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

1. Quasar Absorption line systems: Inside and around galaxies Weipeng Lin (The Partner Group of MPA, SHAO) Collaborators Gerhard Börner (MPA) Houjun Mo (UMASS & MPA) IAUC 199: Probing Galaxies Through Quasar Absorption Lines Shanghai Observatory, 14-18/03/2005

2. 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

3. overview 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.

4. overview 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?

5. overview 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?

6. overview 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)

7. overview 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?

8. Results of spectroscopic observations overview ≈1.7-2.7 N(z)∝N0(1+z) ≈0.48

9. overview 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）

10. overview 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？

11. overview 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。

12. overview Results of imaging surveys • Steidel et al. 95: （MgII） • All types of galaxies can give rise to abs. line； • Average galaxy absorbing radius is about 40 h-1 kpc； • The geometry is spherical。

13. overview 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。

14. overview 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-1kpc; ? Need large number of LSBGs。

15. 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.

16. 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

17. our models 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

18. our models 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

19. Cooling flow：cooling function halo model

20. halo model 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

21. disk model 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

22. satellite haloes Numerical simulation of local group of galaxies Gas in satellite haloes: gravitational confine Isothermal sphere Klypin et al. 1999

23. galaxy sample 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

24. galaxy sample Monte-Carlo simulations • LBcircular velocity Vc: spiral:Tully-Fisher relation E/S0: Faber-Jackson law • Vc physics of haloes and clouds • LB,z,K-correction galaxy apparent magnitude

25. sub-models 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

26. sub-models 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

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

28. result of models 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

29. result of models Monte-Carlo simulations • Model B (galactic halo only): • LL systems  dN/dz=0.45 (0.7) • Strong Ly abs. line systems  dN/dz=3.7 account for 20% of observational results(about 23 at z=0.5)

30. result of models Monte-Carlo simulations • Model C (satellite halo only): • LL systems  dN/dz=0.15 (0.7) • Strong Ly abs. line systems  dN/dz=9.8 account for 40% of observational results(about 23 at z=0.5)

31. result of models Monte-Carlo simulations • Model D(halo+disk): • LL systems  dN/dz=0.48 (0.7) • Strong Ly abs. line systems  dN/dz=4.9 account for 23% of observational results (about 23 at z=0.5)

32. result of models Monte-Carlo simulations • Model F: • LL systems  dN/dz=0.69 (0.7) • Strong Ly abs. line systems  dN/dz=11.9 account for 55% of observational results (about 23 at z=0.5)

34. example Halo only

35. example Halo only

36. example Satellite only

37. example Halo + Disk

38. example

42. 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

43. 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

44. 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

45. “absorber/galaxy pairs” • “physical pairs” • luminous“physical pairs” • “spurious pairs” miss-identification • “missing pairs” Luminous “physical pairs”+ “spurious pairs” - “bright pair”

46. Impact of selection effects • Properties of “absorber/galaxy pairs” after considering selection effects • The impact of selection effects on correlation analysis

47. 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)