Cosmic Baryons: The IGM
description
Transcript of Cosmic Baryons: The IGM
![Page 1: Cosmic Baryons: The IGM](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b6e550346895da47669/html5/thumbnails/1.jpg)
Cosmic Baryons: The IGM
Ue-Li Pen 彭威禮
![Page 2: Cosmic Baryons: The IGM](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b6e550346895da47669/html5/thumbnails/2.jpg)
Overview
• History of Cosmic Baryons: a gas with phase transitions
• Missing baryons
• simulations
• SZ-Power spectrum: direct probe of baryons
• Prospects for detection
![Page 3: Cosmic Baryons: The IGM](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b6e550346895da47669/html5/thumbnails/3.jpg)
Cosmic Gas
• Today, 25% of matter is baryons (ordinary matter), the rest is dark matter (interacts through gravity only). C.f. dark energy.
• Thermal state today very poorly known. Probably in warm/hot/diffuse state, filling most of the universe. Only a small fraction in stars, cold (obervable) gas (Fukogita et al 1999). “Missing Baryons”
• T range 104-109 K
![Page 4: Cosmic Baryons: The IGM](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b6e550346895da47669/html5/thumbnails/4.jpg)
Cosmological Context
• Critical for understanding global cosmology processes: galaxy formation, cluster formation.
• Impacts precision measurement of cosmology: dark energy, dark matter, lensing.
• Major efforts underway to map cosmic distribution using SZ (Compton scattering of CMB)
![Page 5: Cosmic Baryons: The IGM](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b6e550346895da47669/html5/thumbnails/5.jpg)
In the beginning
• Hot big bang: above z>1000, T>3000K. Baryons well understood: linear waves in photon-baryon plasma.
• Recombination: phase transition to neutral: well understood.
• Dark Ages(10<z<1000): non-linear passive evolution: well understood.
• Reionization (6<z<20): phase transition• Epoch of Galaxy formation 2<z<6: Lya forest: m
odestly understood• Present: z<2: poorly understood
![Page 6: Cosmic Baryons: The IGM](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b6e550346895da47669/html5/thumbnails/6.jpg)
WMAP 3yr
Baryons at recombination: T=3000K, n=102/cm3
![Page 7: Cosmic Baryons: The IGM](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b6e550346895da47669/html5/thumbnails/7.jpg)
Reionization
• T:10K--10000K • 21cm @ z=6-15
Iliev, Mellema, Pen 2005. 1o FOV
![Page 8: Cosmic Baryons: The IGM](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b6e550346895da47669/html5/thumbnails/8.jpg)
Present day IGM: 3,000,000K (simulation)
![Page 9: Cosmic Baryons: The IGM](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b6e550346895da47669/html5/thumbnails/9.jpg)
Where are the missing baryons?
• The present day baryons remain undetected. But are not the dark matter
• IGM: what is the state/density• Compact objects: Brown/whitewhite/other dwar
fs. Formed at high-z. Where does gas in clusters come from?
• Fukogita et al (1998) speculated baryons to live in poor groups. Violates XRB (Pen 1999).
![Page 10: Cosmic Baryons: The IGM](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b6e550346895da47669/html5/thumbnails/10.jpg)
IGM conundrum
• Gas falls into gravitational wells. Why haven’t we seen it?
• <kT>=0.3 keV from cosmic virialization: easily visible by ROSAT extragalactic XRB
• Brightness depends on clumping C=ξ(0)<60• PS prediction: C>200. Need to expel 70% of gas.• Simulations: C>>100 (Pen 1999, Dave et al 200
1, Kang&Ryu 2003)
![Page 11: Cosmic Baryons: The IGM](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b6e550346895da47669/html5/thumbnails/11.jpg)
Cosmic Fluid Constraint
• If gas follows dark matter (adiabatic evolution), Press-Schechter theory describes dynamics: all matter in gravitationally bound, hydrostatic halos
• Missing effects: heating/cooling• Cooling: form stars, denser/colder gas, mo
re easily observed. Calculable.• Heating: expel gas from dark matter halos,
harder to observe. Unpredictable.
