Comparison between theory and observations
While analyzing the results of our simulations, we have been struck by
the large number of uncertainties in how best to handle the data.
After making the usual theoretical pictures of our model clusters, we
are often left with the uneasy feeling that real observers might well
have completely different ways of handling the data, and would likely
disagree with us on how best to present it. In a sense, it is almost
a drawback to know too much about the simulated system -- we can't see
the cluster for the stars. For example, even determining which stars
an observer might select as cluster members, or how the observer would
go about measuring the overall binary fraction, require us to throw
away dynamical data in a manner that depends strongly on the specific
observational techniques used. How then do we achieve our goal of
presenting model data in a form that is both comprehensible and useful
to observers?
The obvious solution to this conundrum is to seek advice from the
experts. Incorporating the observer's view of our simulations is
valuable for three main reasons:
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Comparisons between model data and the way an observer would
study a real cluster provide a critical check on the observer's
data reduction process.
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In addition, there are many uncertainties as to how our models
would appear if they were observed as a real cluster on the
sky. Numerical problems, erroneous initial conditions, and
other incorrect assumptions may reveal themselves much more
clearly when the models are analyzed by observers rather than
by theorists.
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Since theoretical models are at last producing sufficiently
detailed data that we can now talk meaningfully about
performing comparisons between theory and observations, it is
critical that we identify robust ways of projecting numerical
data onto the observational plane. Model builders have talked
about this for many years (decades, in fact), but little has
come of it.
Example of two short exposures of an open
star clusters in B (left) and V (right):
As a specific example, we have performed a number of calculations of
the evolution of "Hyades-like" open clusters. We provide the data as
though the models were observed through an Earth-based telesope. Two
example images are presented as flat-fielded CCD frames of a young populous cluster and an
open star cluster. Other
objects, wavelength bands and datasets (from flat-fielded CCD frames
in U,B, V, R and I to fully reduced positions) are available on
request. It may be preferable to use the unreduced CCD data because
it introduces an interesting extra uncertainty into the data analysis
process. We also provide technical
information about the CCDs.
The following FITS
files of various CCDs are available
