2. TODAY, 9PM PBS Program synopsis: “But Hubble's early days nearly doomed it to failure: a one-millimeter engineering blunder had turned the billion-dollar telescope into an object of ridicule. It fell to five heroic astronauts in a daring mission to return Hubble to the cutting edge of science.

3. TODAY, 9PM PBS Program synopsis: “But Hubble's early days nearly doomed it to failure: a one-millimeter engineering blunder had turned the billion-dollar telescope into an object of ridicule. It fell to five heroic astronauts in a daring mission to return Hubble to the cutting edge of science. Wikipedia: “...spectroscopy of point sources was only affected through a sensitivity loss.”

4. From Day 1, HST has produced spectacular and entirely unique results via point-source spectroscopy. This talk: a highly biased and incomplete discussion of HST QSO absorber studies − historical results, puzzles, and potential.

5. HST does QSO Absorption Lines: A Windfall of Missing Baryons Jan. 14-16, 1991, Feb. 23, 1991: UV spectroscopy of 3C 273 with HST (Morris et al. 1991; Bahcall et al. 1991)

6. HST does QSO Absorption Lines: A Windfall of Missing Baryons Jan. 14-16, 1991, Feb. 23, 1991: UV spectroscopy of 3C273 with HST (Morris et al. 1991; Bahcall et al. 1991) GHRS data (Morris et al. 1991)

7. The COS Absorption Survey of Baryon Harbors (CASBaH) 1.Probing warm-hot intergalactic gas at 0.5 < z < 1.3 with a blind Survey for O VI, Ne VIII, Mg X, and Si XII Absorption Systems (and lots of other goodies) 2.CASBaH-x: Near-UV extension to completely cover Lyα (and other key species, e.g., O VI ) from z = 0 to z(QSO) COS vitals High spectral resolution: 15 km/s FWHM FUV+NUV coverage: observed λ = 1150 – 3000 Å Sensitivity: 20x previous HST spectrographs

8. An Untapped Discovery Space: The Extreme UV The high density of lines in the EUV provides an extraordinary array of gas diagnostics. See seminal papers of Verner, Tytler, & Barthel (1994a,b) Fan et al.

9. Diagnostic Power of the Extreme UV The high density of lines in the FUV and EUV provides an extraordinary array of gas diagnostics.

10. Data Quality (CASBaH Program)

11. This sight line reveals: COS FUV spectrum only: 803 absorption lines FUV+NUV data: 1078 absorption lines, and we don’t have all of the NUV data yet! Species detected in this single sight line: –H I Lyα up to Lyτ (i.e., H19) –He I –C II, C III, C IV –N II, N III, N IV, N V –O II, O III, O IV, O V, O VI –Ne V, Ne VIII –Mg II –Al II, Al III –Si II, Si III, Si IV –Fe II, Fe III

12. Data Quality (CASBaH Program) Publications so far: Our group: Ribaudo et al. 2011; Tripp et al. 2011; Lehner et al. 2012,2013; Meiring et al. 2013; Fox et al. 2013; Burchett et al. 2013; Johnson et al. 2014 Archival researchers: Shull et al. 2012; Muzahid et al. 2013; Stevans et al. 2014; Hussain et al. 2015; Johnson et al. 2015

13. HST does QSO Absorption Lines: A Windfall of Missing Baryons Weymann et al. (1998): number of Lyα lines per unit redshift as a function of redshift Log (1+z) Log (dN/dz) (i.e., number per unit redshift) 987 Lyα lines from HST

14. HST does QSO Absorption Lines: A Windfall of Missing Baryons Weymann et al. (1998): number of Lyα lines per unit redshift as a function of redshift Log (1+z) Log (dN/dz) (i.e., number per unit redshift) High redshift decline driven by expansion of the universe At low z, decline is mitigated by disappearance of QSOs and decline of UV bkg.

15. A Sea Change in Theoretical Astrophysics: The Rise of the Cosmological Simulations Mpc BARYONSDARK MATTER GAS TEMP.

16. At the present epoch, stars account for a tiny fraction of the baryons, ≤ 10% (Persic & Salucci 1992; Gnedin & Ostriker 1992, Fukugita et al. 1998, Bell et al. 2003) Cosmological simulation (Oppenheimer et al.) HST does QSO Absorption Lines: A Windfall of Missing Baryons

17. Hydrodynamic cosmological simulations predict that 30 - 50% of the baryons are in low-density, shock-heated gas at 10 5 - 10 7 K at z = 0 WHIM = robust prediction from many studies (e.g., Cen & Ostriker 1999; Davé et al. 2001; Cen & Ostriker 2006; Cen & Chisara et al. 2011; Smith et al. 2011) Cen & Chisara (2011) Lyα forest STARS “Warm-hot” intergalactic Medium (WHIM)

18. OVI: a most excellent WHIM probe HST does QSO Absorption Lines: A Windfall of Missing Baryons Non-eq., cooling models Collisional eq.

