From HVCs to WHIM:
Download
1 / 33

From HVCs to WHIM: Equilibrium & Non-Equilibrium Ionization in Metal Ion Absorbers - PowerPoint PPT Presentation


  • 126 Views
  • Uploaded on

From HVCs to WHIM: Equilibrium & Non-Equilibrium Ionization in Metal Ion Absorbers. Orly Gnat & Amiel Sternberg Tel Aviv University ISRAEL. H I High-Velocity Clouds.  Wakker et al. 2003 ApJS, 146, 1. High-Velocity Metal Absorbers. Sembach et al. 2003, ApJ, 146, 165S.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' From HVCs to WHIM: Equilibrium & Non-Equilibrium Ionization in Metal Ion Absorbers' - tobias


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.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

From HVCs to WHIM:

Equilibrium & Non-Equilibrium

Ionization in

Metal Ion Absorbers

Orly Gnat & Amiel Sternberg

Tel Aviv University

ISRAEL


HI High-Velocity Clouds

 Wakker et al. 2003

ApJS, 146, 1


High-Velocity Metal Absorbers

Sembach et al. 2003,

ApJ, 146, 165S

  • High-velocity gasprobed by UV/optical metal-line absorption.

    (Sembach et al. 1999, 2000, 2002, 2003;

    Murphy et al. 2000; Wakker et al. 2003;

    Collins et al. 2004, …)


Absorption toward Mrk 509 & PKS 2155-304

log column cm-2

C IV 1548.2 Å 13.5 - >14.20

N V 1238.8 Å <13.08 - <13.24

Si III 1012.5 Å 12.44 - 13.31

Si IV 1393.8 Å <12.33 - >13.44

S III 1190.2 Å <13.68 - <13.93

O VI 1031.9 Å 13.56 - 13.93

Collins et al. 2004 ApJ, 605, 216


Key questions:

  • What are the photoionization properties of metals in minihalo clouds?

  • Are the HI CHVCs, dwarfs &

    ionized-absorbersrelated objects?


Hot

ionized

Warm ionized

Warm

neutral

Minihalo models: H+He properties

  • Warm = 104K

  • Spherical symmetry

  • In DM halos

  • External HIM Pressure

  • Ionizing field

Sternberg, McKee &

Wolfire 2002

ApJS 143, 419

  • Hypothesis:CHVCs trace DM substructurein Galactic halo / Local Group

    (Blitz et al. 1999, Braun & Burton 1999)

  • Explicit minihalo Models for:

    • LG dwarfs (Leo A, Sag DIG)

    • HI CHVCs

      (Sternberg, McKee & Wolfire 2002)

  • Hydrostatic equilibrium

  • Radiative Transfer

Dark Matter Minihalo


Minihalo models – H+He Results:

  • Dwarf Galaxy model (gravitationally confined):

    • Mvir=2x109 M , Mgas=2x107 M , P/k=1 cm-3K

    • Best fit: typical LCDM Burkert halo

  • CHVC model (pressure confined):

    • Mvir=1x108 M , Mgas=1x106M , P/k=50 cm-3K

    • Multi-phased cores expected.

    • Implied distance: ~150 kpc.

Sternberg, McKee &

Wolfire 2002

ApJS 143, 419


Dark matter

LCDM Burkert profiles.

Virial masses: 108 – 2x109 Mʘ.

Gas

106 – 107 Mʘ , T=104K.

P/kB: 0.01–50 cm-3K.

Metallicity: 0.1-0.3 solar.

Metagalactic radiation field.

Metal absorbers – model parameters

Moore et al. 2002


Metagalactic radiation field

IR

optical

UV

EUV

X-ray

nJn[erg s-1 cm-2 sr-1 ]

Lyman

limit

0.25 keV

Jn0 = 2 x 10-23 cgs

n[Hz]


8.2 eV

Si II

Low-Ions

10.4 eV

S II

11.3 eV

C II

13.6 eV

H II

High-Ions

16.4 eV

Si III

23.3 eV

S III

33.5 eV

Si IV

47.9 eV

C IV

77.5 eV

N V

113.9 eV

O VI

Metals: Ionization potentials


  • Step 1:

    H/He gas density profile; ionization structure;

Local radiation field.

  • Step 2:

    • CLOUDY ionization state (Ferland, 1998).

    • Integrate line-of-sight columns.

r

Metals photo-ionization structure

radiative transfer (spherical),


Dwarf-scale halos

Photoionized models - Results

CHVCs models –

High bounding pressures (~50 cm-3K) low ionization.

Not enough high ions:

E.g. - CIV column: Observed - ~1x1014 cm-2

CHVC Model - 3x1011 cm-2


Example: Dwarf-scale halo

  • High mass: Mvir = 2 x 109 Mʘ, Burkert halo.

  • Mgas = 2 x 107 Mʘ,Metallicity = 0.3 solar.

  • Low Pressure: 0.1 cm-3K.

  • Maximal radiation field.

Nicastro et al.

