IAPToulouse 3/19/09Hakim ATEK Lyman-alpha Emitters in the Local Universe Atelier MUSE – Toulouse, 19 mars 2009 Hakim ATEK Daniel Kunth, Matthew Hayes, Claus Leitherer, J. Miguel Mas-Hesse, Göran Östlin, Artashes Petrosian, Daniel Schaerer, Anne Verhamme

IAPToulouse 3/19/09Hakim ATEK The Lyman-alpha Puzzle  Early observations with IUE: Ly  was not detected in many cases A damped absorption was observed instead When detected, Ly  was well below the theoritical value predicted by recombination theory Which factors are actually driving the visibility of Lyman-alpha emission in star-forming galaxies ? This question will remain unclear after the IUE era …

IAPToulouse 3/19/09Hakim ATEK The Lyman-alpha Puzzle  Attempts to solve the puzzle in the early 90’s Charlot & Fall (1993) Giavalisco et al. (1996) Attenuation by dust : Only very early starbursts are detectable ? -- Ly  NOT correlated with dust -- Ly  emission, even after extinction correction, is still below CASE B

IAPToulouse 3/19/09Hakim ATEK New Insight with HST/GHRS High resolution spectroscopy with HST/GHRS of local BCGs:  First results by Kunth et al. (1994) : Very low metallicity and dust deficient galaxy IZw 18 : A prominent Ly  emission is expected for a young unevolved starburst IZw18 [O/H] =-1.66 W Ly  <- 30Å Suprisingly, a strong damped absorption is observed

IAPToulouse 3/19/09Hakim ATEK New Insight with HST/GHRS  Similar results by Thuan and Izotov (1997) : Low metallicity BCGs SBS & Tol 65 A prominent Ly  emission was found in a more metallic and dusty starburst Haro 2 Lequeux et al. 1995

IAPToulouse 3/19/09Hakim ATEK GHRS Sample of BCGs: The Role of Kinematics  8 local BCGs: 4 Ly  emitters, 4 absorbers In all Ly  emitters the neutral, metallic absorption lines were blueshifted by km/s. In the damped systems, the neutral absorptions were always at the systemic velocities All Ly  emission lines showed a clear P Cyg profile, indicating the presence of an expanding shell of neutral gas.  The profiles could be well fitted assuming the measured expansion velocity Kunth et al. 1998

IAP Lyman Break Galaxies: have P-Cyg profiles superwinds of neutral gas at z ~ 3 : outflows are ubiquitous Only 25% of the LBG sample show Lya in emission !! Shapley et al Lyman Break Galaxies Toulouse 3/19/09Hakim ATEK

IAPToulouse 3/19/09Hakim ATEK HST/STIS: Spatial Analysis  Long slit spectroscopy with STIS To map the kinematics of the neutral gas In 3 galaxies: Mas-Hesse et al. (2003) Ly  emission extends over more than 10” (~1 kpc) Large expanding shell in 2 cases with An ionised front in IRAS associated With a secondary Ly  emission No leaking photons from IZw 18 over the whole slit The visibility of Lya might be driven mostly by the neutral gas distribution (porosity) and kinematics

IAPToulouse 3/19/09Hakim ATEK HST/ACS Imaging of Local Starburst Galaxies  Need to map the diffuse Lya emission: complementary to UV-bright targeted spectroscopic studies  Resonant scattering  Emission and absorption at small scale  To infer the relative importance of the factors regulating the detectability of Lya emission Emission “Absorption” Haro 2 (STIS)Haro 11 (ACS) Kunth et al. 2003

IAPToulouse 3/19/09Hakim ATEK HST/ACS Imaging : Pilot Study  6 selected local galaxies : < z < orbits in total ” sampling  span a range of : - Lya morphology and profiles - Luminosity and metallicity - dust  Preliminary results: - Complex emission + absorption - Lya emission with no continuum counterpart - Global damped absorption Continuum subtraction issue Kunth et al HST / ACS / F550M MBMB Z

IAPToulouse 3/19/09Hakim ATEK HST/ACS Imaging: SBC Observations F122M F140LP Haro 11 SBS 0335 IRAS 08 Tol 65 NGC 6090 ESO 338  = -2  = +1  = 0

IAPToulouse 3/19/09Hakim ATEK HST/ACS Imaging Continuum subtraction technique

IAPToulouse 3/19/09Hakim ATEK HST/ACS Imaging Results: Haro 11 FUV H  Ly  Net Ly  emitter Ly  does NOT resemble FUV Ly  does NOT resemble H  90% of flux in diffuse compnt. (Hayes et al. 2007a; Östlin et al. 2007)

