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The density structure of the interstellar medium determines where stars form and release energy, momentum and heavy elements, driving galaxy evolution 1 – 4 . Density variations are seeded and amplified by gas motion, but the exact nature of this motion is unknown across spatial scales and galactic environments 5 . Although dense star-forming gas probably emerges from a combination of instabilities 6 , 7 , convergent flows 8 and turbulence 9 , establishing the precise origin is challenging because it requires gas motion to be quantified over many orders of magnitude in spatial scale. Here we measure 10 – 12 the motion of molecular gas in the Milky Way and in nearby galaxy NGC 4321, assembling observations that span a spatial dynamic range 10 −1 –10 3  pc. We detect ubiquitous velocity fluctuations across all spatial scales and galactic environments. Statistical analysis of these fluctuations indicates how star-forming gas is assembled. We discover oscillatory gas flows with wavelengths ranging from 0.3–400 pc. These flows are coupled to regularly spaced density enhancements that probably form via gravitational instabilities 13 , 14 . We also identify stochastic and scale-free velocity and density fluctuations, consistent with the structure generated in turbulent flows 9 . Our results demonstrate that the structure of the interstellar medium cannot be considered in isolation. Instead, its formation and evolution are controlled by nested, interdependent flows of matter covering many orders of magnitude in spatial scale. Statistical analysis of velocity fluctuations in the interstellar medium (ISM) of the Milky Way and NGC 4321 show that the motion of molecular gas over scales ranging from 0.1 to 1,000 pc is similar, and consistent with that generated by a combination of gravity and turbulence. ISM structure at one scale is therefore linked to structure at other scales.

Over the last decades, high-mass star formation research has concentrated on either the large-scale molecular cloud environments or on the smallscale hot dense molecular cores surrounding massive proto-stars/clusters and young stellar objects. However, questions regarding the gas flow from large to small scales, and how the gas is transferred via intermediate-scale filaments and clumps have so far been largely neglected. With “Cygnus Allscale Survey of Chemistry and Dynamical Environments (CASCADE)”, a part of the Max Planck IRAM Observatory Program (MIOP), we want to overcome this missing gap via studying one well-known molecular cloud complex with the IRAM NOEMA and 30m facilities from small to large scales, thereby connecting these important physical processes. In the nearby (1.4 kpc) luminous Cygnus X region, recent and on-going star formation combine to present a rich Northern hemisphere laboratory in which star formation and feedback processes can be studied globally as well as locally. Using the new and unique 4 mm capabilities of NOEMA, together with the IRAM 30m telescope, the flow of gas from cloudto core-scales is being probed with observations of large mosaics covering the ground state lines of many molecules, including their deuterium substituted isotopologs, with the unique large bandwidth only possible with this facility. Here a brief introduction into the program, together with initials results, is presented.

The dominant mechanism forming multiple stellar systems in the high-mass regime ( M *  ≳ 8  M ⊙ ) remained unknown because direct imaging of multiple protostellar systems at early phases of high-mass star formation is very challenging. High-mass stars are expected to form in clustered environments containing binaries and higher-order multiplicity systems. So far only a few high-mass protobinary systems, and no definitive higher-order multiples, have been detected. Here we report the discovery of one quintuple, one quadruple, one triple and four binary protostellar systems simultaneously forming in a single high-mass protocluster, G333.23–0.06, using Atacama Large Millimeter/submillimeter Array high-resolution observations. We present a new example of a group of gravitationally bound binary and higher-order multiples during their early formation phases in a protocluster. This provides the clearest direct measurement of the initial configuration of primordial high-order multiple systems, with implications for the in situ multiplicity and its origin. We find that the binary and higher-order multiple systems, and their parent cores, show no obvious sign of disk-like kinematic structure. We conclude that the observed fragmentation into binary and higher-order multiple systems can be explained by core fragmentation, indicating its crucial role in establishing the multiplicity during high-mass star cluster formation. High spatial resolution ALMA observations reveal a group of gravitationally bound quintuple, quadruple, triple and binary protostellar systems in the early stages of formation in a high-mass protocluster. This finding provides a direct measurement of the multiplicity of high-mass star formation.

The IRAM CORE large program combines data from NOEMA and the IRAM 30m telescope to study a diverse set of physical and chemical processes during the formation of high-mass stars. Here, we present a selected compilation of exciting results obtained during the survey.

