ALMA observations investigate disk and jet of a massive protostar

17 Dec 2024, 13:30 by Tomasz Nowakowski

This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility:

fact-checked

preprint

trusted source

proofread

Moment-8 maps in various molecular tracers of the jet in IRAS 20126+4104. Credit: arXiv (2024). DOI: 10.48550/arxiv.2412.06589

Astronomers from Italy and Spain have used the Atacama Large Millimeter/submillimeter Array (ALMA) to observe a massive protostar designated IRAS 20126+4104. The observational campaign, detailed in a paper published Dec. 9 on the arXiv preprint server, delivers important insights into the protostar's disk and jet system.

Protostars, also known as young stellar objects (YSOs), are generally stars in the early stages of formation, observed embedded in dense molecular clumps, environments containing plenty of molecular gas and interstellar dust. They increase in mass by accumulating surrounding material through accretion.

IRAS 20126+4104 is a protostar at a distance of about 5,300 light years away from Earth. It has a bolometric luminosity of 13,000 solar luminosities and its mass is estimated to be approximately 12 solar masses.

Previous observations of IRAS 20126+4104 have found that it has a thermal radio jet and a circumstellar structure that appears to undergo Keplerian rotation around the protostar. Due to its relative proximity and simple structure, IRAS 20126+4104 is an excellent target for studying a disk and jet system.

That is why a team of astronomers led by Riccardo Cesaroni of the Arcetri Observatory in Italy decided to employ ALMA to analyze the structure and kinematics of IRAS 20126+4104.

"Despite the high declination of IRAS 20126+4104, it has been possible to perform successful observations with ALMA at 1.4 mm in the continuum emission and a number of molecular tracers of high-density gas (for the disk) and shocked gas (for the jet)," the researchers explained.

ALMA observations allowed Cesaroni's team to better define the geometrical and kinematical parameters of the jet and to obtain maps of the temperature and column density in the bow-shock regions at the tips of the jet lobes. It was found that the jet of IRAS 20126+4104 is highly collimated, lies close to the plane of the sky, and expands with velocity increasing with distance.

When it comes to the disk of IRAS 20126+4104, the study found that it is not only undergoing Keplerian rotation, but also has an inward velocity component. The disk turned out to be slightly inclined, stable at all radii, and its accretion rate was calculated to be at a level of 0.001 solar masses per year.

The observations also indicate that the disk has a dusty envelope that absorbs the emission from the disk surface. Moreover, the collected data suggest the existence of a significant deviation from axial symmetry in the southwest part of the disk. This, according to the authors of the paper, may be caused by a nearby, lower-mass companion to IRAS 20126+4104 or may be the result of disk material being dragged into expansion along the jet.

More information: R. Cesaroni et al, Dissecting the disk and the jet of a massive (proto)star. An ALMA view of IRAS20126+4104, arXiv (2024). DOI: 10.48550/arxiv.2412.06589

Journal information: arXiv