We present XMM-Newton observations of three X-ray under-luminous elliptical galaxies , NGC 3585 , NGC 4494 and NGC 5322 .
All three galaxies have relatively large optical luminosities ( log L _ { \mathrm { B } } =10.35-10.67 L _ { \odot } ) but have X-ray luminosities consistent with emission from discrete sources only .
In conjunction with a Chandra observation of NGC 3585 , we analyse the XMM-Newton data and show that the three galaxies are dominated by discrete source emission , but do possess some X-ray emitting gas .
The gas is at relatively low temperatures , kT \simeq 0.25-0.44 keV .
All three galaxies show evidence of recent dynamical disturbance and formation through mergers , including kinematically distinct cores , young stellar ages , and embedded stellar disks .
This leads us to conclude that the galaxies formed relatively recently and have yet to build up large X-ray halos .
They are likely to be in a developmental phase where the X-ray gas has a very low density , making it undetectable outside the galaxy core .
However , if the gas is a product of stellar mass loss , as seems most probable , we would expect to observe supersolar metal abundances .
While abundance is not well constrained by the data , we find best fit abundances < 0.1 Z _ { \odot } for single-temperature models , and it seems unlikely that we could underestimate the metallicity by such a large factor .