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Durham University

Department of Physics

Staff profile

Publication details for Prof Tim Roberts

Jenkins, L.P., Brandt, W.N., Colbert, E.J.M., Koribalski, B., Kuntz, K.D., Levan, A.J., Ojha, R., Roberts, T.P., Ward, M.J. & Zezas, A. (2011). Investigating the Nuclear Activity of Barred Spiral Galaxies: The Case of NGC 1672. Astrophysical Journal 734(1): 33.

Author(s) from Durham


We have performed an X-ray study of the nearby barred spiral galaxy NGC 1672, primarily to ascertain the effect
of the bar on its nuclear activity. We use both Chandra and XMM-Newton observations to investigate its X-ray
properties, together with supporting high-resolution optical imaging data from the Hubble Space Telescope (HST),
infrared imaging from the Spitzer Space Telescope, and Australia Telescope Compact Array ground-based radio
data.We detect 28 X-ray sources within the D25 area of the galaxy; many are spatially correlated with star formation
in the bar and spiral arms, and two are identified as background galaxies in the HST images. Nine of the X-ray
sources are ultraluminous X-ray sources, with the three brightest (LX > 5 × 1039 erg s−1) located at the ends of
the bar. With the spatial resolution of Chandra, we are able to show for the first time that NGC 1672 possesses
a hard (Γ ∼ 1.5) nuclear X-ray source with a 2–10 keV luminosity of 4 × 1038 erg s−1. This is surrounded by
an X-ray-bright circumnuclear star-forming ring, comprised of point sources and hot gas, which dominates the
2–10 keV emission in the central region of the galaxy. The spatially resolved multiwavelength photometry indicates
that the nuclear source is a low-luminosity active galactic nucleus (LLAGN), but with star formation activity close
to the central black hole. A high-resolution multiwavelength survey is required to fully assess the impact of both
large-scale bars and smaller-scale phenomena such as nuclear bars, rings, and nuclear spirals on the fueling of