Southern Hemisphere Open Cluster Dreams

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Southern Hemisphere Open Cluster
Dreams (Distance, Reddening, Extinction, Age, and
metallicity)
2005 Lucas Award
Brittany Shaw Scott Waitukaitis Kurtis Williams
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The Lucas Award

• Endowed by William F. Betty Lucas
• From Kentucky, served in Army Air Corps
  intelligence in WWII
• After war moved to San Diego married Betty
• Early member of San Diego Astronomy Association
• Taught telescope design construction at Reuben
  Fleet Science Center in Balboa Park
• Wanted to go back to school become professional
  astronomer
• Died in 1970s Betty took ill died shortly
  thereafter.
• Gave 150k endowments to San Diego State U of A
• U of A award granted annually to postdoc, 5000
  for a proposed research project not otherwise
  funded -- Watch for email from EdO and Sharon
  Jones!

Bill receives 1st place at 1970 Riverside
Telescope Makers Conference
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A Purely Personal Motivation

• White dwarf initial-final mass relation
• Highest-mass white dwarf progenitor
• AgeCluster-AgeWD?Minit
• Uncertainty dominated by cluster age
  uncertainties
• Need accurate cluster ages!

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Heading south for the winter (Southern Winter,
that is)

• Southern Milky Way rich in open clusters
• Many poorly studied, some with only photographic
  plate or limited photoelectric photometry
• Selected sample of 17 open clusters
• 50-200 Myr old (some older)
• dlt1 kpc
• Previous photometry has believable MS

Gemini South SOAR 16 May 2005
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Now Presenting Scott Waitukaitis
From Sierra Vista is a junior majoring in
Astronomy and Physics recipient of a 2005-2006
NASA SpaceGrant (salary half paid by Lucas Award)
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General Method

• Obtain UBVRI optical photometry
• Combine with JHK photometry from 2MASS to help
  determine reddening
• Use Hipparcos TYCHO catalog to determine proper
  motion membership probabilities for each star
  (Dias, et. al. 2002)
• Use Bayesian statistics program to determine
  cluster parameters (age, metallicity, distance,
  etc.)

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Bayesian Statistics

• Regular statistics assumes we know a parent
  distribution and asks What is the probability
  of getting a certain data set from that
  distribution?

• Bayesian statistics assumes we have a certain
  data set, and then asks Given the data set we
  have, what is the most probable parent
  distribution?

Bayes Theorem
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Our Bayesian Analysis

• We will analyze our UBVRI photometry and the
  2MASS JHK photometry with a Bayesian Algorithm
  (Ted Von Hippel and Graduate students, University
  of Texas)
• We will provide algorithm with appropriate parent
  distributions (e.g. stellar isochrones, reddening
  law, etc.) and associated data
• Given the UBVRIJHK photometry, Hipparcos data and
  our guess, the algorithm will determine a most
  probable parent distribution and associated
  parameters.
• The algorithm can then use this new most probable
  parent distribution and associated parameters as
  a new guess and iterate the process in attempt
  of finding an even more accurate parent
  distribution.

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Acknowledgments

• Dias, et. Al. 2002
• Ted Von Hippell and Graduate Students, UT
• Arizona Space Grant Consortium

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Now Presenting Brittany Shaw
A senior undergraduate from Phoenix majoring in
Astronomy Physics with a Mathematics
minor. Brittany worked this summer on this as an
independent study project and completed a
phenomenal amount of data reduction
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Data and Reduction

• Data was taken May 4th, 5th, and 6th of 2004 at
  CTIO using the 0.9 meter telescope. This
  telescope has a 13.5 FOV.
• The second night was photometric, while the other
  two nights had some cloud cover.
• Basic aperture photometry was done using DAOPHOT
  and calibrated with Landolt (1992) standard
  fields.
• Padova isochrones were fitted to the CMDs using
  previous measurements for the distance, age and
  metallicity. This was done as a check to ensure
  no systematic errors were introduced during
  reduction.

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Previous Measurements

• NGC 2516
• Age 158 ?36 Myr
• Distance 409 pc
• E(B-V) 0.112 ?0.024 mag
• Reference Sung et al 2002

• NGC 6494
• Age 302 Myr
• Distance 655 pc
• E(B-V) 0.36 mag
• Reference Meynet et al 1993

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Color Magnitude Diagrams
V-I color magnitude diagram of NGC 2516 with
isochrone corresponding to Z0.019 and an age
of112 Myr
V-I color magnitude diagram of NGC 2516 with
isochrone corresponding to Z0.019 and an age of
282 Myr
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Conclusions

• We present a project to obtain distances,
  extinction, ages and metallicities to 17 southern
  hemisphere open clusters
• Will use these data primarily for studies of
  white dwarfs the initial-final mass relation and
  the upper mass limit of white dwarf progenitors
• Obtained UBVRI photometry with CTIO 0.9m, match
  with TYCHO catalog proper motion memberships and
  2MASS JHK data
• Reduced data will be fed into Bayesian analysis
  program to get cluster parameters
• Vast majority of the work being done by two
  great undergraduates
• We are indebted to Williams Betty Lucas for
  their generosity