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Description
We have used Cousins RI CCD photometry from the Isaac Newton telescope and intermediate-resolution spectroscopy from the Gemini North telescope to identify and characterize low-mass (0.15<M/M_{sun}_<1.3) pre-main-sequence stars in the young open cluster NGC 2169. Isochrone fitting to the high- and low-mass populations yields an intrinsic distance modulus of 10.13^+0.06^_-0.09_mag and a model-dependent age of 9+/-2Myr. Compared to the nearby, kinematically defined groups of a similar age, NGC 2169 has a large low-mass population which potentially offers a more precise statistical investigation of several aspects of star formation and early stellar evolution. By modelling the distribution of low-mass stars in the IC versus RC IC diagram, we find that any age spread among cluster members has a Gaussian full width at half-maximum (FWHM) 2.5Myr. A young age and a small age spread (<10Myr) are supported by the lack of significant lithium depletion in the vast majority of cluster members. There is no clear evidence for accretion or warm circumstellar dust in the low-mass members of NGC 2169, bolstering the idea that strong accretion has ceased and inner discs have dispersed in almost all low-mass stars by ages of 10Myr.
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