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Monthly Notices of the Royal Astronomical Society


We present an XMM–Newton observation of the massive edge-on Sb galaxy NGC 2613. We discover that this galaxy contains a deeply embedded active nucleus with a 0.3–10 keV luminosity of 3.3 × 1040 erg s−1 and a line-of-sight absorption column of 1.2 × 1023 cm−2. Within the 25 mag arcsec−2 optical B-band isophote of the galaxy, we detect an additional four sources with an accumulated luminosity of 4.3 × 1039 erg s−1. The bulk of the unresolved X-ray emission spatially follows the near-infrared (NIR) K-band surface brightness distribution; the luminosity ratio LX/LK∼ 8 × 10−4 is consistent with that inferred from galactic discrete sources. This X-ray–NIR association and the compatibility of the X-ray spectral fit with the expected spectrum of a population of discrete sources suggest that low-mass X-ray binaries (LMXBs) are the most likely emitters of the unresolved emission in the disc region. The remaining unresolved emission is primarily due to extraplanar hot gas. The luminosity of this gas is at least a factor of 10 less than that predicted by recent simulations of intergalactic gas accretion by such a massive galaxy with a circular rotation speed Vc∼ 304 km s−1. Instead, we find that the extraplanar hot gas most likely represents discrete extensions away from the disc, including two ‘bubble-like’ features on either side of the nucleus. These extensions appear to correlate with radio continuum emission and, energetically, can be easily explained by outflows from the galactic disc.


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