A Stroll Through the Local Lyman Alpha Forest

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A Stroll Through the Local Lyman Alpha Forest
G G G
G
G
G
G
G
Lya
G Galactic Line
Lya Line
G G G G
GG
HST/GHRS Spectrum of 3C273 Morris, Weymann
et al. 1991
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QSO ABSORBER GALAXY ASSOCIATIONSFINDS THE KEYS
AT THE LOWEST REDSHIFTS COLORADO GROUP JOHN
STOCKE, MIKE SHULL, STEVE PENTON, CHARLES
DANFORTH, BRIAN KEENEY ALUMNI MARK GIROUX
(ETSU), JASON TUMLINSON (YALE), JESSICA
ROSENBERG (CfA), MARY PUTMAN (MICHIGAN), KEVIN
McLIN (Sonoma State) ELSEWHERE RAY WEYMANN
(NIRVANA), J. VAN GORKOM (COLUMBIA), CHRIS
CARILLI ( NRAO) Results based on gt200
QSO ABSORBERS found by HST Spectrographs at z
lt0.1 and at low column densities (NHI
1012.516.5 cm-2 ) AND gt 1.2
Million galaxy locations and redshifts from the
CfA galaxy redshift survey, 2DF/6DF, SLOAN
Digital Sky Spectroscopic Survey (DR-4), FLASH
others, including our own pencil-beam surveys
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(No Transcript)
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(Nicastro et al. 2005)
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SUMMARY OF STATISTICAL RESULTS

• COSMIC BARYON CENSUS WLy a / Wbaryon 29 4
  (most of the mass
  is in the low column density (NHI lt 1014 cm-2)
  absorbers)
• Wb(voids) / Wb 4.5 1.5 AS PREDICTED BY
  SIMULATIONS (Gottlöber et al 2003)
• At least 55 of all Ly a absorbers with NH I gt
  1013 cm-2 are METAL-BEARING at 10 SOLAR (
  based on O VI and C III detections with FUSE )
• Spread of metals from nearest L galaxies
  150800h-170kpc but L galaxies probably not
  primary source of metals.
• A typical galaxy filament is gt 33 - 50
  covered by 10 SOLAR gas.
• For details see PENTON et al. (2000a,b, 2002,
  2004) ApJ (Ly alpha absorbers) and STOCKE et al.
  (2006) ApJ, 641, 217 (OVI absorbers)

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THE IGM BECOMES MORE STRUCTURED AND HETEROGENOUS
WITH TIME
The 33 Solution ! Galaxies Warm IGM (Lya
Forest) Warm-Hot IGM (WHIM)
From Dave et al. 1999
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IGM Gas without feedback from Galactic
Superwinds YELLOW T gt 106 oK (OVII/OVIII
WHIM)
RED T105--6 oK (OVI WHIM)
GREEN BLUE T103.5--5 oK
(Warm IGM
Lya Forest) IGM Gas WITH Galactic Superwind
Feedback This prescription requires that
feedback is proportional to the local star
formation rate, and thus mass density per pixel)

( This maybe an incorrect prescription) Simulati
on finds 50 of local IGM in WHIM gas Cen
Ostriker 2005 astro-ph/0601008 and Cen
Fang 2005 astro-ph/0601009
30 h-170 Mpc
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TWO-POINT CORRELATION FUNCTION (TPCF)
AMPLITUDE GALAXY-GALAXY TPCF SHOWS EVIDENCE FOR
SUPERCLUSTER FILAMENTS AT ? V lt 600 km/s AND
VOIDS AT ? V gt 1000 km/s Ly a ABSORBER-ABSORBER
TPCF ALSO SHOWS EXCESS ( 7s LEVEL) DUE TO
FILAMENTS AT ? V lt 600 km/s. (UPPER-RIGHT)
LOWER LEFT PANEL SHOWS THAT THIS EXCESS IS DUE
ENTIRELY TO STRONGER Ly a LINES (NHI gt 1013
cm-2). LOWER LEFT PANEL ALSO SHOWS A HINT OF
VOIDS (deficit at larger ?V). O VI ABSORBERS
WITH Ly a LINES IN PAIRS CAN ACCOUNT FOR THIS
ENTIRE EXCESS. THE LOWER-RIGHT PANEL SHOWS THAT
WEAKER Ly a ABSORBERS SHOW NO EVIDENCE FOR
CLUSTERING IN SPACE
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MATTER DENSITY IN COSMIC VOIDS

• When corrected for pathlength surveyed, 22 of
  Lya absorbers are in galaxy voids
• Statistically lower N(H I) absorbers in voids
• If Lya absorbers are only mass in voids then
  Ob(voids)/ Ob(total) 4.5 1.5
• If these absorbers have the cosmic fraction of
  baryons to dark matter then this density agrees
  with the mean density at the center of voids
  found in simulations. ?
• Also, we have searched the void regions around
  Lya absorbers and found no H I in bound halos
  down to 108 M (Solar) in 30 Mpc3
• This absence of dark matter halos is not
  stringent enough to be inconsistent with
  simulations.

