arXiv subjects

Patricio Sanhueza

Publications and source records attributed to Patricio Sanhueza.

At least 37 records · Page 2Linked to original sources

arXiv2026

The Keplerian disk, envelope, and streamers surrounding an early O-type protostar in the Sagittarius C cloud of the Central Molecular Zone

Disk-mediated accretion is central to theories of massive star formation, setting the initial conditions for their evolution. Yet observations of Keplerian disks around early O-type protostars remain scarce, as they are often blended into complex surrounding structures. We report ALMA Band 6 observations (300 au resolution) of an accretion disk surrounding a high-mass protostar in the Sagittarius C (Sgr C) cloud in the Central Molecular Zone (CMZ) around the Galactic Center. We identify spectral lines and analyze the spatial distribution of the emission of the complex organic molecules. We use a dynamical model with an inner Keplerian disk and an outer free-fall envelope to fit the three-dimensional position-position-velocity data of the stacked CH$_3$OCHO molecular lines and constrain the mass of the central protostar to be $\sim40^{+2}_{-3} M_{\odot}$. The fitting results additionally show that the disk has a centrifugal radius at about 1300 au. Considering the infall velocity, radius, and mass of the envelope, we estimate the accretion rate from the envelope onto the disk to be $\sim7\times 10^{-3}\ M_{\odot}\,\mathrm{yr^{-1}}$. We also identify spiral-like structures in the disk that can be described by free-falling streamers. Our results highlight the critical role of accretion disks and streamers in the mass accumulation of early O-type stars in the CMZ.

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arXiv2026

Unveiling an Hourglass-Shaped Magnetic Field toward IRDC G351.77-0.53

We present the SOFIA/HAWC+ 214 $μ$m polarimetric observations toward the infrared dark cloud G351.77-0.53 (hereafter G351), complemented by existing multi-wavelength data sets. Infrared excess from the embedded sources indicate ongoing star formation activity in the cloud. The G351 cloud hosts two prominent star-forming clumps, i.e., c1 and c2. The plane-of-the-sky magnetic field lines from Planck observations are predominantly oriented perpendicular to the filament's major axis. Magnetic field orientations from SOFIA/HAWC+ 214 $μ$m observations reveal distinct hourglass-shaped field configuration toward c1, while the field lines remain perpendicular to the rest of the filament. Using the Davis-Chandrasekhar-Fermi method, we estimate a mean plane-of-the-sky magnetic field strength of $\sim$147 $\pm$ 60 $μ$G in the G351 filament, with values reaching $\sim$0.8 mG toward c1. The mass-to-flux ratio analysis indicates that the filament is magnetically transcritical, where the gravitational and magnetic field energies are comparable. The hourglass-shaped magnetic field observed toward c1 could result from magnetically regulated gravitational collapse, the alignment of converging sub-filaments with the magnetic field, or a combination of both processes. The energy budget analysis further indicates that magnetic fields play an important role in governing the cloud's gas dynamics, followed by contributions from turbulence and gravity.

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arXiv2026

The ALMA-QUARKS Survey: Evidence of an Explosive Molecular Outflow in IRAS 15520--5234

We present a study of the massive protocluster IRAS 15520$-$5234, which displays evidence of an explosive molecular outflow that unleashed a kinetic energy of at least 10$^{48}$ erg. The protocluster contains 16 dense cores detected in the ALMA band 6 continuum emission maps, having masses in the range from 0.2 to 11.0 M$_{\odot}$. Our analysis of CO $(2-1)$ emission reveals 28 well collimated outflow fingers, the majority of which follow a Hubble-Lemaître velocity law. The outflow fingers show no preferred orientation in the plane of sky and emerge from a common center of origin. We estimate the total mass, momentum, and kinetic energy of the outflow fingers and find that the values are at least one order of magnitude higher than the typical bipolar outflows associated with massive protostars. The morphology and kinematics of the outflow fingers suggest that the outflow associated with IRAS 15520$-$5234 is explosive in nature. We calculate the dynamical age of the explosive event to be approximately 6550 years. Additionally, we estimate the frequency of such explosive outflows in the Galaxy, which is one event every 83 years. Finally, we speculate that the rearrangement of masses within the massive protocluster and the dynamical interaction among the massive cores may result in the formation of such an energetic event.

