Hot Gas in Damped Lyman-a SystemsHidden Baryons & Metals in Galactic Halos at z=2-4

Andrew Fox (ESO-Chile)

with P. Petitjean, C. Ledoux, R. Srianand, J. Prochaska, A. Wolfe

z=0 Baryon Budget*

WHIMDiffuse IGMGalaxies

* In IGM Simulations by Oppenheimer & Davé

z=3 Baryon Budget

z=2-4: Most Baryons still in Diffuse IGM

IGM Simulations by Oppenheimer & Davé

Damped Lyman-a Systems: Observing gas in/around protogalaxies

Pontzen et al. (2008)DLA Simulations

N(H I)>2x1020 cm-2

• Identified by damping wings on Lyman- line

• Select galaxies (or their halos) through absorption (independent of galaxy mass)

• Large samples exist at both medium and high resolution

O VI 1031, 1037

Ion. Potential

=114 eV

N V 1238, 1242

Ion. Potential

=77 eV

C IV 1548, 1550

Ion. Potential

=48 eV

Si IV 1393, 1402

Ion. Potential

=33 eV

Survey for High Ions in DLAs

O5+

O+4 O+5

electron (T300 000 K)Collisional ionization

photon (E>113.9 eV)Photoionization

O+6 O+5

Ion Detection rate in DLAs at z=2-3

Ref

C IV,Si IV

100%(74/74)

Wolfe & Prochaska 2000 Fox et al. 2007b

O VI >34 %(12/35)

Fox et al. 2007aLehner et al. 2008

N V 13±4 % Fox et al. 2009

v (km s-

1)v (km s-

1)

Spectra from VLT/UVES

–200 km/s 0 200 km/s

System line width (Dv)Component line width (b-value)

DLA Plasma: Kinematic Measurements

Component line width distributionBased on Voigt Profile Fits to 12 DLAs with O VI

Evidence for multiple plasma phases

Characteristic of warm photoionized plasma

Characteristic of hot, collisionally-ionized plasma

Fox et al. 2007a

DLA High-ion Kinematics

Wolfe & Prochaska (2000)Fox et al. (2007b)

Broader Dv for high ions than low ions different energy source, ionizing and dispersing metal atoms over large Dv . Gal. winds? Accretion?

High-ion system velocity width correlates with metallicity

DLA Plasma: A Baryon & Metal Reservoir?

sub-DLA at z=2.67[O/H] =[O I/H I]= –1.64 ±

0.07

In both cases, the O VI line is ~70% deep→ O VI in DLAs/sub-DLAs is surprisingly strong given the metallicity

O VI 1031

N(H II,hot) N(OVI)

f (OVI)(O /H)

Milky Way (DLA)[O/H]=0

Ionization versus temperature

Models from Gnat & Sternberg (2007); f(O VI)<0.2 in photo-ionized models too

O VI (purple): N(Hot H II)/N(H I) > 0.4we know (H I in DLAs, z=3)=(1.0±0.1)10-3 (Prochaska+ 2005, Péroux+ 2005)

Baryon content (Hot H II, DLAs) > 410-4

Metal content (Hot H II, DLAs) >1.510-7 (~1% of z=2.5 metal budget)

Fox et al. 2009

N(H II,hot) N(OVI)

f (OVI)(O /H)

Production of warm/hot plasma in galaxy halos (at z=2-4)

Galactic Winds(Outflow)

Hot-mode accretion(Inflow)

Simulations from Kawata & Rauch (2007)

Simulations from Dekel & Birnboim (2007)

WHAT WE KNOW (OBSERVATIONALLY)• Detection rate of C IV & Si IV in DLAs (observed at high res.) is 100%

→ neutral gas always “shadowed” by ionized gas• High-ion col. densities & Dv correlate with neutral-phase metallicity• Dv broader for high ions than low ions:

Dv(C IV)~250 km s-1; Dv(Si II)~80 km s-1

• b-values broader for O VI than for C IV & Si IV → plasma is multi-phase

Large dataset for constraining simulations

High Ions in z=2-4 DLAs: Summary

tcool (60 Gyr) (T/106)2.7 (d/50)-1 if Z=0.1 Z

WHAT WE’D LIKE TO KNOW• What is metallicity in high-ion phase? Does it equal low-ion metallicity?

→ can refine N(H II) & baryon budget estimates• Is warm/hot plasma around galaxies produced by accretion, outflow, or both?• Outflow naturally explains metals without need for pre-

enrichment• Hot-mode accretion predicted in galaxies with M ≥ 1011.5 M

• What is fate of metals in warm/hot plasma? Locked up?

QAL Category log N(H I)

Notes

Ly forest <17 IGM low overdensity ionized

Lyman limit systems (LLS)

1719

Sub-damped Lyman-a (sub-DLA)

1920.3

Damped Lyman- (DLA) systems

>20.3Galaxies overdense neutral

zQSO=2.85

Almost 1 dex uncertainty in Jn at 113.9 eV!

Simcoe et al. (2004), z=3

Q) Do we expect photoionized O VI in galaxy halos at z=2-3?A) It depends (on the radiation field)

Mass-Metallicity relation?Ledoux et al. 2006, using VLT/UVES: 6 correlation between metallicity and velocity width of low-ion profiles.

If L M ( Dv2)

Same slope as L-Z relation for local galaxies

(Tremonti et al.)

See also Pettini (1999, 2004), Pagel (2002), Ferrara+ (2005), Sommer-Larsen & Fynbo (2007)

stars

gas

Metal Budget at z~2.2

Sub-DLA contribution higher than DLA:• more of them; CDDF rises to lower N(H I) (O’Meara+ 2007, Péroux+ 2005)• higher mean [Z/H] (Prochaska+ 2006, Kulkarni+ 2007)• higher ionization level (hidden metals) (Prochaska 1999, Fox+ 2007,

don’t forget O VI phase!)

~

4

Imaging of DLA Host Galaxies

Chen et al. 2005, z<0.65 DLAs range of host galaxy properties

Møller et al. (2002), HST/STIS

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