The Physical Properties of Low-z OVI Absorbers in the OverWhelmingly Large Simulations

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1 The Physical Properties of Low-z OVI Absorbers in the OverWhelmingly Large Simulations Thorsten Tepper García in collaboration with: Philipp Richter (Universität Potsdam) Joop Schaye (Sterrewacht Leiden) Tom Theuns (Durham) Craig Booth (Sterrewacht Leiden) Rob Wiersma (Sterrewacht Leiden) Institut für Physik und Astronomie Universität Potsdam Astroseminar September 24, 2009

2 The Baryon Budget (z 2) OBSERVATIONS: e.g. Weinberg+97, Butler & Tytler 97, 98, Rauch+98 SIMULATIONS: e.g. Cen+94, Zhang+95, Miralda-Escudé+96, Hernquist %: Lyα Forest 10 %: gravitationally bound structures (clusters, galaxies, etc.) 75-90%: diffuse component ( intergalactic gas ) 10-25%: contained in other phases, mainly condensed gas ( stars and galaxies ) Good News: Simulations in good agreement with observational results

3 The Baryon Budget (z 0) OBSERVATIONS SIMULATIONS 10% 30% 40% 10%? 20% WHIM Diffuse Gas Hot Gas Stars Condensed

4 Warm-Hot-Intergalactic Medium (WHIM) Characteristics shock-heated intergalactic gas high temperatures: T K low densities: n H cm 3 highly-ionised plasma HII, HeII, HeIII, and traces of higly-ionized O, Ne, C Observationally Challenging: diffuse, soft (< 0.25 kev) X-ray emission (Davé+01) broad and shallow Lyα absorption (BLAs; e.g. Richter+04) X-ray / E(F)UV line absorption from highly-ionized O, Ne, C (e.g. Cen & Ostriker 99)

5 OVI Observations & Simulations (z 0) Savage+98, Danforth & Shull 08, Thom & Chen 08, Tripp+08, Fang & Bryan 01, Chen+03, Cen & Fang 06, Oppenheimer & Davé 09 OVERALL RESULTS High incidence rate (relative to e.g. Mg II) Heavy metal content 10% Solar well reproduced by simulations Multi-phase systems (as traced by HI and OVI) Significant baryon reservoirs ( 0.1 Ω b ) No general consensus about: OVI absorbers being tracers of WHIM e.g. Tripp+08, Thom & Chen 08, Oppenheimer & Davé 09 vs. Danforth & Shull 08, Cen & Fang 06 Ionization state (photoionized, collisionally ionized, or both) of OVI bearing gas Uncertainty in the baryon content of the gas traced by OVI

6 OverWhelmingly Large Simulations Schaye et al. in prep. Cosmological SPH Simulations of Structure Formation: Initial conditions taken from WMAP3 CDM, gas, stars, optically thin radiation Evolution of structure from z = 127 z = 0 Self-consistently Computed : OWLS SImulations (C.Booth) Star Formation (Dalla Vecchia & Schaye 08, Schaye & Dalla Vecchia) SNe Feedback (Galactic Winds) (Wiersma+09b) Timed Release of Heavy Elements (Wiersma+09b) Radiative Cooling including photoionization (Wiersma+09a) (AGN Feedback (Booth & Schaye 09))

7 z [Mpc] 48 los 32 z0.403 DEFAULT-L100N y [Mpc] x [Mpc] log 10 (1+!) z [Mpc] y [Mpc] x [Mpc] log 10 Temperature

8 Spectrum 32 short z0.403 o6 DEFAULT!L100N512 S/N= region: 1 / 1 lines: 9 / Transmission N o6 = ± b=9.41±0.18 EW=57.41 z= N o6 = ± b=17.17±0.24 EW=86.35 z= N o6 = ± b=15.35±2.25 EW=26.04 z= N o6 = ± b=7.42±0.47 EW=26.19 z= N o6 = ± b=6.81±0.07 EW=41.15 z= N o6 = ± b=5.90±0.04 EW=39.24 z= N o6 = ± b=8.53±0.09 EW=51.63 z= N o6 = ± b=7.96±0.09 EW=50.59 z= N o6 = ± b=10.17±0.02 EW= z= SpecWizard Spec Fit (modified AutoVP)!400! Restframe Velocity [km/s]

9 Probability Distribution Function short!los!z!o6!fit!overdensity!int!odw!sn50.als OVI absorbers mass weighted MOST mass in LARGE volume OVI traces tail at moderate densities 2009/9/1!120! !3 10!2 10! !

10 1.2 short!los!z!o6!fit!sn50!temperature!k!int!odw.als OVI absorbers mass weighted 2009/9/1!120! Probability Distribution Function photoionized shock-heated Temperature [K]

11 2009/9/1!120! short!los!z!o6!fit!sn50!metal!mass!fraction!int!odw.als 1.4 OVI absorbers mass!weighted 1.2 Probability Distribution Function OVI is found in gas with Z 0.1Z !8 10!7 10!6 10!5 10!4 10!+ 10!2 10! Metal Mass Fraction [Z ]

12 10 4 baricentre ! % 68% 50% Oppenheimer & Davé 2009a 10 7 Temperature [K]

13 10 4 t cool < t Hubble 10 3 t cool > t Hubble ! t cool 3 k T 2 n Λ Z 0.1Z no metals Cooling time contours adapted from Wiersma+08 Temperature [K]

14 10 4 t cool < t Hubble 10 3 t cool > t Hubble ! t cool 3 k T 2 n Λ Photoionization cannot be neglected Z 0.1Z no metals Cooling time contours adapted from Wiersma+08 Temperature [K]

15 short!z!o6!phys!params!*verdensity!k!vs!noverb!sn50.als, bin = N = 2743 N/b 2009/9/15!120! e+11 1e+12 1e+13 1e !4 *verdensity [K] !5 10!6 n 7 [8m!3 ] Stronger absorbers trace higher (over-)densities ! Line Depth (! 0 )

16 short!z!o6!phys!params!temperature!k!vs!noverb!sn50.als, bin = N = N/b 2009/9/15!120! e+11 1e+12 1e+13 1e Temperature [K] observations might be biased towards lower temperatures ! Line Depth (! 0 )

17 Summary UNCERTAINTY in the nature and physical properties of OVI bearing gas inferred from observations Need for simulations RESULTS: OVI traces gas in the low-temperature regime of the predicted WHIM phase, with a mean heavy-element content around 10% solar and overdensities in the range estimated averge baryon content of 6.22 %, i.e. Ω WHIM (Ovi) 0.062Ω b DISAGREEMENT between different studies of OVI absorbers using simulations need for more detailed analysis and more contraints from observations