High Energy Astrophysical Phenomena
Anisotropic Ejecta from Binary Neutron Star Mergers: Self-Consistent Main Thermal and Late-Time Radio Emission of NS-Powered Kilonovae
Jia-Xiang Chen and Shao-Ze Li
The interaction between the fast-moving ejecta and the interstellar medium can produce long-lasting
radio signals after binary
neutron star mergers. Searching for such
radio signals is a way to test the central engine of kilonovae and short gamma-ray bursts. With a magnetar as the central engine, the
spin-down energy powers the main thermal and late-time
radio emissions of the kilonova. However, both the thermal and
radio emissions are strongly affected by the ejecta distribution, e.g., the two-component “blue" and “red" emissions of AT 2017gfo corresponding to the GW 170817 event. In this study, we investigate the distribution of the merger ejecta, analyzing several possible anisotropic distributions and demonstrating their impacts on the emission properties, particularly the late-time
radio light curves. Under a bipolar and equatorial ejecta configuration, corresponding to the wind and dynamical components of the merger ejecta, the late-time
radio light curves reveal distinct two-peak features, which are consistent with the main thermal light curves. The anisotropic distribution of the ejecta intrinsically connects the main thermal and late-time
radio emissions, forming a self-consistent evolutionary picture. A combined analysis of the main thermal and late-time
radio emissions provides a way to constrain the geometry of the merger ejecta and to probe the properties of the central engine. Furthermore, using the fitting parameters from the main thermal emission of AT 2017gfo, we calculate the corresponding potential late-time
radio light curves. The results show that, under typical parameters, the non-detection of
radio signals in observations is consistent with the theoretical expectation.
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High Energy Astrophysical Phenomena
Spectral energy-loss bump and $\gamma$-ray pulsar halos
Kun Fang
The parent electron spectrum of $\gamma$-ray
pulsar halos is determined by continuous injection and radiative energy losses, with the nonlinear nature of the latter expected to produce an age-dependent energy-loss bump in the
halo spectrum. We demonstrate that the broadband $\gamma$-ray spectrum of the Geminga
halo measured by
Fermi-LAT and HAWC is consistent with this expectation. Its energy-loss bump appears in the GeV region and is primarily produced by electrons injected at the earliest stage. Therefore, fitting the data allows us to constrain parameters governing early electron injection, such as the
pulsar braking index $n$ and initial
spin period $P_0$. In addition, we show that another crucial condition for explaining the Geminga
halo spectrum is a power-law index of the injection spectrum close to $1$, consistent with the X-ray observations of the Geminga
pulsar wind nebula. Currently, no significant energy-loss bump has been detected in the spectrum of the Monogem
halo; based on this, we also place preliminary constraints on $n$ and $P_0$ of Monogem. This work demonstrates that
pulsar halo spectra can be used not only to constrain electron injection parameters, but also to provide independent estimates of certain intrinsic
pulsar properties.
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Solar and Stellar Astrophysics · Cross-listed from nucl-th
Proton-to-Alpha branching ratio in the $^{12}$C+$^{12}$C fusion reaction at astrophysical energies
Ruojun Yang, Ruiqi Chen, Xiao Fang et al. (+4 more)
The unique resonance features in the $^{12}$C+$^{12}$C fusion reaction lead to significant fluctuations in the branching ratio $R_{p/\alpha}=\sigma_p/\sigma_\alpha$, making it difficult to determine the $R_{p/\alpha}$ at astrophysical energies. By combining Hauser–Feshbach statistical-model calculations with constraints from direct charged-particle and gamma-ray measurements, we investigate the energy dependence of the averaged $R_{p/\alpha}$ and predict its behavior within the Gamow window. Owing to the strong energy dependence of $R_{p/\alpha}$, the corresponding reaction-rate ratios, $\langle \sigma v \rangle_p / \langle \sigma v \rangle_\alpha$, during core and shell carbon burning are determined to be 0.29, 0.45, and 0.52 at $T_9 = 0.5$, 1.0, and 1.2, respectively, significantly lower than the widely adopted CF88 constant value of 0.79. The implications of the revised $\langle \sigma v \rangle_p / \langle \sigma v \rangle_\alpha$ ratio for
stellar nucleosynthesis and white-
dwarf evolution are also discussed.
