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Missing Photons that Count: Galaxy Evolution via Absorbing Gas

Missing Photons that Count: Galaxy Evolution via Absorbing Gas. (and a little bit of fundamental physics to boot). Chris Churchill. (Penn State). Quasars: physics laboratories in the early universe. quasar. To Earth. Ly b. Ly a. SiII. CIV. SiII. CII. SiIV. Lyman limit. Ly a em.

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Missing Photons that Count: Galaxy Evolution via Absorbing Gas

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  1. Missing Photons that Count: Galaxy Evolution via Absorbing Gas (and a little bit of fundamental physics to boot) Chris Churchill (Penn State)

  2. Quasars: physics laboratories in the early universe quasar To Earth Lyb Lya SiII CIV SiII CII SiIV Lyman limit Lyaem Lybem NVem Lya forest CIVem SiIVem

  3. Categories by Neutral Hydrogen Damped Lyman-a Absorbers (DLAs): N(HI) > 2x1020 cm-2 Compact Star forming objects Galaxy centers Metal lines, low ionization dominate Lyman Limit Systems (LLSs): N(HI) > 2x1017 cm-2 Proto-galaxy structures Galaxy outskirts (extended halos, disks) Metal lines, low, intermediate, and high ionization Lyman-a Forest N(HI) < 6x1016 cm-2 Cosmic Web Sheets and Filaments Metal lines, weak to non-existent

  4. Categories by Metal Lines in the Optical Historical - Optical C IV systems 1.8<z<4.9 Mg II + C IV Mg II systems 0.3<z<2.2 Mg II associated with LLS : C IV associated with sub-LLS

  5. “The Lyman Alpha Forest” Piercing the Cosmic Web Tracing Structure Growth Constraining Ionization Evolution N(HI) < 1016 cm-2 Lya forest

  6. Great Insights are gained from simulations of structure growth, but these simulations are starved for hard data to constrain the physics… (courtesy M. Haehnelt) Note structure growth is rapid at for z>5 (a short cosmological time frame), and then evolution is slower, especially from z<1 (majority of time)…

  7. The Power of Simply Counting Lines The redshift path density, dN/dz, places constraints on simulations of structure growth as a function of redshift… (Dave’ etal 1999)

  8. The Power of Simply Counting Lines The redshift path density, dN/dz, places constraints on simulations of structure growth as a function of redshift… (Dave’ etal 1999)

  9. The Power of Simply Counting Lines The redshift path density, dN/dz, places constraints on simulations of structure growth as a function of redshift… (Dave’ etal 1999)

  10. The Power of Simply Counting Lines The redshift path density, dN/dz, places constraints on simulations of structure growth as a function of redshift… or (Dave’ etal 1999)

  11. The Power of Simply Counting Lines (Weymann’ etal 1999) (Dave’ etal 1999)

  12. “C IV Systems” • Proto-galactic clumps • Tracing Pre-galactic Structure Growth • Constraining Kinematic/Dynamic Evolution N(HI) ~ 2 x 1017 cm-2 Metal Lines

  13. QSO Absorption Lines: Anatonomy of a Simulation (courtesy M. Steinmetz) Efforts have been made to include ionization feedback, both in terms of spectral energy distributions, photon transport, and mechanical stirring of the gas…

  14. QSO Absorption Lines: Anatonomy of a Simulation Ly-a C IV Velocity (courtesy M. Steinmetz) Technology and innovation is quickly outpacing observational data…

  15. The Power of Simply Counting Lines Mg II shows no evolution (co-moving), butnothing in known above z=2.2 Lyman Limit systems (LLS) show no evolution, measured from continuum “break” at 916 A in the rest frame, N(HI)>1017.3 cm-2 C IV systems evolve rapidly! They increase with cosmic time until z=1.5 and then show no evolution Structure, Ionization, or Chemical Evolution? Evolution measures product of: • number • size • ionization fraction Is this an increase in number, in ionization level, or in the chemical abundance of carbon? We need low ionization data. Mg II.

  16. Motivations and Astrophysical Context Mg II arises in environments ranging over five decades of N(H I) Damped Lyman-a Absorbers (DLAs): N(HI) > 2x1020 cm-2 eg. Biosse’ etal (1998); Rao & Turnshek (2000); Churchill etal (2000b) Lyman Limit Systems (LLSs): N(HI) > 2x1017 cm-2 eg. Steidel & Sargent (1992); Churchill etal (2000a) sub-LLSs: (low redshift forest!) N(HI) < 6x1016 cm-2 eg. Churchill & Le Brun (1998); Churchill etal (1999); Rigby etal (2001) Mg II a-process ion – Type II SNe – enrichment from first stars (<1 Myr) Fe II iron-group ion – Type Ia SNe – late stellar evolution (>few Gyr) Mg II selection probes a wide range of astrophysical sites where star formation has enriched gas; these sites can be traced from redshift 0 to 5

  17. Present Day Coverage and Astrophysical Context 2796 2803

  18. Simple Kinematic Models of Absorbing Gas from Galaxies (Charlton & Churchill 1998) Absorption kinematics is symmetric about the galaxy’s systemic velocity Absorption kinematics is offset in the direction of stellar rotation compared to the galaxy’s systemic velocity Halo/infall + Rotating/disk produces both signatures in single profile

  19. Mg II 2796 Absorption Profiles from HIRES/Keck (Churchill 2001) Galaxy redshifts can be matched to the absorbers…

  20. Mg II 2796 Absorption Profiles from HIRES/Keck (Churchill & Vogt 2001)

  21. Mg II 2796 Absorption Profiles from HIRES/Keck Each Mg II system has several Fe II transitions and Mg I (neutral) The clouds are modeled using Voigt profile decomposition… Obtain number of clouds, temperatures, column densities, ionization conditions (from modeling)…

  22. Build the Database and the Simulations will Follow Ultimately, the simulations need to be driven by the data… as we have seen the great successes in this arena for the Lya forest to z=5, and are seeing the new successes for metal enriched diffuse objects to z=5…. (courtesy M. Haehnelt) We will begin to see the successes of galaxy evolution in more detail, including structure evolution, kinematics, metallicity, and ionization. The data are lacking. Wholesale inventory of Mg II absorbers is the best approach.

