Upload
ramon-savage
View
218
Download
4
Tags:
Embed Size (px)
Citation preview
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
5