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Weipeng Lin (The Partner Group of MPA, SHAO)Collaborators Gerhard Börner (MPA) Houjun Mo (UMASS & MPA)

Quasar Absorption line systems:

Inside and around galaxies

IAUC 199: Probing Galaxies Through Quasar Absorption Lines Shanghai Observatory, 14-18/03/2005

Overview

• Why and What to do?

Are the low-redshift quasar absorption line systems arising from galactic halos? Which part of galaxy gives rise to abs. lines?

What is the nature of absorber-galaxy connection?

• Our works: Models & Monte-Carlo simulations

• Summary

Absorbing gases inside and around galaxies

• Galactic dark matter haloes contain lots of multi-phase gases some of which are cold and dark and can only be probed through quasar absorption lines.

• Without knowing the gas procedures (such as shock heating, cooling, collision, tidal stripping, evaporation, super-wind, etc.) inside galactic halo, one can NOT completely understand galaxy formation.

• Therefore, the studies of quasar absorption lines have useful constraints on theories of galaxy formation: gas and star formation procedures, enrichment history, feedback, etc.

Origin of QSO Abs. Line systems

At high redshift (z>1)Lyman- forest:

Intergalactic MediumLyman Limit systems: Mini-Halo?Damped Lyman systems: galaxy disks? Metal abs. line systems:

Galactic haloes? IGM?

Origin of QSO Abs. Line systems

At low redshift (z<1)Strong Lyman abs. line systems(W>0.3Å):

by IGM or galaxies ？★Strong metal abs. line systems ： by galaxies or other sources? ★Weak metal abs. line systems:

by IGM ？ Galaxies ？ Winds? Other sources?

Debate on the origin of low-redshift abs. line systems

• Which absorbing components are more important, IGM? galaxies? or both?

• Cloud properties: cold, warm, hot• Is there an anti-correlation between

equivalent line width and projected distance from galaxy center to LOS ？How strong is it?

(various authors,various LOS, different results)

Debate on the origin of low-redshift abs. line systems

And is there environmental effect on the quasar abs. line systems? For example, galaxy groups, clusters of galaxies , or on the contrary voids?

N(z) N0(1+z)∝

Results of spectroscopic observations

≈0.48

≈1.7-2.7

Imaging surveys of the absorbers• How to locate the galaxy which gives rise to a ab

sorption line?• What are the characteristics of the absorbing gala

xies ？（ projected distance ， morphology ， luminosity/brightness ， redshift ， inclination of disk, color, etc. ）

• Are there any relations between the abs. line equivalent width and the characters of the corresponding galaxy?

• How large is the average absorbing radii of galaxies? （ eg., relation to galaxy luminosity ）

Imaging surveys of the absorbers

• From galaxy absorbing cross-section and luminosity, can we derive the fraction of abs. lines which origin from galaxies and explain the observed number densities of lines? （ N n∝ ）

• Which parts of galaxy give rise to absorption line? galactic halo ？ Galaxy disk ？ Satellite galaxies ？

Results of imaging surveys

Lanzetta et al. 95, Chen et al.98:(Ly)All types of galaxies can give rise to abs. line ；

Equivalent width is anti-correlated with project

ed distance ；Average galaxy absorbing radius (for lines wit

h W>0.3Å) is ： 150 h-1 kpc-170h-1 kpc ；At least 50% of the strong Ly abs. lines 。

Results of imaging surveys

Steidel et al. 95: （ MgII ）All types of galaxies can give rise to abs.

line ；Average galaxy absorbing radius is abou

t 40 h-1 kpc ；The geometry is spherical 。

Introduction of theorectical worksNumerical simulations of Ly forest ： success at high redshift; at low redshift?Mini-halos model (Abel et al. 99) ： explain high redshift Lyman Limit systems 。Gaseous galactic haloes （ Mo & Mirald

a-Escudé 1996 ） :

explain low redshift Lyman Limit systems and MgII abs. line systems 。

Introduction of theoretical worksGalaxy disk model （ Maloney 92;93 ）： explain some metal absorption line systems 。

Extended galaxy disk model (Linder 99,2000) ：

explain low redshift strong Ly abs.line systems 。 ? Exponential disk+power law disk;

？ Extending to 100 h-1kpc; ? Need large number of LSBGs 。

Our worksGalactic haloes+galaxy disks+satellite

galaxies model （ Lin, Boerner, Mo 2000 ）： explain all low redshift DLA systems 、 LL systems and strong Ly abs.line systems 。

Galactic haloes+galaxy disks （ Lin & Zou 2001 ） : study low redshift strong MgII abs.line systems 。

Improved Models for more metal absorption-line systems.

Motivations• Can models predict reasonable number

density of abs. lines?• To study the relation of equivalent line

width with galaxy optical properties• To predict average galaxy absorbing

radius• To study selection effects in imaging

surveys

cosmogoniesCDM:

0=0.3, =0.7, h=0.7

• SCDM:

0=1.0, =0.0, h=0.5

UV backgroundAt z>2:

J-21=0.05At z<2: J-21=0.5[(1+z)/3]2

Absorbing components• Galactic haloes: (Mo & Miralda-Escudé 96) a two-phase medium, pressure-confine cold c

louds, photo-ionized by UV background• Galaxy disks:(Mo, Mao &White, 98) exponential disks, photo-ionization• Satellite haloes around big central galaxies:

(Klypin et al. 99) adopted from numerical simulations

Cooling flow ： cooling function

Model parameters

• Gas mass fraction ： fg=0.05

• Metallicity ： 0.1-0.3Z ⊙• Cold clouds:

mass function is log-normal

mean mass ： 5x105M⊙

temperature ： 20 ， 000 K

infall velocity ： ~Vc

Galaxy disk model (MMW98 model)

• Exponential disk

• MMW model predict correct Tully-Fisher relation

• Photo-ionization by UV background

• HI column density is a function of path of sightline through galaxy disk

Numerical simulation of local group of galaxies

Klypin et al. 1999

Gas in satellite haloes: gravitational confine

Isothermal sphere

Monte-Carlo simulations

Distribution of galaxies:

• Along the sightline, in a column with a radius of 400 h-1 kpc

• Luminosity functiongalaxy sample

• Redshift spacegalaxy redshift z

Monte-Carlo simulations

• LBcircular velocity Vc:

spiral:Tully-Fisher relation

E/S0: Faber-Jackson law

• Vc physics of haloes and clouds

• LB,z,K-correction galaxy apparent magnitude

Monte-Carlo simulations

• Model A: galaxy disk only

• Model B: galactic halo only

• Model C: satellite halo only

• Model D: disk+halo

• Model F: disk+halo+satellite

To test: model parameters, fraction of absorption by each components

Monte-Carlo simulations

◎simulations for many LOS

Redshift span: [0,1]

To predict:

1 dN/dz for sub-models

2 correlation of abs.line to galaxy properties

3 absorbing radius and covering factor

Observational results of dN/dz

DLA(0.015±0.004)(1+z)2.27 ±0.25

at z=0.5, dN/dz=0.038 ±0.014LL systems dN/dz=0.5±0.3(z=0.5)

dN/dz=0.7±0.2(<z>=0.7) Strong Ly abs.line systems dN/dz=(18.2±5.0)(1+z)0.58

Monte-Carlo simulations

Model A (galaxy disk only):=0.1 dN/dz(DLA)=0.03

=0.2 dN/dz(DLA)=0.06

=0.1 0.038

Monte-Carlo simulations

Model B (galactic halo only):oLL systems

dN/dz=0.45 (0.7)oStrong Ly abs. line systems

dN/dz=3.7 account for 20% of observational resul

ts(about 23 at z=0.5)

Monte-Carlo simulations

Model C (satellite halo only):o LL systems dN/dz=0.15 (0.7)oStrong Ly abs. line systems

dN/dz=9.8 account for 40% of observational res

ults(about 23 at z=0.5)

Monte-Carlo simulations

Model D(halo+disk):o LL systems dN/dz=0.48 (0.7)o Strong Ly abs. line systems

dN/dz=4.9 account for 23% of observational res

ults (about 23 at z=0.5)

Monte-Carlo simulations

Model F:o LL systems dN/dz=0.69 (0.7)oStrong Ly abs. line systems

dN/dz=11.9 account for 55% of observational res

ults (about 23 at z=0.5)

Halo only

Halo only

Satellite only

Halo + Disk

Correlation analysis

• log Wr =- log +C

• log Wr =- log + log(LB/LB*)+C

• log Wr =- log + log(LB/LB*) - log(1+z)+C

～ 0.5

～ 0.15

～ 0.5

Covering factor and average absorbing radius

• Inside 250 h-1 kpc, covering factor~0.36

• Average abs. radius ～ 150 h-1 kpc

For comparison:

Chen et al. 98 gave:

covering factor ～ 0.31

average abs. Radius~ 170 h-1 kpc

Selection effects in image surveys

• Selection criteria (Chen et al. 1998; Lanzetta et al.1995,1997):

Wr≥0.1Å

m_B≤24.3

≤1.3’

|V| ≤500 km/s

“absorber/galaxy pairs”

• “physical pairs”

• luminous“physical pairs”

• “spurious pairs” miss-identification

• “missing pairs”

Luminous “physical pairs”+ “spurious pairs” - “bright pair”

Impact of selection effects

• Properties of “absorber/galaxy pairs” after considering selection effects

• The impact of selection effects on correlation analysis

Mock spectroscopic-imaging surveys

• 10 known quasar LOS (Chen et al. 98) We made 100 mock observations for 10 LOS with

each quasar which is placed at the same redshift as in the observations.

• Number of strong abs. lines: (observational results : 26)

21.0±4.8 (model F1) 26.1±4.8 (model F3) 29.9±5.3 (model F5)

physical pairs

Bright Pairs

Bright Pairs with Vcir≥100km/s

log Wr =- log +C

Need z>10

Mock spectroscopic-imaging surveys

• Selection effects strengthen the anti-correlation between equivalent line width and projected distance

• One can get correct correlation only if there are enough redshift path length ： how large is required? ~10

only 5 in present day observations.

conclusionsOur models predict • reasonable number densities of low-redshift absorp

tion lines• reasonable correlations between line width and gal

axy properties• Reasonable galaxy absorbing radius which is consi

stent with that derived from observations.• Selection effects are important.• To get accurate correlation, more LOS are needed.

MgII abs. line systems

• The anti-correlation

• Absorbing radius

before considering selection effects:

29 h-1 kpc (LB/LB*)0.35

after considering selection effects:

38 h-1 kpc (LB/LB*)0.18

more works

• Apply to more metal abs.line systems, such as FeII,SiII,CIV,OVI systems. +Collision ionization.

• Kinematics models

km/s

FeII line

S/N=10

S/N=20

MgII S/N=20

SiII S/N=10

Recent Interests and Future works

• High-velocity Clouds and extragalactic analogues

• Absorbing gases in tidal tails ？

Thank you!