Studies of evolved massive stars indicate that they form in a clustered mode. During the earliest evolutionary stages, these regions are embedded within their natal cores. Here we present high-spatial-resolution interferometric dust continuum observations disentangling the cluster-like structure of a young massive star-forming region. The derived protocluster mass distribution is consistent with the stellar initial mass function. Thus, fragmentation of the initial massive cores may determine the initial mass function and the masses of the final stars. This implies that stars of all masses can form via accretion processes, and coalescence of intermediate-mass protostars appears not to be necessary.

The formation of astrophysical objects of different nature, from black holes to gaseous giant planets, involves a disk–jet system, where the disk drives the mass accretion onto a central compact object and the jet is a fast collimated ejection along the disk rotation axis. Magnetohydrodynamic disk winds can provide the link between mass accretion and ejection, which is essential to ensure that the excess angular momentum is removed and accretion can proceed. However, until now, we have been lacking direct observational proof of disk winds. Here we present a direct view of the velocity field of a disk wind around a forming massive star. Achieving a very high spatial resolution of about 0.05 au, our water maser observations trace the velocities of individual streamlines emerging from the disk orbiting the forming star. We find that, at low elevation above the disk midplane, the flow co-rotates with its launch point in the disk, in agreement with magneto-centrifugal acceleration. Beyond the co-rotation point, the flow rises spiralling around the disk rotation axis along a helical magnetic field. We have performed (resistive-radiative-gravito-)magnetohydrodynamic simulations of the formation of a massive star and record the development of a magneto-centrifugally launched jet presenting many properties in agreement with our observations. The direct observation of the velocity field of a disk wind around a forming massive star has been achieved with high-spatial-resolution (0.05 au) observations of water masers.

Over the last decades, high-mass star formation research has concentrated on either the large-scale molecular cloud environments or on the smallscale hot dense molecular cores surrounding massive proto-stars/clusters and young stellar objects. However, questions regarding the gas flow from large to small scales, and how the gas is transferred via intermediate-scale filaments and clumps have so far been largely neglected. With “Cygnus Allscale Survey of Chemistry and Dynamical Environments (CASCADE)”, a part of the Max Planck IRAM Observatory Program (MIOP), we want to overcome this missing gap via studying one well-known molecular cloud complex with the IRAM NOEMA and 30m facilities from small to large scales, thereby connecting these important physical processes. In the nearby (1.4 kpc) luminous Cygnus X region, recent and on-going star formation combine to present a rich Northern hemisphere laboratory in which star formation and feedback processes can be studied globally as well as locally. Using the new and unique 4 mm capabilities of NOEMA, together with the IRAM 30m telescope, the flow of gas from cloudto core-scales is being probed with observations of large mosaics covering the ground state lines of many molecules, including their deuterium substituted isotopologs, with the unique large bandwidth only possible with this facility. Here a brief introduction into the program, together with initials results, is presented.

Disk-jet systems are common in astrophysical sources of different nature, from black holes to gaseous giant planets. The disk drives the mass accretion onto a central compact object and the jet ejects material along the disk rotation axis. Magnetohydrodynamic disk winds can provide the link between mass accretion and ejection, which is essential to ensure that the excess angular momentum is removed and accretion can proceed. However, up to now, we have been lacking direct observational proof of disk winds. This work presents a direct view of the velocity field of a disk wind around a forming massive star. Achieving a very high spatial resolution of 0.05 au, our water maser observations trace the velocities of individual streamlines emerging from the disk orbiting the forming star. We find that, at low elevation above the disk midplane, the flow co-rotates with its launch point in the disk, in agreement with magneto-centrifugal acceleration. Beyond the co-rotation point, the flow rises spiraling around the disk rotation axis along a helical magnetic field. We have performed (resistive-radiative-gravito-) magnetohydrodynamic simulations of the formation of a massive star and record the development of a magneto-centrifugally launched jet presenting many properties in agreement with our observations.

The revolutionary discovery of thousands of confirmed and candidate planets beyond the solar system brings forth the most fundamentalquestion: How do planets and their host stars form and evolve? Protostars and Planets VI brings together more than 250 contributing authors at the forefront of their field, conveying the latest results in this research area and establishing a new foundation for advancing our understanding of stellar and planetary formation.Continuing the tradition of the Protostars and Planets series, this latest volume uniquely integrates the cross-disciplinary aspects of this broad field. Covering an extremely wide range of scales, from the formation of large clouds in our Milky Way galaxy down to small chondrules in our solar system, Protostars and Planets VI takes an encompassing view with the goal of not only highlighting what we know but, most importantly, emphasizing the frontiers of what we do not know.As a vehicle for propelling forward new discoveries on stars, planets, and their origins, this latest volume in the Space Science Series is an indispensable resource for both current scientists and new students in astronomy, astrophysics, planetary science, and the study of meteorites.