The environment of QSO triplets at 1 $\lesssim$ z $\lesssim$ 1.5
  We present an analysis of the environment of six QSO triplets at 1 $\lesssim$
z $\lesssim$ 1.5 by analyzing multiband (r,i,z, or g,r,i) images obtained with
Megacam at the CFHT telescope, aiming to investigate whether they are
associated or not with galaxy protoclusters. This was done by using photometric
redshifts trained using the high accuracy photometric redshifts of the
COSMOS2015 catalogue. To improve the quality of our photometric redshift
estimation, we included in our analysis near-infrared photometry (3.6 and 4.5
$\mu m$) from the unWISE survey available for our fields and the COSMOS survey.
This approach allowed us to obtain good photometric redshifts with dispersion,
as measured with the robust Sigma NMAD statistics of $\sim$ 0.04 for our six
fields. Our analysis setup was reproduced on lightcones constructed from the
Millennium Simulation data and the latest version of the L-GALAXIES
semi-analytic model to verify the protocluster detectability in such
conditions. The density field in a redshift slab containing each triplet was
then analyzed with a Gaussian kernel density estimator. We did not find any
significant evidence of the triplets inhabiting dense structures, such as a
massive galaxy cluster or protocluster.