19. OVI: a most excellent WHIM probe HST does QSO Absorption Lines: A Windfall of Missing Baryons Non-eq., cooling models Collisional eq. Tripp et al. (1998, 2000a, 2000b, 2001, 2003, 2008, 2012)

20. OVI: a most excellent WHIM probe HST does QSO Absorption Lines: A Windfall of Missing Baryons Non-eq., cooling models Collisional eq. Tripp et al. (1998, 2000a, 2000b, 2001, 2003, 2008, 2012)

21. HST does QSO Absorption Lines: A Windfall of Missing Baryons Tripp et al. 2008 Danforth & Shull 2005,2008; Shull et al. 2006; Stocke et al. 2006; Wakker & Savage 2009; Prochaska et al. 2004,2006,2011a,b; Thom & Chen 2008a,b; Howk et al. 2009; Lehner et al. 2009; Mulchaey & Chen 2009; Chen & Mulchaey 2009

22. HST does QSO Absorption Lines: Wait, wut? Tripp et al. 2008 Aligned OVI absorbers are photoionized?

30. IonX i-1 (eV)X i (eV) C III24.447.9 O III35.154.9 O IV54.977.4 S IV34.947.2 S V47.272.6 Ne VIII207.3239.1 Ionization Potentials

37. Tripp et al. (2011)

38. Cold gas: photoionized When CLOUDY fits the observed S III/S IV, it slightly underpredicts the S V and vastly underpredicts the Ne VIII (off by many orders of magnitude). The Ne VIII arises in hot gas. Hot gas: hot

40. HST does QSO Absorption Lines: Testing Cosmological Simulations H I Column Density (cm -2 ) b value (km s -1 ) High resolution (7 km s -1 ) STIS observations Simulation measurements (from mock STIS data)

41. HST does QSO Absorption Lines: Testing Cosmological Simulations H I Column Density (cm -2 ) b value (km s -1 ) High resolution (7 km s -1 ) STIS observations Simulation measurements (from mock STIS data)

42. HST does QSO Absorption Lines: Testing Cosmological Simulations Column Density Distribution log [H I Column Density (cm -2 )]

43. HST does QSO Absorption Lines: Testing Cosmological Simulations Column Density Distribution log [H I Column Density (cm -2 )] Kollmeier et al. (2014)

44. HST does QSO Absorption Lines: Testing Cosmological Simulations Column Density Distribution log [H I Column Density (cm -2 )] Kollmeier et al. (2014) Many (most?) of these H I absorbers are NOT intergalactic; this is gas in the gaseous halos and circumgalatic media of galaxies. Many (most?) of these H I absorbers are NOT intergalactic; this is gas in the gaseous halos and circumgalatic media of galaxies.

45. Result 1: Star-Forming Galaxies Have Huge, Metal-Enriched, Highly Ionized Halos Tumlinson et al. 2011 Red sequence  Blue Cloud  Grayscale: galaxy color-stellar mass data from SDSS+GALEX (Schiminovich et al. 2007)

46. Result 1: Star-Forming Galaxies Have Huge, Metal-Enriched, Highly Ionized Halos Are these huge halos substantial mass reservoirs? A back-of-the envelope calculation: To estimate the total mass, we must account for the gas metallicity: With f hit = 0.8, R = 150 kpc, and = 10 14.5 cm -2, M O ≈ 10 7 M  With f OVI = 0.2 and solar metallicity, M gas ≈ 10 9 M 

47. Result 1: However, there are some caveats Some of the absorbers show indications of very high metallicities OVI system, z=0.70152, log N(OVI)=14.42 Meiring, Tripp et al. (2013, in press, arXiv 1209.0939) -200+200 Absorber Velocity (km/s)

48. z=0.70152 Log N(HI) < 13.6 Z > 1.6 Z  log N(OVI)=14.42 Z=0.72152 Log N(HI) < 13.7 Z > 1.0 Z  Log N(OVI) = 13.86 Result 1: However, there are some caveats Meiring, Tripp et al. (2013, in press, arXiv 1209.0939) -200+200 Absorber Velocity (km/s)

49. z=0.70152 Log N(HI) < 13.6 Z > 1.6 Z  log N(OVI)=14.42 Z=0.72152 Log N(HI) < 13.7 Z > 1.0 Z  Log N(OVI) = 13.86 Result 1: However, there are some caveats Meiring, Tripp et al. (2013, in press, arXiv 1209.0939) -200+200 Absorber Velocity (km/s) Impact parameter = 217 kpc SFR = 6.4 M  yr -1 [O/H] = +0.22

50. QSO-Galaxy Connections: Large-Scale Environment is important! Survey of very low-z absorbers with 100% completeness for L > 0.01 L* No. Galaxies within 1500 kpc log [C IV column density (cm -2 )]

51. C IV DETECTIONS

52. C IV NON-DETECTIONS

53. C IV DETECTIONS C IV NON-DETECTIONS

54. Some take-aways High-resolution UV spectroscopy can yield huge samples of absorbers rich in information; these data will remain uniquely valuable for years/decades OVI/NeVIII absorbers are not photoionized and arise in complex, multi-multi phase entities; physics here is poorly understood These absorbers sometimes exhibit extremely high metallicities; again, wut? Cosmological simulations have difficulty with even the most simple case of intergalactic (?) Lyα clouds