Missing Photons that Count:Galaxy Evolution via Absorbing Gas

(and a little bit of fundamental physics to boot)

Chris Churchill(Penn State)

To Earth

CIVSiIVCIISiII

Lyem

Ly forest

Lyman limit Ly

NVem

SiIVem

CIVem

Lyem

Ly SiII

quasar

Quasars: physics laboratories in the early universe

Metal absorption

Quasar Q1759+75

H I absorption

H I emission

QSO Absorption Lines: Anatonomy of a Spectrum

C IV doublet

QSO Absorption Lines: Anatonomy of a Spectrum

C IV 1550ÅC IV 1548Å

QSO Absorption Lines: Anatonomy of a Spectrum

Efforts have been made to include ionization feedback, both in terms of spectral energy distributions, photon transport, and mechanical stirring of the gas…

QSO Absorption Lines: Anatonomy of a Simulation

(courtesy M. Steinmetz)

Technology and innovation is quickly outpacing observational data…

QSO Absorption Lines: Anatonomy of a Simulation

(courtesy M. Steinmetz)

Great Insights are gained from simulations of structure growth, but these simulations are starved for hard data to constrain the physics…

Note structure growth is rapid at for z>5 (a short cosmological time frame), and then evolution is slower, especially from z<1 (majority of time)…

(courtesy M. Haehnelt)

The Power of Simply Counting Lines

The redshift path density, dN/dz, places constraints on simulations of structure growth as a function of redshift…

(Dave’ etal 1999)

The Power of Simply Counting Lines

(Dave’ etal 1999)

(Weymann’ etal 1999)

The Power of Simply Counting Lines

Mg II shows no evolution (co-moving), but nothing in known above z=2.2

Lyman Limit systems (LLS) show no evolution, measured from continuum “break” at 916 A in the rest frame, N(HI)>1017.3 cm-2

C IV systems evolve rapidly! They increase with cosmic time until z=1.5 and then show no evolution

Structure, Ionization, or Chemical Evolution?

Evolution measures product of:• number• size• ionization fraction

Is this an increase in number, in ionization level, or in the chemical abundance of carbon?

We need low ionization data. Mg II.

Motivations and Astrophysical Context

Mg II arises in environments ranging over five decades of N(H I)

• Damped Lyman-Absorbers (DLAs): N(HI) > 2x1020 cm-2

• Lyman Limit Systems (LLSs): N(HI) > 2x1017 cm-2

• sub-LLSs: (low redshift forest!) N(HI) < 6x1016 cm-2

eg. Biosse’ etal (1998); Rao & Turnshek (2000); Churchill etal (2000b)

eg. Steidel & Sargent (1992); Churchill etal (2000a)

eg. Churchill & Le Brun (1998); Churchill etal (1999); Rigby etal (2001)

Mg II selection probes a wide range of astrophysical sites where star formation has enriched gas; these sites can be traced from redshift 0 to 5

Mg II -process ion – Type II SNe – enrichment from first stars (<1 Myr)

Fe II iron-group ion – Type Ia SNe – late stellar evolution (>few Gyr)

Mg II 2796 Absorption Profiles from HIRES/Keck

(Cwc & Vogt 2001)

Mg II 2796 Absorption Profiles from HIRES/Keck

Each Mg II system has several Fe II transitions and Mg I (neutral)

The clouds are modeled using Voigt profile decomposition…

Obtain number of clouds, temperatures, column densities, ionization conditions (from modeling)…

Ultimately, The UV and IR Spectra Are Required

Mg II System in Full Glory

(Cwc & Charlton 1999)

Mg II 2796 Absorption Profiles from HIRES/Keck

Galaxy redshifts can be matched to the absorbers…

(Cwc 2001)

Simple Kinematic Models of Absorbing Gas from Galaxies

Absorption kinematics is symmetric about the galaxy’s systemic velocity

Absorption kinematics is offset in the direction of stellar rotation compared to the galaxy’s systemic velocity

Halo/infall + Rotating/disk produces both signatures in single profile

(Charlton & Cwc 1998)

Q0827+243 Q1038+064 Q1148+387

(Steidel etal 2002)

A New Taxonomy of Absorbers: How do they evolve?

A multivariate (multi-dimensional) analysis, including cluster-tree analysis, yielded 5 classes of Mg II selected absorbers based upon the Lya, Fe II, Mg II, C IV strengths and Mg II kinematics…

Tree Diagram

(Cwc etal 2000)

A New Taxonomy of Absorbers: How do they evolve?

It is driven by kinematics, as seen on the C IV – Mg II plane!What can we learn about the chemical and ionization conditions?What can we learn about environment and evolution?

(Cwc etal 2000)

Mg II Kinematics and Higher Ionization: Multiphase Ionization

STIS/HST

The C IV, N V, and O VI arise in a separate ionization ionization phase- models of Mg II clouds cannot produce higher ionization absorption…

WIYN image of Q1206 field shows four galaxies…

Group environment absorbers, or galaxy hosted absorbers?

(Cwc & Charlton 1999; Ding etal 2003)

Kinematics: Stellar, Mg II 2796, and C IV 1548, 1551

Mg II traces stellar kinematics yet is difficult to explain as extended disk rotation (at 72 kpc impact parameter!). C IV traces Mg II kinematics but has strongest component at galaxy’s systemic velocity, as highlighted in 1551.

