Unhidden monsters: Are unobscured quasars the late stages of obscured quasar activity? Carolin Villforth University of Bath! Timothy Hamilton (Schawnee State), M. Pawlik, T. Hewlett, K. Rowlands (St Andrews), H. Herbst (University of Florida), F. Shankar (Southampton), A. Koekemoer (STScI), F. Hamann (Florida/UC Riverside)
Triggering AGN: Possible Mechanisms funnel cold gas (~ 10-4 -10 M / yr) into the center accretion rate scales with AGN luminosity strip the gas of angular momentum (by about 10 5 ) Mergers? Luminous AGN? Bars? Secular Processes? Low luminosity AGN?
galaxy (gas-rich or poor), inactive black hole AGN fueling event gas supplied and/or driven to central kpc Δt AGN triggering event gas driven to pc scale Central starburst? Δt Δt AGN!! AGN Phase Feedback?
galaxy (gas-rich or poor), inactive black hole AGN fueling event gas supplied and/or driven to central kpc Δt AGN triggering event gas driven to pc scale Central starburst? Δt Δt AGN!! AGN Phase Feedback?
galaxy (gas-rich or poor), inactive black hole AGN triggering event gas driven to pc scale Δt Δt Obscured AGN AGN fueling event gas supplied and/or driven to central kpc Central starburst? Unobscured AGN Δt
>1/3 Do major mergers trigger luminous unobscured AGN? optical + X-ray log(lbol) 45.5 Are the hosts of luminous unobscured AGN consistent with late mergers? later than supposed transition population, but not exceeding AGN lifetimes Alexander & Hickox 2012
Do mergers only matter for luminous unobscured AGN? 20 SDSS Quasars at z=0.6 HST WFC3 IR H Imaging Villforth et al. to be submitted
z ~ 0.6 Lbol ~10 46 erg/s Villforth et al. to be submitted
Luminous AGN Hosts: Merger features Villforth et al. to be submitted
Methodology 2D decomposition (15/20 hosts resolved) Sersic indices indicate a small majority of disks over bulges control sample from CANDELS matched in absolute magnitude, tracing the old stellar population create fake AGN by adding point sources and refitting quantitative and qualitative morphological analysis Villforth et al. to be submitted
Quantitative morphology measures No statistically significant differences (p>>0.05) Villforth et al. to be submitted
Visual Classification Morphologies of AGN hosts consistent with those of control galaxies, even at high luminosities Undisturbed Disturbed Strong PSF Merger Villforth et al. to be submitted
Are the 5 unresolved AGN hiding a major merger signature? Visual Inspection: unresolved AGN are visually inspected, merger features seen in the resolved sample would be visible in 3/5 sources, assuming the 2 others hide major mergers, still no significant difference No Quantitative Morphology: assuming all unresolved AGN have the 5 highest asymmetries measured in the whole sample, still no significant difference No
Constraints on merger properties! visible merger features consistent with major (>1/3) mergers up to 500 Myr-1 Gyr after coalescence (Ji et al. 2015)! data sensitive to such features, more minor mergers and later times unconstrained
How do the merger fractions compare? Not all luminous AGN connected to major mergers (see also Mechtley et al. 2016 for z=2) Glikman et al. 2016
The Host Galaxies of obscured AGN Urrutia+2008: major mergers (post-coalescence) High AV Glikman+2015: mergers High AV Compton Thick DOGs??? Herbst+in prep (talk earlier): some mergers in FeLoBAL hosts, but not ubiquitous Schawinski+2012: Disks, not mergers
Merger obscured unobscured AGN Three concessions to the cartoon Minor Mergers: μ ~ 1/10 Long Delays: Δt > 0.5-1Gyr Different populations Alexander & Hickox 2012
Summary No significant increase of major merger fractions in host galaxies of unobscured AGN up to high luminosities. lack of observed connection not due to unresolved AGN in sample major merger features up to ~1Gyr should be detected in our sample Major mergers either not dominant at highest AGN luminosities or delays between merger and onset of AGN activity long (500 Myr -1 Gyr) Inconsistent with post-blow-out phase after major mergers