No More Active Galactic Nuclei in Clumpy Disks Than in Smooth Galaxies
  at z~2 in CANDELS / 3D-HST
  We use CANDELS imaging, 3D-HST spectroscopy, and Chandra X-ray data to
investigate if active galactic nuclei (AGNs) are preferentially fueled by
violent disk instabilities funneling gas into galaxy centers at 1.3<z<2.4. We
select galaxies undergoing gravitational instabilities using the number of
clumps and degree of patchiness as proxies. The CANDELS visual classification
system is used to identify 44 clumpy disk galaxies, along with mass-matched
comparison samples of smooth and intermediate morphology galaxies. We note
that, despite being being mass-matched and having similar star formation rates,
the smoother galaxies tend to be smaller disks with more prominent bulges
compared to the clumpy galaxies. The lack of smooth extended disks is probably
a general feature of the z~2 galaxy population, and means we cannot directly
compare with the clumpy and smooth extended disks observed at lower redshift.
We find that z~2 clumpy galaxies have slightly enhanced AGN fractions selected
by integrated line ratios (in the mass-excitation method), but the spatially
resolved line ratios indicate this is likely due to extended phenomena rather
than nuclear AGNs. Meanwhile the X-ray data show that clumpy, smooth, and
intermediate galaxies have nearly indistinguishable AGN fractions derived from
both individual detections and stacked non-detections. The data demonstrate
that AGN fueling modes at z~1.85 - whether violent disk instabilities or
secular processes - are as efficient in smooth galaxies as they are in clumpy
galaxies.
