The ODYSSEUS Survey. Spatial correlation of magnetospheric inclinations points to parsec-scale star-cloud connection

TL;DR

The paper addresses whether parsec-scale natal cloud conditions imprint coherent orientations on CTTS magnetospheric inclinations $i_{ m mag}$. It combines an expanded Lupus CTTS sample with accretion-flow modeled $i_{ m mag}$ and applies a 4D consensus clustering approach using HDBSCAN on 3D positions plus $i_{ m mag}$, with Monte Carlo uncertainty propagation. The analysis uncovers parsec-scale correlations on ~3 pc scales, organizing stars into five robust groups that align with Lupus subregions and large-scale shells, indicating a physical star-cloud connection from Myr-scale cloud dynamics down to sub-au accretion zones. The findings have significant implications for understanding exoplanet occurrence biases that may arise from region-dependent orientation trends and motivate similar regional studies in other star-forming environments.

Abstract

The properties of stars and planets are shaped by the initial conditions of their natal clouds. However, the spatial scales over which the initial conditions can exert a significant influence are not well constrained. We report the first evidence for parsec-scale spatial correlations of stellar magnetospheric inclinations ($i_{\rm mag}$), observed in the Lupus low-mass star forming region. Applying consensus clustering with a hierarchical density-based clustering algorithm, we demonstrate that the detected spatial dependencies are stable against perturbations by measurement uncertainties. The $i_{\rm mag}$ correlation scales are on the order of ~3 pc, which aligns with the typical scales of the Lupus molecular cloud filaments. Our results reveal a connection between large-scale forces -- in the form of expanding shells from the Upper Scorpius and Upper-Centaurus-Lupus regions -- and sub-au scale system configurations. We find that Lupus has a non-uniform $i_{\rm mag}$ distribution and suggest that this results from the preferential elongation of protostellar cores along filamentary axes. Non-uniformity would have significant implications for exoplanet occurrence rate calculations, so future work should explore the longevity of these biases driven by the star-cloud connection.

Figures (10)

• Figure 1: Top left panel: Map of the Lupus targets analyzed in this work with the IRIS 100 $\mu$m map IRIS2005 shown in grayscale. The color bar shows the nominal magnetospheric inclination $i_{\rm mag}$ found from the accretion flow model (see Tables \ref{['tab:sample']} and \ref{['tab:flowresults']}). Point sizes indicate $d_{\rm Gaia}$ such that more distant sources appear smaller. A labeled version can be found in Figure \ref{['fig:LupusApp']} in Appendix \ref{['sec:Appendix']}, along with zoomed images of individual subregions. Position angles (PAs) are shown as colored arrows, indicating the projected major axes of the gas disks. They come from Yen2018 and Trapman2025 and are measured from $0^\circ\leq {\rm PA} < 360^\circ$, defined counterclockwise from north (see compass in lower right). In the remaining subfigures, the PAs are indicated by black arrows. Top right panel: HDBSCAN group assignments (colors) of the Lupus CTTSs, taking 3D spatial location and $i_{\rm mag}$ into account with equal weight. Non-grouped CTTSs are indicated by gray x markers. The shaded blue region indicates the inner and outer boundaries of the Upper Scorpius HI shell projected onto the plane of the sky, and the dotted lines show the projected orientation of the Upper-Centaurus-Lupus wind shell deGeus1992Gaczkowski2017. Bottom panels: Three-dimensional versions of the top right panel plotted in ICRS cartesian coordinates using the nominal $d_{\rm Gaia}$ values, with each axis spanning 30 pc. The blue curve indicates the outer edge of the USco shell, at 36 pc from its center. The white curve indicates the UCL bubble, which does not have a fixed extent but is plotted at a radius of 21 pc from its center for ease of comparison. The dashed lines show lines of sight between the cluster centroids and Earth. An animated version of this figure is available in the online journal, which rotates the figure 360$^\circ$ around the $z$ axis to show the 3D structure. The video shows three full rotations over a duration of 1 minute 12 seconds.
• Figure 2: Comparison between $i_{\rm mag}$ and $i_{\rm disk,gas}$. The dashed line indicates equality, and the shaded region marks $\pm$20$^\circ$. Red outlines indicate transition disks, and blue outlines indicate measurements from AGE-PRO Zhang2025Vioque2025Trapman2025.
• Figure 3: Top panel: Same as Figure \ref{['fig:LupusIncl']} (top left), but with CTTS names labeled. Small arrows again denote disk PAs. Bottom panels: Zoomed regions around Lupus I (middle left), Lupus II (middle right), Lupus III (bottom left), and Lupus IV (bottom right). Dashed white lines show the approximate orientation and extent of the primary filaments in the plane of the sky. Blue lines show the mean magnetic field direction, and the line length is 3 pc in the plane of the sky to give a broad indication of the detected correlation scale. High-resolution background images show the Herschel SPIRE 250 $\mu$m dust continuum maps from the Herschel Gould Belt Survey Andre2010, and low resolution images show the IRIS 100 $\mu$m map IRIS2005. Points are colored by $i_{\rm mag}$ according to the color bar in the top panel.
• Figure 4: Consensus matrix for the 3D groups found from 5000 MC iterations of HDBSCAN, using min_cluster_size=3, min_samples=3, and cluster_selection_method=excess of mass. Dark squares indicate groups with high pairwise co-membership probabilities ($P_{ij}$), and Roman numerals indicate the associated Lupus subregions. Red labels indicate CTTSs that are marked as noise in more than 30% of the MC iterations, all of which are off-cloud sources.
• Figure 5: Same as Figure \ref{['fig:matrix']}, but for the 4D groups. Roman numerals indicate the assigned groups, and red labels indicate CTTSs that are marked as noise in more than 30% of the MC iterations.