Evidence for non-stellar rest-frame near-IR emission associated with
  increased star formation in galaxies at $z \sim 1$
  We explore the presence of non-stellar rest-frame near-IR ($2-5 \ \mu
\mathrm{m}$) emission in galaxies at $z \sim 1$. Previous studies identified
this excess in relatively small samples and suggested that such non-stellar
emission, which could be linked to the $3.3 \ \mu \mathrm{m}$ polycyclic
aromatic hydrocarbons feature or hot dust emission, is associated with an
increased star formation rate (SFR). In this Letter, we confirm and quantify
the presence of an IR excess in a significant fraction of galaxies in the
3D-HST GOODS catalogs. By constructing a matched sample of galaxies with and
without strong non-stellar near-IR emission, we find that galaxies with such
emission are predominantly star-forming galaxies. Moreover, star-forming
galaxies with an excess show increased mid- and far-IR and H$\alpha$ emission
compared to other star-forming galaxies without. While galaxies with a near-IR
excess show a larger fraction of individually detected X-ray active galactic
nuclei (AGNs), an X-ray stacking analysis, together with the IR-colors and
H$\alpha$ profiles, shows that AGNs are unlikely to be the dominant source of
the excess in the majority of galaxies. Our results suggest that non-stellar
near-IR emission is linked to increased SFRs and is ubiquitous among
star-forming galaxies. As such, the near-IR emission might be a powerful tool
to measure SFRs in the era of the James Webb Space Telescope.
