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Constraining Evolving Metallicities in high-z ULIRGs

Constraining Evolving Metallicities in high-z ULIRGs. Susannah Alaghband-Zadeh Scott Chapman Institute of Astronomy, Cambridge. Outline. Background on Metallicity [ F(NeIII )/F(OII)] as a metallicity indicator Mass-Metallicity results in high- z ULIRGs Simulations and future.

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Constraining Evolving Metallicities in high-z ULIRGs

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  1. Constraining Evolving Metallicities in high-z ULIRGs Susannah Alaghband-Zadeh Scott Chapman Institute of Astronomy, Cambridge

  2. Outline • Background on Metallicity • [F(NeIII)/F(OII)] as a metallicity indicator • Mass-Metallicity results in high-zULIRGs • Simulations and future

  3. Mass-Metallicity Relation Locally: Tremonti et al (2004)‏ SDSS‏ z=0.7: Savaglio et al (2005)‏ z=2.2: Erb et al (2006)‏ LBGs z=3.5: Maiolino et al (2008)‏ LBGs

  4. High-z ULIRG metallicities Where do high-z ULIRGS fit into mass-metallicity relations? ULIRGS: Galaxies with LFIR > 1012Lʘ and extremely high SFRs Simulations: • Davé et al. (2010) Massive galaxies being harassed by smaller fragments lower metallicities at given M* • Narayanan et al. (2009) Hydrodynamical simulations Mergers ULIRG phase at different stages in merger spread in metallicities

  5. SMGs and SFRGs 2 populations of high-z ULIRGS Selected by submm and radio emission This work: • Robustly detected radio sources with JCMT/ SCUBA 850μm measurements • If >3σ Submm Galaxy • Otherwise Submm Faint Radio Galaxy Keck-II DEep Imaging Multi-Object Spectrograph (DEIMOS) VLT-Infrared Spectrograph And Array Camera (ISAAC) Blue: SMGs Red: SFRGs X: AGN Magnelli et al. (2010) Herschel

  6. Redshift Distribution • Motivation for this • Keck-DEIMOS survey: • Fill in redshift-desert • Calibrate [NeIII]/[OII] as metallicity indicator SMGs SFRGs

  7. Metallicity Indicators • NII/Hα – atmospheric windows at z~1,1.5,2.3 • Why F([NeIII])/F([OII]) may be good (Nagao et al. 2006, Maiolino et al. 2008): • lines not separated by large wavelength • can be observed from the ground up to high z • low metallicity galaxies characterized by higher S/N • The two compliment each other well

  8. Metallicity indicators Maiolino et al. (2008)

  9. Modelling [NeIII]/[OII] as metallicity indicator SDSS (see Kewley et al. (2006)) • Photoionization models: • Instantaneous starburst of age 3x106yrs • Models of Levesque et al. (2010) • Plotted using ITERA – Groves and Allen et al. (2010) Galaxies must have decreasing metallicity WITH increasing ionization parameter [NeIII]/[OII] is good indicator of metallicity

  10. Photometry and Stellar Masses • M* estimates from H-band magnitude and mass to light ratio of 5.6 (Hainline et al 2010) • Photometric points covering the rest-frame 1.6μm (peak stellar emission) • HYPERZ photometric code (Bolzonella et al. 2009) Photometry from: Spitzer-IRAC, Dye et al. (2008), Clements et al. (2008), Cirasuolo et al. (2010), Pope et al. (2006), Giavalisco et al. (2004)

  11. AGN diagnostics • [NeV] detected • [NeIII]/[OII] > 0.5 • Match to Xray catalogs Brunner et al. (2008), Ueda et al. (2008), Waskett et al. (2004) • 8μm excess from HYPERZ SED fit (>3σ)

  12. Mass-Metallicity Results NeII not detected: 12+log(O/H)>8.95 log(M/M)=10.35±0.41 NeIII detected: 12+log(O/H)=8.13±0.11 log(M/M)=10.11±0.26 Overlap sample with ISAAC Hα and NII observations match well Redshift tracks: -Maiolino et al. (2008) -AEGIS dataset Limits (ASURV): <12+log(O/H)>=8.841±0.084 <log(M/M)>=10.30±0.39

  13. Mass-Metallicity Discussion • Large scatter: • rapid evolution • wide range of properties • merger • not seen locally and in LBGs • Limits imply high metallicity: • selections effects/bias? • extreme starburst? • 3 low metallicity sources: • - Similar to Peeples et al. (2009) • - Low metallicity gas flows to centre from outskirts

  14. Future ***Preliminary results*** • Increase sample and use multiple indicators • ~100 ULIRGS • Mass – metallicity relation evolution Combines: Swinbank et al. (2004) Takata et al. (2006) DEIMOS survey ISAAC survey – 4 nights done + 7 upcoming

  15. Future: Expanding the sample 44hr Gemini – NIFS (Near-Infrared Integral Field Spectrometer) Data like Swinbank et al. 2005,2006 but for >10 sources CFRS 03.15 N2.4

  16. Future: Simulations • Look at simulation outputs and compare to observed Universe • Identify trigger of ULIRG phase Collaboration with Romeel Dave and Desika Narayanan

  17. Conclusions • [NeIII]/[OII] makes a good metallicity indicator for high – z SMGs and SFRGs • Sample observed with DEIMOS fills z desert • Large scatter in metallicities • Evidence for low metallicity gas in 3 sources • Limits place mass-metallicity relation above the coeval track • Sample will be expanded • Use metallicity information and simulation outputs to identify ULIRG trigger

  18. VLT-ISAAC spectra

  19. VLT-ISAAC results Overlapping sample with NII/Hα observations Upper limit if NII not detected Limits: - Match in 2 sources - Reversed in 1 source Combined scatter in conversion is large

  20. Observations Keck-II DEep Imaging Multi-Object Spectrograph (DEIMOS) • wavelength range 0.56-0.98μm • redshifts from OII + other emission and absorption lines VLT-Infrared Spectrograph And Array Camera (ISAAC) • 0.6’’ slit + instrumental FWHM of 16Å – velocity resolution of ~200km/s at Hα (redshifted)

  21. AGN and SMG/SFRG Differences SMGs: <12+log(O/H)>=8.638±0.171 <log(M/M)>=10.47±0.38 SFRGs: <12+log(O/H)>=8.925±0.038 <log(M/M)>=10.18±0.36 • 3 SFRGs observed with Herschel: • Lock493, Lock437, Lock517 • All classified as AGN • BUT Lock493 and Lock 517 are luminous in farIR • Active star formers! • SFRGs marked as AGN may not be AGN dominated • Cannot use [NeIII]/[OII] for metallicity in these cases

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