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Metallicity: A Smoking Gun for Gas Flows in Mergers

Metallicity: A Smoking Gun for Gas Flows in Mergers. Lisa Kewley U. Hawaii. Margaret Geller (SAO), Betsy Barton (UC Irvine). Summary. Motivation Metallicity diagnostics Luminosity-Metallicity Relation Central Star Formation Blue Bulges Merger Models

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Metallicity: A Smoking Gun for Gas Flows in Mergers

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  1. Metallicity: A Smoking Gun for Gas Flows in Mergers Lisa Kewley U. Hawaii Margaret Geller (SAO), Betsy Barton (UC Irvine)

  2. Summary • Motivation • Metallicity diagnostics • Luminosity-Metallicity Relation • Central Star Formation • Blue Bulges • Merger Models • Conclusions & Future Work

  3. Motivation Effect of mergers on metallicity? unknown Predicted gas flows? elusive Fe Si Mg Fabbiano et al. (2004)

  4. Galaxy Pairs • 502 galaxies from the CfA redshift catalog • (v > 2300 km/s, Dv < 1035 km/s, DD < 77 h-1 Mpc) • Nuclear spectra for ~200 galaxies in pairs • (Barton et al. 2000) Field Galaxies • 198 galaxies from the CfA redshift catalog • full range in Hubble type & Magnitudes in CfA survey • (Jansen et al. 2000) • http://cfa-www.harvard.edu/~jansen/nfgs/nfgssample.html

  5. Metallicity Diagnostics “R23” Kewley & Dopita (2002, ApJS, 142, 35) Also: Pagel (1979), McCall et al. (1985), ..., Skillman et al. (1989), McGaugh (1991),..., Zaritsky et al. (1994), Charlot (2001), ...

  6. Galaxy Pairs Luminosity-metallicity Relation 1. shifts for close pairs Kewley, Geller, & Barton (2005, AJ, 131, 2004)

  7. Luminosity Effect? wwide pairs close pairs Need 1-2 Mag rise NFGS cz < 2300 km/s Kewley, Geller, & Barton (2006, AJ, 131, 2004)

  8. Luminosity Effect? wwide pairs No shift in upper bound : MB Negative shift in right bound: metallicity close pairs NFGS cz < 2300 km/s Kewley, Geller, & Barton (2006, AJ, 131, 2004)

  9. Luminosity Effect? R-Band Luminosity-metallicity Relation 1. still shifts for close pairs Kewley, Geller, & Barton (2006, AJ, 131, 2004)

  10. Galaxy Pairs Luminosity-metallicity Relation 1. shifts for close pairs metallicity effect? gas infall? Kewley, Geller, & Barton (2006, AJ, 131, 2004)

  11. Central Burst Strength, SR(t) Barton, Geller & Kenyon (2003): Stellar population synthesis models + colors + EWs assuming 2 populations (old & young) SR(t) = current fraction of R-band light from young burst

  12. Central Burst Strength Barton, Geller & Kenyon (2003)

  13. Galaxy Pairs Luminosity-metallicity Relation 1. shifts for close pairs 2. correlated with central burst strength Kewley, Geller, & Barton (2006, AJ, 131, 2004)

  14. Galaxy Pairs Luminosity-metallicity Relation 1. shifts for close pairs 2. correlated with central burst strength Kewley, Geller, & Barton (2006, AJ, 131, 2004)

  15. Blue Bulges Kannappan et al. (2003): “blue bulge parameter” • (B-R) = (B-R)outer - (B-R)inner where (B-R)outer = (B-R) at 75% light radius (B-R)inner = (B-R) at 1/2 light radius

  16. Galaxy Pairs Blue Bulges Luminosity-metallicity Relation 1. shifts for close pairs 2. correlated with central burst strength 3. correlated with blue bulges Kewley, Geller, & Barton (2006, AJ, 131, 2004)

  17. Metallicity Gradient Keck LRIS Spectroscopy Kewley, Geller, & Barton (2005, AJ, submitted)

  18. Metallicity Gradient Keck LRIS Spectroscopy See also: Li Hsin Chien’s Poster Kewley, Geller, & Barton (2005, AJ, submitted)

