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Feedback at High Redshift

Feedback at High Redshift. Alice Shapley (UC Berkeley) May 4th, 2004. Overview and Motivation. Importance of feedback Observations at z~3: winds and ionizing radiation Observations at z~2: more winds, the smoking gun What’s next: morphologies, ages, masses, z~1

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Feedback at High Redshift

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  1. Feedback at High Redshift Alice Shapley (UC Berkeley) May 4th, 2004

  2. Overview and Motivation • Importance of feedback • Observations at z~3: winds and ionizing radiation • Observations at z~2: more winds, the smoking gun • What’s next: morphologies, ages, masses, z~1 • High-res QSO spectra plus large galaxy samples serve as a powerful tool for understanding feedback during an important epoch of the Universe’s history

  3. Schematic model of superwinds • Collective effect of multiple SNe: mechanical energy input causes shock-heated expanding superbubble with T~108 K, expands, entrains cold ISM • Superwind seen in local starbursts with S>0.1 Msun/year/kpc2 • (Heckman et al. 1990, Heckman 2002)

  4. Outflows: Local Starbursts • M82 • Nearby starburst galaxy • Red is Ha emission from ionized gas above the plane of the galaxy • outflow speed: >500 km/s • plenty of detailed spatial information • (Subaru Image)

  5. Importance of feedback/outflows • Enrichment and heating of IGM • Enrichment and entropy floor in ICM • Problems in models of galaxy formation: overcooling and angular momentum • Feedback often invoked as solution, but crudely modeled in both semi-analytic and numerical codes • Observationally important to constrain mass, energy, metals escaping, and how these depend on galaxy properties

  6. Observational Constraints on Feedback at High Redshift

  7. Feedback at z~3

  8. Typical L* LBG Spectrum Unsmoothed Smoothed by 5 pix RAB=24-25.5 1.5 hr exposure  S/N ~ 2/pix, 9-12 AA resolution

  9. Evidence for outflows in spectra • Velocity offsets (em-abs) • Redshifted Lya • Blueshifted IS abs • Avg offset is 650 km s-1 (Dz=0.008)  outflow • Stellar photospheric features are too weak to detect, so we need to guess what the systemic redshift is • (Shapley et al. 2003)

  10. Total LBG Composite Spectrum • Features • UV cont: O & B stars • Stellar: photospheric and wind • Outflow-related: Lya (Dv=+360), low and high ions (Dv=-170) • Nebular emission • Fine-structure emission • (Shapley et al. 2003)

  11. Empirical Outflow Results • Stronger Lya • Bluer UV continuum • Weaker low-ion absorption • Smaller Dv(em-abs) • Dependence of low- and high-ions decoupled

  12. z~3 Galaxy/IGM Connection • 8 fields with QSOs at z~3.5 • Survey galaxies and Lya forest in same cosmic volume • Determine relative distributions of galaxies, HI, metals • (Adelberger et al. 2003) Unsmoothed

  13. z~3 Galaxy/IGM Connection less HI more HI Deficit of HI near LBGs and strong LBG/CIV cross-correlation function (Adelberger et al. 2003)

  14. A Physical Picture Outflows of neutral and ionized gas: different neutral and ionized covering fractions? Hotter gas we don’t see What radius?

  15. A Physical Picture Dust: UV extinction in outflow Outflow geometry vs. what is seen in local superwinds

  16. A Physical Picture Effect on IGM: Gal/IGM correlations --> Expected sphere of influence: 180 kpc (0.5-1 comoving Mpc) Vwind >= vesc

  17. The Search for Lyman-Continuum Emission • Ionizing background: important for understanding reionization and Lya forest props; measured with QSO “proximity effect” • Question: relative contribution of QSOs & gals vs. z??? (drop-off in QSO number density at high redshift) • Lyman-Continuum Observations of Galaxies • z~0: HUT spectra at z~0, fesc<0.01-0.15 (Leitherer et al.) • z=1.1-1.7:HST/STIS UV imaging, fesc <0.002 (Malkan et al.) • z~3: LBG composite spectrum, fesc~0.10 (Steidel et al.) • Controversy at z~3!! • HST/WFPC2 UBVi colors, fesc <0.039 (Fernandez-Soto et al.) • VLT spectra of 2 gals, fesc<0.01 (Giallongo et al. 2002)

