The massive star-forming region W75N (B) is thought to host a cluster of massive protostars (VLA 1, VLA 2, and VLA 3) undergoing different evolutionary stages. In this work, we present radio continuum data with the highest sensitivity and angular resolution obtained to date in this region, using the VLA-A and covering a wide range of frequencies (4-48 GHz), which allowed us to study the morphology and the nature of the emission of the different radio continuum sources. We also performed complementary studies with multi-epoch Very Large Array (VLA) data and Atacama Large Millimeter Array (ALMA) archive data at 1.3 mm wavelength. We find that VLA 1 is driving a thermal radio jet at scales of approximate to 0.1 arcsec (approximate to 130 au), but also shows signs of an incipient hypercompact HII region at scales of less than or similar to 1 arcsec (less than or similar to 1300 au). VLA 3 is also driving a thermal radio jet at scales of a few tenths of arcsec (few hundred of au). We conclude that this jet is shock exciting the radio continuum sources Bc and VLA 4 (obscured Herbig-Haro objects), which show proper motions moving outward from VLA 3 at velocities of approximate to 112-118 km s(-1). We have also detected three new weak radio continuum sources, two of them associated with millimetre continuum cores observed with ALMA, suggesting that these two sources are also embedded young stellar objects in this massive star-forming region. © 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
The work of AR-K and CC-G was supported by Universidad Nacional Autonoma de Mexico DGAPA-PAPIIT grant number IN108218. JC acknowledges support from grant PAPIIT-UNAM-IG100218. AR-K thanks the Consejo Nacional de Investigaciones Cient ' ificas y T ' ecnicas (CONICET) to support postdoctoral research. AR-K and JMT acknowledge support from the European Union's Horizon 2020 Research and Innovation program under the Marie Sklodowska-Curie grant agreement number 734374 -Project acronym: LACEGAL. NA-L, JFG, and JMT are supported by the Spanish grant AYA201784390-C2-R (AEI/FEDER, UE). SC acknowledges support from DGAPA, UNAM and CONACYT, Mexico. JFG acknowledges financial support from the State Agency for Research of the SpanishMinisterio deCiencia, Innovacion yUniversidades (MCIU) through the `Center of Excellence Severo Ochoa' award for the Instituto de Astrof ' isica de Andaluc ' ia (SEV-2017-0709). This paper makes use of the following ALMA data: ADS/JAO.ALMA 2017.1.01593.S. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), MOST and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ.