the post-starburst quasars
DESCRIPTION
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?. - PowerPoint PPT PresentationTRANSCRIPT
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?
Brotherton et al. (1999, 2002), Canalizo et al. (2000)
Prototype: UN J1025-0040Nuclear starburst: 400 Myr
Also known as Q+A
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.
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
Post-starburst Quasars in the SDSS
Post-starburst Quasars in the SDSS
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).
PSQ Spectral Modeling: starburst + quasar
PSQ Spectral Modeling: starburst + quasar
PSQ Spectral Modeling: Preliminary results
• 80 objects• 0.25 < z < 0.45• significant starburst
No obvious correlation.
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.
PSQ Environment: SDSS Images
• Resolution 1.4 arcsec• 40 X 40 arcsec• 40% appear to be
interacting or have nearby companions
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?
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
Environment: Number of Companions
No difference.Faint companions?
No difference.Faint companions?
Average Number of Companions:PSQ: 2.12Quasar: 1.82
Environment: Number of Companions
PSQs do not seem to be in a much richer environment than normal quasars in large scale.
PSQ Local Environment: Interacting
SDSS
30”x30”
HST/ACS
PSQ Local Environment: Interacting
SDSS
30”x30”
HST/ACS
PSQ Local Environment: Interacting
SDSS
30”x30”
HST/ACS
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.