---
author:
- 'G. Galletta'
- 'V. Casasola'
- 'L. Piovan'
- 'E. Merlin'
- 'D. Bettoni'
date: 'Received ; Accepted 20 September 2006'
title: Relations between ISM tracers in galaxies
---

[We study the relations existing between fluxes emitted at CO(1-0) line, 60 and 100 $\mu$m wavelengths, B and soft X-ray wavebands for galaxies of all morphological types. The large set of data that we created allows to revisit some of known relations existing between the different tracers of the Interstellar Medium (ISM): the link between the FIR flux and the CO line emission, the relation between X-ray emission in non active galaxies and the blue or FIR luminosity.]{} [Using catalogues of galaxies and works presented in the literature, we collected fluxes in FIR, 21 cm, CO(0-1) line and soft X-ray for two samples, consisting of normal and interacting galaxies respectively. Joining together these samples, we have data for a total of 2953 galaxies, not all observed in the four above wavebands.]{} [ All the relations found are discussed in the frame of the star formation activity that is the link for most of them. We note that when an active star formation is present, it may link the 