A compact Keplerian-like disc and H30α emission towards the radio jet in the massive protostar W75N(B)-VLA3
Journal article, 2025

Studying young, high-mass stellar objects is challenging for testing models of massive star formation due to their great distances, often kiloparsecs away. This requires extremely high-angular resolution to resolve features like accretion discs around massive protostars. Consequently, while powerful, collimated outflows are evident in massive protostars, the compact accretion discs anticipated at their centres are still proving difficult to pinpoint. This study presents Atacama Large Millimeter/submillimeter Array (ALMA) continuum and molecular line observations at 1.3mm of the massive protostar W75N(B)-VLA3. The observations achieve an angular resolution of ∼0. 12 ( ∼156 au). Dense gas tracers reveal a circumstellar disc of ~450 au in radius surrounding VLA3, with an orientation perpendicular to its associated thermal radio jet. From the millimetre continuum, a total mass of ≈0.43–1.74 M is estimated for the disc. The disc’s velocity profile is consistent with Keplerian rotation around a protostar of ≈16 M. This adds VLA3 to the small number of massive disc-protostar-jet systems documented in the literature with a centrifugally supported disc with a radius less than 500au. Additionally, we detected H30 α recombination line emission towards the radio jet powered by VLA3. Despite limitations in the spatial and spectral resolution, our data reveal a very broad line, indicative of high-velocity motions, as well as a tentative velocity gradient in the jet’s direction, thus favouring the H30 α emission to originate from the radio jet. Should this interpretation be confirmed with new observations, W75N(B)-VLA3 could represent the first protostellar radio jet for which a thermal radio recombination line has been detected.

stars: jets

stars: massive

ISM: individual objects: W75N(B)

stars: protostars

stars: formation

Author

A. Sanchez-Monge

Spanish National Research Council (CSIC)

Centre Tecnològic de Telecomunicacions de Catalunya (CTTC)

J. F. Gomez

Spanish National Research Council (CSIC)

J. M. Torrelles

Spanish National Research Council (CSIC)

Centre Tecnològic de Telecomunicacions de Catalunya (CTTC)

S. Curiel

Universidad Nacional Autónoma de México

J. M. Girart

Centre Tecnològic de Telecomunicacions de Catalunya (CTTC)

Spanish National Research Council (CSIC)

G. Surcis

Istituto nazionale di astrofisica (INAF)

C. Carrasco-Gonzalez

Universidad Nacional Autónoma de México

G. Anglada

Spanish National Research Council (CSIC)

G. A. Fuller

University of Cologne

University of Manchester

C. Goddi

University of Cagliari

University of Sao Paulo (USP)

Istituto nazionale di astrofisica (INAF)

Wouter Vlemmings

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

A. Rodríguez-Kamenetzky

Instituto de Astronomía Teórica y Experimental (IATE)

H. J. van Langevelde

Joint Institute for Very Long Baseline Interferometry European Research Infrastructure Consortium (JIVE)

Leiden University

J. S. Kim

Chinese Academy of Sciences

Korea Astronomy and Space Science Institute

S. W. Kim

Korea Astronomy and Space Science Institute

J. Canto

Universidad Nacional Autónoma de México

Monthly Notices of the Royal Astronomical Society

00358711 (ISSN) 13652966 (eISSN)

Vol. 543 1 662-690

Subject Categories (SSIF 2025)

Atom and Molecular Physics and Optics

Fusion, Plasma and Space Physics

Astronomy, Astrophysics, and Cosmology

DOI

10.1093/mnras/staf1451

More information

Latest update

10/2/2025