SDSS and VLST Probe the IGM-Galaxy ConnectionJason TumlinsonUniversity of Chicago

Very Large Space Telescope WorkshopSTScIFebruary 26, 2004

SDSS 2.5 m

ARC 3.5 m

SDSS PT 1 m

NMSU 1.0 m

Apache Point Observatory

Science Theme – The IGM-Galaxy Connection

How do baryons get from the IGM into galaxies?

How and when do they return?

Where, and in what phase, do the “missing baryons” reside?

Do either galaxy feedback or IGM evolution control the global star formation rate?

How are metals transported and distributed?

What are the observable features of these processes?

Good questions! But galaxy-IGM interfaces are hidden, we have not probed the relevant scales . . .

Theoretical Issues In Interface Regions

Ne VIII

O VI

Galaxies

WHIM

IGM

Davé et al. 1999

Most of the baryons are thought to reside in a “Warm-hot IGM”,

with T = 105 – 107 K (WHIM; Cen et al. 1999; Davé et al. 1999). Only 5 – 10% of this phase has

been found via O VI (Tripp 2002) with FUSE and HST.

At high z, most gas that enters galaxies does so via the “cold mode” (T ~ 104 K). At low z,

filaments are larger, and gas is heated to T ~ 106 K before

entering galaxies. Does this occur on filament or group scales, and

what is its relationship to the WHIM and/or HVCs? To answer, we must probe structures on all

these scales.

Conclusion:

Hot gas may hold the missing baryons, mediate IGM accretion into galaxies, and regulate the cosmic SFR.

These open questions of baryon evolution require access to 105 - 107 K tracers and QSO/galaxy

probes on small scales.

Katz et al. 2002O VI: 1032,1038; Ne VIII: 770,780

However, even if local conditions come to be known, we cannot connect them to larger theories of galaxy formation and

evolution without statistical evidence – currently lacking – that other galaxies possess such hot surroundings.

Recent Observations: Galactic HVCs

The FUSE survey of O VI in the vicinity of the Galaxy found

HVC OVI in > 60 % of all extragalactic sightlines. Some probably arises in cooler gas

shocked against a hot Galactic halo with R ~ 100 kpc,

perhaps a consequence of past galaxy mergers.

However, the origins of the local group O VI HVCs is still

uncertain, due in large part to the radial viewing geometry

that precludes accurate distances.

Galactic HVCs suggest the presence of a ~100 kpc coronal halo around the Galaxy, but the physical picture is uncertain owing to the radial viewing

geometry.

If typical of all galaxies, this result would provide important clues about galaxy formation.

Sembach et al. 2003

Recent Observations: Extragalactic O VI HVCs?

Toward PG1211+143, we have usedHST/STIS and FUSE to discover two O VI systems – they appear to be associated with galaxy halos at < 150 kpc, but the stronger system

also lies in a group and so is ambiguous. Nevertheless, these may be HVC analogs and/or accreting 105 K gas.

18941 km s

-1 15322 km s-1

146 kpc

137 kpc

PG1211+143

Tumlinson et al. 2004

Hot gas (105 K) can arise in galaxy halos and/or intragroup gas at < 150 kpc from galaxies (i.e. HVC

analogs).

This may trace accreting or ejected material, or the hidden influence of an extended coronal halo – but in

only two (ambiguous) cases.

Recent Observations: Multiphase Group Gas

FUSE has found H I and O VI in association with O VIII toward PKS2155-304. This appears to be multiphase IGM gas (Shull, Tumlinson, &

Giroux 2003; O VIII from Fang et al. 2002). The O VI is thought to arise in a shock

interface between infalling photoionized gas and a hot intragroup medium.

This system shows that hot gas (107 K) can arise in a ~Mpc intragroup medium and can be indirectly

traced by OVI (~105 K).

If typical, this individual case could ultimately point to the missing baryons.

Shull, Tumlinson, & Giroux 2003

Shull et al. 1998

The Linearized IGM Equations

Hot galactic halos?

Missing baryons?

FUSE O VI Survey PG1211+143+ =

Local O VII WHIM?

PKS2155-304+ =

Clear physical origin Many cases+ =Clues about galaxy formation

Clear physical origin Many cases+ =Complete baryon census

=Different viewing geometry

=O VI in external galaxiesMany close pairs= O VI in group material-

Q.E.D.

Access to OVI/NeVIII +Many group probes =

Access to UV lines

Good statistics for galaxies and LSS

Conclusion:

To solve these closely coupled physical problems, to resolve questions about known cases, and to

confidently generalize their results, we require >100x better statistics.

