Richness of compact radio sources in NGC 6334D to F

¹ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
e-mail: smedina@mpifr-bonn.mpg.de
² Instituto de Astronomía, Universidad Nacional Autónoma de México, Ensenada, B. C., CP 22830, Mexico
³ Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, 58089 Morelia, Mexico
⁴ Instituto de Astronomía, Universidad Nacional Autónoma de México, Apartado Postal 70-264, CdMx CP 04510, Mexico

Received: 14 August 2017
Accepted: 3 November 2017

Abstract

Context. The presence and properties of compact radio sources embedded in massive star forming regions can reveal important physical properties about these regions and the processes occurring within them. The NGC 6334 complex, a massive star forming region, has been studied extensively. Nevertheless, none of these studies has focused in its content in compact radio sources.

Aims. Our goal here is to report on a systematic census of the compact radio sources toward NGC 6334, and their characteristics. This will be used to attempt to define their very nature.

Methods. We used the VLA C band (4–8 GHz) archive data with 0.̋36 (500 AU) of spatial resolution and noise level of 50 μJy bm⁻¹ to carry out a systematic search for compact radio sources within NGC 6334. We also searched for infrared counterparts to provide some constraints on the nature of the detected radio sources.

Results. A total of 83 compact sources and three slightly resolved sources were detected. Most of them are here reported for the first time. We found that 29 of these 86 sources have infrared counterparts and three are highly variable. Region D contains 18 of these sources. The compact source toward the center, in projection, of region E is also detected.

Conclusions. From statistical analyses, we suggest that the 83 reported compact sources are real and most of them are related to NGC 6334 itself. A stellar nature for 27 of them is confirmed by their IR emission. Compared with Orion, region D suffers a deficit of compact radio sources. The infrared nebulosities around two of the slightly resolved sources are suggested to be warm dust, and we argue that the associated radio sources trace free-free emission from ionized material. We confirm the thermal radio emission of the compact source in region E. However, its detection at infrared wavelengths implies that it is located in the foreground of the molecular cloud. Finally, three strongly variable sources are suggested to be magnetically active young stars.