1 / 32

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).

marie
Download Presentation

Galactic Gas Kinematics and High Velocity Clouds at z~1

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  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!

More Related