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Galactic Gas Kinematics and High Velocity Clouds at z~1

Galactic Gas Kinematics and High Velocity Clouds at z~1. Chris Churchill (Penn State). Mg II 2796,2803 absorption from galaxies and ??? in quasar spectra observed with HIRES/Keck. Motivations and Astrophysical Context. Mg II arises in environments ranging over five decades of N(HI).

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Galactic Gas Kinematics and High Velocity Clouds at z~1

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  1. Galactic Gas Kinematics andHigh Velocity Clouds at z~1 Chris Churchill (Penn State) Mg II 2796,2803 absorption from galaxies and ??? in quasar spectra observed with HIRES/Keck

  2. Motivations and Astrophysical Context Mg II arises in environments ranging over five decades of N(HI) Statistical Cross-Sections, ns • DLAs: N(HI)>2x1020 cm-2 Giant molecular clouds?; 0.1 L* and LSB galaxies with wide range of morphologies; intergalactic clumps; ns~15 kpc; black-bottom absorption with Dv~200 km s-1; average C IV absorption (eg. Le Brun et al 1997; Rao & Turnshek 2000; Bouche’ etal 2000; cwc etal (II) 2000) • LLSs: N(HI)>2x1017 cm-2 “Normal” HSB galaxies with >0.1 L*; ns~40 kpc; complex kinematics with “high velocity” components with Dv~100-400 km s-1; range of C IV absorption (eg. Steidel et al 1994; cwc etal 1996; cwc 1997; cwc & Vogt 2000) Sub-LLS assuming F*=0.03 h3 Mpc-3 • sub-LLSs: N(HI)<6x1016 cm-2 “forest clouds”? LSB galaxies?; dwarf galaxies?; few associated with HSB galaxies; mostly single unresolved clouds; ns~70 kpc; sizes ~10 pc to 1 kpc; Z>0.1 solar; [a/Fe]~0 to +0.5; Cf~0.15; range of C IV absorption (eg. cwc & Le Brun 1998; cwc etal ApJS 1999 ; Rigby etal 2001) Mg II selects a wide range of astrophysical sites, which can be traced from redshift 0 to 5

  3. Redshift and Sensitivity Coverage Wmin = 0.3 A; 0.3<z<2.2(Steidel & Sargent 1992) Wmin = 0.02 A; 0.4<z<1.4(cwc etal, ApJS 1999)

  4. What the sensitivity and resolution buy… Steidel & Sargent (1992) cwc (1997); cwc & Charlton (1999)

  5. How to objectively quantify rich, complex kinematics? • Multiple subsystems • Complex subcomponents • Overall kinematics • Subsystem kinematics • Comparative subsystem kinematics Define “kinematic subsystems” and then measure their relative velocities, equivalent widths, velocity widths, and asymmetries Conventional Voigt profile fitting- which yields subcomponent column densities, Doppler widths, and velocities; however…

  6. Voigt Profiles: Do you believe them? cwc (1997); cwc, Vogt, & Charlton, ApJ, (2001) Assume minimum number of components that are statistically significant (MINFIT). Parameterization does not account for asymmetric line-of-sight streaming motion.

  7. B: 0.30-0.59 A C: 0.60-0.99 A E: >1.0 A cwc & Vogt, 2000, AJ, submitted

  8. cwc 2001

  9. Statistically, Profiles are Consistent with … Monte-Carlo Models of Absorbing Galaxies (Charlton & cwc 1998) What is probability distribution for such models? Assume r~r-2 probability distribution of clouds in disk and in halo Assume Vrot=Vinfall kinematics of clouds in disk and in halo

  10. Column Density per Unit Velocity Interval Probability Distribution For Disk+Halo Model Observed Distribution For Selected Sample C Systems cwc & Vogt 2000

  11. “Moderate-” to “High-Velocity” Clouds Equivalent Width vs. Velocity Velocity Width vs. Velocity • Dominant, or “main” kinematic subsystem • Moderate-velocity 40<v<160 km s-1 • High-velocity v>160 km s-1 cwc & Vogt (2000) What you do not see is multiple >0.3 A subsystems; only single >0.3 A subsystems with weak clouds having velocities from 40-400 km s-1

  12. There is a paucity of “small” intermediate- and high-velocity kinematic subsystems (clouds) … Equivalent Widths Column Densities cwc & Vogt (2000) Turnover below Wr=0.08 A for v>40 km s-1 kinematic subsystems

  13. cwc & Charlton 1999

  14. The Kinematics of C IV Absorption cwc etal II (2000)

  15. cwc etal, ApJL (1999)

  16. Weak Galactic HVCs: Clouds with N(HI)<1017 cm-2 ?

  17. NEEDED: High Resolution C IV, C II, Si IV, Si II, Lyman-series, etc. • HST/STIS Cycle 9 Program: 22, 0.4<z<1.4 Systems with R=30,000 Study weak systems and hvc components, ionization conditions, metalicities, And kinematics • HST/STIS Cycle 10 Proposed: 30 Galactic Systems with R=30,000 Proposed Program • Rosetta Stone for high z • Chart low N(HI) HVCs • Kinematic substructure in • known large N(HI) HVCs • Trends with sky location Aitoff Projection showing sky locations of proposed extragalactic lines of sight through the Galaxy

