New H2O masers in Seyfert and FIR bright galaxies

Using the Effelsberg 100-m telescope, detections of four extragalactic water vapor masers are reported. Isotropic luminosities are similar to 50, 1000, 1 and 230 L-circle dot for Mrk 1066 ( UGC 2456), Mrk 34, NGC 3556 and Arp 299, respectively. Mrk 34 contains by far the most distant and one of the most luminous water vapor megamasers so far reported in a Seyfert galaxy. The interacting system Arp 299 appears to show two maser hotspots separated by approximately 20''. With these new results and even more recent data from Braatz et al. ( 2004, ApJ, 617, L29), the detection rate in our sample of Seyferts with known jet-Narrow Line Region interactions becomes 50% ( 7/14), while in star forming galaxies with high ( S-100 mu m > 50 Jy) far infrared fluxes the detection rate is 22% (10/45). The jet-NLR interaction sample may not only contain jet-masers but also a significant number of accretion disk-masers like those seen in NGC4258. A statistical analysis of 53 extragalactic H2O sources ( excluding the Galaxy and the Magellanic Clouds) indicates ( 1) that the correlation between IRAS Point Source and H2O luminosities, established for individual star forming regions in the galactic disk, also holds for AGN-dominated megamaser galaxies; ( 2) that maser luminosities are not correlated with 60 mu m/100 mu m color temperatures; and ( 3) that only a small fraction of the luminous megamasers ( L-H2O > 100 L-circle dot) detectable with 100-m sized telescopes have so far been identified. The H2O luminosity function (LF) suggests that the number of galaxies with 1L(circle dot) < L-H2O < 10L(circle dot), the transition range between kilomasers ( mostly star formation) and megamasers ( active galactic nuclei), is small. The overall slope of the LF, similar to-1.5, indicates that the number of detectable masers is almost independent of their luminosity. If the LF is not steepening at very high maser luminosities and if it is possible to find suitable candidate sources, H2O megamasers at significant redshifts should be detectable even with present day state-of-the-art facilities.