Palomar 14: A Young Globular Cluster in the Outer Galactic Halo
We present deep BV CCD color-magnitude diagrams of the outer-halo Galactic globular cluster Palomar 14 based on observations taken at the WIYN and KPNO 4m telescopes. Pal 14 is an intermediate metallicity ([Fe/H] = -1.60) cluster with a horizontal branch populated predominantly redward of the RR Lyrae instability strip. As such, it is affected by the ``second parameter effect'' which, in addition to metallicity, influences the morphology of the horizontal branch. From the position of the main sequence turnoff, we conclude that Pal 14 is 3 to 4 Gyr younger than typical globular clusters at its metallicity. Several other ``second parameter'' globular clusters have been found to be relatively young. All of this evidence, taken together, presents a powerful case in favor of age as the second parameter.
The Astronomical Journal
- Pub Date:
- February 1997