A Powerful Sample – The Sloan Digital Sky Survey

SDSS: To date, 1360 deg2 = 53M photometric sources, 186000 spectra (up to DR1).

~17000 QSOs in main sample down

to gQSO ~ 20.5. Many more available by photometric screens

down to g ~ 22 – 23 (in blue at right).

Photometric redshifts accurate to z = 0.04 can yield candidates for QSO/galaxy pairs.

Group catalog (z < 0.1) derived from spectroscopic galaxy sample (Berlind 2003).

Clusters and filament-scale structures are identifiable in both photometric and spectroscopic redshift surveys.

DR1

HST/STIS

FUSE

VLST?

www.sdss.org

Photo-QSO

The WHIM and HVCs with O VI and Ne VIII

Access to gQSO = 20 and = 900 – 1200 Å, will yield ( < 150 kpc) >102 of pairs ( < 150 kpc) for Ne VIII and >103 of pairs for O VI (HST and FUSE ranges in color).

Large numbers allow careful selection for galaxy properties and more choice cases.

At z < 0.2, there are Npairs = 2 – 10 pairs per QSO, with <Npairs> = 2.

FUSE O VI

HST O VI

FUSE Ne VIII

HS

T H

e V

IIII

Statistics On Galaxy Properties

SDSS provides excellent statistics on color, luminosity, position, and separation.

For example, FUV wavelengths offer access to faint galaxies (dwarfs, LMC/SMC) for study of their feedback on surrounding IGM.

SDSS at z < 0.1 offers full coverage of the = 150 kpc region near galaxies.

z > 0.1

QSO Pairs for “Cosmic Web” Tomography

Close spacing of faint QSOs gives many QSO pairs or multi-QSO asterisms with < 1 Mpc separations, crucial for tests of absorber size and filament growth.

This is an aperture driver for a VLST, as the number of close pairs is a steep function of gQSO for g = 20 – 23.

At z < 0.1, we will have >1000 groups with 2 – 10 QSOs per group.

GroupsHalos

g < 23g < 22 g < 21

4.5'

Derived Requirements for a VLST

D ~ 30 m

Access to O VI and Ne VIII in SDSS redshift range

Efficiently multiplexed pairs (>2 – 10/QSO @ z < 0.1)

Efficiently multiplexed probes of groups @ z < 0.1

Multiple (N = 2 – 6) QSO probes of individual galaxies

IGM tomography with small QSO/QSO separations

Flexibility for Optimal Samples

+

+

> 107 Galaxies=

> 105 QSOs

+

=

<1200

D

Conclusions

SDSS provides a Complete Laboratory of IGM-Galaxy Connections

As the largest-ever survey of galaxies and larger structures, SDSS provides a vast basis for exhaustive study of IGM-Galaxy Connections,

including numbers sufficient to yield many “choice” cases. This will be a major piece of future efforts to fully understand and generalize local

conditions over 5 Gyr of evolution.

SDSS and VLST Provide Maximum FlexibilityThe large candidate pool and access to faint QSOs provides a good

measure of flexibility and multiplexing efficiency for a joint survey, and the upcoming completion of SDSS means it can guide planning for VLST

and its instruments.

SDSS and VLST Transcend SerendipityFor the first time, we will be able to select QSOALS samples based on their galaxy and LSS properties, not solely on QSO availability. Thus

VLST will initiate the “choose-your-quasar” era, and mark the transition from individual cases to routine statistical samples of what is state-of-

the-art today.

The Linearized IGM Equations

Galactic HVCs Generality+ = Hot galactic halos (abstract)

Nearby Group WHIM Generality+ = Missing baryons (abstract)

FUSE O VI Survey PG1211+143+ =“existence proof” (concrete)

Local O VII WHIM?

PKS2155-304+ = “existence proof” (concrete)

Clear physical origin Many cases+ =Clues about galaxy formation

Clear physical origin Many cases+ =Complete baryon census

=Different viewing geometry

=O VI in external galaxiesMany close pairs= O VI in group material-

Q.E.D.

Access to OVI/NeVIII +Many group probes =

Access to UVtracers Good statistics for

pairs and groups

Conclusion:

To solve these closely coupled physical problems, to resolve questions about known cases, and to

confidently generalize their results, we require >100x better statistics.

O VI in SDSS Galaxy Groups

Close spacing of faint QSOs gives many QSOs group probes for mass infall tests and correction of galaxy halo results.

This is a wavelength and aperture driver for VLST - because the group catalog is complete at z < 0.1, where there is generally >1 QSO per group.

g < 20g < 19 g < 18