Surveying the Highly Ionized HVCs with FUSE and HST

Joe Collins (University of Colorado)

Mike Shull (University of Colorado)

Mark Giroux (East Tennessee State University)

Sembach et al. (2003)

The Highly Ionized HVCs

L.G.B.

M.W. motion

OVI HVCs not detected in HI 21-cm emission

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)

Kinematic sky distribution can be explained in several ways

Local Group WHIM

infall to L.G.B

Galactic Infall

• Rshell = 15 kpc

• Vinfall = 50 km/s

• standard Galactic rotation

L.G.B.

M.W. motion

Mass in Local Group WHIM

(Cen & Ostriker 1999)

NOVI = 10 cm

T = 10 K

Z = 0.1 Zsolar

RWHIM = 1 Mpc

Mhot ~ 10 Msolar

14 –2

5.5

12

Survey of Highly Ionized HVCs

• 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

Highly Ionized HVCs from Sembach et al. (2003)

The Sight Lines

3C 273 (Sembach et al. 2001)

HE 0226-4110 (A. Fox talk)

MRC 2251-178

Mrk 1513PG 0953+414 (A. Fox talk)

PG 1116+215 (R. Ganguly poster)

PHL 1811

PKS 1302-102

Ton S180

UGC 12163

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

The Sight Lines

L.G.B.

M.W. motion

3C 273PG 1116+215

PKS 1302-102

PG 0953+414

HE 0226-4110 Ton S180MRC 2251-178

PKS 2155-304

PHL 1811

Mrk 509

Mrk 1513

UGC 12163

PHL 1811O 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

Ton S180O 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

PKS 1302-102O 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

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

CLOUDY Modeling

• AGN/QSO background– log Φ = 4.0

– power law, α = 1.8

• Z = 0.1 Zsolar

• 2σ errors on Nion

Ton S180

log N(H I) = 16.6

log nH = –3.3

Ionization ModelingCLOUDY photoionization models• C II, Si II detections imply

nH > 10 cm

• O VI, C IV, Si IV are underpredicted

collisional ionization

–3.5 –3

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

Summary: Highly Ionized HVCs• Low ion (CII, SiII) detections in 9 of 12 cases:

– 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)