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 Medium   Lyman 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  ≈

Imaging surveys of the absorbers How to locate the galaxy which gives rise to a absorption line? What are the characteristics of the absorbing galaxies ？（ 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 projected distance ； Average galaxy absorbing radius (for lines with 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: （ Mg II ） All types of galaxies can give rise to abs. line ； Average galaxy absorbing radius is about 40 h -1 kpc ； The geometry is spherical 。

Introduction of theorectical works  Numerical 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 & Miralda- Escudé 1996 ） : explain low redshift Lyman Limit systems and MgII abs. line systems 。

Introduction of theoretical works  Galaxy 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 -1 kpc; ? Need large number of LSBGs 。

Our works  Galactic 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

cosmogonies  CDM:  0 =0.3,   =0.7, h=0.7 SCDM:  0 =1.0,   =0.0, h=0.5 UV background At z>2: J -21 =0.05 At 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 clouds, 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 ： f g =0.05 Metallicity ： Z ⊙ Cold clouds: mass function is log-normal mean mass ： 5x10 5 M ⊙ temperature ： 20 ， 000 K infall velocity ： ~V c

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 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 function  galaxy sample Redshift space  galaxy redshift z

Monte-Carlo simulations L B  circular velocity Vc: spiral:Tully-Fisher relation E/S0: Faber-Jackson law Vc  physics of haloes and clouds L B,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 ±0.014  LL systems  dN/dz=0.5±0.3(z=0.5) dN/dz=0.7±0.2( =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   =

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 results( 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 results(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 results (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 results (about 23 at z=0.5)

Halo only

Satellite only

Halo + Disk

Correlation analysis log Wr =-  log  +C log Wr =-  log  +  log(L B /L B* )+C log Wr =-  log  +  log(L B /L B* ) -  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.

conclusions Our models predict reasonable number densities of low-redshift absorption lines reasonable correlations between line width and galaxy properties Reasonable galaxy absorbing radius which is consistent 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 (L B /L B* ) 0.35 after considering selection effects: 38 h -1 kpc (L B /L B* ) 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!