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Surveying the Highly Ionized HVCs with FUSE and HST

Surveying the Highly Ionized HVCs with FUSE and HST. Sembach et al. (2003). Joe Collins (University of Colorado) Mike Shull (University of Colorado) Mark Giroux (East Tennessee State University). The Highly Ionized HVCs. M.W. motion. L.G.B.

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Surveying the Highly Ionized HVCs with FUSE and HST

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  1. Surveying the Highly Ionized HVCs with FUSE and HST Sembach et al. (2003) Joe Collins (University of Colorado) Mike Shull (University of Colorado) Mark Giroux (East Tennessee State University)

  2. The Highly Ionized HVCs M.W. motion L.G.B. OVI HVCs not detected in HI 21-cm emission

  3. Are these HVCs WHIM? Nicastro et al. (2002, 2003) propose that these objects trace Local Group WHIM The Evidence: 1) “Dipole” sky distribution of HVC velocities 2) Possible correlation with poorly-resolved z=0 OVII/VIII absorption (PKS 2155-304, 3C 273, Mrk 421, H 1821)

  4. Kinematic sky distribution can be explained in several ways  Local Group WHIM  infall to L.G.B M.W. motion L.G.B. • Galactic Infall • Rshell = 15 kpc • Vinfall = 50 km/s • standard Galactic rotation

  5. Mass in Local Group WHIM 14 NOVI = 10 cm T = 10 K Z = 0.1 Zsolar RWHIM = 1 Mpc –2 5.5 12 Mhot ~ 10 Msolar (Cen & Ostriker 1999)

  6. Survey of Highly Ionized HVCs Highly Ionized HVCs from Sembach et al. (2003) • FUSE data with S/N > 5 • HST-STIS (public April 2004) • E140M • G140M  coverage of O I, C II/III/IV, Si II/III/IV, NV, and O VI

  7. The Sight Lines PG 1116+215 (R. Ganguly poster) PHL 1811 PKS 1302-102 Ton S180 UGC 12163 3C 273 (Sembach et al. 2001) HE 0226-4110 (A. Fox talk) MRC 2251-178 Mrk 1513 PG 0953+414 (A. Fox talk) PKS 2155-304 Mrk 509 (Sembach et al. 1999; Collins, Shull, & Giroux 2004)  12 sight lines  Can consider whether these objects are more similar to Galactic halo HVCs or WHIM

  8. The Sight Lines PG 1116+215 PG 0953+414 3C 273 PKS 1302-102 M.W. motion UGC 12163 Mrk 1513 L.G.B. Mrk 509 PHL 1811 PKS 2155-304 MRC 2251-178 HE 0226-4110 Ton S180

  9. PHL 1811 O VI 1031.93 Å N V 1238.82 Å C IV 1548.20 Å Si IV 1393.76 Å Si III 1206.50 Å C II 1334.53 Å Si II 1526.71 Å O I 1302.17 Å

  10. Ton S180 O VI 1031.93 Å N V 1238.82 Å C III 977.02 Å Si III 1206.50 Å C II 1036.34 Å Si II 1260.42 Å

  11. PKS 1302-102 O VI 1031.93 Å N V 1238.82 Å C IV 1548.20 Å Si III 1206.50 Å C II 1334.53 Å Si II 1260.42 Å

  12. Survey Results • 9 of 12 HVCs are detected in low ions (C II, Si II) • 10 of 12 are detected in Si III or C III • 2 in O VI only (3C 273, PKS 1302-102)  go to ionization models

  13. AGN/QSO background log Φ = 4.0 power law, α = 1.8 Z = 0.1 Zsolar 2σ errors on Nion CLOUDY Modeling Ton S180 log N(H I) = 16.6 log nH = –3.3

  14. Ionization Modeling CLOUDY photoionization models • C II, Si II detections imply nH > 10 cm • O VI, C IV, Si IV are underpredicted  collisional ionization –3.5 –3

  15. Ionization Modeling • Collisional Ionization • Turbulent Mixing Layers (Slavin et al. 1993) • Conductive Interfaces (Borkowski et al. 1990) • can reproduce high ion ratios • N(CIV)/N(OVI)=0.2–1.1 N(NV)/N(OVI) < 0.1–0.3 • kinematic connection between low/high ions •  both photo- and collisionally ionized components occur in the same cloud

  16. Summary: Highly Ionized HVCs • Low ion (CII, SiII) detections in 9 of 12cases: • imply photoionization with log nH > –3.5 • are inconsistent with WHIM log nH = –5 to –6 • High ions (CIV, SiIV, OVI) • share similar kinematics with the low ions • arise via collisional ionization at cloud interface • Only 2 HVCs are detected solely in O VI • cannot rule out WHIM origin • multiphase objects similar to Galactic halo HI HVCs, albeit at low-Ntotal(H)

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