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All authors Ruojun Yang, Ruiqi Chen, Xiao Fang, Yihua Fan, Xiaodong Tang, Yunju Li, Fengqiao Luo
Earth and Planetary Astrophysics
Chemistry and IR emission of acetylene in planet-forming regions of T Tauri disks. Impact of elemental abundances and dust properties
Pacôme Estève, Benoît Tabone, Emilie Habart et al. (+5 more)
(Abridged) We aim to explore the parameters that influence the mid-infrared emission of C$_2$H$_2$ and H$_2$O, and if the spread observed in $F\rm{_{C_2H_2}}$/$F\rm{_{H_2O}}$ is tracing a variation of the C/O ratio. Our work is based on the DALI 2D thermochemical model to predict spectra readily comparable to JWST/MIRI observations. To robustly model organics in inner disks, several improvements have been made: (1) carbon chemistry adapted for warm environments, (2) updated UV shielding treatment, and (3) mutual line overlap in the raytracing. We are able to reproduce the observed C$_2$H$_2$ fluxes of T Tauri disks with a
solar C/O ratio. Acetylene abundance is primarily set by a balance between formation initiated by CO dissociation by X-rays and destruction of carbon chains by atomic oxygen, the latter being generated by X-ray-induced destruction of H$_2$O and CO. The water UV shielding and hot temperatures of the inner disk also favor acetylene formation, as they prevent the destruction of carbon chains and allow overcoming activation barriers of reactions with H$_2$. C$_2$H$_2$ and H$_2$O emissions are not only sensitive to the C/O ratio but also to the total O/H elemental abundance, supporting recent claims. In particular, we find that enhanced O/H reduces acetylene emission due to an excess of atomic oxygen. $F_{\rm{C_2H_2}}$/$F_{\rm{H_2O}}$ is thus a promising tracer of the elemental composition of inner disks. Still, the
dust size distribution also plays a key role in this line flux ratio. We find that increasing the abundance of small grains relative to large grains favors C$_2$H$_2$ flux over H$_2$O flux. Grain depletion does not affect the line flux ratio as previously suggested by observational works. A preliminary comparison with published JWST observations indicates a gas-phase C/O ratio below unity and suggests that enhanced O/H ratios may be common in T Tauri disks.
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All authors Pacôme Estève, Benoît Tabone, Emilie Habart, Ewine F. van Dishoeck, Marissa Vlasblom, Inga Kamp, Aditya M. Arabhavi, Simon Bruderer
High Energy Astrophysical Phenomena
Search for the Highest-energy Quasiperiodic Oscillation in the Black Hole X-Ray Binary Candidate Swift J1727.8-1613
Xiang Ma, Qing-Cang Shui, Ming-Yu Ge et al. (+8 more)
We report the first detection of a low-frequency quasiperiodic oscillation (QPO) extending above 250 keV in the black hole X-ray binary candidate Swift J1727.8-1613 using Insight-HXMT observations during its 2023 outburst. Swift J1727.8-1613 is one of the brightest X-ray transients discovered and presents a valuable opportunity for studying high-energy properties of QPOs. Owing to the large effective area of Insight-HXMT in hard X-ray, our observations indicate a remarkably strong QPO signal in the power spectrum above 100 keV. We utilize advanced
Hilbert-Huang transform techniques to analyze phase-folded light curves across a wide range of energy bands, observing significant QPOs from 100 to 300 keV in the NaI and CsI detectors, respectively. The detection of QPO profiles above 250 keV can achieve significance levels of ${\sim} 8.9{\sigma}$ for the NaI detector and ${\sim} 5.7{\sigma}$ for the CsI detector. Our results indicate a decrease in QPO fractional rms above 100 keV and an increased soft phase lag with energy, suggesting a
geometric origin for the QPOs, likely linked to the precession of a small-scale jet.
