Galaxies and Other Gaseous Structures Through Quasar Absorption Lines

1. Galaxies and Other GaseousStructures Through QuasarAbsorption Lines Jane Charlton Penn State Collaborators: Chris Churchill (NMSU), Jie Ding (NYU), Anand Naryanan (PSU), Nikola Milni (PSU), Jane Rigby (UofA), Stephanie Zonak (Maryland), Nick Bond (Princeton), Rick Mellon (Virginia), Rajib Ganguly (STScI), Ryan Lynch (PSU), Toru Misawa (PSU)

2. Unbiased Probes of Almost All Gas • Giant spiral galaxies (halos, disks, cold clouds, debris). • Elliptical and S0 galaxies. • Dwarf galaxies. • Intragroup medium. • Intergalactic filaments and sheets. All have some absorption cross section.

3. A Common Theme Where is the boundary between what is left behind from galaxy formation and what is ejected from galaxies?

4. Outline: Classes of MgII Absorbers • Strong >0.3A

5. Outline: Classes of MgII Absorbers • Strong >0.3A • Super Strong >1.5A

6. Outline: Classes of MgII Absorbers • Strong >0.3A • Super Strong >1.5A • DLAs N(HI)>1020.3

7. Outline: Classes of MgII Absorbers • Strong >0.3A • Super Strong >1.5A • DLAs N(HI)>1020.3 • Weak <0.3A

8. Strong MgII Absorbers AriseNear Giant Galaxies • Within 38h-1 kpc of a >0.08 LK* galaxy. • Rarely found outside this “boundary”. • Most produce Lyman limit breaks. Steidel 1996

9. Seeing Within the Galaxies

10. Kinematic Models of Strong Mg II Absorbers: Halos and Disks • Halos - cloud components spread out in velocity • Disks - cloud components clustered within 10’s of km/s

11. Kinematic Models of Strong Mg II Absorbers: Halos and Disks Observed profiles Pure disk model Charlton and Churchill 1998

12. Kinematic Models of Strong Mg II Absorbers: Halos and Disks Observed profiles Pure halo model

13. Kinematic Models of Strong Mg II Absorbers: Halos and Disks Observed profiles 75% disk 25% halo model

14. Direct Information About Relationship to Galaxies Rotation curve shows MgII profile at velocity consistent with extended disk. Some halo contribution needed as well. Steidel et al. 2001

15. Absorption Signatures of Coronae? Some strong MgII systems have strong, broad CIV profiles that encompass the dominant MgII absorption in velocity. The CIV cannot arise in the same phase of gas as the MgII, but is rather in a lower density, “diffuse” region. Ding et al. 2003

16. Absorption Signatures of Coronae? Churchill et al. 2001 Systems with satellite clouds in MgII have stronger CIV

17. CIV Deficient Systems • Systems below the CIV absorption strength vs. MgII kinematics correlation line, members of the “CIV deficient class”, tend to have red galaxy hosts. • However, some are early type spirals rather than ellipticals. • Lack of CIV absorption may signify weak or absent corona.

18. High Velocity Clouds • Satellite clouds in z~1 MgII absorbers are similar to HVCs seen around the Milky Way • The CIV absorption related to z=0 HVCs may be systematically weaker than at z=1,but beware of systematic effects! NGC2155

19. Superstrong MgII Absorbers:Superwinds?

20. A Gallery of Superwinds at z=1.5? • 4/4 of the strongest MgII absorbers have these distinctive kinematics • Subcomponents are apparent in the weaker FeII and MgI transitions • Separation between saturated MgII troughs 100-300 km/s Bond et al. 2001

21. Multiphase Superwinds and Expected Evolution • Predict kinematic similarities between MgII and CIV, perhaps with velocity shifts from multiphase wind model (Martin et al., in prep). • The number of >1A MgII systems is seen to decrease with increasing z for z>2; but not for >1.5A systems (Prochter et al., submitted).

22. What Are DLAs? • About half of z<1 DLAs are associated with dwarf or low surface brightness galaxies. • Other than that, very few of the z<1 Lyman limit systems are associated with dwarfs or low surface brightness galaxies. Why do dwarf and low surface brightness galaxies present a significant cross-section for damped Lyman-alpha absorption but not for N(HI) = 1017 - 1020 cm-2 absorption?

23. What Are DLAs? • In some DLAs a phase is apparent in 21-cm that gives rise to a very narrow (< few km/s) profile. • Mg I is not consistent with arising in the same phase of gas as Mg II. Small parsec scale pockets (~1 km/s velocity spreads) are consistent with the Mg I. Consistent with detailed work by Wolfe et al. 2003 DLAs may be small, star forming pockets and their surroundings, located in a variety of environments. In dwarfs and LSBGs the surrounding gas may escape such that sub-DLA Lyman limit systems are rare. Lane et al. 2000

24. Multiple and Single Cloud Weak MgII Absorbers: Separate Populations • Some weak MgII absorbers are likely to be an extension of the strong MgII absorber population. • However, there is an excess of single-cloud, weak MgII systems: separate population Rigby et al. 2003

25. Two Populations of Multiple Cloud Weak MgII Absorbers? Ding et al. 2004 Extensions of strong MgII absorber population and absorbers related to dwarf galaxies and their winds (Stocke et al. 2004).

