Deep VLA Images of the HH 124 IRS Radio Cluster and its Surroundings and a New Determination of the Distance to NGC 2264

TL;DR

This study presents deep radio images of the HH 124 IRS Radio Cluster, identifying its members, analyzing their properties, and proposing a revised distance of approximately 400 parsecs to NGC 2264 based on proper motions and kinematic data.

Contribution

The paper provides new deep radio observations of HH 124 IRS, identifies cluster members, and offers a revised, closer distance estimate to NGC 2264 using multiple kinematic methods.

Findings

Detected 50 radio sources, most compact, in the HH 124 IRS region.

Identified about 11 Galactic objects, mostly young stars, within a small area.

Revised the distance to NGC 2264 to approximately 400 pc, closer than previous estimates.

Abstract

We present new deep ($\sigma\sim6~\mu$Jy) radio images of the HH~124~IRS Radio Cluster at 4.8 and 7.5 GHz. We detect a total of 50 radio sources, most of them compact. Variability and spectral indices were analyzed in order to determine the nature of the sources and of their radio emission. A proper motion study was also performed for several of these radio sources using radio observation previously reported. Our analysis shows that 11 radio sources can be related with Galactic objects, most of them probably young stars. Interestingly, eight of these sources are in an area less than 1 square arcminute in size. The importance of such compact clusters resides in that all its members can be observed in a single pointing with most telescopes, and are, therefore, ideal for multi-wavelength studies of variability. Another 4 of the detected sources are clearly extragalactic. Finally, we propose from statistical arguments that from the remaining sources, about 10 are Galactic, but our study does not allow us to identify which of the sources fall in that specific category. The relatively large proper motions observed for the sources in HH~124~IRS suggest that this region is located at about 400 pc from the Sun. This is significantly smaller than the $\sim$800--900 pc distance usually assigned to the nearby open cluster NGC~2264 with which HH~124 is thought to be associated. However, a reanalysis of the Hipparcos parallaxes for members of NGC~2264, a convergent point approach, and a kinematic analysis all argue in favor of a distance of order 400 pc for NGC~2264 as well.