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All authors Xiang Ma, Qing-Cang Shui, Ming-Yu Ge, Liang Zhang, Jin-Lu Qu, Shuang-Nan Zhang, Lian Tao, Li-Ming Song, Shu Zhang, Hua Feng, Yue Huang
Astrophysics of Galaxies
Nuclear Activity and Host Galaxy Properties of Low-Luminosity AGN Identified from VLA Observations
M. N. Rosli and A. Annuar
Low-luminosity active
galactic nuclei (LLAGN; $L_{\rm bol} < 10^{42}$~erg~s$^{-1}$) may comprise a significant fraction of the local AGN population, yet their weak emission makes them difficult to detect. In this paper, we analyse 38 LLAGN identified from a 15~GHz sub-arcsecond Very Large Array survey and assess the effectiveness of X-ray, optical, and infrared wavelengths in identifying LLAGN. We found that optical emission-line diagnostics recovered $84.2^{+15.8}_{-22.9}$% (32/38) of the sample, X-rays detected $63.2^{+25.7}_{-19.6}$% (24/38), and infrared methods only identified $13.2^{+14.5}_{-8.0}$% (5/38), reflecting limited X-ray sensitivity, weak or absent optical lines, and strong host
galaxy contamination in the infrared. Compared to Swift–BAT AGN, our LLAGN are $\sim$ 4.1~dex fainter in bolometric luminosity (log $L_{\mathrm{bol}} \approx$ 39.3 - 41.9 erg s$^{-1}$), host smaller black holes ($\sim$0.7~dex lower), and accrete at much lower rates (log $\lambda_{\text{Edd}} \approx$ -6.5 to -1.3, i.e., $\sim$ 4.2~dex lower). Host
galaxies span a broad range of morphologies, from disk- to bulge-dominated, with a subset exhibiting prominent bulges, potentially representing systems where
nuclear activity has faded while the bulge remains dominant. LLAGN also reside in
galaxies with lower
stellar masses ($\sim$0.3~dex) and suppressed
star formation rates ($\sim$0.5~dex) relative to Swift–BAT AGN. Overall, LLAGN in our sample systematically host smaller and weakly accreting black holes, residing in
galaxies with diverse morphologies, but lower
stellar masses and reduced
star formation activity, demonstrating the connection between low-level black hole
accretion and host
galaxy properties in the local Universe.
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High Energy Astrophysical Phenomena
Higher-order statistics of the stochastic gravitational wave background from supermassive black hole binaries
Hinano Hisamatsu and Koutarou Kyutoku
Recent progress in gravitational wave observations has positioned
pulsar timing arrays as a key tool for detecting the
stochastic gravitational wave background in the nanohertz band. It is widely believed that this background is primarily attributed to the
cosmic ensemble of inspiraling supermassive black hole binaries. While traditional analyses have predominantly focused on the spectral amplitude and frequency dependence of the gravitational wave background, higher-order statistics such as variance, skewness, and excess kurtosis could potentially be useful for extracting further physical information. However, these statistical moments are known to diverge when the
redshift integration is extended down to z=0. In this study, we propose a strategy to resolve this issue by introducing a physically motivated lower integration limit, z_min, defined by the sensitivity for detecting individual sources. Since higher-order statistics are primarily determined by local sources, we may adopt the lowest-order approximation with respect to
redshift in their computations. Under this approximation, we demonstrate that all higher-order statistics beyond the expectation value depend on the mass function only through a weighted average of the chirp mass, <\mathcal{M}^{10/3}>, irrespective of the
redshift evolution model. We show that the ratio of the variance to the expectation value provides information on <\mathcal{M}^{10/3}>/<\mathcal{M}^{5/3}> independently of the total number of mergers. We also find a consistency relation between the excess kurtosis and the squared skewness, paving the way for testing the binary-origin hypothesis of the gravitational wave background. Our findings demonstrate that higher-order statistics provide a new window for interpreting the gravitational wave background, offering a methodology to break existing degeneracies and refine our understanding of the mass function.
