (revolution 2659) is in blue and the 2014 high flux spectrum (revolution 2664) is in green. The 2024 observation is brighter than all of the previous epochs. The right panels show the Swift XRT (0.3--10 keV, red) and Swift UVOT (U band, black) light-curves comparing the 2014 versus 2024 campaigns. Dotted vertical blue lines corresponds to the interval of the 2024 XRISM observation. Overall, PG 1211+143 is brighter in both the UV and X-rays in 2024, where the XRISM and XMM-Newton observations caught the AGN near to a strong flare. Note the U data points are divided by 100 to fit the scale of the plot.
• Figure 2: 2024 XMM-Newton EPIC-pn and NuSTAR spectrum of PG 1211+143, fitted from 0.3--40 keV in the AGN rest frame. The upper panels show the data points (black) fitted with a simple continuum model, consisting of a $\Gamma\approx2.2$ power-law (blue line) and a soft X-ray excess represented by a warm Comptonization component (orange), while the total emission is in red. The lower panel shows the $\sigma$ residuals of the data about this model, which show strong emission and absorption features. The energies of the UFO absorber troughs are marked by solid red lines. The upper right panels plot the best fit model, modified by the addition of three UFO absorbers, as well as a broad iron K$\alpha$ line. The UFO absorbers correspond to outflow velocities of $-0.07c$, $-0.12c$ and $-0.40c$ and are parameterized in Table 2. The lower panel shows the best-fit model and continuum components, after the addition of a highly ionized reflector.
• Figure 3: The 2024 RGS spectrum of PG 1211+143, plotted as residuals (in $\sigma$) to the power-law plus comptt continuum model described in the text. The upper panel shows the broad $7-30$ Å range, with the strongest absorption features occurring in the short wavelength portion of the spectrum, e.g. due to Fe L-shell ions. The lower panels shows zoom-in portions around the Fe L band (left) and the O K-shell band (right). The likely identification of the blue-shifted absorption troughs are marked, as per Table 3 and are color coded according to their outflow velocity. Here, red corresponds to $-0.074c$, green to $-0.120c$ and blue to $-0.33c$. The black labels correspond to the expected positions of the O vii, O viii and Ne ix resonance emission lines in the AGN rest frame, with no velocity shift.
• Figure 4: Fluxed RGS spectrum, in $\nu F_{\nu}$ units, with the best fit absorber model overlayed in blue. The upper panel shows the fit over the whole band, while the lower panel shows zoom-in portions around the Fe L band (left) and the O K-shell band (right). The likely identification of the blue-shifted absorption troughs are marked, and are color coded according to their outflow velocity as per Figure 3, where the outflow velocities of $-0.074c$ (red), $-0.12c$ (green) and $-0.33c$ (blue) correspond to RGS absorber zones 1, 3 and fast (see Table 3). In addition, neutral and ionized absorption lines from O i, N i and O vi-vii are also marked (at $z=0$). The most prominent emission lines occur from Ne ix (13.5 Å) and O viii (18.9 Å) which have little blue-shift.
• Figure 5: The transmission through the 4 RGS absorber zones; zone 0 (at $z=0$), zone 1 (at $v=-0.074c$), zone 3 (at $v=-0.120c$) and zone RGS--fast ($v=-0.33c$). The $z=0$ zone is likely associated to weak ionized absorption from our Galaxy. The other zones contribute most of their opacity through blue-shifted iron L lines, as marked, as well as from O viii Ly$\alpha$.