Observations and Physical Parameters Leah Simon Feb. 3, 2006 AGN OUTFLOWS
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. 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
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!
References 1)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