A survey for h_2o megamasers in active galactic nuclei. 2. A comparison of detected and undetected galaxies

Jun, 1997
19 pages
Published in:
  • Astrophys.J.Suppl. 110 (1997) 321
e-Print:

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Abstract: (arXiv)
A survey for H2O megamaser emission from 354 active galaxies has resulted in the detection of 10 new sources, making 16 known altogether. The galaxies surveyed include a distance-limited sample (covering Seyferts and LINERs with recession velocities < 7000 km s^{-1}) and a magnitude-limited sample (covering Seyferts and LINERs with m(B) <= 14.5). In order to determine whether the H2O-detected galaxies are typical AGN or have special properties which facilitate the production of powerful masers, we have accumulated a database of physical, morphological, and spectroscopic properties of the observed galaxies. The most significant finding is that H2O megamasers are detected only in Seyfert 2 and LINER galaxies, not Seyfert 1s. Implications for this finding are discussed. LINERs are detected at a similar rate to Seyfert 2s, constituting a strong argument that at least some nuclear LINERs are AGN rather than starbursts, since starbursts have not been detected as H2O megamasers. We preferentially detect H2O emission from the nearer galaxies and from those which are apparently brighter at mid- and far-infrared and centimeter radio wavelengths. There is also a possible trend for the H2O-detected galaxies to be more intrinsically luminous in nuclear 6 cm radio emission than the undetected ones, though these data are incomplete. We find evidence that Seyfert 2s with very high (N(H) > 10^{24} cm^{-2}) X-ray absorbing columns of gas are more often detected as H2O maser emitters than Seyfert 2s with lower columns. It may be that the probability of detecting H2O maser emission in Seyfert galaxies increases with increasing column of cool gas to the nucleus, from Seyfert 1s through NLXGs to Seyfert 2s.
  • & Lo, K.-Y. 1986 De Robertis, M.M.Dahari, O. & 1988 Vaucouleurs, G., de Vaucouleurs, A.de Buta, R., Paturel, G., & Fouqué, P., Corwin Jr., H.G 1991, Third Reference Catalog of Bright Galaxies ( Feigelson, E.D. & Nelson, P.I.-Verlag: New York) 1985 Baum, S.A., O’Dea, C.P., Brinks, E. & Pedlar, A.Gallimore, J.F 1996 Gwinn, C.R., Antonucci, R.R.J. & Barvainis, R.Greenhill, L.J Haschick, A.D. & Baan, W.A. 1996, ApJ Letters (in press) 1990 Baan, W.A., Schnepps, M.H., Reid, M., Moran, J.M. & Güsten, R.Haschick, A.D 1990
    • M.J. Claussen
      • Astrophys.J. 308 (1986) 592
  • Proc. N 1995 Moran, J., Herrnstein, J., Greenhill, L., Nakai, N., Diamond, P., & Inoue, M.Miyoshi, M 1995 Mulchaey, J.S., Mushotzky, R.F. & Weaver, K.A.Moshir, M. et al. 1989, Explanatory Supplement to the IRAS Faint Source Survey (Pasadena: JPL) 1992 Lepp, S. & Maloney, P.R.Neufeld, D.A 1995 Maloney, P.R.Neufeld, D.A. & 1995 Maloney, P.R., & Conger, S.Neufeld, D.A 1994 Salvati, M., Moorwood, A.F.M., Marconi, A.Oliva, E 1994 Crawford, J.Rowan-Robinson, M. & 1989
    • J.S. Miller
      • Mon.Not.Roy.Astron.Soc. 92 11422
  • not in any of our samples), (3) the number of Seyfert 1 galaxies, (4) the number of Seyfert 2 galaxies, (5) the number of LINERs, (6) the number of AGNs included which have no detailed classification available, (7) the number from the Huchra catalog, (8) the number from the Véron & Véron-Cetty catalog, and (9) the number common to both the Huchra and Véron & Véron-Cetty catalogs. Table 4 a et al. (1989 of H2O Megamaser Galaxies Source NH LX a Refb (cm-2) (erg s-1) NGC 1068 > 1025 1043 - 1044 1 NGC 1386 5 ± 3 × 1023 - 2 Mrk 1210 1.1 ± 0.8 × 1023 - 2 NGC 3079 1.6 +2.4 -1.6 × 1022 5.8 × 1040 3 NGC 4258 1.5 ± 0.2 × 1023 4 ± 1× 1040 4 NGC 4945 5.4 ± 0.5 × 1024 1 × 1042 5 Circinus > 1024 4 × 1041 - 4 × 1043 6 NGC 5506 2.8 ± 0.5 × 1022 1.7 × 1043 7 ESO 103-G35 1.35 +.33 -.23 × 1023 3.3 × 1043 7 a 2 - 10 keV luminosity, corrected for photoelectric absorption. b (1) Koyam (2) Awaki (1996)
    • Hard X-ray Observations
    • )
      • Mitsos
      • (3) Serle )
        • Hima
        • (4) Makis )
          • Wa
          • (5) Iwasa ) (6) Matt ) (7) Turner & Pounds (1989)