Distance and the Initial Mass Function of Young Open Clusters In The Eta Carina Nebula: Tr 14 and Tr 16

TL;DR

This study provides new photometric data and analysis of young clusters Tr 14 and Tr 16 in the eta Carina nebula, revealing their distances, reddening law, initial mass function, and age, with implications for star formation in the region.

Contribution

It offers the first detailed determination of the clusters' distances, reddening law, and initial mass function, along with identifying optical counterparts of X-ray and IR sources.

Findings

Distance modulus of 12.3 mag for both clusters

Initial mass function slope of approximately -1.3

Cluster ages estimated at 1-3 million years

Abstract

We present new UBVI_C CCD photometry of the young open clusters Trumpler 14 (Tr 14) and Trumpler 16 (Tr 16) in the eta Carina nebula. We also identify the optical counterpart of Chandra X-ray sources and Two Micron All Sky Survey point sources. The members of the clusters were selected from the proper motion study, spectral types, reddening characteristics, and X-ray or near-IR excess emission. An abnormal reddening law R_V,cl=4.4\pm0.2 was obtained for the stars in the eta Carina nebula using the 141 early-type stars with high proper motion membership probability (P_u\geq70). We determined the distance to each cluster and conclude that Tr 14 and Tr 16 have practically the same distance modulus of V_0-M_V=12.3\pm0.2 mag (d=2.9\pm0.3 kpc). The slope of the initial mass function was determined to be {\Gamma}=-1.3\pm0.1 for Tr 14, {\Gamma}=-1.3\pm0.1 for Tr 16, and {\Gamma}=-1.4\pm0.1 for all members in the observed region for the stars with log m\geq0.2. We also estimated the age of the clusters to be about 1 -- 3 Myr from the evolutionary stage of evolved stars and low-mass pre-main-sequence stars.