galactic gas kinematics and high velocity clouds at z~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

Chris Churchill (PSU) 2

Motivations and Astrophysical ContextMg II arises in environments ranging over five decades of N(HI)

• DLAs: N(HI)>2x1020 cm-2

• LLSs: N(HI)>2x1017 cm-2

• sub-LLSs: N(HI)<6x1016 cm-2

Statistical Cross-Sections, n

Giant molecular clouds?; 0.1 L* and LSB galaxies with wide range of morphologies; intergalactic clumps; n~15 kpc; black-bottom absorption with v~200 km s-1; average C IV absorption(eg. Le Brun et al 1997; Rao & Turnshek 2000; Bouche’ etal 2000; cwc etal (II) 2000)

“Normal” HSB galaxies with >0.1 L*; n~40 kpc;complex kinematics with “high velocity” componentswith v~100-400 km s-1; range of C IV absorption(eg. Steidel et al 1994; cwc etal 1996; cwc 1997; cwc & Vogt 2000) assuming *=0.03 h3 Mpc-3

“forest clouds”? LSB galaxies?; dwarf galaxies?; few associated with HSB galaxies; mostly single unresolved clouds; n~70 kpc; sizes ~10 pc to 1 kpc; Z>0.1 solar; [/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)

Sub-LLS

Mg II selects a wide range of astrophysical sites, which can be traced from redshift 0 to 5


Redshift and Sensitivity Coverage

Wmin = 0.3 ; 0.3<z<2.2 (Steidel & Sargent 1992)

Wmin = 0.02 ; 0.4<z<1.4 (cwc etal, ApJS 1999)


What the sensitivity and resolution buy…

Steidel & Sargent (1992)

cwc (1997); cwc & Charlton (1999)


How to objectively quantifyrich, 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…


Voigt Profiles: Do you believe them?

Assume minimum number of components that are statistically significant (MINFIT). Parameterization does not account for asymmetric line-of-sight streaming motion.

cwc (1997); cwc, Vogt, & Charlton, ApJ, (2001)

Chris Churchill (PSU) 7cwc & Vogt, 2000, AJ, submitted

B: 0.30-0.59 A C: 0.60-0.99 A E: >1.0 A

Chris Churchill (PSU) 9cwc 2001


Statistically, Profiles are Consistent with …

(Charlton & cwc 1998)Monte-Carlo Models of Absorbing Galaxies

What is probability distribution for such models?Assume ~r-2 probability distribution of clouds in disk and in haloAssume Vrot=Vinfall kinematics of clouds in disk and in halo


Column Density per Unit Velocity Interval Probability DistributionFor Disk+Halo Model

Observed DistributionFor Selected Sample C Systems

cwc & Vogt 2000


“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

What you do not see is multiple >0.3 subsystems; only single >0.3 subsystems with weak clouds having velocities from 40-400 km s-1

cwc & Vogt (2000)


There is a paucity of “small” intermediate- and high-velocity kinematic subsystems (clouds) …

Equivalent Widths Column Densities

Turnover below Wr=0.08 for v>40 km s-1 kinematic subsystems

cwc & Vogt (2000)


cwc & Charlton 1999


cwc etal II (2000)

The Kinematics of C IV Absorption

Chris Churchill (PSU) 16cwc etal, ApJL (1999)


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


1. HST/STIS Cycle 9 Program: 22, 0.4<z<1.4 Systems with R=30,000

2. HST/STIS Cycle 10 Proposed: 30 Galactic Systems with R=30,000

NEEDED: High Resolution C IV, C II, Si IV, Si II, Lyman-series, etc.

Study weak systems and hvc components, ionization conditions, metalicities,And kinematics

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 skylocations of proposed extragalacticlines of sight through the Galaxy


Q. Where Can We Get Further Clues?

A. The population of “weak systems”

Summary: Moderate- to High-Velocity Subsytems

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

Are these high redshift analogues of Galactic HVCs?

4. Overall profile asymmetries are consistent with a model in which their kinematics is symmetric about an offset, dominant subsystem


“Weak Systems”• Single Clouds, Wr(MgII)<0.3 , isolated in redshift• Unresolved line widths at 6 km s-1

• Power law equivalent width distribution down to Wr(MgII)=0.02

cwc etal, ApJS (1999)Steidel & Sargent (1992)


Weak Systems are Optically Thin, i.e. N(HI)<1017 cm-2

Statistical Direct Measurements of Lyman Limit

Wr(MgII)=0.3

cwc etal I (2000)


Statistically, Weak Systems Z>0.1 Solar

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).

log N(HI), cm-2

log U, = n/nH

• Line core F/Fc=0.5 for unresolved line is log N(MgII) = 12.5 cm-2


Variations in Fe II and in C IVindicate wide range of ionizationparameters/densities

When both Fe II and C IV arestrong, multiphase conditions aresuggested, inferred to be due todifferent densities.

Ionization Conditions Constrained by Fe II and C IV

• 0.5 dex uncertainty in [/C] is ~0.2 dex uncertainty in ionization parameter, U

Rigby, Charlton, & cwc (2001)

• 0.5 dex uncertainty in [/Fe] is ~2.5 dex uncertainty in U for log U < -2.5


+.5

Isolated weakModerate- High-Velocity

Fe II Variations: Ionization or Abundance?

Single, unresolved only

When upper limits on C IV are stringent, then we have an upper limit on ionization parameter, and thus an upper limit on [/Fe]

Typically, we have Si II, Si III, Si IV, C II, C III and/or Ly

Abundance[/Fe]~.5 [Fe/H]<-1

[/Fe]~0 [Fe/H]>-1

Star formation chronometer

26aligned aligned+blended aligned+blended+offset

Strong: blended+offset

offset


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• [/Fe]=0 abundance pattern, rare for -group enhancement • Cloud “sizes” follow power-law distribution- no lower cut off to 0.02 • 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?


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• [/Fe]=0 abundance pattern common, some can be -group enhanced• Cloud “sizes” follow power law, but with lower cut off at 0.08 • Typically within 40 kpc (projected) of normal, bright galaxies

Clues to be sought with z=0 Galactic HST Program


Redshift and Sensitivity Coverage

Wmin = 0.3 ; 0.3<z<2.2 (Steidel & Sargent 1992)

Wmin = 0.02 ; 0.4<z<1.4 (cwc etal, ApJS 1999)

(revisited)


Evolution of Strongest SystemsAs Wmin increased – evolution is stronger

Steidel & Sargent (1992)

dN/dz = N0(1+z)

What is the nature of the evolution???Is it related to high velocity clouds???


Charting the Evolution of Galaxy-IGM EvolutionSophisticated simulations reveal direct, dynamic connections between theIGM and galaxy evolution- Mg II is the best tracer for star forming objects

For z>2.2, Infrared high-resolution spectrograph required: JCAM/HET

Uniform survey with R=11,000-60,000 and Wr(2796)=0.05 limit (5)

• 0.3 A • 0.02 A • 0.05 A


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!

galactic gas kinematics and high velocity clouds at z~1

Documents

cwc charlton

charlton cwc

weak clouds

cwc etal apjs

velocity widths

vinfall kinematics of

velocity dominant

highvelocity subsytems1