1. SDSS and VLST Probe the IGM-Galaxy Connection Jason Tumlinson University of Chicago Very Large Space Telescope Workshop STScI February 26, 2004 SDSS 2.5 m ARC 3.5 m SDSS PT 1 m NMSU 1.0 m Apache Point Observatory

2. 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...

3. 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 = 10 5 – 10 7 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 ~ 10 4 K). At low z, filaments are larger, and gas is heated to T ~ 10 6 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 10 5 - 10 7 K tracers and QSO/galaxy probes on small scales. Katz et al. 2002 O VI: 1032,1038; Ne VIII: 770,780

4. 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

5. Recent Observations: Extragalactic O VI HVCs? Toward PG1211+143, we have used HST/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 10 5 K gas. 18941 km s -1 15322 km s -1 146 kpc 137 kpc PG1211+143 Tumlinson et al. 2004 Hot gas (10 5 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.

6. 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 (10 7 K) can arise in a ~Mpc intragroup medium and can be indirectly traced by OVI (~10 5 K). If typical, this individual case could ultimately point to the missing baryons. Shull, Tumlinson, & Giroux 2003 Shull et al. 1998

7. The Linearized IGM Equations Hot galactic halos? Missing baryons? FUSE O VI SurveyPG1211+143 += Local O VII WHIM?PKS2155-304 += Clear physical originMany cases += Clues about galaxy formation Clear physical originMany cases += Complete baryon census = Different viewing geometry = O VI in external galaxies Many 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.

8. A Powerful Sample – The Sloan Digital Sky Survey SDSS: To date, 1360 deg 2 = 53M photometric sources, 186000 spectra (up to DR1). ~17000 QSOs in main sample down to g QSO ~ 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

9. The WHIM and HVCs with O VI and Ne VIII Access to g QSO = 20 and = 900 – 1200 Å, will yield (  10 2 of pairs (  10 3 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 = 2. FUSE O VI HST O VI FUSE Ne VIII HST He VIIII

10. 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

11. 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 g QSO for g = 20 – 23. At z 1000 groups with 2 – 10 QSOs per group. GroupsHalos g < 23 g < 22 g < 21 4.5'

12. 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 + + > 10 7 Galaxies = > 10 5 QSOs + = < 1200 DD

13. 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 Flexibility The 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 Serendipity For 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.

14. The Linearized IGM Equations Galactic HVCsGenerality += Hot galactic halos (abstract) Nearby Group WHIMGenerality += Missing baryons (abstract) FUSE O VI SurveyPG1211+143 += “existence proof” (concrete) Local O VII WHIM?PKS2155-304 += “existence proof” (concrete) Clear physical originMany cases += Clues about galaxy formation Clear physical originMany cases += Complete baryon census = Different viewing geometry = O VI in external galaxies Many close pairs = O VI in group material - Q.E.D. Access to OVI/NeVIII + Many group probes = Access to UV tracers 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.

15. 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 1 QSO per group. g < 20 g < 19 g < 18