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arXiv2026

ALMAGAL VII. Cataloging Hierarchical Mass Structure from Cores to Clumps across the Galactic Disk

Investigating the multi-scale fragmentation of dense clumps into compact cores is essential for understanding the processes that govern the initial distribution of mass in stellar clusters and how high-mass stars ($>8~M_{\odot}$) form. We present a catalog of the hierarchical continuum structure from 904 clumps observed in the ALMAGAL program, a high resolution ($0.15-0.8$\arcsec) 1.38 mm Atacama Large Millimeter/submillimeter Array (ALMA) large program targeting dense clumps capable of high-mass star formation throughout the Galactic disk. We use \verb|astrodendro|, a dendrogram-based algorithm, on a uniform linear resolution (2000 au) version of the data to extract 5160 continuum structures with effective radii spanning $800-42000$ au and estimated masses between $~0.05-670~M_{\odot}$. With our large sample, we statistically examine differences in clump properties for regions with varying levels of hierarchical complexity. We find that clumps exhibiting the richest hierarchical morphology have distributions with higher dust temperatures, surface densities, luminosity-to-mass (\textit{L/M}) ratios, and most massive core (MMC) masses, indicating that these regions tend to be at later evolutionary stages. We find a positive correlation between the mass of cores from the ALMAGAL core catalog and the surface density of their surrounding structures identified in this work. However, this correlation is weaker for cores in more evolved clumps, where lower mass cores can be found at higher local surface densities. This could indicate that some cores accrete mass less efficiently from the intra-clump reservoir than others, despite the total available mass increasing over time, a scenario that is congruent with a clump-fed core accretion model.

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arXiv2026

Digging into the Interior of Hot Cores with ALMA (DIHCA). VI. The Formation of Low-mass Multiple Systems in High-mass Cluster-forming Regions

Most stars form in multiple systems, with profound implications in numerous astronomical phenomena intrinsically linked to multiplicity. However, our knowledge about the process on how multiple stellar systems form is incomplete and biased toward nearby molecular clouds forming only low-mass stars, which are unrepresentative of the stellar population in the Galaxy. Most stars form within dense cores in clusters alongside high-mass stars (>8 M$_{\odot}$), as likely the Sun did. Here we report deep ALMA 1.33 mm dust continuum observations at ~160 au spatial resolution, revealing 72 low-mass multiple systems embedded in 23 high-mass cluster-forming regions, as part of the Digging into the Interior of Hot Cores with ALMA (DIHCA) survey. We find that the companion separation distribution presents a distinct peak at ~1200 au, in contrast to the one at ~4000 au observed in nearby low-mass regions. The shorter fragmentation scale can be explained by considering the higher pressure exerted by the surrounding medium, which is higher than the one in low-mass regions, due to the larger turbulence and densities involved. Because the peak of the companion separation distribution occurs at much larger scales than the expected disk sizes, we argue that the observed fragmentation is produced by turbulent core fragmentation. Contrary as predicted, the multiplicity fraction remains constant as the stellar density increases. We propose that in the extremely dense environments where high-mass stars form, dynamical interactions play an important role in disrupting weakly bound systems.

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arXiv2026

Dense Molecular Clumps with Large Blue Asymmetries: Evidence for Collapse

An analysis of the Millimetre Astronomy Legacy Team 90 GHz (MALT90) survey has produced a sample of 27 candidate dense molecular clumps with large collapse motions, as revealed by large ``blue'' asymmetrical line profiles of the optically thick \hcop\, line. %with respect to the optically thin \nthp\, line. New, more sensitive molecular line observations of this sample, conducted with the Mopra 22-m telescope, confirm the blue asymmetries in the \hcop\, line profiles, with large, positive values of the asymmetry parameter $A$ ($\bar{A}_{HCO^+} = 0.69\pm0.01$), and positive, but smaller asymmetries in the \hcn\, and \hnc\, lines: ($\bar{A}_{HCN} = 0.35\pm0.01$ and $\bar{A}_{HNC} = 0.28\pm0.01$), as expected for a less optically thick tracer in collapsing clumps. The small, positive mean asymmetry parameters for \cch\, and \htcop, $\bar{A}_{C_2H} = 0.15\pm0.02$ and $\bar{A}_{H^{13}CO^+} = 0.18\pm0.03$, likely indicate slightly optically thick emission for at least some clumps. The hyperfine ratios for \nthp\, are in their optically thin, LTE, values, but for \hcn\ they are not; the $F=1 \to 1$ hyperfine line shows abnormally weak intensities. A simple two-component model shows that self-absorption of the background $F = 1 \to 1$ hyperfine line by the main $F = 2 \to 1$ hyperfine line of a cold, foreground, redshifted cloud can reproduce the observed \hcn\, hyperfine intensities and match the \hcn\, and \hcop\, line profiles. All of these results are consistent with self-absorption of the optically thick lines on the red side of the profile, as expected for collapsing clumps. A simple two-cloud model suggests that this sample represents dense clumps with extreme collapse velocities, $V_{inf} \sim 2.4$ \kms.

