AAS 205th Meeting, 9-13 January 2005
Session 60 Secular Evolution Potpourri: Star Formation to Galactic Structures
Poster, Tuesday, January 11, 2005, 9:20am-6:30pm, Exhibit Hall

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[60.18] Are Mass Estimates of Galaxies Using Tracer Populations Biased by Tidal Streams?

B. Yencho, K.V. Johnston (Wesleyan University)

A common method for estimating the mass of a galaxy involves taking the average of vlos2 R over some tracer population, such as globular clusters or planetary nebulae, where vlos refers to the line-of-sight velocity of each object and R is the projected distance from the center of the galaxy. A key assumption in this approach is that members of the system lie on random orbits uncorrelated with the other members. In contrast, numerical simulations of the heirarchical assembly of galaxies result in systems that are often composed of tidal streams of debris, which could break this assumption and lead to biases in the estimates. Using such a model, datasets of 100 particles were selected from streams to simulate a globular cluster survey. When distributing the samples across several of the more luminous disrupted bodies, the mass estimates for the parent galaxy were typically within a factor of two of the true mass. However, confining the samples to a single stream provided widely varying results, sometimes by factors as great as an order of magnitude.

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