We use ROSAT PSPC data to study the X-ray properties of a sample of twelve poor groups that have extensive membership information ( Zabludoff & Mulchaey 1997 ; Paper I ) .
Diffuse X-ray emission is detected in nine of these groups .
In all but one of the X-ray detected groups , the X-ray emission is centered on a luminous elliptical galaxy .
Fits to the surface brightness profiles of the X-ray emission suggest the presence of two X-ray components in these groups .
The first component is centered on the central elliptical galaxy and is extended on scales of 20–40 h _ { 100 } ^ { -1 } kpc .
The location and extent of this component , combined with its X-ray temperature ( \sim 0.7–0.9 keV ) and luminosity ( \sim 10 ^ { 41 - 42 } h _ { 100 } ^ { -2 } erg s ^ { -1 } ) , favor an origin in the interstellar medium of the central galaxy .
Alternatively , the central component may be the result of a large-scale cooling flow .

The second X-ray component is detected out to a radius of at least \sim 100–300 h _ { 100 } ^ { -1 } kpc .
This component follows the same relationships found among the X-ray temperature ( T ) , X-ray luminosity ( L _ { X } ) and optical velocity dispersion ( \sigma _ { r } ) of rich clusters .
This result suggests that the X-ray detected groups are low-mass versions of clusters and that the extended gas component can properly be called the intragroup medium , in analogy to the intracluster medium in clusters .
The failure to detect an intragroup medium in the three groups with very low velocity dispersions is consistent with their predicted X-ray luminosities and temperatures based on the relationships derived for clusters and X-ray detected groups .
The best-fit value of \beta derived from the \sigma _ { r } -T relationship for groups and clusters is \sim 0.99 \pm { 0.08 } , implying that the galaxies and hot gas trace the same potential with equal energy per unit mass and that the groups are dynamically relaxed .

We also find a trend for the position angle of the optical light in the central elliptical galaxy to align with the position angle of the large-scale X-ray emission .
This trend is consistent with that found for some rich clusters containing cD galaxies ( Rhee , van Haarlem & Katgert 1992 ; Sarazin et al .
1995 ; Allen et al .
1995 ) .
The alignment of the central galaxy with the extended X-ray emission suggests that the formation and/or evolution of the central galaxy is linked to the shape of the global group potential .
One possible scenario is that the central galaxy formed via galaxy-galaxy mergers early in the lifetime of the group and has not been subject to significant dynamical evolution recently .