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arXiv2026

The ALMA-QUARKS Survey: Discovery of Dusty Fibrils inside Massive Star-forming Clumps

We report the discovery of more than 323 superfine dusty filamentary structures (fibrils) inside 121 massive star forming clumps that are located in widely different Galactic environments (Galactocentric distances of $\sim$0.5-12.7 kpc). These fibrils are identified from the 1.3~mm continuum emission in the ALMA-QUARKS survey, which has a linear resolution of $\sim900$ AU for a source at $\sim$3 kpc, using the \textit{FilFinder} software. Using \textit{RadFil} software, we find that the typical width of these fibrils is $\sim$0.01 pc, which is about ten times narrower than that of dusty filaments in nearby clouds identified by the \textit{Herschel} Space Observatory. The mass ($M$) versus length ($L$) relation for these fibrils follows $M\propto L^{2}$, similar to that of Galactic filaments identified in space (e.g., \textit{Herschel}) and ground-based single-dish (e.g., \textit{APEX}) surveys. However, these fibrils are significantly denser ($\mathrm{N_{H_2} = 10^{23}-10^{24}\ cm^{-2}}$) than the filaments found in previous \textit{Herschel} surveys ($\mathrm{N_{H_2} = 10^{20}-10^{23}\ cm^{-2}}$). This work contributes a large sample of superfine fibrils in massive clumps, following the identification of large 0.1-pc wide filaments and associated internal velocity coherent fibers in nearby molecular clouds, further emphasizing the crucial role played by filamentary structures in star formation at various physical scales.

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arXiv2026

MAJORS II: HCO+& HCN Abundances in W40

We present observations of HCN and HCO$^+$ J = $3 - 2$ in the central $424'' \times 424''$ region of the W40 massive star forming region. The observations were taken as part of a pilot project for the MAJORS large program at the JCMT telescope. By incorporating prior knowledge of N(H$_2$) and $T_K$, assuming a constant density, and using the RADEX radiative transfer code we found that the HCN and HCO$^+$ abundances range from $X$(HCN) = $0.4-7.0 \times 10^{-8}$ and $X$(HCO$^+$) = $0.4-7.3 \times 10^{-9}$. Additional modelling using the NAUTILUS chemical evolution code, that takes H$_2$ density variations into account, however, suggests the HCN and HCO$^+$ abundances may be fairly constant. Careful modelling of three different positions finds $X$(HCN) = $1.3-1.7 \times 10^{-8}$, $X$(HCO$^+$) = $1.3-3.1 \times 10^{-9}$. Cross-comparison of the two models also provides a crude estimate of the gas density producing the HCN and HCO$^+$ emission, with H$_2$ densities in the range $5 \times 10^4 - 5 \times 10^5$ cm$^{-3}$, suggesting that the HCN and HCO$^+$ emission does indeed arise from dense gas. High UV intensity (e.g. $G_o >$ a few thousand) has no effect on the abundances in regions where the visual extinction is large enough to effectively shield the gas from the UV field. In regions where $A_V < 6$, however, the abundance of both species is lowered due to destructive reactions with species that are directly affected by the radiation field.

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arXiv2026

The ALMA-ATOMS survey: Methanol emission in a large sample of hot molecular cores

Methanol (CH$_{3}$OH) is a key complex organic molecule (COM) in the interstellar medium, widely used as a tracer of dense gas and hot molecular cores (HMCs). Using high-resolution ALMA observations from the ATOMS survey, we investigate the excitation and abundance of methanol nuclear spin isomers and their relationship to chemical complexity in massive star-forming cores. We identify 20 methanol transitions, including A- and E-type lines in the v=0 state and E-type lines in the v$_{t}$=1 state, and detect 94 HMC candidates. Rotational temperature analysis under the LTE assumption yields average values of 194 $\pm$ 33 K for CH$_{3}$OH-E v$_{t}$=1, 178 $\pm$ 33 K for CH$_{3}$OH-A v=0, and 75 $\pm$ 33K for CH$_{3}$OH-E v=0. Emission from COMs other than methanol is detected in 87 of the 94 cores, with the CH$_{3}$OH-E v$_{t}$=1 line intensity showing a strong correlation with the channel detection ratio (CDR). These results demonstrate that CH$_{3}$OH-E v$_{t}$=1 lines are reliable tracers of HMCs and chemical complexity, and that the CDR provides a robust indicator of molecular richness. The temperature difference between A- and E-type methanol transitions is driven by anomalously strong J(2,J-2)$-$J(-1,J-1) lines, highlighting the importance of analyzing methanol symmetry types separately.

