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Models and Observations of the Warm Ionized ^ Magnetised Medium (WI M M) of the Galaxy

Dame & Thaddeus 2011 submitted. Models and Observations of the Warm Ionized ^ Magnetised Medium (WI M M) of the Galaxy. Talk Outline WHAM update Modeling WHAM Magnetised HVCs!. Low frequency free-free absorption of radio synchrotron halo (Hoyle & Ellis 1963).

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Models and Observations of the Warm Ionized ^ Magnetised Medium (WI M M) of the Galaxy

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  1. Dame & Thaddeus 2011 submitted Models and Observations of the Warm Ionized ^MagnetisedMedium (WIMM) of the Galaxy Talk Outline WHAM update Modeling WHAM Magnetised HVCs! LOFAR-MKSP workshop • Robert Benjamin (U of Wisconsin) • Apr 6, 2011

  2. Low frequency free-free absorption of radio synchrotron halo (Hoyle & Ellis 1963) Galactic Diffuse Ionized Gas (DIG) Layers Milky Way (Reynolds 1989): Pulsar DM in globular clusters [at known distance] External galaxies NGC 891 (1990): H emission from edge-on spirals Dettmar 1990 Rand et al. 1990 LOFAR-MKSP workshop • Robert Benjamin (U of Wisconsin) • Apr 6, 2011

  3. • Ground-based high throughput velocity resolved survey • 15 cm aperature dual-etalon Fabry-Pérot spectrometer—largest used in astronomy—attached to 0.6m aperature sidereostat •Velocity resolution: 12 km/s •Spectral window: 4800 to 7300 Å•Angular resolution: 1o • 3sensitivity: 0.15 Rayleigh (106/4 ph cm-2 s-1 sr-1 = 2.4 x 10-7 ergs cm-2 s-1 sr-1 at H) Wisconsin H Mapper goes to Chile LOFAR-MKSP workshop • Robert Benjamin (U of Wisconsin) • Apr 6, 2011

  4. Ionizing source: two late-type O stars near the center of the bubble HD 135240=d Cir (l=319.69, b=-2.91, O8.5 V, mV=5.07) and HD 135591 (l=320.13, b=-2.6, O8 IIIp, mV=5.43). Log LLC= 48.72 and 49.22, consistent with Ha emission. Distance greater than 430 pc. [SII]  6716 Galactic plane observations(Gostisha et al 2011) 330o 320o LOFAR-MKSP workshop • Robert Benjamin (U of Wisconsin) • Apr 6, 2011

  5. Mysteries of the WiMM Q: What powers it?A: Ionizing photons from O stars that apparently leak from disk…—Puts constraints on spatial organization of ISM, but attempts to “photoionize” Joung & MacLow (JM06) simulations don’t create our WIM (Wood et al. 2010, ApJ, 721, 1379). Q: What temperature is it?A: A mixture? Dong & Draine, 2011, ApJ 727:35 address question of discrepancy of optical (8000 K) vs. free-free (3000 K) by appealing to mix of components/mechanisms. Q: What stirs it?A: High latitude EM distribution very well fit by log-normal function (Berkhuijsen & Fletcher 2008, MNRAS, 390, L19; Hill et al 2008, ApJ, 686, 363). Idealized models of (M)HD turbulence that is mildly supersonic (Ms~2) but sub-Alfvénic (MA~0.6) can match (1) EM distribution, (2) H line widths, and (3) pulsar DM|sin b| distribution. Q: What supports it?A: Scaleheight of 1-2 kpc much thicker than the scaleheight of 104 K gas in the gravitational potential. Cox (2005, ARAA, 43, 337) shows that the observed vertical distribution is consistent with hydrostatic equilibrium given observational estimates of magnetic, CR, turbulent pressures. But what is the physics that establishes this equilibrium and how would it change with SFR, gas, stars? LOFAR-MKSP workshop • Robert Benjamin (U of Wisconsin) • Apr 6, 2011

  6. Can we create a numerical WImM (and then photoionize it?) A: We will see… Previous results: Hydrodynamic simulations (JM06) + Monte Carlo photoionization (Wood et al 2010) show photons escape clumpy ISM, but do not produce an extended thick ionized layer and produce much broader distributions of EM than observed. Hypothesis: Addition of magnetic field will provide additional pressure support, producing a more vertically extended layer with less compression (and narrower EM distribution). Simulations: FLASH v2.5 adaptive-mesh hydrodynamic model of a turbulent, supernova-driven ISM (Joung & MacLow 2006,2009). A. Hill has added the MHD solver of Waagan, Federath & Klingenberg (2011, astro-ph/1101.3007). Basic characteristics: 1 kpc x 1 kpc x [2 x 20 kpc], xres(z)=2-30 pc, B x, ini=0, 6.5, 13 G evolved for 400 Myr. Galactic gz, gas, SNe rate fixed. Found sensitivity to (a) grid size, (b) Thalo, i , (c) xres. LOFAR-MKSP workshop • Robert Benjamin (U of Wisconsin) • Apr 6, 2011

