Testing the Low-Mass End of X-Ray Scaling Relations with a Sample of
  Chandra Galaxy Groups
  Well-determined scaling relations between X-ray observables and cluster mass
are essential for using large cluster samples for cosmology. Cluster relations
such as the Lx-T, M-T, Lx-M relations, have been investigated extensively,
however the question remains whether these relations hold true also for groups.
Some evidence supports a break at low masses, possibly caused by the influence
of non-gravitational physics on low-mass systems. The main goal of this work is
to test scaling relations for the low-mass range to check whether there is a
systematic difference between clusters and groups, and to extend this method of
reliable cluster mass determination for future samples down to the group
regime. We compiled a statistically complete sample of 112 X-ray galaxy groups,
26 with Chandra data. Temperature, metallicity, and surface brightness profiles
were created, and used to determine the main physical quantities and scaling
relations. We then compared the group properties to the HIFLUGCS clusters and
other samples. We present profiles and scaling relations of the whole sample. T
and Z profiles behave universally, except for the cores. The Lx-T, M-T, Lx-M,
Mg-M, M-Yx, and Lx-Yx relations are in good agreement with clusters. The Lx-T
relation steepens for T<3keV, which could point to a larger impact of heating
mechanisms on cooler systems. We found a strong drop in the gas mass fraction
below 1keV, which indicates the ICM is less dominant in groups and the galaxies
have a stronger influence on the system. In all relations the intrinsic scatter
for groups is larger, which appears not correlated with merger activity but
could be due to scatter caused by baryonic physics in the group cores. We also
demonstrate the importance of selection effects. We have found evidence for a
similarity break between groups and clusters. However this does not have a
strong effect on scaling relations.