  23. Q0827+243 Q1038+064 Q1148+387 (Steidel etal 2002)

  24. Kinematics: Stellar, Mg II 2796, and C IV 1548, 1551 Mg II traces stellar kinematics yet is difficult to explain as extended disk rotation (at 72 kpc impact parameter!). C IV traces Mg II kinematics but has strongest component at galaxy’s systemic velocity, as highlighted in l1551. What physical entity is giving rise to this C IV component? (Churchill 2003; Churchill etal, in prep)

  25. Equivalent Width Distribution Using HIRES/Keck, we discovered that the EW distribution followed a power law, with no observable cut off down to W=0.02 A. - these are high metallicity “forest” clouds. 5 papers over 10 years predicted that none of these “weak” systems existed! They outnumber galaxies by 1:106. Differential Number Density Distribution As the lower EW cutoff of the sample, Wmin, is increased, the number of systems per unit redshift decreases… (As Wmin increases, the mean redshift increases – ) differential redshift evolution Redshift Path Density Comoving redshift path density is consistent with no structure/ionization evolution for Wmin=0.02 A (red) and Wmin=0.3 A (blue). dN/dz ~ ns(1+z)g .

  26. Evolution of Strongest Systems Scenario of kinematic evolution of gas… As Wmin increased – evolution is stronger R E D S H I F T dN/dz = N0(1+z)g What is the nature of the evolution??? Is it related to high velocity clouds, presence of supperbubbles, or superwinds???

  27. Present Day Coverage and Astrophysical Context The epochs of greatest evolution are un-probed… (Based upon Pei etal 1999)

  28. Constraints on Global Galaxy Evolution Models No coverage for Mg II for z>2.2 No high resolution coverage for Mg II for z>1.4 W(stars) W(gas) W(IGM metals) Mg II provides metalicity for high-z forest in lower ionization gas- heretofore un-probed W(baryons) W(gas flow) (Pei etal 1999)

  29. Population of Weak Systems: Where do they arise? • Their equivalent width distribution follows a power law down to 0.02 A • Arise in optically thin H I (Lya clouds) 25%-100% of all Lya forest clouds with column densities 1015.5<N(HI)<1016.5 cm-2 at 0.4<z<1.4 • almost all have z>0.1 solar metallicity • Many are iron rich, suggesting later stages of star formation • 90% cannot be associated with galaxies (within 70 kpc) (Churchill etal 1999; Rigby etal 2002)

  30. Population of Weak Systems: Where do they arise? 1990-1992 Yanny & York used narrow band imaging to find OII emission at Mg II absorber redshifts They found several emission line objects within 200-300 kpc of the QSOs; substantialy further out than the “big, normal galaxy picture” The technique is prime for searching wide fields for OII emission in the weak systems… do they exhibit indicators of star formation? Either way, what are the astrophyiscal implications? Fabry-Perot at APO is perfect for this job. • weak systems • revisit strong systems

  31. Some Future Plans • High Resolution optical spectra of QSOs to get Mg II kinematics to cover 1.4<z<2.2 • High Resolution HST ultraviolet spectra of higher ionization gas • Low Resolution infrared spectra of QSOs to get Mg II statistics for 2.2<z<4.0 • Moderated Resolution HST ultraviolet spectra of higher ionization gas • High Resolution infrared spectra of QSOs to get Mg II kinematics for 2.2<z<4.0 Leading international collaboration: Keck, Subaru, VLT, HET, LBT Student opportunities include observing, echelle data reduction, data analysis --- VP decomposition, statistics, distribution function (DF) evolution Collaborating with N. Kobayashi (Subaru/IRCS), future VLT Student opportunities include observing, UV and IR data reduction, data analysis --- visibility function, sample completeness, statistics, DF evolution This is 5-10 years future:VLT, LBT

  32. “And now… for something completely different.”

  33. Evidence For Cosmological Evolution of the Fine Structure Constant? a = e2/hc Da = (az-a0)/a0

  34. Procedure 1. Compare heavy (Z~30) and light (Z<10) atoms, OR 2. Compare s p and d p transitions in heavy atoms. Shifts can be of opposite sign. Illustrative formula: Ez=0 is the laboratory frequency. 2nd term is non-zero only if a has changed. q is derived from relativistic many-body calculations. Relativistic shift of the central line in the multiplet K is the spin-orbit splitting parameter. Numerical examples: Z=26 (s p) FeII 2383A: w0 = 38458.987(2) + 1449x Z=12 (s p) MgII 2796A: w0 = 35669.298(2) + 120x Z=24 (d p) CrII 2066A: w0 = 48398.666(2) - 1267x where x = (az/a0)2 - 1 MgII “anchor”

  35. Da/a= -5×10-5 Low-z High-z

  36. Uncorrected: Quoted Results

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