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|Mass Profile of the Infall Region of the Abell 2199 Supercluster|
Using a redshift survey of 1323 galaxies (1092 new or remeasured) in aregion of 95 deg2 centered on the nearby galaxy cluster Abell2199, we analyze the supercluster containing A2199, A2197, and an X-raygroup. The caustic technique accurately reproduces the true massprofiles of simulated simple superclusters (i.e., superclusters forwhich the virial mass of one cluster is 2-10 times the virial mass ofall other clusters in the supercluster). We calculate the masses of thetwo main components of A2197 (A2197W and A2197E) by using archival X-rayobservations and demonstrate that the A2199 supercluster is simple (themass of A2199 is 5 and 12 times larger than A2197W and A2197E,respectively) and thus that the caustic technique should yield anaccurate mass profile. The masses of A2199, A2197W, and A2197E withinr500 (the radius within which the enclosed density is 500times the critical density) are 22.0, 3.8, and 1.7 times 1013h-1 Msolar, respectively. The mass profile isuncertain by ~30% within 3 h-1 Mpc and by a factor of 2within 8 h-1 Mpc and is one of only a few for a superclusteron such large scale. Independent X-ray mass estimates agree with ourresults at all radii where they overlap. The mass profile stronglydisagrees with an isothermal sphere profile but agrees with profilessuggested by simulations. We discuss the interplay of the superclusterdynamics and the dynamics of the bound subclusters. The agreementbetween the infall mass profile and other techniques shows that thecaustic technique is surprisingly robust for simple superclusters.
|Accurate Positions for MCG Galaxies|
We have measured accurate celestial coordinates for 4741 extragalacticobjects, primarily drawn from a list of MCG galaxies with no recentlypublished accurate positions. The standard deviations in the newpositions depend slightly on the measurement method but are on the orderof 1.0" to 1.2". Standard deviations in the original MCG positions areconfirmed to be at the 1.5′-2.0′ level. These new positionswere integrated into NED in 1997 December.
|The ages of Galactic globular clusters|
The ages of 10 Galactic globular clusters are determined from theintegrated B-V color and found to be no more than 15 billion years old.It is hypothesized that metal-poor globular clusters (Fe/H less than-1.2) are 4-5 billion years older than metal-rich ones. In themetallicity range of -1.3 to -2.3, no such metallicity-age correlationis found.
|The A2197 and A2199 galaxy clusters|
Seventy-four new galaxy redshifts in the A2197/A2199 region arepresented. When these are added to data in the literature, 117 galaxieswith known redshifts are found within the two clusters, and 19 galaxieswith known redshifts are found generally north of A2197. These samplesare used to determine the dynamical properties and M/L ratios for thetwo clusters and to examine the broad supercluster properties of thisregion.
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