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Instrumentation and Methods for Astrophysics
Impact of Satellite Constellations on Observations with the 80-cm Telescope and the Mini-SiTian at the Xinglong Observatory, NAOC
Jing Ren, Zhou Fan, Hong-rui Gu et al. (+6 more)
The rapid development of mega-constellations in low Earth orbit (LEO) severely impacts ground-based optical astronomical observations. By combining WorldWide
Telescope (WWT) simulations with 2019 and 2023 observational data from the Xinglong Observatory 80-cm
telescope and 2023 data from the Mini-SiTian (MST), we find that satellite visibility increases with deployment, particularly during the summer. For the 80-cm
telescope, the fraction of images containing satellite trails increased from an average of 0.34% in 2019 to 0.7% in 2023; meanwhile, for the MST in 2023, the fraction rose from 5% in January to 12% by December, peaking at 19% in the summer. Through stratified analysis of
solar elevation and local time, we find that observations during twilight and summer are particularly susceptible to satellite trail interference. Photometric analysis reveals that the interference intensity increases for fainter sources and those closer to the trails. Furthermore, a comparative analysis across different seeing conditions shows that the deviation of median standardized residuals ({\sigma}) is significantly greater under poor seeing than under good seeing conditions.
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All authors Jing Ren, Zhou Fan, Hong-rui Gu, Qi-qian Zhang, Yun-fei Xu, Jun-ju Du, Xiao-han Chen, Lin-ying Mi, Hong Wu
Astrophysics of Galaxies
Assessing the Impact of Source Confusion for GREX-PLUS based on Deep JWST NIRCam Imaging
Yoshiaki Ono, Akio K. Inoue, Yuma Sugahara et al. (+9 more)
We investigate the effects of source confusion expected in observations with GREX-PLUS, a JAXA L-class space infrared
telescope mission candidate with a wide-field infrared camera covering 2-8 um with a field of view of 0.50 deg$^2$. For the deep imaging band near 4 um, we calculate the GREX-PLUS PSF and ghost based on the latest optical design, and consider two representative imaging performance cases with PSF FWHM values of 0.9 and 1.2 arcsec. We construct simulated GREX-PLUS images at different depths by convolving JWST NIRCam imaging data from JADES, GLASS, CEERS, and COSMOS-Web with the PSF+ghost kernel. Comparing the limiting magnitudes estimated from random aperture photometry using the same aperture sizes, we find that the simulated GREX-PLUS images are shallower than the original JWST images, with larger deviations for deeper original JWST images. This likely reflects unresolved faint sources and extended PSF+ghost wings from bright sources, which elevate background fluctuations in blank regions. Nevertheless, the limiting magnitudes continue to improve with increasing integration time down to ~27 mag, without a clear plateau at depths comparable to the planned GREX-PLUS deep survey, although the improvement becomes progressively less efficient toward longer integrations. Based on Monte Carlo simulations, we estimate detection completeness and correct the number counts for magnitude bias and incompleteness, finding that confusion-induced blending can reduce the completeness even at magnitudes well above the nominal 5-sigma depth. The completeness-corrected number counts agree well with the JWST-based number counts down to around the detection limit. Overall, our results suggest that statistical studies of faint
galaxies remain feasible for GREX-PLUS; however, survey planning should account for less efficient depth improvement toward longer integrations due to source confusion.