What physical entity is giving rise to this C IV component?

(Cwc 2003; Cwc etal, in prep)

Population of Weak Systems: Where do they arise?

1. Their equivalent width distribution follows a power law down to 0.02 A

2. Arise in optically thin H I (Ly clouds)

25%-100% of all Lya clouds with column densities 1015.5<N(HI)<1016.5 cm-2

3. Constrained to not have supersolar metallicity, almost all have z>0.1 solar

4. Many are iron rich, suggesting later stages of star formation

5. 90% cannot be associated with galaxies (within 70 kpc)

(Cwc etal 1999; Rigby etal 2002)

LBT: A Quasar Spectroscopy-Galaxy Evolution Machine

PEPSI ……………………………….. High resolution spectra of QSOsWide Field Prime Focus Cam ……….. Images of QSO fields to find galaxy candidatesMulti-Object Double spectrograph ….. Spectra to confirm galaxy candidates, kinematicsLucifer ……………………………….. Near infrared spectra of QSOs (high z!)

Present Day Coverage and Astrophysical Context

Equivalent Width Distribution

Differential Number Density Distribution

Redshift Path Density

Using HIRES/Keck, we discovered that the EW distribution followed a power law, with no observable cut off down to W=0.02 A. - these are high metallicity “forest” clouds.

5 papers over 10 years predicted that none of these “weak” systems existed! They outnumber galaxies by 1:106.

As the lower EW cutoff of the sample, Wmin, is increased, the number of systems per unit redshift decreases…

(As Wmin increases, the mean redshift increases – ) differential redshift evolution

Comoving redshift path density is consistent with no structure/ionization evolution for Wmin=0.02 A (red) and Wmin=0.3 A (blue).

dN/dz ~ n(1+z) .

Evolution of Strongest Systems

As Wmin increased – evolution is stronger

dN/dz = N0(1+z)

What is the nature of the evolution???

Is it related to high velocity clouds, presence of supperbubbles, or superwinds???

REDSHIFT

Scenario of kinematic evolution of gas…

Present Day Coverage and Astrophysical Context

The epochs of greatest evolution are un-probed…

(Based upon Pei etal 1999)

(stars)

(gas)

(baryons)(gas flow)

(IGM metals)

No coverage for Mg II for z>2.2No high resolution coverage for Mg II for z>1.4

Mg II provides metalicity for high-z forest in lower ionization gas- heretofore un-probed

Constraints on Global Galaxy Evolution Models

(Pei etal 1999)

Unleashing LUCIFER’s Powers (R=5000)

J=19 z=4.2 Quasar: R=10,000 (0.1 arcsec/pix, t=2.5hrs)

Simulated Mg II systems at z=3.13 and z=3.71 in the J-band

Unleashing LUCIFER’s Powers (R=10,000)

These observations are challenging; but all the far UV transitions can be observed in the optical! So, wholesale analysis can be performed…

(Kobayashi etal 2002)

Constraints on Correlated Supernovae: Superbubbles

As bubble expands, nears side is blue shifted and far side is redshifted to give uniform velocity splittings; ~4 superbubbles at z=0.7446!

Local Example of Superbubble!

• These are generated by 50-1000 SNe exploding in a time frame of 105 yr;

• Expansion rate depends upon ratio of SNe power to ISM density

(Bond etal 2001)

Constraints on Correlated Supernovae: Superbubbles

Constrained quantities: ratio of L38 = energy released by SNe in units of 1038 erg/s n0 = density of ISM in units of atoms cm-3

(Rauch etal 2002)

Constraints on Correlated Supernovae: Superbubbles

(Rauch etal 2003)

(Bond etal 2002)

Constraints on Nuclear Activity: Superwinds

Starburst Galaxies are strong H emitters: by associating H emitters with superwinds we can constrain the evolution of galactic superwinds (Bond et al.)

The profiles (right) are similar to those observed for local starburst/superwind galaxies

(coutesy D. Strickland)

(Bond etal 2002)

Build the Database and the Simulations will Follow

Ultimately, the simulations need to be driven by the data… as we have seen the great successes in this arena for the Lya forest to z=5, and are seeing the new successes for metal enriched diffuse objects to z=5….

We will begin to see the successes of galaxy evolution in more detail, including structure evolution, kinematics, metallicity, and ionization. The data are lacking.Wholesale inventory of Mg II absorbers is the best approach.

(courtesy M. Steinmetz)(courtesy M. Haehnelt)

Evidence For Cosmological Evolution of the Fine Structure Constant?

= (z-0)/0

= e2/hc

Relativistic shift of the central line in the multiplet

Procedure1. Compare heavy (Z~30) and light (Z<10) atoms, OR

2. Compare s p and d p transitions in heavy atoms.

Shifts can be of opposite sign.

Illustrative formula:

1qEE2

0

z0zz

Ez=0 is the laboratory frequency. 2nd term is non-zero only if has changed. q is derived from relativistic many-body calculations.

)S.L(KQq K is the spin-orbit splitting parameter.

Numerical examples:

Z=26 (s p) FeII 2383A: = 38458.987(2) + 1449x

Z=12 (s p) MgII 2796A: = 35669.298(2) + 120x

Z=24 (d p) CrII 2066A: = 48398.666(2) - 1267xwhere x = z02 - 1 MgII “anchor”

/ = -5×10-5High-z Low-z

Uncorrected: Quoted Results

The End