![Page 12: Cosmic Baryons: The IGM](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b6e550346895da47669/html5/thumbnails/12.jpg)
Zhang, Pen & Trac 2004
![Page 13: Cosmic Baryons: The IGM](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b6e550346895da47669/html5/thumbnails/13.jpg)
Gas traces DM too well, inconsistent with XRB data
XRB limit
10243 grid
Zhang, Pen and Trac 2004.
![Page 14: Cosmic Baryons: The IGM](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b6e550346895da47669/html5/thumbnails/14.jpg)
Hiding Baryons
• Heat and eject: ΔE of 1 keV, maybe less if SN are intergalactic (entropy).
• Cool and hide: cooling catastrophe
• Problem with simulations? Data interpretation (XRB shadowing)?
• How can we find them and show that we found them? How does that affect SZ clusters?
![Page 15: Cosmic Baryons: The IGM](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b6e550346895da47669/html5/thumbnails/15.jpg)
IGM balance
• Heating: hydrostatic equilibrium vs free expansion
• Gravitational potential determined by dark matter, only weakly affected by baryons
• Heating scenarios: 1. halo centers 2. uniform
![Page 16: Cosmic Baryons: The IGM](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b6e550346895da47669/html5/thumbnails/16.jpg)
Central Heating
• Initial halo state: isothermal halo, strong entropy stratification
• Add heat adiabatically at center, due to winds from SNe, BH outflows, etc. (HII regions are not energetic enough)
• Raise central entropy adiabatically at convective stability limit
• Final state: central isentropic “core”, isothermal stratified envelope
![Page 17: Cosmic Baryons: The IGM](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b6e550346895da47669/html5/thumbnails/17.jpg)
Hydrostatic Solution
Halo Mass. Given vc (observable)
Virial radius
Isothermal profile
Post heating core profile
Core radius
From Pen (1999, ApJ 510 L1)
![Page 18: Cosmic Baryons: The IGM](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b6e550346895da47669/html5/thumbnails/18.jpg)
IGM dilemma
• Cosmic virial temperature is 3,000,000K
• 1 keV is uncomfortably hot (107 K) for SNe and feedback scenarios.
• What about warm (105-106K) phase? Difficult to understand in Press-Schechter picture: hydrostatic equilibrium results in high density, rapid cooling. Warm phase may be numerical artifact.
![Page 19: Cosmic Baryons: The IGM](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b6e550346895da47669/html5/thumbnails/19.jpg)
Hunting Baryons
• Baryons (electrons) interact with light (Thomson scattering): SZ & KSZ against CMB.
• KSZ is photon Doppler shift from bulk velocity.
• TSZ is Compton y =τkT/(m c2) ~ 10-3
• SZ is redshift independent! Where are the baryons?
![Page 20: Cosmic Baryons: The IGM](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b6e550346895da47669/html5/thumbnails/20.jpg)
Simulated Universe in tSZ
![Page 21: Cosmic Baryons: The IGM](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b6e550346895da47669/html5/thumbnails/21.jpg)
• Power spectrum of baryons: thermal and kinetic
Zhang, Pen & Trac 2004
![Page 22: Cosmic Baryons: The IGM](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b6e550346895da47669/html5/thumbnails/22.jpg)
Redshift resolution
• Equation of state of gas: how hot/dense is the IGM?
• Hotter means smoother, less correlated than galaxies
• Cross-correlation with photo-z crucial to quantify results
![Page 23: Cosmic Baryons: The IGM](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b6e550346895da47669/html5/thumbnails/23.jpg)
Zhang & Pen 2001
![Page 24: Cosmic Baryons: The IGM](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b6e550346895da47669/html5/thumbnails/24.jpg)
Prospects
• New experiments: SPT, SZA, ACT will map SZ and KSZ for large areas of sky, measuring baryon inventory
![Page 25: Cosmic Baryons: The IGM](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b6e550346895da47669/html5/thumbnails/25.jpg)
Conclusions
• Baryons poorly understood today. Heating/cooling probably important.
• Adiabatic prediction is Evirial = 0.3 keV, inconsistent with observations (groups, XRB)
• Feedback requires a lot of energy (>Evirial). 1 keV consistent with XRB, LTR (group properties).
• Debate on temperature (warm?), pressure equilibrium, simulations.
• SZ a promising physical probe of baryon distribution. This needs to be understood for precision measurement of cosmological parameters, galaxy and cluster formation.