Bringing the Norma Dark Cloud to Light in X-Rays
August 2025 • 2025AJ....170..114S
Abstract • The filamentary dark cloud complex in Norma reveals signs of active low-mass star formation including protostars, Hα emission line stars, Herbig–Haro objects, and the eruptive FU Orionis-like star V346 Nor. We present results of the first pointed X-ray observations of the Norma dark cloud, focusing on the westernmost Sandqvist 187 region. Chandra detected 75 X-ray sources, and a complementary XMM-Newton observation detected 92 sources within the Chandra field of view, of which 46 are cross-matched to Chandra, yielding 121 unique X-ray sources. We present a catalog of X-ray sources along with basic X-ray properties and candidate IR and optical counterparts. Existing near-IR photometry reveals several X-ray sources with color excesses typical of young stars with disks. Gaia parallaxes single out foreground stars and X-ray sources at distances of 500–1000 pc that are probable cloud members. The known emission line stars Sz 136 and Sz 137 were detected but V346 Nor was not. Interestingly, the optical and IR counterparts of the brightest Chandra source are not known with certainty but the prime suspects are very faint. Thus, the nature of the object responsible for the bright X-ray emission remains speculative. The X-ray observations presented here will serve as a pathfinder for identifying and characterizing the young stellar population in the Norma dark cloud.
Links
- PDF https://iopscience.iop.org/article/10.3847/1538-3881/ade8f4/pdf
- PREPRINT http://arxiv.org/abs/2507.09047
- DATA http://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/biblink.pl?code=2025AJ....170..114S
- DATA https://cda.harvard.edu/chaser?obsid=23387,24511,26283,27464
- ELECTR https://doi.org/10.3847/1538-3881/ade8f4
