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Where are all the baryons? Baryon census (2013) of the local universe, contd. Now that we've introduced DM, chemistry and gas evolution, we'll put these all together in a story starting with the first stars, the first galaxies, moving towards modern day galaxies.

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Where are all the baryons?

Baryon census (2013) of the local universe, contd.

Now that we've introduced DM, chemistry and gas evolution, we'll put these all together in a story starting with the first stars, the first galaxies, moving towards modern day galaxies.

Joss Bland-Hawthorn University of Sydney


Baryon census (z~0)

WARNING:

fixed cosmic abundances

This is a real problem since we don’t know how metals vary between ISM and IGM

Most recent summary

from Shull+ 2012


Baryon census overview

  • Collapsed baryons (18%)

  • Uncollapsed baryons (82%)

  • 2013 baryon census

    • Galaxies

    • Cold gas

    • ICM

    • CGM

    • LyaF

    • WHIM

    • ? missing ?

Baryon census - overview

collapsed

transition

uncollapsed


Schechter luminosity function 1976
Schechter luminosity function (1976)

n★ is a normalization factor which defines the overall density of galaxies (number per cubic Mpc)

L★ is a characteristic galaxy luminosity. An L★ galaxy is a bright galaxy, roughly comparable in luminosity to the Milky Way. A galaxy with

L < 0.1 L★ is a dwarf.

α defines the `faint-end slope’ of the luminosity function. α is typically negative, implying large numbers of galaxies with low luminosities.


GALAXIES (7%)

Large galaxy surveys of the local universe – 2dFGRS (Colless+ 2001), SDSS (Blanton+ 2001), GAMA (Driver+ 2012)

GF favours disks over spheroids

2:1 (Driver+07; cf. FHP96)


Schechter luminosity function 19761
Schechter luminosity function (1976)

we see this function vary across galaxy types and in cosmic time




Cold gas 2

Cold gas (2%)

There is a good reason for why we only include cold gas in galaxies (and not in the IGM) in the inventory.


COLD GAS (2%)

corrected for cold He I, H2 (FP04)

Confirmation: ALFALFA survey (Darling+11)


parkes

arecibo


COLD GAS (2%)

Chynoweth+07


Sancisi dictat: All cold gas is associated with galaxies (i.e. dark matter)

Extragalactic HI always associated with galaxies, e.g. tidal tails like the Magellanic Stream.

If you can find a truly isolated cloud, you will be famous!

Leo Ring

(Schneider+81)

COLD GAS (2%)



We see it in massive ellipticals which are often in big clusters that have their own intracluster gas (ICM)

blue = hot x-ray gas (107 K)

bremmstrahlung = emission ("braking rays" when e- decelerated by p)


What about hot gas in spirals
What about hot gas in spirals ? clusters that have their own intracluster gas (ICM)



Pedersen+ 06; Rasmussen+ 06 1959 for the LG)

not confirmed: smoothed out nuclear source!


(2011) 1959 for the LG)

Vrot ~ 400 km/s

This appears to be first reliable detection in emission after the Galaxy

see also Dai+12 (UGC 12591; Vrot ~ 470 km/s)


INTRACLUSTER MEDIA (4%): can often dominate over stars 1959 for the LG)

Perseus

Where does this hot gas come from?


Large-scale shocks associated with accretion onto A3376 1959 for the LG)

This provides us with a clue about why so much gas is rendered (almost) invisible to modern instruments.


Cooling times are longer than the age of the Universe (Hubble time) at low densities (n α r-2) beyond the virial radius...

Sutherland & Dopita (1993):

Solar, 0.3, 0.1, 0.01, 0.001 Solar

This is an important clue that lots of gas can escape detection by being hot and at low densities...


Mass vs temp calibration
Mass vs Temp calibration (Hubble time) at low densities (n

harder to detect

(hard UV photons)

easier to detect

(soft and hard x-rays)


2012 (Hubble time) at low densities (n

Rvir=1.6 Mpc

The first systematic survey has found warm gas at the outskirts of the Virgo cluster

(100%; NHI > 1013 cm-2) – circumcluster medium ? Not just as simple as hot halos.


Baryon fractions in groups & clusters (Hubble time) at low densities (n

Joss' rule of thumb:

below 0.1Z from outside, above 0.2Z

from inside

1013 Mo

1015 Mo

group

Way more scatter than implied by McGaugh+ 2010 figure.


