Disc kinematics and stability in high-mass star formation

Semenov

et al. 2021

A&A

Self Cite

Section: Physical Structurementioning

confidence: 99%

Physical and chemical structure of high-mass star-forming regions

Semenov

et al. 2021

A&A

Self Cite

“…Oliva & Kuiper 2020) predict disk fragmentation and formation of companion stars and spiral-like structures. Synthetic observations created using these (Ahmadi et al 2019) and other models (Jankovic et al 2019) predict that the substructures of the disks are observable with interferometers such as ALMA and NOEMA. In the models discussed by Ahmadi et al (2019), the gravitationally unstable disk fragments and forms multiple companion cores in hydrostatic equilibrium within the disk, where each core is observed to form its own disk.…”

Section: Disk Fragmentation and Kinematicsmentioning

confidence: 99%

“…Synthetic observations created using these (Ahmadi et al 2019) and other models (Jankovic et al 2019) predict that the substructures of the disks are observable with interferometers such as ALMA and NOEMA. In the models discussed by Ahmadi et al (2019), the gravitationally unstable disk fragments and forms multiple companion cores in hydrostatic equilibrium within the disk, where each core is observed to form its own disk. In our observations, we detect a single fragmented disk with three companion cores with separations of 800 and 1400 AU.…”

Section: Disk Fragmentation and Kinematicsmentioning

confidence: 99%

“…A disk undergoing a Keplerian rotation is prone to fragmentation when self-gravity and thermal pressure are no longer in equilibrium (Toomre 1964). Using 3D radiation-hydrodynamic simulations (for a detailed modeling description see Oliva & Kuiper 2020), Ahmadi et al (2019) study the fragmentation of a massive disk and the "observability" of such fragmentation given a variety of source inclinations and distances. This study reveals that a Toomre-unstable disk fragments on scales below 500 AU, where each fragment hosts its own smaller scale accretion disk that is best resolved in the synthetic Atacama Large Millimeter/submillimeter Array (ALMA) observations reaching an angular resolution of ∼80 mas at a distance of 800 pc (corresponding to a spatial resolution of ∼60 AU).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Disk fragmentation in high-mass star formation

Suri

et al. 2021

A&A

Self Cite

Context. Increasing evidence suggests that, similar to their low-mass counterparts, high-mass stars form through a disk-mediated accretion process. At the same time, formation of high-mass stars still necessitates high accretion rates, and hence, high gas densities, which in turn can cause disks to become unstable against gravitational fragmentation. Aims. We study the kinematics and fragmentation of the disk around the high-mass star forming region AFGL 2591-VLA 3 which was hypothesized to be fragmenting based on the observations that show multiple outflow directions. Methods. We use a new set of high-resolution (0 . 19) IRAM/NOEMA observations at 843 µm towards VLA 3 which allow us to resolve its disk, characterize the fragmentation, and study its kinematics. In addition to the 843 µm continuum emission, our spectral setup targets warm dense gas and outflow tracers such as HCN, HC 3 N and SO 2 , as well as vibrationally excited HCN lines. Results. The high resolution continuum and line emission maps reveal multiple fragments with subsolar masses within the inner ∼1000 AU of VLA 3. Furthermore, the velocity field of the inner disk observed at 843 µm shows a similar behavior to that of the larger scale velocity field studied in the CORE project at 1.37 mm. Conclusions. We present the first observational evidence for disk fragmentation towards AFGL 2591-VLA 3, a source that was thought to be a single high-mass core. While the fragments themselves are low-mass, the rotation of the disk is dominated by the protostar with a mass of 10.3±1.8 M . These data also show that NOEMA Band 4 can obtain the highest currently achievable spatial resolution at (sub-)mm wavelengths in observations of strong northern sources.

“…In low-mass star-forming regions, both the disk and outflow are commonly observed around protostars. Toward high-mass protostars, large bipolar outflows are found (e.g., Beuther et al 2002b;Arce et al 2007;Frank et al 2014), but disk structures remain challenging to observe (e.g., Cesaroni et al 2017;Ahmadi et al 2019;Maud et al 2019;Beltrán 2020;Johnston et al 2020).…”

Section: Molecular Outflowsmentioning

confidence: 99%

Clustered star formation at early evolutionary stages

Semenov

et al. 2021

A&A

Self Cite

Context. The process of high-mass star formation during the earliest evolutionary stages and the change over time of the physical and chemical properties of individual fragmented cores are still not fully understood. Aims. We aim to characterize the physical and chemical properties of fragmented cores during the earliest evolutionary stages in the very young star-forming regions ISOSS J22478+6357 and ISOSS J23053+5953. Methods. NOrthern Extended Millimeter Array (NOEMA) 1.3 mm data are used in combination with archival mid-and far-infrared Spitzer and Herschel telescope observations to construct and fit the spectral energy distributions (SEDs) of individual fragmented cores. The radial density profiles are inferred from the 1.3 mm continuum visibility profiles and the radial temperature profiles are estimated from H 2 CO rotation temperature maps. Molecular column densities are derived with the line fitting tool XCLASS. The physical and chemical properties are combined by applying the physical-chemical model MUSCLE in order to constrain the chemical timescales of a few line-rich cores. The morphology and spatial correlations of the molecular emission are analyzed using the histogram of oriented gradients (HOG) method.Results. The mid-infrared data show that both regions contain a cluster of young stellar objects. Bipolar molecular outflows are observed in the CO 2 − 1 transition toward the strong mm cores indicating protostellar activity. We find strong molecular emission of SO, SiO, H 2 CO, and CH 3 OH in locations which are not associated with the mm cores. These shocked knots can be either associated with the bipolar outflows or, in the case of ISOSS J23053+5953, with a colliding flow that creates a large shocked region between the mm cores. The mean chemical timescale of the cores is lower (∼20 000 yr) compared to that of the sources of the more evolved CORE sample (∼60 000 yr). With the HOG method, we find that the spatial emission of species tracing the extended emission and of shock-tracing molecules are well correlated within transitions of these groups. Conclusions. Clustered star formation is observed toward both regions. Comparing the mean results of the density and temperature power-law index with the results of the original CORE sample of more evolved regions (Gieser et al. 2021), it appears that both do not change significantly from the earliest evolutionary stages to the hot molecular core stage. However, we find that the 1.3 mm flux, kinetic temperature, H 2 column density, and core mass of the cores increase in time, which can be traced both in the M/L ratio and the chemical timescale τ chem .