The surface brightness profile of the remote cluster NGC 2419

TL;DR

This paper provides a detailed surface brightness profile of the remote globular cluster NGC 2419, confirming its peculiar extended structure and refining its structural parameters through combined datasets and independent analyses.

Contribution

It offers a new, reliable surface brightness profile for NGC 2419 and independently confirms its structural parameters, improving understanding of its unique extended structure.

Findings

Surface brightness profile extends to ~25 core radii.

Best-fit King model parameters: r_c=0.32 arcmin, mu_V(0)=19.55.

Total V magnitude and half-light radius are precisely estimated.

Abstract

It is well known that the bright and remote Galactic globular cluster NGC2419 has a very peculiar structure. In particular its half-light radius is significantly larger than that of ordinary globular clusters of similar luminosity, being as large as that of the brightest nuclei of dwarf elliptical galaxies. In this context it is particularly worth to check the reliability of the existing surface brightness profiles for this cluster and of the available estimates of its structural parameters. Combining different datasets I derive the surface brightness profile going from the cluster center out to ~ 480 arcsec, i.e. ~25 core radii. (Abridged). The newly obtained surface brightness profile is in excellent agreement with that provided by Trager, King & Djorgovski for r>= 4 arcsec; it is best fitted by a King model having r_c=0.32 arcmin, mu_V(0)=19.55 and C=1.35. Also new independent estimates of the total integrated V magnitude (V_t=10.47 +/- 0.07) and of the half-light radius (r_h=0.96 arcmin +/- 0.2 arcmin) have been obtained. (Abridged). The structure of NGC2419 is now reliably constrained by (at least) two fully independent observational profiles that are in good agreement one with the other. Also the overall agreement between structural parameters independently obtained by different authors is quite satisfying.