  7. Medium resolution results: xres=8-64 pc Initial conditions that definitely (or may) matter ? Thalo,i  xrange ≥ 1 kpc  yrange ≥ 1 kpc  zrange≥ 20 kpc  tmax≥400 Myr  fSN ? Bx,i LOFAR-MKSP workshop • Robert Benjamin (U of Wisconsin) • Apr 6, 2011

  8. Vertical profiles (after 100 Myr) Dickey-Lockman HI + Reynolds WIM LOFAR-MKSP workshop • Robert Benjamin (U of Wisconsin) • Apr 6, 2011

  9. Midplane slices Will definitely change with higher resolution runs… LOFAR-MKSP workshop • Robert Benjamin (U of Wisconsin) • Apr 6, 2011

  10. An oscillatory surprise! Similar to that predicted by Walters & Cox (2001, ApJ 549, 353) Models of Vertical Disturbances in the Interstellar Medium LOFAR-MKSP workshop • Robert Benjamin (U of Wisconsin) • Apr 6, 2011

  11. Magnetized HVCs? Unsolved Mysteries of High Velocity Clouds—Benjamin (2004) RM reversal coincident with HI HVC (from Taylor et al 2009 RM catalog from NVSS 1364.9 MHz/1435.1 MHz) Using an estimate of neL: PB comparable to estimated ram pressure. Ordered field higher than in SMC/LMC. McClure-Griffiths et al (2010, ApJ, 725,275) Measurement of Magnetic Field in a [Magellanic Stream] Leading Arm High-Velocity Cloud LOFAR-MKSP workshop • Robert Benjamin (U of Wisconsin) • Apr 6, 2011

  12. Smith Cloud (Smith 1963) Lockman et al 2008, ApJL 679, L21d=10.5-14.5 kpc; 12.4±1.3 kpc z=-3 kpc Projected size=3x1 kpcMain body has two kinematic components vspace=296±20/ 271±6 km/s vISM=130±14/130±5 km/s NHI(cloud)=1-5 x 1020 cm-2Assuming cloud moves as a coherent linear object projection on our line of sight--> L LOFAR-MKSP workshop • Robert Benjamin (U of Wisconsin) • Apr 6, 2011

  13. Ionized component of Smith Cloud Brightest region of H at the tip of HI cloud, but an almost equally bright H cloud with low N(HI). Hill et al. 2009, ApJ 703, 1832 LOFAR-MKSP workshop • Robert Benjamin (U of Wisconsin) • Apr 6, 2011

  14. An extended search? Another clump of RM reversal suggests a deeper search for high velocity gas. LOFAR-MKSP workshop • Robert Benjamin (U of Wisconsin) • Apr 6, 2011

  15. • WHAM all-sky velocity-resolved H survey almost complete. Data reduction should be done by end of the spring. • Several surprises include a nearby off-plane HII region and increased depth through the Galaxy. • 3D adaptive mesh MHD simulations underway to explore the vertical structure, porosity/ionization, and dynamics of warm ionized medium. First two papers by this summer. Questions on B field evolution/topology welcomed! • Magnetic fields definitely provide additional vertical support, narrow range in PDF than hydro-only models. Match to our galaxy not yet clear. • Under certain conditions, simulations result in a damped oscillatory motion, with a period predicted by Walters & Cox (2001). —A. Hill, R. Joung, M. Mac Low, K. Wood, K. Waggan, C. Federath, C. Klingenberg, R. Benjamin • Evidence for a second magnetized high velocity cloud where key parameters (position, velocity, neutral/ionized mass) are known.Significance? —R. Benjamin, A. Hill, ? Conclusions —M. Haffner, A. Hill, K. Barger, R. Reynold, M. Gostisha, R. Benjamin LOFAR-MKSP workshop • Robert Benjamin (U of Wisconsin) • Apr 6, 2011

  16. Please Remove All Slides After This LOFAR-MKSP workshop • Robert Benjamin (U of Wisconsin) • Apr 6, 2011

  17. The problems with averages Volume vs. mass weighted? Very resolution dependent xres=8-64 pc Very height dependent Black <125 pcRed 0.4-0.6 kpcGreen 0.8-1.2 kpc LOFAR-MKSP workshop • Robert Benjamin (U of Wisconsin) • Apr 6, 2011

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