MOLECULAR ABSORPTIONS TOWARDS THE AGN-1504+377

We have defected seven different molecular lines in absorption towards the remote radio source 1504+377. The absorption occurs in an edge-on galaxy al a redshift z = 0.672. The absorption splits into several co mponents, gathered in two groups separated by 330 km s(-1). The two gr oups are interpreted as coming from a spiral arm and a nuclear ring in noncircular motion. Given the spatial coincidence of the remote radio source, and the galaxy as well as the absence of gravitationally lens ed images, the absorption is likely to originate in the galaxy hosting the AGN. Comparing different Lines, we fmd a large density for the ab sorbing molecular clouds, and an excitation temperature of 10-20 K. Th e HCO+ abundance is enhanced by at least one order of magnitude with r espect to current chemical equilibrium models. The HNC/HCN ratio yield s a kinetic temperature in accordance with the excitation temperature. This suggests a dense medium, however with a low column density, sinc e the absorption lines are optically thin. A molecular cloud composed of small dense clumps with a low filling factor could account for that . We also present a list of upper limits for additional candidates sea rched for molecular absorption. With previously published negative res ults, the total number of objects searched is about 50, while 4 absorp tion systems have been found. We discuss the efficiency of various sel ection criteria.