2002

ApJ, 573, 157


IF

Warm

neutral

Hot

ionized

Warm

ionized

total H density

neutral H

Dwarf-scale halo: volume densities

density [cm-3]

Radius [kpc]


Dwarf-scale halo: column densities

C IV : model: 1.5 x 1014 cm-2

observed: (0.3 – 2) x 1014 cm-2

O VI : model: 1 x 1013 cm-2

observed: (4 - 8) x 1013 cm-2

Column density [cm-2]

Impact parameter [kpc]


Dwarf Model versus observations:

Nmodel / Nobserved

Impact parameter [kpc]


C IV : 1 x 1014 cm-2

observed: (0.3 – 2) x 1014 cm-2

O VI : 8 x 1012 cm-2

observed: (3 - 8) x 1013 cm-2

Ionized dwarf-scale halo: columns

Mgas = 9.5 x 105 Mʘ

Column density [cm-2]

Impact parameter [kpc]


Summary: photoionized clouds

  • CHVC-scale models – not enough high-ions.

  • Dwarf-scale models -Match to observed metal columns requires:

    • Metallicity ~ 0.3 solar.

    • Low pressure ( ≤1 cm-3 K ).

    • Maximal ionizing spectrum.

  • Ionized starless “dwarf galaxies” could be detected as metal-ion absorbers.

  • Except for O VI→ collisional processes…

Gnat & Sternberg 2004

ApJ, 608, 229


Turbulent

Mixing

Layers

log ( NCIV / NOVI )

Shock

Ionization

Conductive

Interfaces

Cooling

Flows

Fox et al. 2005

ApJ 630, 332

log ( NNV / NOVI )

Non-Equilibrium Collisional Processes?


Non-Equilibrium Collisional Processes

  • Time scale for change in temperature:

    tTemp

  • Time scale for change in ionization state:

    tIonization

  • Non-equilibrium: tTemp<< tIonization

tc (cooling)

tH (heating)

tr (cooling)

ti (heating)


Non-Equilibrium Collisional Processes?

  • Conductive Interfaces Surrounding Evaporating Clouds

  • Time-Dependent Radiative Cooling


HI CHVC model

cloud boundary: 1.3 kpc

PHIM = 50 cm-3K

THIM = 2x106 K

(Galactic corona)

photoionized

cloud

conductive

interface

Temperature [K]

heat flow

OVI

HIM

(hot)

density [cm-3]

CIV

Radius [kpc]

cloud evaporates

Radius [kpc]

Conductive interfaces – work in progress:

  • Non-equilibrium ionization in the flow.

WIM

(warm)

to 2 CHVC radii:

CIV central column ~10 times larger

OVI central column ~106 times larger


Non–Equilibrium Radiative Cooling

  • Cooling is faster than recombination(tc<<tr)

  • Gas stays “over-ionized”

  • Independent of gas density

  • Modified ionization affects cooling rates:for over-ionized gas cooling is suppressed

  • Cooling rate depends on metallicity


H

He

C

N

O

Ne

Mg

Si

S

Fe

Rate

coefficients (T)

Coolingrate (xi)

Numerical Computation

  • Cooling from CIE at T>5x106K.

  • Follow time-dependent ionizationdxi/dt=…

~

  • Step 1: No Photoionization

  • dxi/dT independent of density

  • …But depends on metallicity

  • The energy equation (Cloudy Cooling) dT/dt=…


time

Results: Ionization - Hydrogen

Equilibrium

Non-Equilibrium

100

10-1

10-2

104

105

106

104

105

106

Temperature (K)

Temperature (K)

Recombination Lag


Results: Ionization - Carbon

Equilibrium

Non-Equilibrium

100

10-1

10-2

104

105

106

104

105

106

Temperature (K)

Temperature (K)


Results: Ionization – Z dependence

100

equilibrium

Z = 2

Z = 1

Z = 10-1

Z = 10-2

Z = 10-3

10-1

xOVI

10-2

10-3

104

105

106

Temperature (K)


He Cooling

Metal Line

Cooling

Hydrogen Cooling

(Lya)

Bremsstrahlung

Results: CIE Cooling

Z = 2

Z = 1

Z = 10-1

Z = 10-2

Z = 10-3

10-21

10-22

Leq (erg cm3 s-1)

cooling efficiency

10-23

10-24

104

105

106

107

108

Temperature (K)


Equilibrium

Non-Equilibrium

time

Results: Non-Equilibrium Cooling


Turbulent

Mixing

Layers

log ( NCIV / NOVI )

Shock

Ionization

Conductive

Interfaces

Cooling

Flows

log ( NNV / NOVI )

Results: Diagnostic Ratios


High Velocity Metal Absorbers

Fox et al. 2005

ApJ, 630, 332


Time-Dependent Cooling - Summary

  • Equilibrium and Non-EquilibriumIonization States and Cooling Efficiencies ofH, He, C, N, O, Ne, Mg, Si, S, & Fe,For 104 < T < 108 Kand 10-3 < Z < 2 solar.

  • Isochoric / Isobaric – conditions & results.

  • Impact of Self Radiation.


Future Work

  • Photoionization by External Radiation

  • Cooling Columns in Flows

  • Applications - E.g.:

    • High-velocity ionized clouds &the Galactic Halo (E.g.: Sembach & Savage 92, Spitzer 1996)

    • IGM - WHIM (E.g.: Tripp et al. 00, Shull et al. 03, Richter et al. 03, Sembach et al. 04, Nicastro et al. 05, Savage et al. 05)

    • AGNs

    • Galaxy Clusters and Groups


ad