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OCAAT: automated analysis of star cluster colour-magnitude diagrams for gauging the local distance scale

Published online by Cambridge University Press:  01 July 2015

Gabriel I. Perren
Affiliation:
Facultad de Ciencias Astronómicas y Geofísicas (UNLP) IALP-CONICET, La Plata, Argentina email: gperren@fcaglp.unlp.edu.ar
Ruben A. Vázquez
Affiliation:
Facultad de Ciencias Astronómicas y Geofísicas (UNLP) IALP-CONICET, La Plata, Argentina email: gperren@fcaglp.unlp.edu.ar
Andrés E. Piatti
Affiliation:
Observatorio Astronómico, Universidad Nacional de Córdoba Córdoba, Argentina
André Moitinho
Affiliation:
SIM, Faculdade de Ciências da Universidade de Lisboa Ed. C8, Campo Grande, 1749-016 Lisboa, Portugal
Corresponding
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Abstract

Star clusters are among the fundamental astrophysical objects used in setting the local distance scale. Despite its crucial importance, the accurate determination of the distances to the Magellanic Clouds (SMC/LMC) remains a fuzzy step in the cosmological distance ladder. The exquisite astrometry of the recently launched ESA Gaia mission is expected to deliver extremely accurate statistical parallaxes, and thus distances, to the SMC/LMC. However, an independent SMC/LMC distance determination via main sequence fitting of star clusters provides an important validation check point for the Gaia distances. This has been a valuable lesson learnt from the famous Hipparcos Pleiades distance discrepancy problem. Current observations will allow hundreds of LMC/SMC clusters to be analyzed in this light.

Today, the most common approach for star cluster main sequence fitting is still by eye. The process is intrinsically subjective and affected by large uncertainties, especially when applied to poorly populated clusters. It is also, clearly, not an efficient route for addressing the analysis of hundreds, or thousands, of star clusters. These concerns, together with a new attitude towards advanced statistical techniques in astronomy and the availability of powerful computers, have led to the emergence of software packages designed for analyzing star cluster photometry. With a few rare exceptions, those packages are not publicly available.

Here we present OCAAT (Open Cluster Automated Analysis Tool), a suite of publicly available open source tools that fully automatises cluster isochrone fitting. The code will be applied to a large set of hundreds of open clusters observed in the Washington system, located in the Milky Way and the Magellanic Clouds. This will allow us to generate an objective and homogeneous catalog of distances up to ~ 60 kpc along with its associated reddening, ages and metallicities and uncertainty estimates.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2015 

References

Cabrera-Cano, J. & Alfaro, E. J. 1990, A&A, 235, 94Google Scholar
Hernandez, X. & Valls-Gabaud, D. 2008, MNRAS, 383, 1603CrossRefGoogle Scholar

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OCAAT: automated analysis of star cluster colour-magnitude diagrams for gauging the local distance scale
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