Evidence for Feedback in the IGM at High Redshift

1. Evidence for Feedback in the IGM at High Redshift Barlow (CIT), Becker (CIT), Boksenberg(IoA), Sargent (CIT), Simcoe (MIT), Rauch (OCIW) (based on QSO absorption line data from Keck HIRES, ESI and LRIS)

2. How does the undisturbed IGM look ? A cosmic web of baryons formed mainly by gravitational instability Cen & Ostriker et al Main observational manifestation: the Lyman alpha forest Keck HIRES

3. Interactions between Galaxies and the IGM Galaxies z=4 • accrete gas (infall velocities ~ 100 km/s) • merge (approaching c.o.m. with velocities ~ 200km/s) • interact tidally, lose gas by ram pressure stripping • move about, stir and heat the IGM ( T ~10^7 K) • may have strong winds (outflows w. many 100 km/s) • chemically enrich the IGM • produce ionizing radiation z=3 Boxsize 2 Mpc comov; vc=200km/s; Steinmetz (sim.) z=1.8

4. gas phases in a hypothetical large scale filament 100 kpc

5. Observable Effects • Metal enrichment:how much, when, how ? • Ionization: stellar/AGN ? • Signatures of in/outflows • Bulk motion and turbulence • Accretion vs winds

6. By z~3 the IGM is widely enriched with metals (C,O) See talk by Joop Schaye Lognormal distribution with Latest results (Simcoe et al 2004): • describes metallicity of about 50% of the mass and 5% of the volume of the universe • probes down to overdensities > 1.6, i.e., to the edge of large scale filaments (Simcoe, Sargent & Rauch 2004)

7. The ‘Ultimate Closed Box’ model (Simcoe et al 2004) Universal chemical evolution: treat galaxies as sources of metals and the IGM as the mass reservoir requires that on average more than 14 % of a galaxy’s metals must be lost to the IGM to explain the observed IGM metallicity

8. The effect of the galactic radiation field least explored aspect of feedback: highly important for reionization but observational evidence difficult to obtain. Idea: different spectral shapes of the ionizing radiation produce different ratios among common metal ions • strong CIV metal absorption systems (interior of LSS filaments, outer halos) are ionized by a stellar radiation field (T~40,000 K) (Boksenberg, Sargent & Rauch 1998,2003) • matching observed relative C and O metallicities in the IGM to those of metal-poor stars ([C/O]= -0.5) requires soft (stellar) radiation field (Simcoe et al 2004)

9. Signatures of Bubbles and Winds in the ISM • “spherical”, expanding shells • compressed, shocked gas • hot interior (10^6 K) • transitory, cooling zone (OVI; 10^5 K) • cool dense layer (MgII; few x 10^4 K) • collisional + photoionization 30 Dor (LMC); Wang 1999

10. Probe ISM gas with multiple lines of sight to lensed QSOs

11. A possible galactic HI shell MgIIabsorption system at z~0.56 Curious two-component structure coherent over ~1kpc : LoS intersecting two bubble walls ?

12. Two approaches: • look directly into galaxies and their immediate neighbourhood • - learn about individual winds, connection of winds and stelpops. • 2. look at random places in spaces and do a blind search for winds • - learn about global statistics of winds Do high z winds manage to get out of galaxies ?

13. Can we observe winds outside of galaxies ? Lyman break galaxies have outflows with several 100 km/s, similar to present day superwinds (Pettini et al 2000) A lack of neutral hydrogen within 0.5 comoving Mpc from those objects may correspond to wind-blown cavities (Adelberger et al 2003)

14. 2. Search the IGM directly for • shock heated (collisionally ionized) gas • large, rapidly expanding shell structures • metal enriched gas use OVI ion as a tracer of galactic winds OVI survey at z ~2.5 with Keck HIRES (Simcoe et al 2002)

15. Evidence for symmetric in/outflow: (Simcoe et al 2002) OVI HI Ly alpha OVI HI Ly alpha ~ ¼ of strong OVI absorbers show conspicuous double component structure in HI and other ions. Shocked shell ? Bi-polar outflow ?

