Galaxies and Other Gaseous Structures Through Quasar Absorption Lines

Galaxies and Other GaseousStructures Through Quasar

Absorption 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)

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.

A Common Theme

Where is the boundary between what is left behind from galaxy formation and what is ejected from galaxies?

Outline: Classes of MgII Absorbers

• Strong >0.3A


• Strong >0.3A

• Super Strong >1.5A


• Strong >0.3A


• DLAs N(HI)>1020.3


• Strong >0.3A


• DLAs N(HI)>1020.3

• Weak <0.3A

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

Seeing Within the Galaxies

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


Pure disk modelObserved profiles

Charlton and Churchill 1998


Pure halo modelObserved profiles


75% disk 25% halo model Observed profiles

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

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

Absorption Signatures of Coronae?

Systems with satellite clouds in MgII have stronger CIV

Churchillet al. 2001

•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.

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

Superstrong MgII Absorbers:Superwinds?

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

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).

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?

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

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

Two Populations of Multiple Cloud Weak MgII Absorbers?

Extensions of strong MgII absorber population and absorbers related to dwarf galaxies and their winds (Stocke et al. 2004).

Ding et al. 2004

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

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

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

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.


• 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.


• 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.

Examples of z=0 Weak MgII Absorbers

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

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


•CIV component centered on low ionization gas stronger than others.

•“CIV-only” systems have N(CIV) similar to offset CIV in “low+high” systems.

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?

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.

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.


• 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.

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

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

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.

Documents

Galaxies and Other Gaseous Structures Through Quasar Absorption Lines