An X-ray View of Two Infrared Dark Clouds G034.43+00.24 and G035.39-00.33

TL;DR

This study uses high-resolution Chandra X-ray observations to identify and analyze young stellar objects in two infrared dark clouds, revealing their early star formation stages and estimating their stellar mass and efficiency.

Contribution

It provides the first detailed X-ray analysis of these IRDCs, identifying young stellar populations and estimating their star formation properties.

Findings

Detected 112 and 209 X-ray sources in the IRDCs.

Estimated up to 1,700 solar masses of stars in G035.39-00.33.

Star formation efficiency is at most 5%, indicating early stage of star formation.

Abstract

We present a high spatial resolution Chandra X-ray study of two Infrared Dark Clouds (IRDCs), G034.43+00.24 and G035.39-00.33, which are expected to be in the early phases of star cluster formation. We detect 112 and 209 valid X-ray point sources towards G034.43+00.24 and G035.39-00.33, respectively. We cross-match the X-ray point sources with 2MASS, GLIMPSE and WISE catalogs and find 53% and 59% of the X-ray sources in G034.43+00.24 and in G035.39-00.33 have corresponding infrared counterparts, respectively. These sources are probable members of young massive clusters in formation, and using stellar isochrones we estimate that a population of 1--2 Myr old, intermediate to high mass young stellar objects (YSOs) exist in both IRDCs. Two and ten Class II counterparts to X-ray sources were identified in G034.43+00.24 and in G035.39-00.33, respectively, which are located in or near dark filaments. The X-ray Luminosity Function (XLF) of G035.39-00.33 implies that the total mass consists of up to $\sim1,700\:M_\odot$ of stars, using the XLF of the well-studied Orion Nebula Cluster as calibrator. This corresponds to a star formation efficiency of at most 5%, indicating the system is still very much gas dominated and in an early stage of the star formation process. The population of G034.43+00.24 is less well determined due to the lower sensitivity of its observations.