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arXiv2026

Digging into the Interior of Hot Cores with ALMA (DIHCA). VII. Disk candidates around high-mass stars and evidence of anisotropic infall

We study the kinematics of condensations in 30 fields forming high-mass stars with ALMA at a high-resolution of ~0.08'' on average (~230 au). The presence of disks is important for feeding high-mass stars without feedback halting growth as their masses increase. In the search for velocity gradients resembling rotation that can reveal the presence of disks, we analyze the emission of gas tracers in 49 objects using CH$_3$OH, CH$_3$CN, and tentative detections of HNCO and cis-HCOOH. Most of the velocity distributions show velocity gradients indicative of rotation. We reveal a total of 32 disk candidates, the largest sample to date that has been uniformly analyzed at a few hundred au scales in the high-mass regime. Their position-velocity maps are generally asymmetric with one side brighter than the opposite. We successfully fit a power law to the position-velocity maps of the disk candidates and find indices between -0.5 (Keplerian rotation) and -1 (rotation under specific angular momentum conservation) with a median of -0.7. Under Keplerian rotation assumption, we estimate central masses, uncorrected for inclination, ranging between 7 to 45 M$_\odot$. Excluding outliers, the disk candidates are relatively more compact (<200 au) and less massive (<5 M$_\odot$) than previous results at coarser angular resolution. We calculate an average Toomre-$Q$ parameter and find that most are gravitationally unstable (median of 0.5). We conclude that these observations offer the first opportunity to separate the disk and envelope components of hot cores on a statistically significant sample, and confirm that anisotropic collapse plays an role in feeding high-mass (proto)stars.

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arXiv2026

HOPS-288: A Laboratory for Complex Organics in Proto-multiple Systems

Complex organic molecules (COMs) in young stellar objects (YSOs) have attracted significant attention in recent years due to their potential connection to pre-biotic chemistry and their utility as tracers of warm or shocked gas components. Proto-binary and multiple systems with close separations are particularly valuable targets for investigating chemical inheritance and reaction, as their members are expected to form from similar material in their parental cloud. We present ALMA observations of the hierarchical proto-triple system HOPS-288, focusing on the physical structure, kinematics, and COM compositions. The system is treated as a proto-binary system consisting of HOPS-288-A and HOPS-288-B due to the limited spatial resolutions, with a separation of 200~au. Three COM-rich features are revealed: two hot corinos associated with the two members, rich in a variety of COMs, and an intervening component between the two members traced by CH$_3$OH and tentatively by CH$_3$CHO. The hot corino in HOPS-288-A exhibits rotational features and might trace a disk. The hot corino in HOPS-288-B is also possibly exhibiting rotational motion. The intervening component could possibly trace a shocked region in the circumbinary disk or a bridge between the two members. The column densities of COMs, including $^{13}$CH$_3$OH, CH$_2$DOH, CH$_3$CHO, HCOOCH$_3$, C$_2$H$_5$OH, $^{13}$CH$_3$CN, and NH$_2$CHO, are broadly similar between the two sources, possibly suggesting the complex organic similarities among proto-binary/multiple systems. Given the complexity of the studied physical structures, further detailed investigations will be essential to confirm this result.

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arXiv2025

The ALMA Survey of 70 μm Dark High-mass Clumps in Early Stages (ASHES). XIII. Core Mass Function, Lifetime, and Growth of Prestellar Cores

