Studying Magnetic Fields in Star Formation and the Turbulent Interstellar Medium (1903.08757v1)

Abstract: Understanding the physics of how stars form is a highly-prioritized goal of modern Astrophysics, in part because star formation is linked to both galactic dynamics on large scales and to the formation of planets on small scales. It is well-known that stars form from the gravitational collapse of molecular clouds, which are in turn formed out of the turbulent interstellar medium. Star formation is highly inefficient, with one of the likely culprits being the regulation against gravitational collapse provided by magnetic fields. Measurement of the polarized emission from interstellar dust grains, which are partially aligned with the magnetic field, provides a key tool for understanding the role these fields play in the star formation process. Over the past decade, much progress has been made by the most recent generation of polarimeters operating over a range of wavelengths (from the far-infrared through the millimeter part of the spectrum) and over a range of angular resolutions (from less than an arcsecond through fractions of a degree). Future developments in instrument sensitivity for ground-based, airborne, and space-borne polarimeters operating over range of spatial scales are critical for enabling revolutionary steps forward in our understanding of the magnetized turbulence from which stars are formed.

• The paper demonstrates that magnetic fields counteract gravitational collapse, thereby regulating star formation in turbulent molecular clouds.
• It employs polarized thermal emission measurements from dust to map magnetic field morphology at multiple scales.
• The study advocates for high-resolution polarimetric instruments to overcome current limitations and refine ISM turbulence models.

Studying Magnetic Fields in Star Formation and the Turbulent Interstellar Medium

The paper under discussion presents a comprehensive examination of the role that magnetic fields play in star formation within the turbulent interstellar medium (ISM). Authored by Laura Fissel and collaborators, this contribution to the Astro2020 Science White Paper series aims to highlight the significance of magnetic fields as a regulatory mechanism across various spatial scales in the ISM, from galactic scales to protostellar cores. The paper underscores the critical implications of understanding these fields in the broader context of planetary system development and the conversion of molecular clouds into stars.

Key Insights

The research posits that magnetic fields are a fundamental factor in the inefficient process of star formation, serving as a counterforce against gravitational collapse. Magnetic fields inhibit gas motion perpendicular to the field lines, thereby slowing star formation. Over the last two decades, considerable progress has been achieved in characterizing these fields and related turbulence through the use of both interferometers and diverse single-dish instruments, which operate over various wavelengths and resolutions. The primary tool used in these investigations is the measurement of polarized thermal emission from dust grains aligned with the magnetic field, allowing the mapping of magnetic field morphology in star-forming regions.

The findings indicate that while Planck satellite data offers large-scale mapping of the magnetic polarization across the Milky Way, its resolution and sensitivity are inadequate for detailed investigation of dense structures within molecular clouds. In contrast, ground-based polarimeters provide higher resolution maps, but their effectiveness is frequently limited by atmospheric interference. To address these limitations, the paper advocates for advancements in instrument sensitivity and resolution, pointing out the necessity of developing next-generation ground-based, airborne, and space-based polarimeters capable of facilitating significant developments in our understanding of magnetized turbulence in star formation contexts.

Implications and Future Directions

The theoretical and practical implications of this research are considerable. The understanding of magnetic fields informs models of molecular cloud formation and the evolution of gravitationally unstable structures within these clouds. Recognizing how magnetic fields influence these processes is pivotal in determining star formation efficiency. Additionally, a deeper understanding of magnetized turbulence enriches the paper of magnetohydrodynamic turbulence and offers essential insight into ISM structure formation at various scales.

The paper calls for high-sensitivity polarization maps of the entire sky and highly detailed maps with resolutions of at least 10 arcseconds encompassing a large spatial dynamic range. Such observations would enable a detailed examination of the magnetic fields on scales relevant to cores and filaments within molecular clouds. Future observational facilities, including proposed projects like OST, PICO, and SPICA, are expected to contribute significantly to these endeavors. Ground-based telescopes with advanced polarimetry, such as the TolTEC on LMT and POL-2 on JCMT, are also highlighted for their role in resolving dense structures like protostellar cores and filaments. Enhanced polarimetric capabilities for next-generation interferometers like ALMA and potential facilities such as the ngVLA are identified as critical for locales such as protostellar and protoplanetary disks.

In conclusion, this paper sets the groundwork for furthering the comprehension of magnetic fields within the ISM and their consequential role in star formation. It delineates a clear research trajectory that blends the development of observational technology with theoretical advancements in magnetohydrodynamic studies. This dual focus is crucial for expanding our understanding of the cosmic processes involved in star and planetary formation, promising further insights into the dynamical interrelation between magnetic fields, turbulence, and star formation efficiency.