  18. Summary: Moderate- to High-Velocity Subsytems Q. Where Can We Get Further Clues? 1. They are weak compared to the dominant subsystem 2. There is a cut off below N(MgII)=1011.8 cm-2 3. The C IV absorption strength is proportional to their kinematic spread 4. Overall profile asymmetries are consistent with a model in which their kinematics is symmetric about an offset, dominant subsystem Are these high redshift analogues of Galactic HVCs? A. The population of “weak systems”

  19. “Weak Systems” • Single Clouds, Wr(MgII)<0.3 A, isolated • in redshift • Unresolved line widths at 6 km s-1 • Power law equivalent width distribution • down to Wr(MgII)=0.02 A cwc etal, ApJS (1999) Steidel & Sargent (1992)

  20. Weak Systems are Optically Thin, i.e. N(HI)<1017 cm-2 Statistical Direct Measurements of Lyman Limit Wr(MgII)=0.3 A cwc etal I (2000)

  21. Statistically, Weak Systems Z>0.1 Solar log N(HI), cm-2 log U, = ng/nH cwc etal, ApJS (1999) • Photo-ionization models (Cloudy) for Z=0.1 solar metalicity Grid moves down 1:1 with decreasing Z; Lower Z implies higher N(HI). • Line core F/Fc=0.5 for unresolved line is log N(MgII) = 12.5 cm-2

  22. Ionization Conditions Constrained by Fe II and C IV Variations in Fe II and in C IV indicate wide range of ionization parameters/densities Rigby, Charlton, & cwc (2001) When both Fe II and C IV are strong, multiphase conditions are suggested, inferred to be due to different densities. • 0.5 dex uncertainty in [a/C] is ~0.2 dex uncertainty in ionization parameter, U • 0.5 dex uncertainty in [a/Fe] is ~2.5 dex uncertainty in U for log U < -2.5

  23. Fe II Variations: Ionization or Abundance? When upper limits on C IV are stringent, then we have an upper limit on ionization parameter, and thus an upper limit on [a/Fe] Typically, we have Si II, Si III, Si IV, C II, C III and/or Lya Single, unresolved only Abundance +.5 [a/Fe]~.5 [Fe/H]<-1 [a/Fe]~0 [Fe/H]>-1 Star formation chronometer Isolated weak Moderate- High-Velocity

  24. aligned+blended +offset Strong: blended +offset aligned aligned+blended offset

  25. Weak System Clouds • Optically thin to neutral hydrogen (direct evidence) • Variations in N(FeII)/N(MgII) and N(CIV)/N(MgII) • Multiphase Ionization Conditions; sometimes kinematically aligned • Metalicities commonly solar, almost always greater than 0.1 solar • [a/Fe]=0 abundance pattern, rare for a-group enhancement • Cloud “sizes” follow power-law distribution- no lower cut off to 0.02 A • Typically not within 40 kpc (projected) of normal, bright galaxies Covering Factor, Cf<0.1 Sizes, D~10-100 pc n(weak)/n(galaxies) ~ 106 (!) What they are depends upon how they cluster wrt Galaxies Dwarf Galaxies? Super Star Clusters? IGM condensations?

  26. Intermediate- High-Velocity “Clouds” • Optically thin to neutral hydrogen (indirect evidence) • Variations in N(FeII)/N(MgII) {need high resolution C IV} • Arise in regions coincident with broad C IV absorption (multiphase) • Metalicities commonly solar, almost always greater than 0.1 solar • [a/Fe]=0 abundance pattern common, some can be a-group enhanced • Cloud “sizes” follow power law, but with lower cut off at 0.08 A • Typically within 40 kpc (projected) of normal, bright galaxies Clues to be sought with z=0 Galactic HST Program

  27. Redshift and Sensitivity Coverage (revisited) Wmin = 0.3 A; 0.3<z<2.2(Steidel & Sargent 1992) Wmin = 0.02 A; 0.4<z<1.4(cwc etal, ApJS 1999)

  28. Evolution of Strongest Systems As Wmin increased – evolution is stronger Steidel & Sargent (1992) dN/dz = N0(1+z)g What is the nature of the evolution??? Is it related to high velocity clouds???

  29. Charting the Evolution of Galaxy-IGM Evolution Sophisticated simulations reveal direct, dynamic connections between the IGM and galaxy evolution- Mg II is the best tracer for star forming objects • 0.3 A • 0.02 A • 0.05 A For z>2.2, Infrared high-resolution spectrograph required: JCAM/HET Uniform survey with R=11,000-60,000 and Wr(2796)=0.05 A limit (5s)

  30. Future Projects… • Cycle 9 STIS/HST R=30,000 for z=0.5-1.5 • Cycle 10 STIS/HST R=30,000 of low N(HI) • Galactic HVCs in Mg II • Narrow-Band Imaging for O II] emission of • weak systems for z=0.5-1.0 • HRS/HET R=60,000-120,000 for Mg II for • z=0.6-2.8 • JCAM/HET R=11,000 of Mg II for z=2.8-4.0 Thanks for listening!

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