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<jats:title>Abstract</jats:title> <jats:p>We investigate the interplay between magnetic (<jats:italic>B</jats:italic>) field, gravity, and turbulence in the fragmentation process of cores within the filamentary infrared dark cloud G34.43+00.24. We observe the magnetic field morphology across G34.43, traced with thermal dust polarization at 350 <jats:italic>μ</jats:italic>m with an angular resolution of 10″ (0.18 pc), and compare with the kinematics obtained from N<jats:sub>2</jats:sub>H<jats:sup>+</jats:sup> across the filament. We derive local velocity gradients from N<jats:sub>2</jats:sub>H<jats:sup>+</jats:sup>, tracing motion in the plane of sky, and compare with the observed local <jats:italic>B</jats:italic> field orientations in the plane of sky. The <jats:italic>B</jats:italic> field orientations are found to be perpendicular to the long axis of the filament toward the MM1 and MM2 ridge, suggesting that the <jats:italic>B</jats:italic> field can guide material toward the filament. Toward MM3, the <jats:italic>B</jats:italic> field orientations appear more parallel to the filament and aligned with the elongated core of MM3, indicating a different role of the <jats:italic>B</jats:italic> field. In addition to a large-scale east–west velocity gradient, we find a close alignment between local <jats:italic>B</jats:italic> field orientations and local velocity gradients toward the MM1/MM2 ridge. This local correlation in alignment suggests that gas motions are influenced by the <jats:italic>B</jats:italic> field morphology or vice versa. Additionally, this alignment seems to become even closer with increasing integrated emission in N<jats:sub>2</jats:sub>H<jats:sup>+</jats:sup>, possibly indicating that a growing gravitational pull alignes the <jats:italic>B</jats:italic> field and gas motion more and more. We analyze and quantify <jats:italic>B</jats:italic> field, gravity, turbulence, and their relative importance toward the MM1, MM2, and MM3 regions with various techniques over two scales, a larger clump area at 2 pc scale and the smaller core area at 0.6 pc scale. While gravitational energy, <jats:italic>B</jats:italic> field, and turbulent pressure all grow systematically from large to small scale, the ratios among the three constituents clearly develop differently over scale. We propose that this varying relative importance between <jats:italic>B</jats:italic> field, gravity, and turbulence over scale drives and explains the different fragmentation types seen at subparsec scale (no fragmentation in MM1; aligned fragmentation in MM2; clustered fragmentation in MM3). We discuss uncertainties, subtleties, and the robustness of our conclusion, and we stress that a multiscale joint analysis is required to understand the dynamics in these systems.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The habitable zone (HZ) is commonly defined as the range of distances from a host star within which liquid water, a key requirement for life, may exist on a planet’s surface. Substantially more CO<jats:sub>2</jats:sub> than present in Earth’s modern atmosphere is required to maintain clement temperatures for most of the HZ, with several bars required at the outer edge. However, most complex aerobic life on Earth is limited by CO<jats:sub>2</jats:sub> concentrations of just fractions of a bar. At the same time, most exoplanets in the traditional HZ reside in proximity to M dwarfs, which are more numerous than Sun-like G dwarfs but are predicted to promote greater abundances of gases that can be toxic in the atmospheres of orbiting planets, such as carbon monoxide (CO). Here we show that the HZ for complex aerobic life is likely limited relative to that for microbial life. We use a 1D radiative-convective climate and photochemical models to circumscribe a Habitable Zone for Complex Life (HZCL) based on known toxicity limits for a range of organisms as a proof of concept. We find that for CO<jats:sub>2</jats:sub> tolerances of 0.01, 0.1, and 1 bar, the HZCL is only 21%, 32%, and 50% as wide as the conventional HZ for a Sun-like star, and that CO concentrations may limit some complex life throughout the entire HZ of the coolest M dwarfs. These results cast new light on the likely distribution of complex life in the universe and have important ramifications for the search for exoplanet biosignatures and technosignatures.</jats:p>