AGN OUTFLOWS Observations and Physical Parameters Leah Simon Feb. 3, 2006
Jan 15, 2016
AGN OUTFLOWS
Observations and Physical Parameters
Leah SimonFeb. 3, 2006
Absorption: Types
● Unassociated/Associated: Redshift relative to quasar emission lines
● Intrinsic/Extrinsic: Ejected from Quasar or part of host galaxy OR external to quasar
● Broad Absorption Lines(BALs)/Narrow Absorption Lines(NALs) (mini-BALs): line widths FWHM
● Outflows come from Intrinsic Lines of all types● Outflows occur in ~ 50% of all quasars!
Quasar Spectrum
Rodriguez-Hidalgo, private communication
BALs
● V (FWHM)> 3000 km/s● Redshifts from quasar up ~0.2c -> winds!● HiBALS: high ionizations species
– CIV, NV, SiIV● LoBALS: low ionization species
– CII, MgII,
NALs
● V spread (FWHM)< 100-200 km/s● CIV doublet resolvable● V shift < 5000 km/s -> associated (probably part
of quasar/host)
Intrinsic Absorption:Strong Indicators● BALs
– Large velocity widths– Within ~60,000km/s of quasar redshift
● Variability: timescales of ~year(s)– Caused by continuum source variability affecting
photoionized clouds– Or caused by cloud (outflow) motion across LOS
● Partial coverage – Continuum source is small!– Cloud must be nearby if some continuum source
can pass around cloud to our eye
Variability
Rodriguez-Hidalgo, private communication
Partial Coverage
Barlow, Hamann, Sargent, 1997
Partial Coverage Cont.
I I 0
=1−C f C f e
Hamann, Sabra, 2004
Intrinsic Absorption: Weaker Indicators
● Chemical signatures– Fine structure lines place density limits -> intrinsic
systems (probably) have higher densities● Requires low ionizations – not observed often
– High Ionization and/or Metallicity - N(NV)/N(HI)● Line profiles: broad and smooth ● Statistics: over-density of low-z (w/respect to
quasar) NALs implies these are intrinsic● Properties observed in intrinsic NALs appear
correlated with quasar properties (radio loudness, L etc.
Physical Parameters of Outflows
● Column density ~1022 – 1025 cm-3
● Velocity: 0 < v < 0.2c● Mass loss rate roughly correlated with line
strengths ● Mass loss due
to line driving:● Physical scale: calculate small region, however
variability not observed on short enough time scales (~months) – something else is at work
● Abundances and ionization levels
N =me c
e2 f
M w≃4GM e th
k /31/
Uncertainties in Interpretation● Orientation Angle
– Possibly degenerate with age+evolution– Needed to understand physical environment of QSO!
● Age + Evolution– Shorter lifetimes allow a mixture of ages, evolutionary
states at any given redshift● Lifetimes
– Duty Cycle?
● Shielding/self shielding Uinner
nγ/n ~ 5 – 10
– Set such that gas at inner edge of wind is at ionizations low enough to be pushed by UV flux (Murray + Chiang, 1995)
Acceleration Mechanisms● Radiation Pressure (Photoionization)
– Line Driving – momentum from radiation field through line opacity
– Expect vtransverse
= small
– Require very high L/LEdd
● Thermal Pressure (Parker Wind)– Not strong enough– Requires Isothermal wind...
● Magnetic Pressure (Magnetocentrifugal Driving)– 'Beads on a string'– See John Everett (CITA)
Comparison to BH accretion
● Probably Mdotoutflow
~ Mdotaccretion
● Mass loss rate from accretion : Lacc
= η Mdot c2
● Mass loss rate in winds:
Very uncertain! M w≃4GM e th
k /31/
References1)T.A. Barlow, F. Hamann, W.L.W. Sargent, 1997
astro-ph/9705048
2)D.M. Crenshaw, S.B. Kraemer, I.M. George, 2003 ARAA, 41:117
3)F. Hamann, B. Sabra, 2003 astro-ph/0310668
4)N. Murray, J. Chiang, 1995 ApJ 454: L105
5)N. Murray, J. Chiang, S.A. Grossman, G.M. Voit, 1995 ApJ 451: 498
6)D. Proga, J.M. Stone, T.R. Kallman, 2000 ApJ 543: 686
7)M. Urry, P. Padovani, 1995 PASP 107:803
8)R.J. Weymann, R.F. Carswell, M.G. Smith, 1981 ARAA, 19:41