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The Post-starburst Quasars

The Post-starburst Quasars. Zhaohui Shang (University of Wyoming / Tianjin Normal University) Mike Brotherton (University of Wyoming) Aleks Diamond-Stanic (Wyoming/Steward Observatory) Rebecca Stoll (Wyoming/Wellesley) Cassandra Paul (University of Wyoming). Lijiang 8/16/05. What are they?.

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The Post-starburst Quasars

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  1. The Post-starburst Quasars Zhaohui Shang (University of Wyoming / Tianjin Normal University) Mike Brotherton (University of Wyoming) Aleks Diamond-Stanic (Wyoming/Steward Observatory) Rebecca Stoll (Wyoming/Wellesley) Cassandra Paul (University of Wyoming) Lijiang 8/16/05

  2. What are they? Prototype: UN J1025-0040 Nuclear starburst: 400 Myr Also known as Q+A Brotherton et al. (1999, 2002), Canalizo et al. (2000)

  3. Why Important? Direct link between AGN and starburst • Transition Stage in ULIRG to Quasar Evolutionary Schemes (e.g., Sanders et al. 1998)? • Black Hole/Bulge Correlations (M-sigma) Indicate Mutual AGN/Galaxy Evolution (e.g., Ferrarese & Merritt 2000; Gebhardt et al. 2000) • Clocks on Triggers of AGN Activity? • … But post-starburst quasars are rare.

  4. Post-starburst Quasars in the SDSS • More than 16000 quasars in SDSS DR3 • Spectroscopiclly selecting PSQs using the algorithm similar to Zabludoff et al (1996) • Balmer jump strength • Balmer absorption line equivalent widths • Significance of detecting absorption lines We found • 708 candidates in DR3 => 609 post-starburst quasars • a few percent of quasar population

  5. Post-starburst Quasars in the SDSS

  6. Post-starburst Quasars in the SDSS

  7. Post-starburst Quasars in the SDSS SDSS Images of PSQs • Environment/morphology • Looking for companions and interacting/mergering evidence Spectral Modeling of PSQs (starburst + quasar) • Starburst age and mass.Using Bruzual-Charlot stellar models (1996) of solar metalicity. • Quasar black hole mass and Eddington accretion rate L/Ledd.Using quasar emission line width and continuum luminosity + empirical formula from reverberation mapping results (e.g., Kaspi et al 2000).

  8. PSQ Spectral Modeling: starburst + quasar

  9. PSQ Spectral Modeling: starburst + quasar

  10. PSQ Spectral Modeling: Preliminary results • 80 objects • 0.25 < z < 0.45 • significant starburst No obvious correlation.

  11. PSQ Spectral Modeling: Preliminary results • 80 objects • 0.25 < z < 0.45 • significant starburst Results are not conclusive. • Need higher S/N spectra to reduce uncertainties. • Keck spectra are coming.

  12. PSQ Environment: SDSS Images • Resolution 1.4 arcsec • 40 X 40 arcsec • 40% appear to be interacting or have nearby companions

  13. PSQ Environment: SDSS Images • Resolution 1.4 arcsec • 40 X 40 arcsec • 40% appear to be interacting or have nearby companions Sequence? Pre Merger Merging Post Merger Merger Long Over?

  14. PSQ Environment Different from Quasar Enviroment? Searching for companions: within 100 kpc of the objects Set z > 0.1 • PSQ: 541 • Quasar: 15098 For each PSQ: • Find all sources within 100 kpc at the redshift of the PSQ. • Get photometric redshifts of these sources. • Apply K-corrections. • Obtain the radial separations between the sources and the PSQ. • Count the real companions within 100 kpc. For each Quasar: • Same as above

  15. Environment: Number of Companions Average Number of Companions: PSQ: 2.12 Quasar: 1.82 No difference. Faint companions? No difference. Faint companions?

  16. Environment: Number of Companions PSQs do not seem to be in a much richer environment than normal quasars in large scale.

  17. PSQ Local Environment: Interacting SDSS 30”x30” HST/ACS

  18. PSQ Local Environment: Interacting SDSS 30”x30” HST/ACS

  19. PSQ Local Environment: Interacting SDSS 30”x30” HST/ACS

  20. Conclusions • Post-starburst quasars are now found in statistically significant numbers in SDSS. • The large scale enviroment of PSQs is similar to that of normal quasars. • It is likely that PSQs have close companions and show interacting/mergering evidence. • PSQs may reveal the intrisic connection between AGN and starburst and their mutual evolution, allow us to investigate the origin of the M-sigma relationship. Future work • Obtain higher quality spectra to improve modeling. • Combine starburst and quasar properties with morphological information. • Compare post-starburst quasars with normal quasars in physical parameters, such as black hole masses and Eddington accretion rates. • Compare with non-AGN post-starburst systems in the galaxy survey.

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