?
Figure from Gottlöber et al. 2003 MNRAS 344, 715
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METALS IN VOIDS WHY INTERESTING?COMPOSITE
SPECTRA OF HUNDREDS OF HIGH-Z ABSORBERS FINDS
Z -2 TO -3

• Pixel-addition techniques for NH I lt 1015 cm-2
  absorbers finds C IV, Si IV and OVI consistent
  with wide-spread low metallicity throughout the
  diffuse IGM (Cowie etal. 1995 Simcoe, Sargent
  Rauch 2004 Pieri, Schaye Aguirre 2006).
• No evidence for a metallicity floor since
  2040 of absorbers at NH I gt 1013.6 cm-2 have
  Z lt -3 (Simcoe, Sargent Rauch 2004).
• Some evidence that mean absorber metallicity is
  higher near highly-enriched regions (as marked by
  C IV absorbers) but the correlation with bright
  galaxies (Lyman break galaxies) is not nearly so
  strong. (Pieri, Schaye Aguirre 2006).

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Co-addition of 7 Void Absorbers _at_ C IV
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IS THERE METAL-ENRICHED GAS IN VOIDS? BEST
CURRENT LIMITS Z lt -2.7 SOLAR BASED ON 7 VOID
ABSORBERS WITH BOTH STIS FUSE SPECTRA Log U
-1.5 to -1 expected for low-z
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IS THERE METAL-ENRICHED GAS IN VOIDS
IICOLLISIONALLY-IONIZED MODELS FOR DIFFERENT
WHIM TEMPERATURES
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COSMIC ORIGINS SPECTROGRAPH TO BE INSTALLED
DURING SHUTTLE SERVICING MISSION 4 IN MAY, 2008
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EXAMPLES OF COSMIC ORIGINS SPECTROGRAPH
GUARANTEED TIME OBSERVATIONS TO
BE MADE LATE IN 2008
The Extent, Metallicity and Kinematics of a
Normal, Luminous (L) Spiral Galaxy Using
multiple QSO sightlines
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QSO TOMOGRAPHY OFTHE GREAT WALL LOW-Z VOIDS
(8 DEGREE WIDE WEDGES)
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CONTOURS OF LOCAL GALAXY DENSITY IN GREEN
BRIGHT QSO
SIGHTLINES IN PINK
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MEDIAN DISTANCE TO NEAREST GALAXY

• Sample
  Distance in Sample
• Name
  h-170 kpc Size
• L Galaxies
  350 500
• O VI Absorbers in Ly a Pairs 200
  10
• O VI Absorbers
  290 23
• Stronger half Ly a Sample 450
  69
• Weaker half Ly a Sample 1850
  69
• --------------------------------------------------
  -------------------
• Simulations of WHIM GAS 200
  Dave et al
• Simulations of Photo-ionized Gas 1200
  (1999)
• --------------------------------------------------
  --------------------
• from Stocke et al. 2006 ApJ 641, 217
  astro-ph/0509822
• 
  
  

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SUMMARY OF STATISTICAL RESULTS

• COSMIC BARYON CENSUS WLy a / Wbaryon 29 4
  (most of the mass
  is in the low column density (NHI lt 1014 cm-2)
  absorbers)
• ASSOCIATION WITH GALAXIES? 78 LOCATED IN
  SUPERCLUSTER FILAMENTS 22 IN VOIDS. STRONGER
  absorbers at NH I gt 1013 cm-2 are more closely
  ASSOCIATED WITH GALAXIES
  WEAKER absorbers are more NEARLY
  UNIFORMLY DISTRIBUTED in space.
• Wb(voids) / Wb 4.5 1.5 AS PREDICTED BY
  SIMULATIONS (Gottlöber et al 2003)
• At least 55 of all Ly a absorbers with NH I gt
  1013 cm-2 are METAL-BEARING at 10 SOLAR (
  based on O VI and C III detections with FUSE )
• O VI and CIII-bearing absorbers indicate
  spread of metals from nearest L galaxies
  150800h-170 kpc median distance to L galaxies
  (350h-170 kpc) too small for them to dominate
  metal-enrichment (Tumlinson Fang 2005 ApJ) ? L
  lt 0.1L galaxies must contribute significantly to
  metal enrichment of IGM.
• A typical galaxy filament is gt 33 - 50
  covered by 10 SOLAR gas.
• For details see PENTON et al. (2000a,b, 2002,
  2004) ApJ (Ly alpha absorbers) and STOCKE et al.
  (2006) ApJ and astro-ph/0509822 (OVI absorbers)

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Why study the diffuse gas in the Inter-Galactic
Medium (IGM)?

• . Traces the dominant matter reservoir. Most of
  the baryons in the local Universe are not in
  galaxies but rather in the IGM
• Probes voids in the galaxy distribution. Lyman a
  absorbers are the only baryons detected thus far
  in galaxy voids.
• Traces the evolution of large-scale structure
  with little bias
• Probes diffuse galaxy halos and winds Do
  Starburst Winds escape? How much and how far away
  do they enrich the IGM?
• Measures the evolution of metallicity with
  redshift