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The Starburst-AGN Connection Among COSMOS ( U)LIRGs

Jeyhan Kartaltepe - NOAO COSMOS Meeting – IfA, Honolulu, HI 2010 June 8. The Starburst-AGN Connection Among COSMOS ( U)LIRGs. D. Sanders, V. Smolcic, L. Kewley, M. Salvato, P. Capak, E. Le Floc’h, H. Aussel, D. Frayer et al. COSMOS 70 m m Sample. Paper I

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The Starburst-AGN Connection Among COSMOS ( U)LIRGs

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  1. Jeyhan Kartaltepe - NOAO COSMOS Meeting – IfA, Honolulu, HI 2010 June 8 The Starburst-AGN Connection Among COSMOS (U)LIRGs D. Sanders, V. Smolcic, L. Kewley, M. Salvato, P. Capak, E. Le Floc’h, H. Aussel, D. Frayer et al.

  2. COSMOS 70 mm Sample • Paper I • SEDs  Kartaltepe et al. 2010, ApJ, 709, 572 • Paper II • Morphology  re-submitted, should hear back any day • Next… • The Starburst-AGN Connection Among COSMOS (U)LIRGs • Focus on optical spectroscopy out to z~1

  3. The Starburst-AGN Connection • Starburst/AGN activity are directly linked • Together may regulate black hole/bulge growth in galaxies • Luminous infrared galaxies have high luminosities due to dust enshrouded SF/AGN activity • Each contribute to the bolometric luminosity • How can we separate the two? • What can we do with existing optical spectroscopy?

  4. COSMOS 70 mm Sample • 1503 sources with 0 < z < 3 • Spectroscopy for ~40% • zCOSMOS, DEIMOS, etc. • Eventual goal:correlate activity with luminosity/morphology HyLIRGs ULIRGs log (LIR) LIRGs Redshift (z)

  5. AGN Selection Methods • X-ray luminosity • Radio power • SED shape (i.e., Power-law) • IRAC colors • Infrared to optical ratio (e.g., Fiore et al. 2008, Dey et al. 2008) • Spectroscopic diagnostics

  6. Fraction of Sources with AGN Signatures 100% for HyLIRGs >70% for ULIRGs AGN Fraction 5% at low LIR log (LIR)

  7. At low redshift…. • At low redshift, can classify 135 galaxies using standard line diagnostics • 0 < z < 0.5 (where Ha still observable, 18% of sample at these redshifts) • log(LIR) = 8.8 – 11.7, <log(LIR)> = 10.6

  8. At low redshift…. • 8 (6%) classified as AGN • 34 (25%) classified as composite • 93 (69%) classified as star forming •  Many more sources identified as AGN through spectroscopy than other selection methods

  9. Use color as a proxy for [NII]/Ha? AGN 380 sources (0 < z < 1) 8 sources selected 2 X-ray detected Another 2 (z<0.5) have Ha Both are Seyferts on all 3 low-z diagnostics DEEP2: e.g., Montero-Dorta et al. 2009

  10. Color • Correlation between rest-frame color and galaxy’s position on BPT diagram for radio selected sources • P1 ‘color’ (derived from modified Stromgren system for SDSS galaxies) correlates with metallicity and stellar population, P2 with dust • P1 > 0.15  AGN selection • Appears to work well at low z, results at high z are untested • Is there redshift evolution? • Can composites be separated? Smolcic et al. 2006, 2008

  11. [OII] EW vs. Hb EW 218 Sources (0 < z < 1) 22 sources selected None are AGN by other methods 8 overlap with low-z sample 4 SF on all 3 diagrams Other 4 are either Seyferts, LINERS, or composites on 2 out of 3 DEEP2: e.g.,Yan et al. 2006; Willmer et al. 2006; Montero-Dorta et al. 2009

  12. Future Work • Incorporate new spectra • DEIMOS, 20k sample, etc. • Further tests • Evolution of P1 with redshift • Lamareille et al. (2004, 2010) diagnostics • X-ray stacking • Compare diagnostics with SDSS in the local universe • z > 1 ? • NIR Spectroscopy (FMOS, MOSFIRE, MOIRCS, FLAMINGOS2, etc.)

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