A new look at AGN X-ray spectra

- the imprint of massive and energetic outflows

Ken Pounds

University of Leicester

Prague August 2006

1H 0419

NGC 509

NGC 5548

Mkn 766

L2-10 (1042 ergs/s)

570

175

40

6

most obvious feature is the ‘soft excess’ - a function of luminosity ?

also fluorescent Fe K line, sometimes with ‘red wing’

XMM-EPIC spectra for sample of type 1 AGN

but the same spectral features (and changes) are seen for individual AGN example - the luminous Seyfert 1 PG1211+143

XMM pn data from 2001 (black) and 2004 (red) observations

Appearances can be deceptive - compare the unmodelled data

difference lies between ~0.7 and ~2 keV

due to a change in photoionised absorption?

Spectral ratio supports change in ionised absorption as cause of spectral difference

Gierlinski and Done (2004) and Chevallier et al (2006) have explored this idea as an explanation of strong soft excesses.

Problems with relativistically smeared absorber and with ‘fine tuning’

2001/2004 data

difference spectra showed: dominant spectral change due to steep power law component (Gamma ~ 2.4)

Fluxed spectra of the highly variable Seyfert 1H 0419-577 (*)

Could another component be moderating the spectral change?

Pounds et al, ApJ 2004

PG1211 exhibits a high velocity outflow which, unless highly collimated, has a mechanical energy comparable to the bolometric luminosity (more strictly ~ v/c if continuum driven) *

Could this power the steep, variable continuum component ?

Pounds et al MN 2003 King and Pounds ApJ 2003

But lower velocity claimed by Kaspi and Behar, ApJ 2006

analysis of higher resolution XMM MOS data has improved constraints on high energy outflow (*)

K-shell absorption from H- and He-like ions of Ne, Mg, Si, S and Fe

>> v~0.14+/-0.01c

Pounds and Page (astro-ph 0607099)

Developing a new spectral model

components include:

power law continuum from disc-corona

absorption by high and moderate ionisation gas

re-emission from ionised gas components

second (power law) continuum powered by outflow

the result

- an excellent spectral fit to the EPIC data (chi_sq ~ 840/830 dof) - - with no ‘smearing’

Compare energies and luminosities as further test of model

•Absorption by warm absorber ~ 8.4 x 1043 ergs/s from PL1 and 5.3 x 1042 ergs/s from PL2 >>> 9 x 1043 ergs/s

•Absorption by high Xi absorber ~ 1.4 x 1043 ergs/s from PL1 and 5 x 1042 ergs/s from PL2 >>> 1.9 x 1043 ergs/s

Luminosity of warm emitter ~ 1.7 x 1043 ergs/s >>> CF ~ 0.2

Luminosity of high Xi emitter ~ 1.4 x 1042 ergs/s >>> CF ~ 0.1

•Luminosity (0.35-10) in second power law ~ 6 x 1043 ergs/s

while mechanical energy in fast flow and CF of 0.1 ~ 6 x 1044 ergs/s >>> efficiency ~ 10%

NB warm emission ~ 35 x that of NGC1068 (but only 5-10 x higher Lbol)

Critical fit to high resolution RGS data - yes, but requires emission lines to be strongly broadened

Steep power law continuum consistent with EPIC model

the broadened emission line structure in the RGS spectral fit

N, O, Ne, Mg removed from XSTAR model

Fe also removed, to leave continuum only

Finally - how does the same model fit the 2004 data?

primarily by increase in weakly absorbed power law

Summary

• blue-shifted absorption lines in the luminous Seyfert 1 galaxy PG1211+143 show highly ionized outflow at v ~ 0.14c

• the mechanical energy in the high velocity outflow is sufficient to power a second X-ray continuum component perhaps via internal shocks in the flow (NB efficiency similar to GRB ?)

• re-emission of the absorbed flux from primary power law visible in the soft X-ray spectrum (strong line broadening)

• the need for a relativistic Fe K line is reduced or removed by the spectral curvature caused by continuum absorption

• similar spectral features in other luminous AGN suggest PG1211 + 143 may be characteristic of a high accretion ratio

NB. outflow of 1 MSun/ yr for ~ 5x107 yr will carry mechanical energy to host galaxy ~ 1060 ergs ( cf binding energy ~ 1059 erg of galactic bulge with M ~ 1011 MSun and velocity dispersion ~ 300 km/ s; >>> major effect on growth of host galaxy

Warm absorber/emitter

Ionisation parameter >>> n.r2~1043.7/35 ~ 2 x 1042 column density >>> n.d ~ 8 x 1022 assume d ~ 0.1r >>> r ~ 2 x 1018 cm and n ~ 5 x 105 cm-3

Emission measure ~ 1066 cm-3 from observed luminosity spherical shell with above parameters >>> n2 . volume ~ 3 x 1066 cm-3

>>> CF ~ 0.3

High Xi absorber/emitter Ionisation parameter >>> n.r2~1043/750 ~ 1.3 x 1041 column density >>> n.d ~ 6 x 1022 assume d ~ 0.1r >>> r ~ 2 x 1017 cm and n ~ 4 x 106 cm-3

Emission measure ~ 2 x 1065 cm-3 from observed luminosity spherical shell with above parameters >>> n2 . volume ~ 2 x 1064 cm-3 >>> CF ~ 0.1

Scaling the ionised outflow components

EPIC (and RGS) spectra show evidence for outflowing matter with wide range of ionisation parameter.