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All authors Yoshiaki Ono, Akio K. Inoue, Yuma Sugahara, Takeshi Hashigaya, Fumihide Iwamuro, Taiki Bessho, Yuji Ikeda, Matthew L. N. Ashby, Yuichi Harikane, Jarron Leisenring, Takao Nakagawa, Howard A. Smith
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Pole Skipping, Avoided Crossing, and Resonant Excitation in Kerr Quasinormal Modes near Algebraically Special Frequencies
Kei-ichiro Kubota and Hayato Motohashi
Kerr quasinormal modes near algebraically special frequencies exhibit anomalous behavior, including apparent bifurcation, disappearance, and a nonsmooth connection to the Schwarzschild limit, which has remained puzzling for decades. Tracking poles and zeros of Green-function building blocks across different Riemann sheets, we show that the bifurcation is due to an avoided crossing accompanied by resonant excitation, while the disappearance is due to pole skipping caused by cancellation of a quasinormal-mode pole by a Matsubara-mode zero. This resolves the physical origin of these long-standing anomalies.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
ACT Data and Positive Running of the Spectral Index for Scalar Theory and Modified Gravity
S.D. Odintsov and V.K.Oikonomou
In this work we address the possibility of having a positive running of the spectral index in inflationary theories. The recent ACT data indicate mildly that the running of the spectral index might be positive, and several other physical indications point out this possibility. If the running of the spectral index is confirmed to be positive by future
cosmic microwave background experiments, this can rule out quite popular inflationary scenarios. We investigate how it is possible to obtain a positive running of the spectral index in the context of minimally coupled scalar field
gravity and modified
gravity. For the modified
gravity we choose two mainstream and of string origin candidate theories, $F(R)$
gravity and Einstein-Gauss-Bonnet
gravity. In the case of scalar field inflation and $F(R)$
gravity inflation, we demonstrate the difficulties for obtaining a positive running of the spectral index for a viable inflationary regime, so scalar theories and $F(R)$
gravity are mostly compatible with the Planck data. But nuanced scalar field scenarios can be compatible with the ACT data and produce a positive running of the spectral index. In the context of Einstein-Gauss-Bonnet theories which are compatible with the GW170817 event, the running of the spectral index can easily be positive while in parallel having a viable inflationary era.
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Earth and Planetary Astrophysics
A Hycean Interpretation of K2-18b Supported by Photochemical Atmospheric Compositional
Takuya Fujisawa, Masashi Shimada, Tatsuya Yoshida et al. (+1 more)
The nature of the sub-Neptune K2-18b is debated between Hycean and mini-Neptune interpretations. We test whether self-consistent Hycean atmospheres are compatible with current JWST transmission spectra by combining one-dimensional photochemical modelling, radiative–convective
equilibrium calculations, and forward modelling of transmission spectra. We assume H2-CH4-H2O atmospheres over a
liquid ocean, compute altitude-dependent abundances with a 1D photochemical model, and couple them to P-T profiles that avoid runaway greenhouse states. Using the CH4-dominated 2.8-4.0 $\mu$m band, we constrain wavelength-independent offsets between NIRISS SOSS and NIRSpec G395H for multiple reductions, and then scan grids of CO and CO2 scaling factors, weighted by the CH4-band offset posteriors, to evaluate oxidised-carbon abundances consistent with the 4-5 $\mu$m region. Radiative–convective calculations further map pressures and albedos that yield non-runaway climates. Over a wide range of temperatures and pressures,
liquid oceans can exist, and Hycean models with a 1 bar H2 envelope, percent-level CH4 and CO, and CO2 buffered at $\sim 10^{-3}$-$10^{-2}$ reproduce the NIRISS and NIRSpec spectra from 0.8 to 5.2 $\mu$m without invoking DMS or other additional species. Our photochemical simulations show that H2-CH4-H2O networks generically drive CO to mixing ratios of order 1-2 %. Mass-balance arguments imply that a $\sim$1 bar H2 envelope with percent-level CH4 requires interior replenishment on gigayear timescales, and the resulting vertical gradients naturally generate flat, CH4-dominated plateaux in transmission. While mini-Neptune scenarios remain viable, our results show that Hycean configurations are likewise consistent with the data, and current CO and CO2 constraints alone are not yet sufficient to rule out Hycean interpretations of K2-18b.
