High Resolution X-ray Imaging Observations of two low luminosity Seyfert Galaxies

An extended component of X-ray emission has been detected in Seyfert galaxies - NGC 1365 and NGC 4051, using the ROSAT HRI. Its size is about 2 kpc and it contains 56% +- 8% of the total observed flux in NGC 1365, and 21% +- 6% in NGC 4051. Extended emission in NGC 1365 is aligned with the inner disk structure, has wings along the east and west direction aligned with the inner spiral arms, and has an elongated edge-brightened structure (``chimney'') breaking out of the disk in the north-west direction. In NGC 4051 it is co-spatial with the disk of the galaxy, and shows an elongation coincident with a ``banana''-like feature in the north-east seen in the 6 cm radio band. Starburst activity driving strong winds through the disk of NGC 1365 can account for most of the extended soft X-ray emission in it. Both nuclear activity and starburst induced activity maybe needed to explain extended X-ray emission in NGC 4051. The nuclear component of NGC 4051 shows soft X-ray variability with X-ray intensity changing by a factor of 2-3 on a time-scale of a few 100s. At low frequencies the power spectrum of variability is best characterised by a power-law and a Gaussian. The power-law slope of -1.8 is consistent with the previous EXOSAT observations, and the presence of a Gaussian feature signifies the persistence of a quasi-periodic oscillation that was seen earlier with EXOSAT. During its low intensity and low variability state the extended component of soft X-ray emission dominates the flux in NGC 4051.