AGN Outflows, the tip of the

Iceberg?

X-ray Spectroscopy Workshop, Cambridge,

MA, July 2007

Collaborators:-

Jane Turner (UMBC/GSFC), Valentina Braito (JHU/GSFC), Alex Markowitz (JHU/GSFC), Ken Pounds (Leicester)

James Reeves, Keele University, UK (Formerly at NASA/GSFC/JHU)

Outflows in AGN

(Outflow Schematic; Elvis 2000)

Outflows (in the form of warm absorbers) are seen in the majority of nearby AGN.

Typically velocities ( from a few 100 km/s to a 1000 km/s, which could carry a few solar masses per year (out to pc scales).

In some higher luminosity AGN strong blue-shifted Fe K absorption features are seen above 7 keV - possible high v outflows at v~0.1c

Such outflows can carry significant Kinetic power - equivalent to the bolometric output.

Can provide feedback between BH/bulge mass in galaxy.

Iron K-shell Absorption in Seyfert 1s.MCG-6-30-15, Chandra/HETG (500ks) NGC 1365/XMM, (Risaliti et al. 2005)

Column densities are high, >1023 cm-2.

Can effect broad Fe K modeling.

McKernan et al. (04, 05) suggested some such lines could arise locally, e.g. WHIM, if coincident with AGN recession vel.

Young et al. (2005)

NGC 3783, XMM, Reeves et al. (2004)

Absorption Variability in NGC 3516

XMM April 2001

XMM Nov 2006

XMM Nov 2001

Suzaku Oct 2005

Strong changes in source flux driven by changes in covering fraction of “heavy absorber”.

Increase in column of highest ionized absorber, with strong Fe XXV/XXVI absorption lines emerging in 2006 obs campaign.

XMM 2001 vs 2006

A highly ionized outflow in NGC 3516 (Turner et al. 2007, in prep)

NGC 3516 observed for 200ks with XMM/Newton and Chandra/HETG in 2006.

Source returned to former bright state (5e-11 cgs, 2-10 keV)

Strong (100 eV, EW) absorption lines near 6.7, 6.97 keV rest frame, due to Fe XXV, XXVI 1s-2p. NH >5x1023 cm-2 for vturb=3000 kms-1.

Evidence of P-Cygni profile from outflow to Fe XXVI. Velocity shift ~2000 km/s

Neutral Fe K width ~3000 kms-1.

Observed frame and energies at 6.64, 6.92 (0.02 keV) rules out local (z=0) origin, e.g. WHIM.

Neutral Fe K

Fe XXVI

Fe XXVChandra/HEG

Zones of gas can cover wide range of ionization

Mg/Si K-shell band

O/Ne K-shell, Fe L-shell band

Absorbing gas covers a very wide range in ionization from log =0 up to 5. Fe observed from Fe < XVII (UTA) to Fe XXVI.

Highest ionization gas from largest columns and can form an energetically significant part of outflow.

NGC 3516, Chandra/HETG, 2006

Outflows of ~0.1-0.4c have been claimed from X-ray spectra of several AGN, mainly via absorption features in the Fe K band. Detection of absorption in the Fe K band requires a large column density - together with a high velocity that implies the outflow is both massive and energetic (unless highly collimated)

APM 08279+5255 v~0.2-0.4c (Chartas et al, ApJ, 2002, 579, 169) PG1211+1431, 3 v~0.08-0.1c (Pounds et al, MNRAS, 2003, 345, 705) PG1115+080 v~0.1/0.34c (Chartas et al, ApJ, 2003, 595, 85) PG0844+3492 v~0.2c (Pounds et al, MNRAS, 2003, 346, 1025) PDS 456 v~0.17c (Reeves et al, ApJ, 2003, 593, 65) IRAS13197-1627 v~0.11c (Dadina and Cappi, A&A, 2004, 413, 921) RXJ0136.9-3510 v~0.1/0.14c (Ghosh et al, ApJ, 2004, 607, L111)Mrk5093 v~0.2c (Dadina et al., 2005, A&A, 442, 461) IC 4329a v~0.09c (Markowitz et al. 2006, ApJ, 646, 783)MCG -5-23-16 v~0.1c (Braito et al, 2007, ApJ, submitted).

NB 1. Disputed by Kaspi et al., who claim the outflow may arise from a lower velocity, depending on the specific identification of lines in the spectrum. 2. Disputed on the basis of background subtraction in the EPIC/pn spectrum (Brinkman et al. 2005). 3. Shows red and blue-shifted iron absorption lines.

