A Chandra Observation of the X-ray Environment and Jet of 3C31

M.J.Hardcastle, D.M.Worrall, M.Birkinshaw

Department of Physics, University of Bristol,
Tyndall Avenue, Bristol BS8 1TL


Space Science and Technology Department,
CLRC, Rutherford Appleton Laboratory,
Chilton, Didcot, Oxon OX11 0QX


University of Oxford, Department of Astrophysics,
Denys Wilkinson Building, Keble Road, Oxford OX1 3RH


National Radio Astronomy Observatory
520 Edgemont Road, Charlottesville, VA 22903-2475, U.S.A.

Monthly Notices of the Royal Astronomical Society, in press

Chandra X-ray image of 3C31
3C31: Chandra X-ray image


We have used a deep Chandra observation of the central regions of the twin-jet FRI radio galaxy 3C31 to resolve the thermal X-ray emission in the central few kiloparsecs of the host galaxy, NGC 383, where the jets are thought to be decelerating rapidly. This allows us to make high-precision measurements of the density, temperature and pressure distributions in this region, and to show that the X-ray emitting gas in the centre of the galaxy has a cooling time of only 5 x 107 years. In a companion paper these measurements are used to place constraints on models of the jet dynamics.

A previously unknown one-sided X-ray jet in 3C31, extending up to 8 arcsec from the nucleus, is detected and resolved. Its structure and steep X-ray spectrum are similar to those of X-ray jets known in other FRI sources, and we attribute the radiation to synchrotron emission from a high-energy population of electrons. In situ particle acceleration is required in the region of the jet where bulk deceleration is taking place.

We also present X-ray spectra and luminosities of the galaxies in the Arp 331 chain of which NGC 383 is a member. The spectrum and spatial properties of the nearby bright X-ray source 1E~0104+3153 are used to argue that the soft X-ray emission is mostly due to a foreground group of galaxies rather than to the background broad absorption-line quasar.

2002 June 12