16. Temperatures of OVI, CIV and SiIV If line widths predominantly thermal,the median temperature of the OVI phase is whereas Probably shocked gas or thermal conduction in a hot bubble Simcoe et al 2002

17. Properties of OVI systems High metallicity as opposed to average metallicity in the IGM, Sizes L ~ 60 kpc, densities (Simcoe et al 2002)

18. Number density and cross section from rate of incidence per unit redshift If all bright Ly break galaxies had such an OVI halo around them (with comov. density ; Adelberger & Steidel 2000): At z = 2.5 Lybreak galaxies could account for all of the observed OVI absorption in the Simcoe et al survey if they are embedded in hot bubbles out to radii ~ 40 kpc

19. Summary: Highly ionized (OVI) Gas (Simcoe et al 2002) • OVI kinematically distinct from and hotter than other gas phases (CIV) • shocked gas ? • peculiar double component structure relatively common in strongest systems. shells or cones ? • sizes a few tens of kpc, overdensities around 10 – 30 (as opposed to > 100 for strong CIV/SiIV systems). • external to galaxies • Metallicity [O/H] > -1.5 higher than general IGM • outflow, as opposed to infall • cross-section consistent with R~ 40 kpc hot bubbles around Lyman break galaxies

20. Kinematic effects of feedback:Bulk motion and turbulence in the IGM

21. Kinematicsof the IGM Probe bulk motion and turbulence with multiple lines of sight: grav.lens Lensed QSO observer IGM Velocity and column density differences as a function of spatial scale, density

22. Spatial coherence and kinematics in the IGM sep ~ 0.22 kpc sep ~ 260 kpc Becker et al 2004

23. Expect: Large scale motion represent Hubble expansion Small scale motion are hydrodynamic disturbances (e.g., winds)

24. Large Scale Velocity Shear in the IGM Differences between the velocities of the same absorber in two lines of sight separated by S: • On kpc scales, velocity shear consistent with zero. • On large scales (250 kpc), a significant velocity shear (~ 30km/s RMS) is visible. • Its distribution can be reproduced assuming the clouds are randomly orientated, freely expanding slabs.

25. Is the large scale motion consistent with the Hubble flow ?

26. Adopting a coherence length ~500 physical kpc (e.g., D’Odorico etal 1998), expansion velocity is about 70 % of Hubble flow. Not clear whether one should expect to find clouds to follow Hubble flow exactly (column density limited sample, crude modelling, observational errors)

27. The Lyman alpha forest on kpc scalesas seen in two Lines of sight towards RXJ0911+0551 (z=2.80) 2.2 kpc “0” kpc

28. degree of disturbances among two lines of sight tells us about filling factor of winds

29. upper limit on the volume filling factor of ‘winds’: Mechanical luminosity gas density e.g., winds starting at z~4 cannot fill more than 18% of the volume. (Rauch et al 2002)

30. General low density IGM at z~3 • Large scale motions consistent with full Hubble expansion • Most of the intergalactic medium (by volume) is highly homogeneous on kpc scales. • The volume filling factor for strong winds arising later than z~4 is less than 18% (possibly much less). • Low density Lyman alpha forest probably well described by numerical simulations with finite resolution and without any feedback (but see metal absorption systems)

31. Going to higher density regions…

32. Spectra of UM673 A (red)andB (black)(z(QSO) = 2.72, sep. =2.24”) r = 480 pc metals ! metals ! metals ! metals ! z~z(QSO); r = “0” pc

33. Traces of galactic winds in higher density, metal enriched CIV gas ? a few – 200; velocity width < 300 km/s characteristic of the filamentary matrix in which galaxies are embedded Origin of velocity differences, spatial scales ?

34. Measure differences between lines of sight A and B as a function of transverse separation between the LoS: Fractional difference in column density: Column density weighted projected velocity: • Results: • minimum size of CIV clouds (a few 100 pc) • increasing velocity shear (70km/s @ 10 kpc) transverse separation (kpc)

35. What Does It Mean ? or are measures of the turbulence of the gas on a spatial scale r, and of the rate of energy input, . E.g., for Kolmogorov case, A crude estimate of the energy transfer rate from our data: i.e., the turbulent energy in CIV gas is much less than for an actively starforming region (e.g., factors 100 -1000 less than for Orion).

