Molecular gas and nuclear activity in early-type galaxies: any link with
  radio-loudness?
  Aims. We want to study the amount of molecular gas in a sample of nearby
early-type galaxies (ETGs) which host low-luminosity Active Galactic Nuclei
(AGN). We look for possible differences between the radio-loud (RL) and
radio-quiet (RQ) AGN. Methods. We observed the CO(1-0) and CO(2-1) spectral
lines with the IRAM 30m and NRO 45m telescopes for eight galaxies. They belong
to a large sample of 37 local ETGs which host both RQ and RL AGN. We gather
data from the literature for the entire sample. Results. We report the new
detection of CO(1-0) emission in four galaxies (UGC0968, UGC5617, UGC6946, and
UGC8355) and CO(2-1) emission in two of them (UGC0968 and UGC5617). The
CO(2-1)/CO(1-0) ratio in these sources is $\sim0.7\pm0.2$. Considering both the
new observations and the literature, the detection rate of CO in our sample is
55 $\pm$ 9%, with no statistically significant difference between the hosts of
RL and RQ AGNs. For all the detected galaxies we converted the CO luminosities
into the molecular masses, $M_{H_2}$, that range from 10$^{6.5}$ to 10$^{8.5}$
M$_{\odot}$, without any statistically significant differences between RL and
RQ galaxies. This suggests that the amount of molecular gas does not likely set
the radio-loudness of the AGN. Furthermore, despite the low statistical
significance, the presence of a weak trend between the H$_{2}$ mass with
various tracers of nuclear activity (mainly [O III] emission line nuclear
power) cannot be excluded.
