UMD ASTR 620 - Starbursts and Galactic Winds

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+ Starbursts and Galactic Winds (Smith, Gallagher, & Westmoquette ’05) M82 in Hα Reference: Veilleux, Cecil, & Bland-Hawthorn 2005, ARAA, 43, 769-826Galactic Winds: Sources of Energy • Starbursts: – Mechanical energy / momentum from stellar winds – Mechanical energy / momentum from supernovae (~1051 ergs/SN) Scales with Star Formation Rate • Active Galactic Nuclei (=AGN) (accretion disks around supermassive black holes): – Radiative heating → Compton-heated wind (T ~ 106 – 107 K) – Radiation pressure – Magnetic fields in accretion disks → (loosely) collimated jets in (radio-quiet) radio-loud AGN Scales with mass accretion rate / AGN luminosityExplosions in Galaxies! • Blowout vortex in a stratified atmosphere T(hot gas) ~ E / M ~ 108 ξ Λ-1 [K] ξ = thermalization efficiency < 1 Λ = Mtotal/Mejecta = mass-loading term > 1  V(bubble) ~ 100 (ξ dE/dt42)0.2 n0-0.2 t7-0.4 = expansion speed of adiabatic bubble n0 = nucleon density [cm-3] dE/dt42 = rate of deposition of mechanical energy ………..[1042 erg s-1] t7 = age of bubble [107 yrs]  V(wind) ~ 3000 ξ0.5 Λ-0.5 = terminal velocity  V(cloud) = terminal velocity of cloud accelerated by wind ram pressure ~ 600 dp/dt340.5 Ωw-0.5 r0,kpc-0.5 Ncloud,21-0.5 Ncloud,21 = column density of cloud [1021cm-2] r0 = initial radius [kpc] dp/dt34 = wind momentum flux [1034 dynes] Ωw = solid angle of wind [sr] Galactic Winds: Basic Physics t = 2.5 Myr t = 5.0 Myr t = 7.5 Myr t = 10 Myr (Strickland & Stevens 2000) log n(cm-3) ∙ ∙log n log T (Cooper et al. 2008) 4.0 Myr 2.5 1.01” ~ 50 l-d A Humbling Example: Our own MW ROSAT 1.5 keV  Dusty Bipolar Wind (~ 350 pc) • Galactic Center Lobe / Warm dust (Sofue & Handa 1984; Bland-Hawthorn & Cohen 2003) • Energy Requirement: M(H2) ~ few x 106 Msun V ~ 150 km s-1 (uncertain) ⇒ KE ~ 1055 ergs? • Dynamical timescale: ~ 1 – 2 Myr?  X-rays: • ROSAT 1.5 keV map of inner 45o (Bland-Hawthorn & Cohen 2003) • Diffuse 6.7 keV Kα emission from He-like Fe XXV (Hyodo+06)  Two large γ-ray bubbles in MW: • Fermi-LAT (Su+10; Crocker+11) • Correlated w/ WMAP “Haze” (Finkbeiner+04) ← ~ 3o → MSX 8.3 µm+ (Spitzer: Engelbracht et al. 2006) (Herschel: Roussel et al. 2010) Dust Outflows of M82 Warm Dust (PAH 8 µm) Cold Dust (250 µm) ~ 5 kpc+ (CO 10: Walter, Weiβ, & Scoville ‘02 ) (H2 2.12 um: SV, Rupke, & Swaters ’09) Molecular Outflows of M82 Cold Molecular Gas (~3.6”) Warm Molecular Gas (~4”) outflow disk “ tidal streamers” ~ 1 kpc M ~ 3 x 108 Msun E ~ 1 x 1055 ergs M < 104 Msun E < 1 x 1051 ergs?Powerful Quasar-driven Wind in Mrk 231 (Rupke & SV 2011) • Gemini/IFU: Na I absorption • Vout  1100 km s-1 • > 2-3 kpc from nucleus • dM/dt > 400 Msun yr-1 ~ 2.5 x SFR • dE/dt > 1044 ergs s-1 ~ 2.5 x dE*/dt ~ 0.7% LAGN Jet axis Starburst wind? Nuclear wind Gemini Press Release Consistent with QSO feedback models (e.g., Hopkins & Elvis 2010) Neutral Gas Outflow Velocities kpc


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UMD ASTR 620 - Starbursts and Galactic Winds

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