R-band light-curve properties of Type Ia supernovae from the (intermediate) Palomar Transient Factory

We present the best 265 sampled R-band light curves of spectroscopically identified Type Ia supernovae (SNe) from the Palomar Transient Factory (PTF; 2009-2012) survey and the intermediate Palomar Transient Factory (iPTF; 2013-2017). A model-independent light-curve template is built from our data-set with the purpose to investigate average properties and diversity in our sample. We searched for multiple populations in the light-curve properties using machine learning tools. We also utilized the long history of our light curves, up to 4000 days, to exclude any significant pre- or post- supernova flares. From the shapes of light curves we found the average rise time in the R band to be 16.8^{+0.5}_{-0.6} days. Although PTF/iPTF were single-band surveys, by modelling the residuals of the SNe in the Hubble-Lemaître diagram, we estimate the average colour excess of our sample to be <E(B - V)> ≈ 0.05(2) mag and thus the mean corrected peak brightness to be M_R = -19.02 ± 0.02 +5 log (H_0 [ km s^{-1} Mpc^{-1}]/70) mag with only weak dependennce on light-curve shape. The intrinsic scatter is found to be σ_R = 0.186 ± 0.033 mag for the redshift range 0.05 < z < 0.1, without colour corrections of individual SNe. Our analysis shows that Malmquist bias becomes very significant at z = 0.13. A similar limitation is expected for the ongoing Zwicky Transient Facility (ZTF) survey using the same telescope, but new camera expressly designed for ZTF.