Star Formation in Damped Lyman alpha Systems Art Wolfe Collaborators: J.X. Prochaska, J. C. Howk, E.Gawiser, and K. Nagamine

DLAS are Definition of DLA: N(HI) > 2*10 20 cm -2 Distinguishing characteristic of DLAs : Gas is Neutral

DLAS are Definition: N(HI) > 2*10 20 cm -2 Distinguishing characteristic of DLAs : Gas is Neutral How are DLAs heated?

DLAs Dominate the Neutral Gas Content of the Universe at z=[0,5] Gas Content of DLAs at z=[3,4] Accounts for current visible Mass DLAs Serve as Important Neutral Gas Reservoirs for Star Formation Relevance of DLAs for Star Formation

DLAs Dominate the Neutral Gas Content of the Universe at z=[0,5] Gas Content of DLAs at z=[3,4] Accounts for current visible Mass DLAs Serve as Important Neutral Gas Reservoirs for Star Formation Prochaska, Herbert-Fort, & Wolfe ‘05

DLAs Dominate the Neutral Gas Content of the Universe at z=[0,5] Gas Content of DLAs at z=[3,4] Accounts for current visible Mass DLAs Serve as Important Neutral Gas Reservoirs for Star Formation Current Visible Matter Neutral Gas at High z

Evidence for Star Formation in DLAs? Direct Detection of Starlight Increase of Metallicity with time Evidence for Feedback between Stars and Absorbing Gas

SFRs Inferred from DLA Emission DLARedshiftMethodSFR (M  y -1 ) Ref Ly-alpha> 1.5 Moller etal Ly-alpha0.8 to 7.0 Bunker etal A1.921Cntuum.25 to 50 Moller etal H-alpha< 5.0 Kularni etal H-alpha< 1.6 Kulkarni etal 00

Comparison between DLA and LBG SFRs LBG SFRs between 3 and 100 solar masses per year A few DLAs located at either end of LBG distribution What is SFR Distribution For a fair sample of DLAs?

CII* Technique for Measuring SFRs in DLAs

Outline Heating and Cooling of DLAs Inferring SFRs per unit Area from CII * Absorption Global Constraints SFRs per unit Comoving Volumne Background Radiation Relationship Between DLAs and LBGs

FUV Photon Ionizing Photon Grain Grain Photoeletric Heating of Neutral Gas in DLAS H II Region Electron

Thermal Balance in DLAs

Obtaining Cooling Rates from CII* Absorption [C II] 158 micron transition dominates cooling of neutral gas in Galaxy ISM Spontaneous emission rate per atom l c =n  [CII] obtained from strength of absorption and Lyman alpha absorption Thermal equilibrium condition l c =  pe gives heating rate per atom

HIRES Velocity Profiles of Metal-Rich DLA Multi-component structure of absorbing gas Velocity Structure of CII* and Resonance lines are similar Strength of CII* Absorption gives heating rate of the neutral gas

[C II] 158 micron Emission rates vs N(H I) Median l c = ergs s -1 H -1 for positive Detections Upper limits tend to have low N(H I) DLA l c values about 30 times lower than for Galaxy: explained by lower dust content and similar SFRs per unit area

[C II] 158 micron Emission rates vs N(H I) Critical Emission Rate

Are DLAs Heated by Background Radiation Alone?

Thermal Equilibria: l c versus density

DLAs with Detected N(CII*) l c versus n diagrams

Thermal Equilibria with local FUV Radiation Included

Two-Phase Models of DLAs with Positive Detections WNM CNM “CNM Model” “WNM Model”

DLAs with Upper Limits On N(CII*): l c versus n diagrams

WNM Phase Model for DLAs with Upper Limits WNM

Multi-phase Models and SFRs DLAs with l c > CII* Forms in CNM Phase: moderate SFR/Area 2.CII* Forms in WNM Phase: high SFR/Area DLAs with l c < CII* Forms in WNM Phase: Background Heating Alone 2.CII* Forms in WNM Phase: moderate SFR/Area

Multi-phase Models and SFRs DLAs with l c > CII* Forms in CNM Phase: moderate SFR/ H I Area 2.CII* Forms in WNM Phase: high SFR/ H I Area DLAs with l c < CII* Forms in WNM Phase: Background Heating Alone 2.CII* Forms in WNM Phase: moderate SFR/ H I Area

SFR or Luminosity per unit Comoving volume unit Comoving volume Observed De-reddened Giavalisco etal ‘04

Global Constraints

Consequences of LBG Constraints Most DLA models predict  DLA >>  LBG : high J CII* This rules out models with inefficient heating -All models where CII * absorption occurs in WNM -Models where CII * absorption occurs in CNM gas heated by FUV radiation incident on large grains Even with efficient heating,  DLA =  LBG Strong overlap between DLAs and LBGs 1.DLAs with l c > ergs s -1 H -1

DLAs

LBGs in DLAs with l c > ergs s -1 H -1 LBG Dust DLA

DLA Gas May Replenish LBG Star Formation Activity LBG Star Formation Rate Requires “Fuel” DLA Gas would sustain SFRs for ~ 2 Gyr. Replenishment from IGM may be required

Supporting Evidence for this Scenario 1.Detection of DLA absorption in an LBG 2. Evidence for DLA-LBG cross correlation 3. Evidence for Grain photoelelctric heating 4. Independent Evidence for CNM Gas

An LBG Galaxy Associated with a DLA (Moller etal ‘02) SFR=25 to 50 M  yr -1

An LBG Galaxy Associated with a DLA (Moller etal ‘02) 8.4 kpc Ly  Emission [O III] Emission

Preliminary DLA-LBG Cross-Correlation Function (Cooke etal 2005) LBG-DLA LBG-DLA: r=4.25,  =1.11  LBG-LBG: r=3.96,   =0.15 Mpc

Nature of DLAs with l c < ergs s -1 H - 1

Low CII * Absorption

Implications Implications Local Source of Heat Input Required for the 40% of DLAs with l c > ergs s -1 H -1 These DLAs likely heated by attenuated FUV radiation emitted by embedded LBG. In these DLAs, gas producing CII * absorption is CNM. Background Radiation heats the 60% of DLAs with l c < ergs s -1 H -1. Gas is WNM. LBGs may be in subset of DLAs in which starburst activity occurs. DLA gas may fuel star formation

DLA Age-Metallicity Relationship Sub-solar metals at all z Statistically Significant evidence for increase of metals with time Most DLAs detected at epochs prior to formation of Milky Way Disk Mixed Evidence for star formation

Incidence of DLAs per unit Absorption Distance

Equivalence Between Bulge & Uniform Disk Scenarios Disk Scenario Source Field Bulge Scenario Source Field Mean Intensities: J B =J D if L  H I the same Comoving Luminosity Densities,  B =  D

Bolometric Backgrounds at z=0 due to Sources at z > z min

Multi-phase Diagram for Typical DLA

Evidence Against WNM gas in a DLA SiII * Absorption sensitive to warm gas Absence of SiII * Absorption implies T < 800 K for CII * Gas

Evidence for Grain Photoelectric Heating Statistically significant correlation between l c and dust-to-gas ratio Solid curves are lines of constant J Upper limits are at low Low dust-to-gas ratios