Karen Hamm and Gail Zasowski
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Groupings of stars
Born from the same giant molecular cloud
Young, low stellar density objects
Contain up to several thousand stars
M45: The Pleiades
M67
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Effects of mass on
stellar evolution are
directly visible for star
clusters
Distances can be
calculated more reliably
Better account of stellar
evolution, Milky Way
evolution and structure,
and historical and
present star formation
Artistic depiction of the evolution
of a galaxy
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NASA telescope
High angular
resolution and
sensitivity
Allows us to view our
galaxy in the midinfrared
◦ Less affected by stellar
dust and extinction
Spitzer Space Telescope
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Galactic Legacy
Infrared Mid-Plane
Survey
Extraordinaire 360
(GLIMPSE-360)
NASA/ JPL Caltech
◦ Spans the far, outer
regions of galaxy
(65° < l < 265°)
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Vela Carina
◦ Spans longitudes of
255° < l < 295°
Outer regions are
relatively
unexplored for
open star clusters
Longitudes covered by the GLIMPSE-360
(dark-orange) and Vela Carina (purple)
surveys
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SAOImage DS9
Individual
images scaled
to roughly 1° ×
1° bins
Criteria
– Over-density of
stars
– Similar size and
brightness
Sample screen shot of SAOImage DS9 program
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Searched for previously published cluster
identifications and parameters
Generated color-magnitude diagrams (CMDS)
◦ Color/brightness distribution
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The likelihood of the candidates being
genuine clusters were sorted based on the
clarity of the Spitzer image and the strength
and disparity of the CMDs
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Used a modified application of the RayleighJeans Color Excess method (RJCE; Majewski et al.
2011) to isolate cluster stars
Each cluster CMD represents the stellar sequence
of that cluster, as well as foreground and
background Galactic features
Cluster stars should share similar foreground
reddening
 Used the RJCE reddening estimate for each object in the
cluster field to search for these distinct stellar sequences
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Fit Girardi et al. (2002) isochrones to the stellar
population
Cluster
Comparison
Restrict E(H-[4.5μ]) range to [0.2 – 0.45]
Cluster
Comparison
Cluster
Comparison
Restrict E(H-[4.5μ]) range to [0.0 – 0.1]
Cluster
Comparison
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Identified a number of unknown and
uncharacterized open clusters in the outer
Milky Way
Derived basic cluster parameters
(reddening, metallicity, distance) for objects
with well-populated near-IR CMDs
Of one-hundred open clusters identified in
the GLIMPSE-360 survey, roughly twodozen appear to be new candidates
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Presently finalizing a paper to announce
these new open clusters and provide
parameters for little-studied clusters
Vela Carina as senior-thesis focus
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R.L. Beaton (University of Virginia)
S.R. Majewski (University of Virginia)
B. A. Whitney (University of WisconsinMadison)
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Churchwell, E., Babler, B. L., Meade, M. R., et al. 2009, PASP, 121,
213
Whitney, B., Arendt, R., Babler, B., et al. 2008, in Spitzer Proposal ID
#60020, 60020 (GLIMPSE-360)
Carey, S., Ali, B., Berriman, B., et al. 2008, in Spitzer Proposal ID
#50398, 50398 (SMOG)
Hora, J., Adams, J., Allen, L., et al. 2007, in Spitzer Proposal ID
#40184, 40184 (Cyg-X)
Majewski, S. R., et al. 2008, in Spitzer Proposal ID #
40791,40791 (Vela-Carina)
Whitney, B., Benjamin, R., Meade, M., et al. 2011, in Bulletin of the
American Astronomical Society, Vol. 43, American Astronomical
Society Meeting Abstracts No. 217, 241.16
Majewski, S.R., Zasowski, G., & Nidever, D.L. 2011, ApJ, 739, 25
Girardi, L., Bertelli, G., Bressan, A., et al. 2002, A&A, 391, 195