The core mass function (CMF) of prestellar cores is essential for understanding the initial conditions of star and cluster formation. However, the universality of the CMF and its relationship to the initial mass function (IMF) remain unclear. We study the CMF in the earliest stage of high-mass star formation using 461 prestellar core candidates and 254 protostellar cores as a part of the ALMA Survey of 70 μm Dark High-mass Clumps in Early Stages (ASHES). We find that prestellar core candidates tend to have lower masses than protostellar cores. We also find that the lifetime of prestellar cores is several times longer than the freefall time, although it approaches the freefall time as the core mass increases. The CMF, including both protostellar and prestellar cores, has a power-law slope of $-2.05\pm0.04$, shallower than Salpeter's IMF slope of -2.35. Conversely, the CMF of gravitationally bound, prestellar cores has a steeper slope ($-2.32\pm0.30$), indistinguishable from Salpeter's slope. This finding is consistent with observations in both low-mass star-forming regions and high-mass protoclusters, implying a universal core formation mechanism. The protostellar CMF with a larger maximum core mass can be reproduced by the prestellar CMF when an external gas infall is considered. The inferred mass infall rate is higher than the Bondi-Hoyle-Lyttleton accretion rate and follows a shallower mass dependence (smaller power-law index), more consistent with the tidal-lobe accretion. This may contribute to the evolution of CMFs seen in later stages.

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arXiv2025

The ALMA-QUARKS survey: Evidence of a candidate high-mass prestellar core aside a bright-rimmed cloud IRAS 18290-0924

Although frequently reported in observations, the definitive confirmation of high-mass prestellar cores has remained elusive, presenting a persistent challenge in star formation studies. Using two-band observational data from the 3mm ATOMS and 1.3mm QUARKS surveys, we report a high-mass prestellar core candidate, C2, located on the side of the bright-rimmed cloud IRAS 18290-0924. The C2 core identified from the 3mm continuum data of the ATOMS survey ($\sim$2 arcsecond, $\rm\sim 10000~au$ at 5.3 kpc) has a mass ranging from 27-68 $M_{\odot}$ for temperatures 10-22K within a radius of $\sim$2800 au. The highest-resolution ($\sim$0.3 arcsecond, $\rm\sim 1500 au$) observations of this source presented to date from the QUARKS survey reveal no evidence of further fragmentation. Further analysis of a total $\sim$10 GHz band width of molecular line survey does not find star-formation activity (e.g., outflows, ionized gas) associated with the core, with a few molecular lines of cold gas detected only. Additionally, virial analysis indicates the C2 core is gravitationally bound ($α_{\rm vir} \sim0.1-0.3$) and thus could be undergoing collapse toward star formation. These results strongly establish a candidate for a high-mass prestellar core, contributing to the very limited number of such sources known to date.

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arXiv2025

The ALMA-ATOMS-QUARKS survey: Resolving a chemically rich massive protostellar outflow

We present a comprehensive study on the physical and chemical structures of a chemically rich bipolar outflow in a high-mass star forming region IRAS 16272$-$4837 (SDC335), utilizing high-resolution spectral line data at 1.3 mm and 3 mm dual-bands from the ALMA ATOMS and QUARKS surveys. The high-velocity jet is enveloped by a lower-velocity outflow cavity, containing bright knots that show enhanced molecular intensities and elevated excitation temperatures. Along the outflow, we have identified 35 transitions from 22 molecular species. By analyzing the spatial distribution and kinematics of these molecular lines, we find that the molecular inventory in the outflow is regulated by three processes: (i) direct entrainment from the natal molecular core by the outflow; (ii) shock-induced release of molecules or atoms from dust grains; and (iii) thermal desorption and gas-phase reactions driven by shock heating. These results confirm that outflows are not only dynamical structures but also active chemical factories, where entrainment, shocks, and thermal processing jointly enrich the molecular content. Our findings confirmed that outflow chemistry has multi-origin nature, and provide critical insights into chemical evolution during high-mass star formation.

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arXiv2025

The ALMA-QUARKS survey: Hot Molecular Cores are a long-standing phenomenon in the evolution of massive protostars

We present an analysis of the QUARKS survey sample, focusing on protoclusters where Hot Molecular Cores (HMCs, traced by CH3CN(12--11)) and UC HII regions (traced by H30α/H40α) coexist. Using the high-resolution, high-sensitivity 1.3 mm data from the QUARKS survey, we identify 125 Hot Molecular Fragments (HMFs), which represent the substructures of HMCs at higher resolution. From line integrated intensity maps of CH3CN(12--11) and H30α, we resolve the spatial distribution of HMFs and UC HII regions. By combining with observations of CO outflows and 1.3 mm continuum, we classify HMFs into four types: HMFs associated with jet-like outflow, with wide-angle outflow, with non-detectable outflow, and shell-like HMFs near UC HII regions. This diversity possibly indicates that the hot core could be polymorphic and long-standing phenomenon in the evolution of massive protostars. The separation between HMFs and H30α/H40αemission suggests that sequential high-mass star formation within young protoclusters is not likely related to feedback mechanisms.