X-ray evidence for high velocity outflows in AGN

Relativistic Outflow in PDS 456

(Deep Suzaku Observation, 190ks, Feb 07) High luminosity QSO z=0.184 LBOL~1047 erg s-1

High v outflow originally claimed in 2001 XMM observation (Reeves et al. 2003) and in UV via HST/STIS (O’Brien et al. 2006).

Pair of blue-shifted absorption lines observed with Suzaku at 9.08/9.66 keV (rest frame) or 7.68/8.15 keV (observed).

NOT associated with obvious transition at z=0 frame, ruling out WHIM or local bubble.

Outflow velocity of 0.26/0.32c, if associated with Fe XXVI 1s-2p.

In PDS 456, outflow rate is ~20Msolar/yr assuming only 10% covering. At 1/3c, the KP of outflow is 1047 ergs-1, similar to bolometric output.

Outflow geometry and driving mechanism

Black holes accreting at Eddington or above can produce optically thick winds, (King & Pounds 2003). Optically thick within <100Rg. Mass outflow rate similar to Eddington (Mout ~ Medd).

Alternative is magnetic field driving. Significant energy in magnetic field in PDS456 from rapid X-ray variability, e.g. factor x2 within 10ks with Eflare=1051 erg (Reeves et al. 2002).

Magneto-rotational?Radiation Pressure driven (BAL-like)?

Kato et al. (2004)

Fe K Absorption line variability in PG 1211+143

XMM (2001) vs Suzaku (2005)XMM-Newton data revealed a highly ionised outflow (Pounds et al. 2003), with strong 7.6 keV Fe K absorption line (7.0 keV observed)

Highest ionization absorber has ~ 103.4 and NH ~ 5x1023 cm-2 outflowing at 0.08c (24000 km/s)

Outflow launched from inner disc at <130Rs (~1). Mass-loss rate ~ 3 M

yr-1 K.E. ~ 1045 erg s-1 (~LBOL)

Kaspi et al. (2004) suggested lower velocity for RGS lines (3000 km/s). But does not easily account for Fe K.

Iron K absorption variable - intrinsic to AGN outflow.

Fe XXVI Ly

XMM/2001

Suzaku/2005

In the 3rd spectrum a possible absorption feature is present at ~7.8 keV (Rest Frame). |EW|~50 eV (2~35).

BASELINE MODEL: diskline +narrow K+K + reflection

Significant Absn line variabilty

A transient blue-shifted Fe K absorption line in Seyfert 2, MCG -5-23-16 (Braito et al. 2007).

EPIC-pn (100ks)

A high velocity outflow in IC4329a (Markowitz et al. 2006)

IC4329a, 100ks XMM-Newton obs

Absorption line in IC 4329a spectrum at 7.68 keV (rest-frame). If associated with Fe XXVI, then outflow velocity is 27000 km s-1

Fe K-shell absorption

Feature is significant at >99.9% (Monte-Carlo). Not due to bgd (40x lower)

Well modeled by absorption from Fe XXVI K (6.97 keV rf) with a velocity shift of 27000 km/s (note z=0.016).

Can rule out absorption from Fe XXII or XXIII K near 7.6-7.7 keV with no velocity shift - model predicts K absorption at 6.6 keV (not observed)

Absorption from low ionization K (Fe <XVII at 7.1-7.2 keV) with v=0.07c ruled out - requires too much bound-free abs below 6 keV.

Do the iron K outflows have to be fast?

(a) High ionization fast outflow. Models the 7.6 keV feature well with an outflow of 0.1c.

(b) Low vel, moderate ionization outflow. Absorption due to Fe XVII - XXIV K near 7.6 keV. Overpredicts K at 6.6 keV.

(c) Low ionization outflow. Fe K absorption at 7.2 keV. Also requires fast outflow (0.06c). Overpredicts abs below 6 keV.

logxi=3.5, NH=1.5x1022cm-2, v=0.1c

logxi=2.5, NH=1.5x1022cm-2, v=0

logxi=1.5, NH=1.5x1022cm-2, v=0

Fe XXVI K

Fe XVIII-XXIV K and K

Fe < XVII KNo Fe K

(a)

(b)

(c)

Origins of the Blue-shifted Fe K-shell Absorption

• Local (z=0) absorption, such as the WHIM or local hot bubble unlikely due to variability. In many cases the outflow velocity differs from the AGN recessional velocity

• Therefore likely intrinsic to AGN, via outflow.• Lower velocity solutions have difficulty in fitting Fe K

band data in physically realistic model.• High velocity, high ionization outflow seems the most

plausible solution• Future calorimeter resolution (<6 eV) spectra will

provide a wealth of data at Fe K on high column density outflows.