Periodic Reporting for period 1 - ISM-FLOW (The 3D motion of the Interstellar Medium with ESO and ESA telescopes)
Periodo di rendicontazione: 2023-01-01 al 2025-06-30
The ISM-FLOW AdG aims to measure the three-dimensional flow of local gas by combining near-infrared observations from ESO telescopes with ESA Gaia data. The project also seeks to characterize newly observed, elongated Galactic-scale gas structures—most notably the Radcliffe Wave—which challenge the traditional Gould’s Belt model. In addition, it investigates the formation and dispersal of giant molecular clouds and star-forming regions within these structures. Ultimately, the proposal intends to present a comprehensive picture of the local kiloparsec of the Milky Way, placing it in context within the Galaxy and establishing a reference for comparison with nearby galaxies. This improved understanding will enhance our knowledge of small-scale interstellar medium dynamics, spiral arm interactions, and star and planet formation processes.
The three specific goals of the ISM-FLOW project are:
1) Describe the motion and vertical oscillation of the kiloparsec-long Radcliffe Wave.
2) Characterize the fragmentation of the Radcliffe Wave into approximately 100-pc-scale star-forming regions and quantify feedback.
3) Place the Radcliffe Wave within the broader context of the Milky Way.
The three specific goals of the ISM-FLOW project are:
1) Describe the motion and vertical oscillation of the kiloparsec-long Radcliffe Wave.
2) Characterize the fragmentation of the Radcliffe Wave into approximately 100-pc-scale star-forming regions and quantify feedback.
3) Place the Radcliffe Wave within the broader context of the Milky Way.
We focus first on the main goals of the project:
1) Describe the motion and the vertical oscillation of the kpc-long Radcliffe Wave
We developed a method that uses young stellar clusters associated with the Radcliffe Wave to trace its three-dimensional motion. For the first time, we measured both the overall motion and the vertical oscillation of the Wave, revealing that it oscillates through the Galactic plane while drifting radially away from the Galactic center. These findings were published in Nature (Konietzka et al. 2024).
On the technical side, our intensive testing showed that atomic and molecular spectroscopy measurements alone were insufficient for reliable proper motion estimates—even when supplemented with Gaia proper motions for young stars. Initially, our data did not indicate any oscillatory motion. It was only after developing an algorithm that robustly clusters young stars and employs the averaged motion of each cluster to reduce errors that the oscillatory motion became apparent.
2) Characterize the fragmentation of the Radcliffe Wave into approximately 100-pc-scale star-forming regions and quantify feedback
This goal is progressing well and is near completion. We have made substantial headway on several fronts. The ongoing fragmentation study reveals a periodicity of approximately 400 parsecs between giant molecular clouds within the Radcliffe Wave. A manuscript is currently in preparation. Simultaneously, we are focusing on understanding the largest feedback event within the Radcliffe Wave, the Orion-Eridanus superbubble, and its impact on the structure of the Wave. To this end, we continue developing the SigMA algorithm, created in my group (Ratzenböck et al. 2023), which has proven invaluable in disentangling young stellar populations in large star-forming regions.
3) Place the Radcliffe Wave within the broader context of the Milky Way
This goal is still in progress, with significant work already underway. It is necessarily the last goal as it requires a bird's-eye view of the main results in goals 1 and 2 and the development of a connection between the new results and the current understanding of the Milky Way structure, the latter changing quickly in the literature due to the Gaia revolution.
The most important result so far is that we have identified that the majority of young clusters within 1 kiloparsec of the Sun arise from three distinct spatial volumes. At present, dispersed throughout the solar neighborhood, their past positions more than 30 million years ago reveal that these families of clusters each formed in one of three compact, massive star-forming complexes. We estimate that more than 200 supernovae were produced from these families. These clustered supernovae produced both the Local Bubble and the largest nearby supershell, and perhaps the Radcliffe Wave, dramatically affecting gas distribution in the local kpc. This result was published in Nature (Swiggum et al. 2024)
We also have significant results in answering the most basic question: Is the Radcliffe Wave unique in the Milky Way? The answer is a clear no from our search for similar structures in the local Milky Way. Although the Radcliffe Wave is the largest gas structure in the near kpc, it is by far not unique. We have found about seven large-scale structures that, like the Radcliffe Wave, are undulating and probably oscillating around the plane of the Milky Way. This result represents a major shift in understanding the distribution and motion of the local interstellar medium: the Radcliffe Wave is not the exception but the rule. Our early results point to the formation of these structures as the precursors of giant molecular clouds forming.
