# Presentation: 829445

## Neutrinos and the Lyman-alpha forest

- Rupert Croft (Carnegie Mellon)
- Wayne Hu (Chicago)
- Volker Springel (MPA)
- Lars Hernquist (CfA)
- Romeel Davé (Arizona)

## Plan

- -The Lyman-alpha forest
- How to use it to measure clustering of the mass
- Potential changes to the simple picture
-                    -galactic winds
-                    -radiation fluctuations
-  Constraints on the neutrino mass derived from the
- Lyman alpha forest in 53 Keck spectra.

## Neutrinos suppress power spectrum of mass fluctuations on small scales.

- We would like to measure linear
- clustering on as small a scale as possible

- Hu, Eisenstein and Tegmark (1998)

## Small scale structure in the IGM distribution at z=3

- (33 Mpc/h box)

## Star formation at z=3 in the same volume

##  The atomic transition which is most useful for finding

- material in absorption is the Lyman-alpha transition
- of neutral hydrogen.

-  This is the transition from the 1s to the 2p level.

- The energy levels
- of the Hydrogen
- atom

-  An atom in the ground state which absorbs a photon
- with the correct energy will move to the excited state.
-   -for Lyman-alpha, the photon with this energy has a
-     wavelength of 1216 Angstroms.

##  If we take a spectrum of a quasar, we can see material

- in absorption:

-  Light travelling to us from the quasar gets
- redshifted by the expansion. When the
- wavelength of light gets to the Lyman-alpha
- wavelength, there is a probability that a
- photon will be absorbed by neutral hydrogen
- gas at that redshift.

- Ly-alpha
- emission line
- at quasar
- redshift

## F=e-

- The Lyman-alpha forest can give us a 1D map of the
- density field

- F=e**-******

## F=e-

- F=e**-******

- We rely on A not fluctuating spatially, so that measuring properties of F will give us properties of ρ (such as P(k))

## Temperature of baryons

- Density of baryons in units of the mean.

## We measure power spectrum of quasar flux and convert to mass power spectum using calibrating simulations.

## The temperature of the IGM influences the turnover in

- the power spectrum on scales comparable to the thermal
- width of lines.
-   - we exclude data on the smallest scales.

## Test of the procedure on  a simulated universe which contains “hot” particles with total mass 5eV.

## Our current models of the IGM can reproduce many 

- observations. However, they ignore the possible effect
- of

- galactic winds

- and

- the discrete nature
- of photoionizing
- sources (the radiation field
- is not uniform.)

## New simulations (Springel et al 2002) include addition of kinetic energy to gas close to

- SN in galaxies: creates “wind particles”.
-  -these can spread metals into the Lyman-alpha
- forest to the degree observed.
- - what is their effect on the clustering?

## Slide 16

## Another problem is that the photoionization rate may fluctuate spatially:

- This will happen if the UVBG is generated by discrete sources, such as galaxies or QSOs.
- However, the mean free path of an ionizing photon is ~100 Mpc/h at z=3. This is much larger than our 33 Mpc/h hydro simulation volume.
-  -we will investigate this effect by combining with a large 500 Mpc/h dark matter run.

## Source

- We raytrace photons through the density distribution of the simulation.
-   -quasar sources are taken be at the positions of density peaks
-   -quasar LF from Pei (1995)

## Slide 19

## State of the Universe 100 million years after the turn on of a 

- State of the Universe 100 million years after the turn on of a
- quasar with lifetime 10 million years.

## Quasars with lifetime 100 million years

## Quasars with lifetime 10 million years

- -green points are dead quasars

## Slide 23

## From Croft, Weinberg, Burles, Bolte, Hernquist, Katz, Kirkman and Tytler (2002), ApJ Dec 10th issue.

- From Croft, Weinberg, Burles, Bolte, Hernquist, Katz, Kirkman and Tytler (2002), ApJ Dec 10th issue.

## To determine relative suppression on small scales,

- we  need to constrain amplitude of matter fluctuations on large scales.
- We also have the measurement in km/s at z=3. The relationship
- between this and lengths scales at z=0 depends on cosmology
- Additional constraints used to meet both these objectives:
-      (a) cluster abundance constraint on σ8 (95% range 0.7-1.13 for Ωm=0.35)
-      (b) COBE normalization on large scales.
-      (c)  Universe is flat
-      (d)  Shape of P(k) on scales 0.025 h/Mpc to 0.25 h/Mpc given by PD94
-      (e) Also we use BBN BT99 constraint on Ωb and HST KP constraint on h
-           (but neither has any power to change results).

## We rule out all regions of parameter space where on constraint is violated by 2 sigma (we do not multiply likelihoods together).

## Conclusions

- The Lyman-alpha forest is quite robust:
-    -galactic superwinds at z=3 can propagate into the underdense IGM but don’t affect the majority of Lya forest clustering.
-    -UVBG fluctuations may cause the flux P(k) to vary by up to a factor of 10 on large scales, but not on the scales  that have so far been used to constrain the neutrino mass.
- The Lyman-alpha forest is a useful probe of power in the mass density field on small scales.
-   -combined with other constraints to tie down the large scale end, we find that Mν < 4.5 eV for all values of  Ωm.
-   -for Ωm < 0.3, we find Mν < 0.7 eV