Unless tightly collimated the high velocity implies:

(1) a high mass rate with Mdot.out ~ 1.0 MSun/yr, comparable to Mdot.Edd ~ 1.2 MSun/yr for a BH mass of 3 x 107 MSun accreting at an efficiency of 0.1, and

(2) an energetic outflow ~ 2 x 1044 erg/s (~v/c x LEdd) with mechanical energy significantly larger than the luminosity of the X-ray PL

NB. outflow of 1 MSun/ yr for ~ 5x107 yr will carry mechanical energy to host galaxy ~ 1060 ergs ( cf binding energy ~ 1059 erg of galactic bulge with M ~ 1011 MSun and velocity dispersion ~ 300 km/ s; hence will have a major effect on growth of host galaxy

But is the spectrum compatible with no strong narrow lines in RGS?

- model fit (PO2 + EM1) requires smoothing to get acceptable chi-sq- find similar ratio of line emission to continuum and PL slope is again steep (Gamma ~ 3)

However, best-fit sigma ~ 18 eV at 0.5 keV

Corresponds to v ~ 25000 km s-1 FWHM

additional broadening from line saturation, turbulence or spread in ionisation parameter?

PG1211+143 is a bright, narrow emission line quasar at z ~ 0.0809

Lbol~ 6 x 1045 ergs/s (H0 = 75) MBH ~ 3 x 107 MSun

suggesting accretion rate ~ Eddington rate

Pre-XMM observations showed a strong `soft excess’ over a PL of photon index ~ 2, with some evidence for a broad Fe K line

XMM made a ~ 60 ks observation of PG1211+143 in June 2001 and second similar observation in June 2004

Consider the case of PG1211+143 - where an energetic outflow is well established

Lyman-alpha of FeXXVI MgXII SXVI

* * *

Identification of narrow absorption lines in EPIC pn and MOS with resonance lines of H- like ions of Fe, S, and Mg, consistent with high ionisation, high column density outflow of v ~0.08 – 0.1c

see also IC4329A (Markowicz et al astro-ph/0604353)

in particular the absorption features at ~ 1.5 and 2.7 keV are both resolved into two lines

a closer look at the MOS data for PG1211

best fit now if 7 keV feature is identified with 1s-2p resonance absorption line of Fe XXV

Finally - testing the new model with 2004 pn data

abundances fixed at 2001 valuesfit acceptable (chi-sq / dof ~ 1.1)

• reduced absorption modelled mainly by stronger steep power law component

• weaker soft X-ray emission as indicated by difference spectrum

The initial analysis used 4 of the 5 most significant absorption features to find an outflow velocity of v~0.09c.

- ignoring absorption near the Si edge and an ‘emission line’

Addition of a trace absorber affecting PO2 improved chi-sq from 877/817 to 832/814

NH~1.2x1021 cm-2 log Xi~ 1.95 v_out~ 0.07 – 0.10 c

Removing absorber shows absorption due to Fe-L and UTA

Initial ratio of 2004 data to 2001 model

New fit with increase in PO2 and weaker soft X-ray line emission

conventional plot with PL fit at 1-10 keV

-more spectral structure seen below ~ 3 keV

a closer look at the MOS data for PG1211

1H 0419-577 in

bright, high flux state

and faint, low flux state

But, individual AGN show very similar spectral variations

Perhaps accretion rate is the key?

Conventional analysis of EPIC spectrum (pn black; MOS red) reported in 2003 paper*

Power law fit at 1-10 keV found a photon index ~ 1.85 and a strong SX

1-10 keV spectrum modelled with a power law plus an extreme relativistic line Fe K emission line (EW ~ 1.4 keV)

Plus narrow absorption features at ~1.5, ~2.7, ~7 and ~8 keV

* (MNRAS, 345, 705, 2003)

MOS has equally good statistics at medium and low energies – and better energy resolution (1 sigma~34 eV at 1 keV)

Part of MOS spectrum of NGC 1068

(MNRAS, 368, 707, 2006)

Chi-sq plot shows high significance of the 5 absorption lines and (the same) emission lines (*) as seen in pn data

higher resolution MOS spectra confirms the strong, highly ionised outflow in PG1211 + 143, albeit with velocity increased to v~0.12c

The fitted model includes power law continua with photon indices ~ 2.1 and ~3

plus high ionisation absorber A1 and warm absorber A2 affecting both power laws

E1,E2 re-emission from absorbing gas

NH~2x1023 A1 log Xi~ 2.9 v_out~ 0.120+/-0.005c

NH~3x1022 A2 logXi~ 1.5 v_out~ 0.05+/-0.02c

logXi~ 1.4 E1 v_out~ 3000+/-1000 km/s

logXi~ 2.9 E1 v_out~ 3000+/-1000 km/s

Chi-sq/d.o.f. ~ 820/820

the main spectral change appears to be an increase in flux between ~ 0.7 – 2 keV

narrow absorption lines remain, but weaker

Does model describe spectral change in 2004 ?

-- the plot shows pn data from 2001 (black) and 2004 (red)

2-10

~45%

1-2

~40%

0.3-1

~25%

~32% flare over ~104 sec in full 0.3-10 keV light curve

variation least in soft X-ray band as expected for significant re-processed flux

Footnote: Variability of EPIC light curve also supports model