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arXiv2025

Magnetic Fields in Massive Star-forming Regions (MagMaR). VI. Magnetic Field Dragging in the Filamentary High-mass Star-forming Region G35.20--0.74N due to Gravity

We investigate the magnetic field orientation and strength in the massive star-forming region G35.20-0.74N (G35), using polarized dust emission data obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) as part of the Magnetic fields in Massive star-forming Regions (MagMaR) survey. The G35 region shows a filamentary structure (a length of $\sim$0.1 pc) with six bright cores located along the filament's long axis. Magnetic field strengths across the G35 region range from 0.2 to 4.4 mG with a mean value of 0.8 $\pm$ 0.4 mG. The mass-to-flux ratio ($λ$) varies from 0.1 to 6.0 the critical value. The highest values are found locally around cores, whereas the remains of the filament are subcritical. A H$^{13}$CO$^+$ (3--2) velocity gradient of 29 km s$^{-1}$ pc$^{-1}$ is evident along the filament's long axis, aligned with the magnetic field direction. At larger scales ($\sim$0.1 pc), the magnetic field lines appear roughly perpendicular to the filament's long axis, in contrast to the smaller-scale structure ($\sim$0.003 pc) traced by ALMA. The magnetic field lines could be dragged along the filament as a result of the gas motion induced by the gravitational potential of the filament. Six cores in the filament have similar spacings between 0.02--0.04 pc. The initial filament fragmentation could have produced a core spacing of 0.06 pc, following filament fragmentation theory, and the current core spacing is the result of cores comoving with the gas along the filament. This core migration could occur in a few 10$^4$ years, consistent with high-mass star formation time scales.

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arXiv2025

FIELDMAPS Data Release: Far-Infrared Polarization in the "Bones" of the Milky Way

Polarization observations of the Milky Way and many other spiral galaxies have found a close correspondence between the orientation of spiral arms and magnetic field lines on scales of hundreds of parsecs. This paper presents polarization measurements at 214 $μ$m toward ten filamentary candidate ``bones" in the Milky Way using the High-resolution Airborne Wide-band Camera (HAWC+) on the Stratospheric Observatory for Infrared Astronomy (SOFIA). These data were taken as part of the Filaments Extremely Long and Dark: A Magnetic Polarization Survey (FIELDMAPS) and represent the first study to resolve the magnetic field in spiral arms at parsec scales. We describe the complex yet well-defined polarization structure of all ten candidate bones, and we find a mean difference and standard deviation of $-74^{\circ} \pm 32^{\circ}$ between their filament axis and the plane-of-sky magnetic field, closer to a field perpendicular to their length rather than parallel. By contrast, the 850 $μ$m polarization data from \textit{Planck} on scales greater than 10 pc show a nearly parallel mean difference of $3^{\circ} \pm 21^{\circ}$. These findings provide further evidence that magnetic fields can change orientation at the scale of dense molecular clouds, even along spiral arms. Finally, we use a power law to fit the dust polarization fraction as a function of total intensity on a cloud-by-cloud basis and find indices between $-0.6$ and $-0.9$, with a mean and standard deviation of $-0.7 \pm 0.1$. The polarization, dust temperature, and column density data presented in this work are publicly available online.

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arXiv2025

Magnetic Fields in the Bones of the Milky Way

Stars primarily form in galactic spiral arms within dense, filamentary molecular clouds. The largest and most elongated of these molecular clouds are referred to as ``bones," which are massive, velocity-coherent filaments (lengths ~20 to >100 pc, widths ~1-2 pc) that run approximately parallel and in close proximity to the Galactic plane. While these bones have been generally well characterized, the importance and structure of their magnetic fields (B-fields) remain largely unconstrained. Through the SOFIA Legacy program FIELDMAPS, we mapped the B-fields of 10 bones in the Milky Way. We found that their B-fields are varied, with no single preferred alignment along the entire spine of the bones. At higher column densities, the spines of the bones are more likely to align perpendicularly to the B-fields, although this is not ubiquitous, and the alignment shows no strong correlation with the locations of identified young stellar objects. We estimated the B-field strengths across the bones and found them to be ~30-150 $μ$G at pc scales. Despite the generally low virial parameters, the B-fields are strong compared to the local gravity, suggesting that B-fields play a significant role in resisting global collapse. Moreover, the B-fields may slow and guide gas flow during dissipation. Recent star formation within the bones may be due to high-density pockets at smaller scales, which could have formed before or simultaneously with the bones.

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