  18. Detection of Ly-C Emission? • Lyman Cont. Leakage • 29 gals at <z>=3.4+/-0.09 • Significant Ly-cont flux in composite spectrum  5 times more ionizing flux than QSOs at z~3 • Bluest quartile in (G-R)0, strong Lya emission, IS abs lines weaker than cB58: is it representative? • fesc different from local SB (Leitherer et al. 1995) (Steidel et al. 2001)

  19. The Search for Lyman-Continuum Emission • Ionizing background: important for understanding reionization and Lya forest props; measured with QSO “proximity effect” • Question: relative contribution of QSOs & gals vs. z??? (drop-off in QSO number density at high redshift) • Ly-C Observations of Galaxies • z~0: HUT spectra at z~0, fesc<0.01-0.15 (Leitherer et al.) • z=1.1-1.7:HST/STIS UV imaging, fesc <0.002 (Malkan et al.) • z~3: LBG composite spectrum, fesc~0.10 (Steidel et al.) • Controversy at z~3!! • HST/WFPC2 UBVi colors, fesc <0.039 (Fernandez-Soto et al.) • VLT spectra of 2 gals, fesc<0.01 (Giallongo et al. 2002)

  20. New Ly-C Observations • Spectra with 18+ hours of exp time for a sample of ~15 objects • Red side: detailed observations of interstellar lines • Blue side: sensitive observations of Lyman Continuum region • Overcome some of the limitations of composite spectra • Observations approach the quality of cB58, but larger sample • We may detect Ly-C emission for an individual object!

  21. 2” SSA22a-D3 z=3.07 Rs=23.37 P200 Rs HST/NICMOS F160W

  22. Lyman limit, 912 AA Lya 3710 AA 4950 AA SSA22a-D3 z=3.07 Rs=23.37 HST/NIC F160W Keck/LRIS-B, 8 hours Red side: strong abs lines Blue side: Lya to atm cutoff D3 is double, and upper brighter component appears to have significant flux below 912 AA

  23. SSA22a-D3 z=3.07 Rs=23.37 HST/NIC F160W Lyb Ly-C Lya Apparent detection of flux at rest-frame 880-912 AA (S/N~7). Other pair member is undetected.

  24. SSA22a-D3 z=3.07 Rs=23.37 HST/NIC F160W Lyb Ly-C Lya D3 is only object with apparent Ly-C flux out of 15 on mask. Why is it special?

  25. Evolution of the Lya Forest • dn/dz governed by balance between ionizing bg (ionization) and Hubble expansion (recombination) • At 1.5<z<4, dn/dz~(1+z)2.47 • At lower-z, dn/dz shallower (decrease in QSO density) (Kim et al. 2002)

  26. Feedback at z~2

  27. z>2 color-selection • Adjust z~3 UGR crit. for z~2 (Adelberger et al. 2004) • Spectroscopic follow-up with optimized UV-sensitive setup (Keck I/LRIS-B) (Steidel et al. 2004)

  28. Redshift Distributions LBG: z~3 (940) BX: z=2-2.5 (749) BM: z=1.5-2.0 (107) 700 gals at z=1.4-2.5 5/7 survey fields contain bright bg QSOs (Steidel et al. 2004) Unsmoothed

  29. Evidence for outflows in spectra • Outflow kinematics • Lya em at systematically higher redshift than IS abs • observed in both z~2 and z~3 LBGs • part of the gal/IGM connection

  30. z~3 vs. z~2 outflow kinematics • v=0 from rest-frame optical nebular emission lines: [OIII] at z~3 and Ha at z~2 • ISM kinematics similar at z~3 and z~2 • Typical velocities are 200-400 km/s wrt nebular emission lines • D(Lya-abs)=500-1000 km/s • (Steidel et al. 2004) z~3 z~2 Unsmoothed

  31. z~2 Galaxy/IGM Connection • Much higher galaxy surface density (factor of 4 higher per unit solid angle) • Further explore use of galaxy spectra to probe IGM • Forest evolves extremely rapidly over the redshift range 3.51.8: how does the galaxy/forest relationship change? • Many more QSO sightlines • 17 lines of sight in 5 fields • Simultaneously obtain first extensive information on z~2 galaxies. • Epoch of peak star formation and black hole growth? • Redshifts z=1.9-2.6 are ideal for near-IR spectroscopic follow-up

  32. Q1623: QSOs, gals at z=1.8-2.5 7 QSO probes (HIRES/ESI/LRIS-B spectra) in 16’ by 12’ field

  33. z~2 Galaxy Proximity Effect? z~2: 22 gals w/in 0.8h-1 comoving Mpc of QSO sightline Less HI More HI Less HI z~2 z~3 More HI (yellow:Adelberger et al. 2004, blue:simulations by Kollmeier and Weinberg)