IAPToulouse 3/19/09Hakim ATEK HST/ACS Imaging Results: ESO FUV H  Ly  Net Ly  emitter Ly  largely symmetric around one knot Ly  uncorrelated with H 

IAPToulouse 3/19/09Hakim ATEK HST/ACS Imaging Results: SBS FUV H  Ly  Net Ly  absorber Ring-like Ly  leakage Ha follows FUV tightly Lya almost exact mirror

IAPToulouse 3/19/09Hakim ATEK HST/ACS Imaging Results: IRAS FUV H  Ly  Strong nuclear emission Diffuse component

IAPToulouse 3/19/09Hakim ATEK HST/ACS Imaging Results: NGC 6090 FUV H  Ly  Strong + diffuse Lya from NE core Weak diffuse surrounding SW Brightest Ha region not the brightest in Lya

IAPToulouse 3/19/09Hakim ATEK The Role of Dust in Lya Obscuration: Haro 11 Diffuse emission component independent of the dust Emission from knot C with E(B-V) ~ 0.4 Absorption from knot A with E(B-V) ~ 0.2 EW(Ly  ) vs EW(H  ) Ly  /H  above the theoretical value (8.7 case B extinction corrected)  enhanced Ly  /H  ratio Neufeld, 1991

IAPToulouse 3/19/09Hakim ATEK The Role of Dust in Lya Obscuration: IRAS Spread Ly  emission over the extinction range No correlation EW(Ly  ) EW(H  ) Ly  /H  independent of the extinction  Role of the gas kinematics

IAPToulouse 3/19/09Hakim ATEK The Role of Dust in Lya Obscuration: SBS 0335 Absoprtion correlates with extinction  Role of the static column density EW(Ly  ) declines with the dust content

IAPToulouse 3/19/09Hakim ATEK HST/ACS Imaging Results  Escape fraction decreases with dust No clear correlation between EW(Ly  ) and dust  Different evolutionnary effects :  mixed effects: EW(lya) should be not correlated with age

IAPToulouse 3/19/09Hakim ATEK HST/ACS Imaging Results  Star Formation Rate calibration : What fraction of Ly  photons actually escape from the starburst ? simple dust correction of Ly  luminosity fails to recover the intrinsic SFR ! Atek et al. 2008

IAP Lya from emission to absorption - Profile well fitted with a shell model using observational constraints on Hi column density and dust - Considering observer’s sight-line and N(H)=4x10^21 cm-2 damped absorption is reproduced with NO DUST E(B-V) = 0 - Lya absorbers : with static and high N(Hi) only a small amount of dust is needed to suppress Lya emission - Lya emitters : in presence of outflows high N(Hi) and high dust content is needed. A young, metal- and dust-poor galaxy shows a strong damped absorption !! (atek et al. 2009a)

IAP Lya from emission to absorption Radiation transport of Lya explains the observed profile variations across the galaxy

IAP LAEs number density MUSE Prospects  Need to observe galaxies at higher redshift  Is the evolution of fesc ratio always related to the dust content ? Lya variations at a small scale Emission/absorption usually not local Variety of profiles (The case of P Cygni) High spatial resolution needed (AO, space facilities) IFU mode capabilities with high sampling Investigate spectroscopically the ISM kinematics complementary to GALEX sample at z ~ 0.3 (atek et al. 2009b) Verhamme et al 2008 Toulouse 3/19/09Hakim ATEK

IAP LAEs number density Le Delliou et al. (2005) Discrepancy between models and observations now less severe: Past: - Completeness limit (instr. Sensitivity) - Radiation transfer effects Now: New instrumental capabilities and detection techniques and new models seem to converge with actual observations BUT models assumptions still too simple e.g : using a constant escape fraction … LAEs number density Toulouse 3/19/09Hakim ATEK Nagamine et al. (2008)

IAPToulouse 3/19/09Hakim ATEK Summary  Reliability of Lya emission as a COSMOLOGICAL TOOL ? Lya escape is multi-parameter process :  Intrinsic EW(Lya) (age, mass)  Line broadening  Static HI coverage: Lya greatly attenuated by dust  Out flowing HI gas: effect of dust is reduced  Multi-phase medium: Lya escape if favored  Low escape fractions (< 15%) -- dust corrections fail  New routes to SFR(Lya) calibration !! Demonstrates the need for a detailed, statistically significant investigation !! Instrinsic Emission Radiation Transfer