The Stellar Population and Orbit of the Galactic Globular Cluster Palomar 3

Abstract

Deep stellar photometry of one of the most distant Galactic globular clusters, Palomar 3, based on frames taken with the VLT in Johnson-Cousins broadband V and Ifilters is presented, together with medium-resolution stellar spectroscopy in the central region of the cluster obtained with the CARELEC spectrograph of the Observatoire de Haute Provence and measurements of the Lick spectral indices for the integrated spectrum. Computations of the orbital parameters of Palomar 3 and nine Galactic globular clusters with similar metallicities and ages are also presented. The orbital parameters, age, metallicity, and distance of Palomar 3 are estimated. The interstellar absorption is consistent with and supplements values from the literature. The need to obtain more accurate data on the proper motions, ages, and chemical compositions of the cluster stars to elucidate the origin of this globular cluster is emphasized.

STRucture and Evolution of the GAlaxy (STREGA): The case of Pal 3

“…A possible explanation for this elongation is that Pal 3 interacted with the MW and/or it was originally belonging to another system, such as a dwarf spheroidal galaxy as discussed in literature (e.g. Sharina et al 2018 and references therein). Deeper photometry and accurate proper motion of large areas of the Local Group galaxies from large survey telescopes such as the Large Synoptic Survey Telescope (LSST) are expected to better constrain both the Pal 3 variable star population and the supposed link with the Phoenix dwarf galaxy.…”

“…They suggested a north-south elongation along the directions of the Galactic center and anticenter, and a north-east extension in the direction of the cluster's proper motion. The character of the motion of Pal 3 is debated and a possible extragalactic origin is also suggested, with the Phoenix dwarf spheroidal beeing the best candidate to be associated to Pal 3 (Palma, Majewski & Johnston 2002;Sharina et al 2018).…”

A Search for Gas-Rich Dwarf Galaxies in the Local Universe with ALFALFA and the WIYN One Degree Imager

“…CMD fitting indicates that the cluster belongs to the metal-poor subpopulation of the Milky Way GC system, with [Fe/H] = −1.7, and has an estimated age of ∼10 Gyr (Hilker 2006). The location and orbital properties of Pal 3 have prompted studies of its origin, with some concluding that it may have been accreted into the outer Galactic halo along with its parent dwarf satellite galaxy (Palma et al 2002), and others suggesting it could have been ejected from the Phoenix dwarf irregular galaxy and captured by the Milky Way (Sharina et al 2018). However, stellar abundance studies seem to suggest instead that Pal 3 coevolved with the rest of the Galactic GC system (Koch et al 2009).…”