Open AccessA search for extragalactic H 2 O maser emission towards IRAS galaxies – II. Discovery of an H 2 O maser in the type 1 Seyfert galaxy NGC 4051
Author(s) -
Hagiwara Yoshiaki,
Diamond Philip J.,
Miyoshi Makoto,
Rovilos Emmanouel,
Baan Willem
Publication year - 2003
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2003.07005.x
Subject(s) - maser , physics , astrophysics , galaxy , megamaser , active galactic nucleus , astronomy , nucleus , luminosity , biology , microbiology and biotechnology
ABSTRACT Water vapour maser emission in the 6 16 –5 23 transition towards the narrow‐line type 1 Seyfert (NLS1) galaxy NGC 4051 has been discovered during an ongoing single‐dish extragalactic water maser survey. The Doppler‐shifted maser components appear to bracket maser components lying near the systemic velocity of the galaxy symmetrically. The tentative result of a Very Large Array (VLA) snapshot observation is that the masers are confined within 0.1 arcsec (5 pc at a distance D = 9.7 Mpc ) of the radio continuum peak seen at 8.4 GHz. The low luminosity of the maser (∼2 L ⊙ ) is not typical for masers that coincide with the radio continuum nucleus and appear associated with active galactic nucleus (AGN) activity. A low‐luminosity maser in a type 1 Seyfert nucleus could be explained by a low maser gain resulting from the lower inclination of an obscuring disc around an active nucleus.