36. There is a finite amount of turbulent energy in the gas. Defines a dissipation time scale (time it takes to transform the mean kinetic energy in the gas, at a rate into heat), years. The finite size of the CIV clouds defines relaxation time scale: Without further energy input, pressure and density differences are wiped out by pressure waves during a sound crossing time : years. Structure on larger scales has not been wiped out there is (at least intermittent) energy input into the gas.

37. Origin of the turbulence ? Gas may have been stirred by mergers/tidal interactions or winds, or it may just be circling the drain Timescales are similar to those of recurrent star formation events that have been postulated for various environments: • z~1 field galaxies (Glazebrook et al 1999) • the Galaxy (Rocha-Pinto et al 2000) • fluctuations in SFR in nearby spirals (Tomita et al 1996; Hirashita & Kamaya 2000) • galactic nuclei (Krugel & Tutukov 1993) • Lyman break galaxies (Papovich, Dickinson & Ferguson 2001)

38. CIV absorption from the filamentary LSS structure SPH modelling of pre-enriched gas undergoing gravitational collapse reproduces all know properties of CIV systems (except clustering – box too small) Rauch, Haehnelt & Steinmetz 1997 Distribution of CIV line widths (thermal + turbulent)

39. Velocity-density-scale diagram “structure function” of the universe

40. Summary: evidence for feedback in the IGM ? • Cosmic web widely metal enriched down to mean density • CIV metal absorbers ionized by local stellar radiation field • General low density IGM (the universe by volume) kinematically undisturbed by feedback • kinematic disturbances in the somewhat denser CIV gas; low level (intermittent) energy input; filamentary gas possibly stirred by galaxy motions, winds, circling the drain • Double component structure, temperatures, expansion velocities, and the high metallicity seen in some MgII (low ionization, dense gas) and OVI (high ioniz., tenuous hot gas) point to ISM and IGM winds • velocities and ionization structure around high z starburst gals. consistent with superwinds • Inevitable that some of the “wind” phenomena described here are not due to winds but to gravitationally induced heating, motions,stripping • To date origin and and timing of most of the metal enrichment unclear; probably early (z>5) and by dwarf galaxies

41. E.g., • Early vs. late (ongoing) enrichment • Massive vs. dwarf galaxies • Gravitational vs. winds • ambient universe much denser at high z, ram pressure from infalling gas favors winds from dwarfs (e.g., Fujita et al 2004) • mass-metallicity relation may indicate mass loss to IGM dominated by dwarf galaxies (Tremonti et al 2004) • quiescence of Lyman alpha forest, ubiquity of metals appears to favour early, widespread (= dwarf?) enrichment, ongoing locally (OVI winds, CIV turbulence) When does the wide spread metal enrichment happen ?

42. Gravitational effects vs. winds ?

43. Case I: possible old SN remnant at z = 3.62 • Radius 13 < R < 48 pc • thickness (LoS): 0.015 < L< 1.6 pc • Mass range 0.4 < M < 2700 • Expansion velocity v > 195 km/s • Number density 0.2 < n < 2 • metallicity • age ~ 10,000 years

45. Interactions between Galaxies and the IGM Galaxies • accrete gas (infall velocities ~ 100 km/s) • merge (approaching c.o.m. with velocities ~ 200km/s) • interact tidally,lose gas by ram pressure stripping • move about, stirring and heating the IGM( T up to 10^6 K) • may have strong winds(outflows w. many 100 km/s) • produce ionizing radiation

47. ‘Structure function’ of the universe

49. Evidence for individual winds ?

50. General low density IGM at z~3 • Large scale motions consistent with full Hubble expansion • Most of the intergalactic medium (by volume) is highly homogeneous on kpc scales. • The fraction of the Lyman alpha forest disturbed by more than 5% in optical depth is < 23% (very conservative) • The volume filling factor for strong winds arising later than z~10 is less than 20% (possibly much less). • Low density Lyman alpha forest probably well described by numerical simulations with finite resolution and without any feedback (but see metal absorption systems)