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Transcript of TODAY, 9PM PBS Program synopsis: “But Hubble's early days nearly doomed it to failure: a...
Twenty-five Years of QSO Absorption Studies with HST: A Windfall of Missing Baryons, Gastrophysical Diagnostics, and Puzzles
Todd M. Tripp, University of Massachusetts
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 .
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)
• Extrapolation from high redshift predicted: 0.9 – 2.3 Lyα lines (EQW > 25 mÅ); Morris et al. detected 14!
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, NeVIII, 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
An Untapped Discovery Space: The Extreme UV
The high density of lines in the EUV provides anextraordinary array of gas diagnostics.
See seminal papers of Verner, Tytler, & Barthel (1994a,b)
Fan et al.
Diagnostic Power of the Extreme UVThe high densityof lines in the FUVand EUV provides an extraordinaryarray of gasdiagnostics.
Data Quality (CASBaH Program)
Data Quality (CASBaH Program)
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
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
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.
, num
ber p
er u
nit r
edsh
ift)
987 Lyα lines from HST
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.
, num
ber p
er u
nit r
edsh
ift)
High redshiftdecline drivenby expansion ofthe universe
At low z, decline is mitigated by disappearance of QSOs and decline of UV bkg.
A Sea Change in Theoretical Astrophysics: The Rise of the Cosmological Simulations
Mpc
Mpc
BARYONS DARK MATTER GAS TEMP.
• 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
HST does QSO Absorption Lines: A Windfall of Missing Baryons
• Hydrodynamic cosmological simulations predict that 30 - 50% of the baryons are in low-density, shock-heated gas at 105 - 107 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” intergalacticMedium (WHIM)
• OVI: a most excellent WHIM probe
HST does QSO Absorption Lines: A Windfall of Missing Baryons
Non-eq., cooling modelsCollisional eq.
• OVI: a most excellent WHIM probe
HST does QSO Absorption Lines: A Windfall of Missing Baryons
Non-eq., cooling modelsCollisional eq.
Tripp et al. (1998, 2000a, 2000b, 2001, 2003, 2008, 2012)
• OVI: a most excellent WHIM probe
HST does QSO Absorption Lines: A Windfall of Missing Baryons
Non-eq., cooling modelsCollisional eq.
Tripp et al. (1998, 2000a, 2000b, 2001, 2003, 2008, 2012)
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 & Savage2009; Prochaska et al. 2004,2006,2011a,b; Thom & Chen 2008a,b; Howk etal. 2009; Lehner et al. 2009; Mulchaey & Chen 2009; Chen & Mulchaey 2009
HST does QSO Absorption Lines: Wait, wut?
Tripp et al. 2008
Aligned OVI absorbersare photoionized?
Ion Xi-1 (eV) Xi (eV)
C III 24.4 47.9
O III 35.1 54.9
O IV 54.9 77.4
S IV 34.9 47.2
S V 47.2 72.6
Ne VIII 207.3 239.1
Ionization Potentials
Tripp et al. (2011)
Cold gas:photoionized
When CLOUDY fits the observed S III/S IV, it slightly underpredictsthe S V and vastly underpredictsthe Ne VIII (off by many orders ofmagnitude). The Ne VIII arises in hot gas.
Hot gas: hot
HST does QSO Absorption Lines: Testing Cosmological Simulations
H I Column Density (cm-2)
b va
lue
(km
s-1
)
High resolution (7 km s-1)STIS observations
Simulation measurements(from mock STIS data)
HST does QSO Absorption Lines: Testing Cosmological Simulations
H I Column Density (cm-2)
b va
lue
(km
s-1
)
High resolution (7 km s-1)STIS observations
Simulation measurements(from mock STIS data)
HST does QSO Absorption Lines: Testing Cosmological Simulations
Colu
mn
Den
sity
D
istrib
ution
log [H I Column Density (cm-2)]
HST does QSO Absorption Lines: Testing Cosmological Simulations
Colu
mn
Den
sity
D
istrib
ution
log [H I Column Density (cm-2)]
Kollmeier et al. (2014)
HST does QSO Absorption Lines: Testing Cosmological Simulations
Colu
mn
Den
sity
D
istrib
ution
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.
Result 1: Star-Forming Galaxies Have Huge, Metal-Enriched, Highly Ionized Halos
Tumlinson et al. 2011
Red sequence
BlueCloud
Grayscale: galaxy color-stellar mass data from SDSS+GALEX(Schiminovich et al. 2007)
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 fhit = 0.8, R = 150 kpc, and <NOVI> = 1014.5 cm-2,
MO ≈ 107 M
With fOVI = 0.2 and solarmetallicity,
Mgas ≈ 109 M
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 +200Absorber Velocity (km/s)
• 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 +200Absorber Velocity (km/s)
• 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 +200Absorber Velocity (km/s)
• Impact parameter = 217 kpc• SFR = 6.4 M yr-1
• [O/H] = +0.22
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
col
umn
dens
ity (c
m-2
)]
C IV DETECTIONS
C IV NON-DETECTIONS
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