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All authors Takuya Fujisawa, Masashi Shimada, Tatsuya Yoshida, Kiyoshi Kuramoto
High Energy Astrophysical Phenomena
The First Insights into an Ultraluminous X-ray Pulsar with XRISM: Phase-Resolved High-Resolution Spectroscopy of the Fe K-shell Band of M82 X-2
Shogo B. Kobayashi, Peter Kosec, Kazuki Ampuku et al. (+18 more)
During the performance verification phase, XRISM observed the M82
galaxy for a net exposure of 207.7 ks, with the ultraluminous X-ray
pulsar (ULXP) X-2 included in the field of view. A pulsation search identified a candidate signal with a period close to the previously known value, 1.38727 s, at a significance of $3.15\sigma$ based on Monte Carlo simulations. Using this candidate period, phase-resolved spectral analysis with the high spectral resolution of Resolve was performed. The spectra suggest that, if the candidate pulsation is real, the Fe K$\alpha$ emission line in the pulse peak phase has a larger width ($36^{+60}_{-13}$ eV) than that in the remaining phase at a significance exceeding $3\sigma$. This suggests that at least a fraction of the Fe K$\alpha$ emission is associated with the ULXP system. The observed width corresponds to a velocity dispersion of $(1.7^{+2.8}_{-0.6})\times10^3$ km s$^{-1}$, which is too large to be explained by motions in the companion
star atmosphere. The rise time of the pulsation constrains the line-emitting region to be smaller than $6.3\times10^4$ km, suggesting an origin in the
accretion flow. This work demonstrates the capability of XRISM Resolve for pulsation-resolved high-resolution spectroscopy of ULX
pulsars.
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All authors Shogo B. Kobayashi, Peter Kosec, Kazuki Ampuku, Erin Boettcher, Renata Cumbee, Adam Foster, Yutaka Fujita, Kotaro Fukushima, Skylar Grayson, Gabriel Grell, Edmund Hodges-Kluck, Ann Hornschemeier, Richard Kelley, Caroline Kilbourne, Mike Loewenstein, Ikuyuki Mitsuishi, Dustin Nguyen, Evan Scannapieco, Takeshi Tsuru, Noriko Yamasaki, Mihoko Yukita
Cosmology and Nongalactic Astrophysics
Coupled quintessence with a potential from supergravity exhibits sign-changing interaction
Jincheng Wang, Hongwei Yu and Puxun Wu
Quintessence with a potential motivated by supergravity (SUGRA) exhibits several intriguing features. Depending on its initial conditions, it can behave either as dynamical dark energy or effectively as a cosmological constant. Moreover, when quintessence is coupled to dark matter, the effective dark-energy equation of state can cross the phantom divide. In this paper, we test both coupled and uncoupled SUGRA quintessence models using DESI BAO, DES-Dovekie SNIa, and Planck CMB data. We find that current observations strongly favor a coupling between dark energy and dark matter, with the coupling parameter deviating from zero at more than $4\sigma$. The data also favor the branch of coupled SUGRA quintessence in which the energy transfer between the two dark sectors changes sign, leading to a crossing of the phantom divide by the effective dark-energy equation of state. Interestingly, this coupled SUGRA branch is statistically indistinguishable from dark energy described by the CPL parametrization, with only a very small difference in $\chi^2_\mathrm{min}$. Our results suggest that coupled quintessence with a SUGRA potential provides a field-theoretic realization of the evolving dark energy behavior favored by the latest observations.