Baryon fractions down to galaxy masses (Hubble time) at low densities (n

(note where the Milky Way is)

Dai+ 2012

So even with corrections for missing hot gas (e.g. Anderson, NGC 1961), galaxies appear to fall below the cosmic baryon fraction. So maybe the gas never got in? or maybe the gas was once there but then removed?


Circumgalactic media 5

Circumgalactic media (~5%) (Hubble time) at low densities (n

− the new frontier −

gas distributed on the scale of the dark matter halo, i.e. out to the so-called virial radius


Circumgalactic media (Hubble time) at low densities (n (5%)

Lyα halos at z~3 – 92 LBGs stacked

So huge haloes of warm/cool gas do exist. We need to look to high z to see these because Lyα map only detectable when redshifted out of extreme UV. Where do these come from?


CGM − Why the new frontier? (Hubble time) at low densities (n

It may soon be possible

to resolve how gas gets

into galaxies:

Coherent flows?

Cosmic rain?

Something else?


Keres+ 2005, 2009 (Hubble time) at low densities (n

Do cold/cool/warm flows exist? Are they figments of our imaginative simulations? Not seen to date at any redshift.


Circumgalactic media (Hubble time) at low densities (n (5%)

See also OVI absorbers in the Galaxy (Richter+09)

OVI absorbers in

z=0.1-0.4

L★ galaxies

(Tumlinson+11)

Important clue to

metals in the IGM?


The intergalactic medium sheets filaments voids

The intergalactic medium: (Hubble time) at low densities (n sheets, filaments & voids


How does gas move out of voids? (Hubble time) at low densities (n

Sheth & van de Weygaert 2004

Sheth & vdW 2004


Mo et al 2010: (Hubble time) at low densities (n

a lot of detail handled

in on-line codes that borrow from many sources, e.g. Fyris,

Gadget II, VH-1, etc.


First to simulate the IGM and noted relevance to missing baryons. Very simple shock physics was used.


WHIM: large-scale shocks baryons. Very simple shock physics was used.

You've been introduced to shocks in BMG's lectures.

Cen: you have a lump of dark matter of size L at some redshift z. Gas has been infalling for the age of the Universe, i.e. To = 1/Ho(z). The infall velocity VI ~ HoL.

The potential energy of the gas is converted into internal (heat) energy through the shock, which will heat the gas to the virial temperature TVIR of the halo. The sound speed Cs in the shocked gas (TSH~TVIR) is comparable to the infall speed ~ rotation speed Vc.

The post-shock conditions depend on geometry,

e.g. no = pre-shock, n1 = post-shock density

3D: n1/no = 64 (collapse onto DM sphere)

2D: n1/no = 16 (collapse onto DM filament)

1D: n1/no = 4 (collapse onto DM sheet)

(adiabatic case, i.e. no heat lost or gained from system)


δ > 10 baryons. Very simple shock physics was used.

δ > 100

δ > 1000 (galaxy halos)

T ~ 105-7 K


Formation of the WHIM near sheets and filaments (O'Shea) baryons. Very simple shock physics was used.


Whim large scale shocks

v baryons. Very simple shock physics was used.s < 150 km s-1

Ts < 105 K

WHIM: large-scale shocks

vs > 700 km s-1

Ts > 107 K

Kang+ 2005


Chandra/XMM spectroscopy baryons. Very simple shock physics was used.


HST COS UV spectroscopy baryons. Very simple shock physics was used.

It's not all hot in the IGM. The mysterious Lyman α forest (LyαF) appears to be huge diffuse clouds of photoionized, low density gas. Near to galaxies, groups and filaments?

We detect metals in the LyαF.


Evidence for shocks: baryons. Very simple shock physics was used.

much of this appears

collisionally ionized

Tripp+06,08

Danforth & Shull 05,08

Thom & Chen 08

really need e.g. Ne VIII

missing phase e.g. hotter WHIM?

Richter+04,06

Lehner+06,07

broad Lyα absorbers

Tilton+12:

integrated to log NH > 12.5

rises to 31% if down to 12.0

much of this is photoionized


Summary

15% baryons collapsed (GF is an inefficient & complex process);

85% baryons uncollapsed, half still missing.

We need to understand the physical state of each gas phase before talking about a complete inventory (e.g. CGM inflow? outflow?).

We know little about the dynamics of gas flows onto mass structures on any scale, although there may be some evidence that these processes are now being observed. Most of the action was at high redshift but the same processes are still ongoing.

Summary


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