1) Describe the motion and the vertical oscillation of the kpc-long Radcliffe Wave
We developed a method that uses young stellar clusters associated with the Radcliffe Wave to trace its three-dimensional motion. For the first time, we measured both the overall motion and the vertical oscillation of the Wave, revealing that it oscillates through the Galactic plane while drifting radially away from the Galactic center. These findings were published in Nature (Konietzka et al. 2024).
On the technical side, our intensive testing showed that atomic and molecular spectroscopy measurements alone were insufficient for reliable proper motion estimates—even when supplemented with Gaia proper motions for young stars. Initially, our data did not indicate any oscillatory motion. It was only after developing an algorithm that robustly clusters young stars and employs the averaged motion of each cluster to reduce errors that the oscillatory motion became apparent.
2) Characterize the fragmentation of the Radcliffe Wave into approximately 100-pc-scale star-forming regions and quantify feedback
This goal is progressing well and is near completion. We have made substantial headway on several fronts. The ongoing fragmentation study reveals a periodicity of approximately 400 parsecs between giant molecular clouds within the Radcliffe Wave. A manuscript is currently in preparation. Simultaneously, we are focusing on understanding the largest feedback event within the Radcliffe Wave, the Orion-Eridanus superbubble, and its impact on the structure of the Wave. To this end, we continue developing the SigMA algorithm, created in my group (Ratzenböck et al. 2023), which has proven invaluable in disentangling young stellar populations in large star-forming regions.
3) Place the Radcliffe Wave within the broader context of the Milky Way
This goal is still in progress, with significant work already underway. It is necessarily the last goal as it requires a bird's-eye view of the main results in goals 1 and 2 and the development of a connection between the new results and the current understanding of the Milky Way structure, the latter changing quickly in the literature due to the Gaia revolution.
The most important result so far is that we have identified that the majority of young clusters within 1 kiloparsec of the Sun arise from three distinct spatial volumes. At present, dispersed throughout the solar neighborhood, their past positions more than 30 million years ago reveal that these families of clusters each formed in one of three compact, massive star-forming complexes. We estimate that more than 200 supernovae were produced from these families. These clustered supernovae produced both the Local Bubble and the largest nearby supershell, and perhaps the Radcliffe Wave, dramatically affecting gas distribution in the local kpc. This result was published in Nature (Swiggum et al. 2024)
We also have significant results in answering the most basic question: Is the Radcliffe Wave unique in the Milky Way? The answer is a clear no from our search for similar structures in the local Milky Way. Although the Radcliffe Wave is the largest gas structure in the near kpc, it is by far not unique. We have found about seven large-scale structures that, like the Radcliffe Wave, are undulating and probably oscillating around the plane of the Milky Way. This result represents a major shift in understanding the distribution and motion of the local interstellar medium: the Radcliffe Wave is not the exception but the rule. Our early results point to the formation of these structures as the precursors of giant molecular clouds forming.
Breakthrough 1: The Radcliffe Wave, a 3-kpc-long gas structure, is oscillating. The cause of this oscillation remains unknown, but its very existence represents a breakthrough in our understanding of the interstellar medium. This discovery raises new questions about the origin and dynamics of such large structures, with direct implications for the origins of giant molecular clouds and star formation. Preliminary findings suggest that the Radcliffe Wave is not an anomaly but rather a fundamental feature of large-scale gas organization in the Galaxy.
Breakthrough 2: Most young star clusters near the Solar System formed in just three distinct regions. Current data indicate that we are moving through waves of dispersing clusters, likely originating from the Carina spiral arm. These clusters produced approximately 200 supernovae, whose energy reshaped the local interstellar medium and influenced the environment around the Sun.
Breakthrough 3: About 14 Myr ago, the Solar System was inside the Radcliffe Wave. This crossing coincided with the Middle Miocene transition, a key period in Earth's climate history. The potential implications of this event for the past 20 Myr of Earth's evolution warrant a dedicated interdisciplinary investigation.
The last breakthrough was unexpected.
Breakthrough 2: Most young star clusters near the Solar System formed in just three distinct regions. Current data indicate that we are moving through waves of dispersing clusters, likely originating from the Carina spiral arm. These clusters produced approximately 200 supernovae, whose energy reshaped the local interstellar medium and influenced the environment around the Sun.
Breakthrough 3: About 14 Myr ago, the Solar System was inside the Radcliffe Wave. This crossing coincided with the Middle Miocene transition, a key period in Earth's climate history. The potential implications of this event for the past 20 Myr of Earth's evolution warrant a dedicated interdisciplinary investigation.
The last breakthrough was unexpected.