The metal-line emission of the intergalactic medium in OWLS Serena Bertone (UC Santa Cruz) Joop Schaye (Leiden Observatory) & the OWLS Team Bertone et al 2009 arXiv: Bertone et al 2010a, 2010b, in prep Swinburne University of Technology, Melbourne November 26 th 2009

Outline Introduction: the intergalactic medium: warm, warm-hot, hot… what is it? how do we detect it? New simulations: OWLS Results: X-ray & UV emission at z<1 rest-frame UV emission at z>2 what gas does emission trace? dependence on physics

unbiased info on matter power spectrum on largest scales reservoir of fuel for star and galaxy formation IGM metallicity constrains the cosmic SF history interplay IGM- feedback puts constraints on galaxy formation models Intergalactic medium: Why do we care? Neutrinos: 0.3% Metals: 0.03% Dark energy: 70% Free H & He: 4% Stars: 0.5% Dark matter: 25% > 90% of baryonic mass is in diffuse gas (Persic & Salucci 1992, Fukugita et al 1998, Cen & Ostriker 1999)

100 Mpc z=6 z=2z=0 Springel 2003 IGM evolution cosmic time 100 Mpc/h box

Gas temperature distribution Cen & Ostriker 1999 etc T<10 5 K10 5 K <T<10 7 KT>10 7 K Warm gas: diffused photo-ionised traced by Lyα forest Warm-hot gas: WHIM mildly overdense collisionally ionised shock heated by gravitational shocks Hot gas: dense metal enriched haloes of galaxies and clusters z=0

IGM mass and metals The bulk of the metal mass does not trace the bulk of the IGM mass most mass most metal mass Bertone et al z=0.25

Mass and metal fractions evolution Average IGM temperature increases with time Most metals locked in stars at z=0 Average metal temperature increases with time Metal mass - Wiersma et al 2009 WHIM ICM diffuse IGM halo gas IGM mass - Dave’ et al. 2001

T<10 6 K Rest-frame UV lines Lyα, OVI, CIV… T>10 6 K X-rays metal lines OVII, OVIII Absorption z<1 Nicastro et al 2005 Rasmussen et al 2007 Buote et al 2009 z<1: UV Tripp et al 2007 Lehner et al 2007 Danforth & Shull 2005 z>1.5: optical Kim et al 2001 Simcoe et al 2006 z<1 Fang et al 2005 Werner et al 2008 Bertone et al 2009 z<1: UV Furlanetto et al 2004 Bertone et al 2010a z>1.5: optical Weidinger et al 2004 Bertone et al 2010b Emission How can we detect the IGM? ✔ ✔ ✗ ✔✗✔✗ ? ?

Emission vs. absorption EmissionAbsorption PRO 3-D data on spatial distribution, velocity field, metallicity… PRO Easier to detect Underdense regions investigated with current optical/UV instruments CONS Hard to detect – low fluxes Requires new instruments with high sensitivity and large FoV CONS 1-D info along a LOS Requires bright background sources

OWLS OverWhelmingly Large Simulations The OWLS Team: Joop Schaye (PI, Leiden) Claudio Dalla Vecchia (MPE) Rob Wiersma, Craig Booth Marcel Haas, Freeke Van De Voort (Leiden) Tom Theuns (Durham) Serena Bertone (UCSC) Ian Mc Carthy (Cambridge) Alan Duffy (Perth) Many thanks to the LOFAR and SARA supercomputing facilities

OWLS many runs (>50) with varying physical prescriptions/numerics (Schaye et al 2009) cosmological hydrodynamical simulations: Gadget 3 run on LOFAR IBM Bluegene/L WMAP 3 cosmology largest runs: 2x512 3 particles two main sets: L=25 Mpc/h and L=100 Mpc/h boxes evolution from z>100 to z=2 or z=0

New physics in OWLS New star formation ( Schaye & Dalla Vecchia 2008 ) : Kennicutt-Schmidt SF law implemented without free parameters New wind model (Dalla Vecchia & Schaye 2008) : winds local to the SF event hydrodynamically coupled Added chemodynamics (Wiersma et al. 2009) : 11 elements followed explicitly (H, He, C, N, O, Ne, Si, Mg, S, Ca, Fe) Chabrier IMF SN Ia & AGB feedback New cooling module (Wiersma, Schaye & Smith 2009) : cooling rates calculated element-by-element photo-ionisation by evolving UV background included

Physics variations in OWLS Cosmology: WMAP1 vs WMAP3 vs WMAP5 Reionisation & Helium reionisation Gas cooling: primordial abundances vs metal dependent Star formation: top heavy IMF in bursts isothermal & adiabatic EoS Schmidt law normalisation Metallicity-dependent SF thresholds Feedback: no feedback feedback intensity: mass loading, initial velocity… feedback implementation AGN feedback Chemodynamics: Chabrier vs Salpeter IMF SN Ia enrichment AGB mass transfer Schaye et al 2009

