Karen Hamm and Gail Zasowski

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

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

NASA telescope High angular

resolution and sensitivity

Allows us to view our galaxy in the mid-infrared◦ Less affected by stellar

dust and extinction

Spitzer Space Telescope

Galactic Legacy Infrared Mid-Plane Survey Extraordinaire 360 (GLIMPSE-360) ◦ Spans the far, outer

regions of galaxy (65° < l < 265°)

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

NASA/ JPL Caltech

• 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

Searched for previously published cluster identifications and parameters

Generated color-magnitude diagrams (CMDS)◦ Color/brightness distribution

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

Used a modified application of the Rayleigh-Jeans 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

Fit Girardi et al. (2002) isochrones to the stellar population

Restrict E(H-[4.5μ]) range to [0.2 – 0.45] Restrict E(H-[4.5μ]) range to [0.0 – 0.1]

Cluster Comparison Cluster Comparison

ComparisonComparisonCluster Cluster

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 two-dozen appear to be new candidates

Presently finalizing a paper to announce these new open clusters and provide parameters for little-studied clusters

Vela Carina as senior-thesis focus

R.L. Beaton (University of Virginia) S.R. Majewski (University of Virginia) B. A. Whitney (University of Wisconsin-

Madison)

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