The merger-AGN connection since z~1: causal or circumstantial? Mauricio Cisternas MPIA, Heidelberg COSMOS Meeting IfA, 09/06/2010 + K. Jahnke, K. Inskip, A. Robaina (MPIA) T. Lisker, J. Kartaltepe, A. Koekemoer, M. Scodeggio, J. Trump, K. Sheth

Co-evolution Scaling relations: “proof” for the tied growth of galaxies and their supermassive black holes BH mass: built up during a quasar phase But, what triggers a quasar? z=0 Häring & Rix (2004) MBH/Msun M* /Msun Step 1 Step 2 Step 3 Major mergers Minor mergers Large scale bars Nuclear bars ISM turbulence … -When I say quasar, I mean high luminosity end, actively accreting AGN -What triggers a qso, or what can bring gas to pc scales ???

Appealing scenario: major mergers BUT: Are those representative samples of QSOs? High frequency of mergers compared to what? Signatures heavily dependant on bandpass, image depth Since the 80’s, observations have found: quasars with close companions post merger features on their host galaxies “High frequency of mergers” How is the “merging galaxy” status achieved? After *…depth* stop, say we need an apple to apple comparison blah COSMOS AGN

Our approach We study the distortions of a sample of AGN host galaxies. But, what makes us special? The Data ~2000 X-ray sources detected with XMM and Chandra Classification as type-1/2 from spectroscopic surveys and SED fitting Optical counterparts: HST/ACS Solid sample of 140 type-1/2 (IAB<24, 0.3< z <1) -AGN best detected by xray emission -add redshift, I band

Our approach 2) Comparison Sample Active Galaxy 2) Comparison Sample The key measurement: not just the merger fraction of the AGN hosts, but the enhancement of merging over the “background level” ~10 inactive galaxies per active galaxy Compiled from the same dataset Matched in redshift and brightness (including special treatment for the type-1 AGN) Control Sample

Our approach 3) Visual Classification Smooth 3) Visual Classification No definitive way to identify mergers automatically... …then let’s do it by eye (& brain)! Basically: Hubble type Distortion level Consistency: We use 10 independent classifiers (people) We classify blindly: mixing the AGN hosts with the inactive galaxies Mildly distorted Replace with classes Strongly distorted

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The Result Mean difference between the distortion fractions: 2.4% ± 3.6% This means: No enhancement in the merger fraction of AGN host galaxies over the background level

The K-S test can’t distinct between the 2 sets of measurements The Result The K-S test can’t distinct between the 2 sets of measurements

“AGN do not prefer to live in merging systems” This result allows for 2 possible interpretations: There is a significant time-lag between merging and AGN triggering… … or major merging is not the main fueling mechanism AGN lifetime: Merger timescale: If (1), then what about observed mergers? time

Clues from the Hubble sequence Hubble-type classification: ~60% of AGN hosted by galaxies with a significant disk Since z~1: Methods that do not involve destruction of the disk dominate Minor mergers, accretion of surrounding gas, bar instabilities, nuclear bars, SN explosions, … Tied growth of BHs and their host galaxies? not so much (Preprint coming soon)

Quasar-host galaxy decomposition with GALFIT (originals) z=0.67 z=0.74 z=0.91 (models) (host galaxies)

Comparison sample: creating mock AGN Procedure: i) For each type-1 AGN, we select 10 inactive galaxies that match in redshift and magnitude ii) Using the Host/Nucleus flux relation for a given AGN, we search for a star that fits that ratio against the inactive galaxy iii) By adding the star on top of the galaxy, we create a mock AGN iv) We treat our mock AGN exactly the same way as the original ones, which yields to a set of galaxies with the same conditions than our hosts + (inactive galaxy) (star) = (mock AGN) (galaxy + residuals)

To recap… Some advertising AGN host galaxies show virtually the same frequency of distortions than inactive galaxies Large fraction of disks on our AGN sample implies alternative fueling methods not caused by recent major mergers Since z~1, merging and quasar activity disconnect Preprint coming soon… Some advertising Just today at astro-ph: “The non-causal origin of the black hole-galaxy scaling relations” K. Jahnke & A. Maccio (arXiv:1006.0482) www.mpia.de/coevolution