Gas cooling rates Wiersma, Schaye & Smith 2009 collisional ionisation eq. photoionisation eq. density dependent Photo-ionisation by UV BK + collisional ionisation equilibrium Cooling rates calculated element by element for 11 species: takes into account changes in the relative abundances

Gas emissivity 11 elements – comparable to cooling rates Collisional ionisation + photo-ionisation by UV BK  important at low density UV lines stronger than X-ray ones UV linesX-ray lines Density  Bertone et al a z=0.25

Emission at low redshift: Soft X-rays & UV lines

Emission at low redshift: X-rays 100 Mpc/h boxes 20 Mpc/h thick slices 15” angular resolution 12 X-ray + 6 UV emission lines Bertone et al 2009

X-ray lines O VIII strongest line lines from lower ionisation states and whose emissivity peaks at lower temperatures trace moderately dense IGM: C V, C VI, N VII, O VII, O VIII and Ne IX lines from higher ionisation states trace denser, hotter gas: C VI, O VIII, Ne X, Mg XII, Si XIII, S XV and Fe XVII Fe XVII emission has different spatial distribution than other elements: later enrichment by SN Ia Bertone et al 2009

UV lines C III and C IV strongest lines: trace gas in proximity of galaxies O VI and Ne VIII trace more diffuse gas than C IV - different spatial distribution no emission from the hottest gas in groups UV emission is a good tracer of galaxies and of mildly dense IGM, but not of IGM in very dense environments Bertone et al 2010a

Surface brightness PDFs Bertone et al 2009, 2010a C IV and O VI lines detectable by FIREBALL (Tuttle et al 2008) Detection of X-ray lines requires new instruments: WFI on the Interntional X-ray Observatory (IXO)

What gas produces the emission? emission-weighted particle distributions Bertone et al 2009, 2010a the peak temperature of the emission increases with atomic number and ionisation state X-ray emission traces gas with T>10 6 K O VI and Ne VIII trace diffuse gas C III, C IV and Si IV trace the CGM Emission traces moderately dense gas, not the bulk of the IGM mass and metals.

Impact of physics What happens when changing the physical model?

Impact of physics: X-rays Bertone et al 2009 no feedback: no metal transport  localised emission primordial cooling rates: longer cooling times  stronger emission at high density (≈100 times) momentum driven winds: metals more spread in IGM  weaker emission (≈100 times) AGN feedback: weaker emission in dense regions

no feedback: emission localised in galaxies primordial cooling rates: stronger emission at high density AGN feedback: weaker emission changes in wind parameters: small effect Impact of physics: UV Bertone et al 2010a

Emission at high redshift: rest-frame UV lines emission at 2<z<5 25 Mpc/h simulations 2” angular resolution Bertone et al 2010b

IGM emission at z>1.5 At z>1.5 rest-frame UV lines are redshifted in to the optical band A number of upcoming optical instruments might detect IGM emission lines at 1.5<z<5: Cosmic Web Imager on Palomar (CWI, Rahman et al 2006)  this year! Keck Cosmic Web Imager (KCWI) Antarctic Cosmic Web Imager (ACWI, Moore et al 2008) IFUs with large fields of view & high spatial resolution Great chance to observe the 3-D structure of the IGM for the first time!

Higher ionisation states

Lower ionisation states

Emission PDFs Lower ionisation states: single lines shorter wavelengths C III up to 10x stronger than C IV Higher ionisation states: doublets – easy to identify weaker than lower ion. states

Lines detectable by CWI LineWavelength (Å) Minimum redshift Detectable to z C III ≤ 4 C IV ≤ 3 N IV7653.7× N V ≤ 2 O IV × O V × O VI ≤ 3 Ne VIII × Si III ≤ 3 Si IV ≤ 3 CWI: flux limit: 100 photon/s/cm 2 /sr angular resolution: 2” central regions of groups and galactic haloes Bertone et al 2010b

Summary Dense cool gas in the haloes of galaxies is traced by: UV lines: C III, C IV, Si IV Low density WHIM gas in filaments is traced by: UV lines: O VI, Ne VIII X-ray lines from hydrogen-like atoms: C V, O VII, Ne IX X-ray lines from elements with low atomic numbers: C VI, O VIII Dense hot gas in clusters and groups is traced by: X-ray lines from fully ionised atoms: C VI, O VIII X-ray lines from elements with high atomic numbers: Mg XII etc. Detection of WHIM emission by future telescopes: challenging in low density regions very likely in groups and cluster outskirts CWI very likely to detect metal line emission at high z for the first time

Visually… Density cuts: the strongest X-ray (O VIII) and UV (O VI) emission comes from the densest gas Temperature cuts: the strongest emission comes from the temperature range where the line emissivity peaks

Summary: Dependencies on gas properties Correlation of emission with density and metallicity: highest emission from densest and most metal enriched particles Median temperature of highest emission corresponds to peak temperature of emissivity curve – as seen in T-n HI diagrams Median density, temperature and metallicity of gas particles vs. particle emission Bertone et al 2009, 2010a