  Centaurs are the transitional population between trans-Neptunian objects
(TNOs) and Jupiter-family comets. For this reason it is possible to access the
smaller ones, which is more difficult to do with the TNO population. The goal
of this work is to characterize a set of 16 Centaurs in terms of their size,
albedo, and thermal properties. We study the correlations, for a more extended
sample obtained from the literature, of diameter, albedo, orbital parameters,
and spectral slopes. We performed three-band photometric observations using
Herschel-PACS and used a consistent method for the data reduction and aperture
photometry of this sample to obtain monochromatic flux densities at 70, 100,
and 160 $\mu$m. Additionally, we used Spitzer-MIPS flux densities at 24 and 70
$\mu$m when available. We also included in our Centaur sample scattered disk
objects (SDOs), a dynamical family of TNOS, using results previously published
by our team, and some Centaurs observed only with the Spitzer/MIPS instrument.
We have determined new radiometric sizes and albedos of 16 Centaurs. The first
conclusion is that the albedos of Centaur objects are not correlated with their
orbital parameters. Similarly, there is no correlation between diameter and
orbital parameters. Most of the objects in our sample are dark (pv < 7%) and
most of them are small (D < 120km). However, there is no correlation between
albedo and diameter, in particular for the group of the small objects as albedo
values are homogeneously distributed between 4 to 16%. The correlation with the
color of the objects showed that red objects are all small (mean diameter 65
km), while the gray ones span a wide range of sizes (mean diameter 120 km).
Moreover, the gray objects tend to be darker, with a mean albedo of 5.6%,
compared with a mean of 8.5% (ranging from 5 to 15%) for the red objects.