  19. Merger Scenario Images Courtesy Chris Mihos

  20. Galaxy Pairs Luminosity-metallicity Relation 1. shifts for close pairs 2. correlated with central burst strength 3. correlated with blue bulges Evidence for Gas Infall Kewley, Geller, & Barton (2006, AJ, 131, 2004)

  21. Metallicity Gradients

  22. Metallicity Gradients M101 Kennicutt, Bresolin & Garnett (2003)

  23. Iono et al. (2004): Simulations predict: 1. Gas inflow rate ~ 7 Mo/yr 2. Gas flows within 1st 100 Myr but before disk merger . Merger Scenario

  24. Iono et al. (2004): Simulations predict: 1. Gas inflow rate ~ 7 Mo/yr 2. Gas flow within 100 Myr but before disk merger . Merger Scenario

  25. Assuming: 1. Gas inflow rate ~ 7 Mo/yr 2. Normal Spiral Metallicity gradient . Merger Scenario How much infalling gas is required?

  26. Assuming: 1. Gas inflow rate ~ 7 Mo/yr 2. Normal Spiral Metallicity gradient . Merger Scenario How much central dilution is required? 50-60% Merger models predict: 60% infall

  27. Assuming: 1. Gas inflow rate ~ 7 Mo/yr 2. Normal Spiral Metallicity gradient 3. Central Gas Mass 108 - 109 Mo ave v. high . Merger Scenario . How long will it take to infall?

  28. Assuming: 1. Gas inflow rate ~ 7 Mo/yr 2. Normal Spiral Metallicity gradient 3. Central Gas Mass 108 - 109 Mo . Merger Scenario . How long will it take to infall? 9x106 - 9x107 years Merger models predict: within 1x108 years

  29. Josefa Perez et al. (2006, astro-ph/0605131) • Chemical evolution model (Scannappieco et al. 2005) • L-CDM model (GADGET-2; Springel & Hernquist 2003) • Lower mean central (O/H) in pairs from inflows New Theoretical Models +

  30. Conclusions • Close galaxy pairs have lower than field • central metallicities • “Smoking gun” for gas infall during merger? • Central metallicity correlates with: • central burst strength • blue bulges • Timescale consistent with current • merger simulations

  31. Future Directions • Keck LRIS spectra of matched pair members • Merger simulations of metallicity gradients

  32. Available Now! Starburst99-Mappings On-LineL. Kewley & C. Leitherer • Starburst99-Mappings Interface: • http://www.stsci.edu/science/starburst99/ • Mappings Interface: • http://www.ifa.hawaii.edu/~kewley/Mappings Pre-run model grids Interactive web form to run models

  33. Motivation Effect of mergers on metallicity is unknown Fe Si Mg Fabbiano et al. (2004)

  34. Metallicity Diagnostic Comparisons Kewley & Ellison (2005)

  35. Metallicity: Strong lines vs Auroral Lines Garnett, Kennicutt, Bresolin

  36. Classification Scheme

  37. 1’ Galaxy Pairs Luminosity-metallicity Relation 1. shifts for close pairs 2. correlated with central burst strength 3. correlated with blue bulges Evidence for Gas Infall Kewley, Geller, & Barton (2005, AJ, submitted)

  38. GOODS Survey: 0.3 < z< 1 Kobulnicky & Kewley (2004, ApJ, 617,240)

  39. Metallicity - [NII]/Ha Pettini & Pagel (2004)

  40. Metallicity Diagnostics 1.Theoretical - photoionization models e.g., McGaugh (1991), Kewley & Dopita (2002), Tremonti et al. (2004) 2.Empirical - fit to Te metallicities e.g., Pilyugin (2000), Pettini & Pagel (2004) Combination - fit to Temethod + theoretical metallicities e.g., Denicolo, Terlevich & Terlevich (2002)

  41. Metallicity - [OIII]/Hb,[NII]/Ha Pettini & Pagel (2004)

  42. Metallicity Diagnostic Comparisons Kewley & Ellison (2005, in prep)

  43. Metallicity: Strong lines vs Auroral Lines Garnett, Kennicutt, Bresolin

  44. GOODS Survey: 0.3 < z< 1 Kobulnicky & Kewley (2004, ApJ, 617, 240)

  45. Auroral Line Saturation Stasinska (2002,2005)

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