26. Single-Cloud Weak MgII Absorbers • Comprise most of N(HI)>1015.5cm-2 forest • Not within ~50h-1kpc of a >0.1L* galaxy • MgII profile is unresolved at 6km/s. • Metallicity >0.1 solar and in some cases solar. • Size of MgII phase ~10pc • Density of MgII phase ~0.1 cm-3 • CIV must arise in a separate, lower density phase, ~10-3 cm-3

27. Surprising Implications • Cover same area of sky as bright galaxies. If spherical that would imply a ratio of more than a million to one for the structures producing this absorption relative to L* galaxies. But geometry is unlikely to be spherical. • Single-cloud, weak MgII absorbers could arise in Population III star clusters or shell fragments of supernovae in dwarf galaxies. • They could be small metal-enriched pockets in the elusive, small-mass, dark matter halos predicted by cold dark matter scenarios. Rigby et al. 2003

28. Evolution of Single-cloud Weak MgII Absorbers to z=0 • Survey of E140M spectra from STIS, using SiII1260 and CII1335 as tracers of weak, low ionization systems. • Finds dN/dz consistent with no evolution to z=0. Narayanan et al. 2004

29. Expected Evolution Due to Decline in Extragalactic Background Radiation • Increase in equivalent width of MgII from high density phase. • Significant increase in MgII from low density phase, easily detectable at z=0.

30. Expected Evolution Due to Decline in Extragalactic Background Radiation • Single-cloud weak MgII absorber at z=1 will become a multiple-cloud weak MgII absorber at z=0. • CIV significantly weaker at z=0.

31. Expected Evolution Due to Decline in Extragalactic Background Radiation • This absorber was not quite detected in a survey of <z>=0.9 absorbers. It would be a “CIV-only” system at that time. • At z=0 it would be easily detected, with multiple MgII components.

32. Examples of z=0 Weak MgII Absorbers

33. Evolution of Single-cloud Weak MgII Absorbers to z=0 • Expect dN/dz~1 for evolved MgII phase of z=1 population. • But also expect dN/dz~5 for MgII from “CIV-only” clouds at z=1. • Conclude some structures are evolving away between z=1 and z=0 • Related to decline in star formation rate? Narayanan et al. 2004

34. Constraints on Geometry of Single-Cloud Weak MgII Absorbers • Fewer “CIV-only” systems found than “low+high” systems. • Multiple CIV components in about half the “low+high” systems. Milni et al. 2004

35. Constraints on Geometry of Single-Cloud Weak MgII Absorbers • CIV component centered on low ionization gas stronger than others. • “CIV-only” systems have N(CIV) similar to offset CIV in “low+high” systems.

36. Constraints on Geometry of Single-Cloud Weak MgII Absorbers • Cannot have single small MgII cloud within large CIV “halo” or would observe far too many “CIV-only” systems. • For thousands of spherical MgII clouds in large CIV “halos” the offset CIV components do not arise within overproducing “CIV-only” systems. • Flattened MgII clouds can give rise to large covering factor, small thickness, and not too many “CIV-only” systems. • Could these arise as collapsed, star-forming regions in the cosmic web, or from multiphase layers from supernova-related processes?

37. Possible Geometric Models for Single-Cloud Weak MgII Absorbers • Need many thousands of small, high density clouds within larger, low density halo - doesn’t seem plausible. • Need to find a way to produce offset CIV components.

38. Possible Geometric Models for Single-Cloud Weak MgII Absorbers • Need many thousands of high density spheres inside larger, low density halo. • Additional low density spheres can produce offset CIV, but would also produce a large number of “CIV-only” systems. • Ruled out.

39. Constraints on Geometry of Single-Cloud Weak MgII Absorbers • Flattened low ionization condensations inside filaments. • Surrounding network of filaments give rise to offset CIV. • Low ionization condensations can be transient but then there must be more of them. • Reasonable model.

40. What Are CIV Absorption Systems? • CIV is found within 100kpc of L* galaxies and seldom outside that radius. • Statistically, weak MgII is found in a fair fraction of these. • Hypothesized related to infalling material/satellites. Chen et al. 2001

41. What Are CIV Absorption Systems? • CIV is found within 100kpc of L* galaxies and seldom outside that radius. • Statistically, weak MgII is found in a fair fraction of these. • Hypothesized related to infalling material/satellites. Chen et al. 2001

42. Summary and Future Work • Strong MgII absorbers arise from multiphase medium of many types of giant galaxies. • Superwinds could produce the very strongest MgII absorption. • DLAs are likely to be special little regions relating to star formation in a variety of environments. • Some multiple-cloud, weak MgII absorbers could be related to dwarf galaxies/winds. • Single-cloud weak MgII absorbers seem to be a significant population of self-enriching region in the intergalactic medium. • Plan to model >100 absorbers at z<1 and 100 absorbers at 1<z<2 to establish trends in the midst of large variety.