  34. Q2343-BX587 • Bright bg QSO: z=2.52 • BX587: z=2.24, R=24, Ks=20.3, D=115 kpc • Blue circles have 30”/60” (235/470 kpc) The “Smoking Gun” Direct association between gals and broad OVI, NV, CIV

  35. zgal The “Smoking Gun” • Galaxy Spectra • ∆(vneb-vism) = 460 km/s • O/H~solar • SFR~85 Msun/yr, M*~6 x 1010 Msun D=115 kpc • HIRES QSO Spectrum • ∆v(CIV,NV)~570 km/s (wind: shock-heated and then cooling) • Weak associated Ly

  36. The “Smoking Gun”: OVI v=0 is zgal Z=2.44 Z=2.32 OVI (Simcoe et al. 2002) Galaxy: BX717 z=2.4353 D=218 kpc Galaxy: MD103 z=2.3148 D=115 kpc Q1700: Direct association between gals and OVI absorption!

  37. Future Directions • Data Higher spectral resolution obs of strong absorption lines Outflows vs. opt/IR colors (age, stellar mass) • Outflows vs. Ly-C leakage (vs. covering fraction) • Outflows vs. chemical abundance • Galaxy/galaxy pairs, spatially distinct probes of outflows • Outflow vs. morphology (HST/ACS) • Extend similar studies down to z~1 (HST/FOS) • Simulations • What physical state of galaxies determines conditions in outflow? What is geometry of different phases of outflow? How much mass, energy, metals escape?

  38. Spectra vs. Morphology

  39. Spectra vs. Morphology • Combine Morphological and spectral information: • --> extended disk-like, merger, compact • --> Lya em/abs, low- and high-ionization abs • Attempt to obtain spatial/geometric information about outflows (along with pairs) • 240 UV-selected galaxies at z>1.4 in GOODS/ACS • -->multi-wave: x-ray, radio, submm, Spitzer • 50 z~3 galaxies in SSA22a field with GDDS/ACS

  40. Spectra vs. Morphology Keck/LRIS-B spectrum HST/ACS Bviz z=2.05; RAB=23.38 4”

  41. Spectra vs. Morphology Keck/LRIS-B spectrum HST/ACS Bviz z=2.22; RAB=23.28 4”

  42. Spectra vs. Morphology Keck/LRIS-B spectrum HST/ACS Bviz z=2.23; RAB=23.50 4”

  43. A Special Case: The Pair at z=1.60/2.17 BX201 z=2.17 Keck/ LRIS spectra 3800-4100 AA BM115 z=1.60 HST/WFPC2 F814W image Dq =2” 11 h-1 kpc at z=1.6 • Two UV-selected z~2 galaxies on one slit • Higher z galaxy probes outflow of lower-z gal at 11h-1 kpc • Outflowing gas: velocity & abs strength difference vs. radius

  44. Examples of Deep LBG Spectra • LRIS-R spectra (LRIS-B covers Lya and Lyman continuum) • Use these spectra to measure physical properties of abs. lines; connect with UV-color, Lya, Lyman continuum • Obtain complete data set: near-IR imaging (ages) and spectra (O/H), morphologies

  45. Summary • Evidence for SNe feedback & its effect on IGM at z~2-3 • Possible detection of Ly-Cont radiation at z~3 • Next step: determine detailed properties of galaxies sustaining superwinds: morphologies, ages, masses, geometry (how much mass and energy are involved? What determines appearance of spectra/outflow?) • Combining deep spectroscopic observations with deep ACS images will provide great insight into the nature of feedback, when star-formation, stellar mass build-up, AGN activity were most active in the Universe.

  46. Morphology vs. Outflow props • Use ACS BViz images of GOODS-N field, in which there are 240 galaxies with z>1.4 • Connect morph and spectroscopic outflow props: extended disk-like, merger, compact • Ind. and avg. Galaxies at z=2.1-2.5

  47. Spectra vs. Morphology Keck/LRIS-B spectrum HST/ACS Bviz z=2.22; RAB=23.22 4”

  48. Spectra vs. Morphology Keck/LRIS-B spectrum HST/ACS Bviz z=2.22; RAB=23.22 4”

  49. Spectra vs. Morphology Keck/LRIS-B spectrum HST/ACS Bviz z=2.55; RAB=23.29 4”

  50. Spectra vs. Morphology Keck/LRIS-B spectrum HST/ACS Bviz z=2.10; RAB=23.24 4”

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