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High Energy Astrophysical Phenomena
Classification of IGR J20084+3221 as an Intermediate Polar using X-ray and Optical Observations
Julian Gerber, Jeremy Hare, John A. Tomsick et al. (+2 more)
IGR J20084+3221 is a previously unclassified
Galactic source first detected by INTEGRAL. Chandra observations led to possible classifications of either a
magnetic Cataclysmic Variable (mCV) or high mass X-ray binary (HMXB) based on the hardness of its spectrum. Here, we report follow-up observations taken by XMM-Newton, NuSTAR, and the Hale
Telescope at Palomar Observatory. Based on these observations, we conclude that IGR J20084+3221 is most likely an Intermediate Polar (IP) type mCV. Timing analysis of the X-ray data found a significant peak period of $P=635.0\pm0.4$ s, which we interpret to be the
spin period of the white
dwarf (WD). The X-ray spectrum is well fit to an absorbed Bremsstrahlung model with components accounting for partial covering, reflection, and a fluorescent Fe-line, all typical for an IP. The optical spectrum shows clear emission lines, consistent with emission dominated by an
accretion disk. We find counterparts to the source across the optical and infrared (IR) bands, and, despite uncertainties in the distance and extinction, we estimate that the source is too faint in the IR to be an HMXB. Given the evidence pointing towards an IP classification, we fit the X-ray spectrum to a post-shock region model where we find a WD mass of $M=1.09^{+0.12}_{-0.11}\mathrm{M}_{\odot}$, larger than the average mass for a WD in an mCV.
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All authors Julian Gerber, Jeremy Hare, John A. Tomsick, Daniel Stern, Aarran W. Shaw
Astrophysics of Galaxies
BISTRO Survey: Gravity-Dominated and Magnetically Regulated Star Formation in M17 SW
Mengke Zhao, Keping Qiu, Ji-hyun Kang et al. (+27 more)
We present high-resolution
magnetic field maps of the M17 SW molecular cloud using JCMT 850 $\mu$m
dust polarization at a scale of 14$''$. The
magnetic field exhibits a distinct arc-like structure that encircles three dense clumps (C1, C2, and C3). By combining polarization data with ammonia line observations, the plane-of-sky
magnetic field strength, measured using the Skalidis-Tassis method to minimize angle dispersion errors, ranges from 0.1 to 2.4 mG (mean: 0.54 mG). Energy budget analysis reveals a hierarchy dominated by
gravity ($e_G \approx 10^{-7.8}$ erg cm$^{-3}$), which exceeds both
magnetic ($e_B \approx 10^{-8.3}$ erg cm$^{-3}$) and turbulent ($e_k \approx 10^{-8.7}$ erg cm$^{-3}$) energies. Since all three energy densities lie within one order of magnitude, gravitational dominance acts primarily as the global driver, while the system remains in a state of near-equipartition. Structurally, the northeastern boundary shows
magnetic field lines perpendicular to the shock front, consistent with compression from the adjacent HII region. Within the cloud,
magnetic field lines generally align with
gravity to assist collapse, but turn perpendicular to
gravity within curved
accretion bridges. This configuration provides support against radial collapse while guiding gas flow. Kinematic evidence suggests that these channels transport material from Clump C3 onto the massive Clump C2.
Star formation in M17 SW is globally driven by
gravity but locally regulated by the
magnetic field structure.
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All authors Mengke Zhao, Keping Qiu, Ji-hyun Kang, Xindi Tang, Anthony Whitworth, Derek Ward-Thompson, Takashi Onaka, Chang Won Lee, Tyler L. Bourke, Jihye Hwang, David Eden, Thiem Hoang, Motohide Tamura, Jungmi Kwon, Felix Priestley, Kee-Tae Kim, Doris Arzoumanian, James Di Francesco, Chakali Eswaraiah, Doug Johnstone, Nguyen Bich Ngoc, Zhiwei Chen, Sarah Sadavoy, Archana Soam, Ray S. Furuya, Shih-Ping Lai, Woojin Kwon, Pierre Bastien, Kate Pattle, David Berry
Instrumentation and Methods for Astrophysics
'Unacceptable to our people': Diverse cultural beliefs, Indigenous rights, and the future of human activities on the Moon
John C. Barentine
The human presence in outer space is undergoing a transition from one in which nation states are the dominant actors to an emerging status quo in which states merely supervise the activities of private entities. Such largely commercial ventures include extracting natural materials from the Moon, a celestial body of great cultural and spiritual reverence for some Indigenous societies. However, the existing international legal framework governing activities in space focuses on its "exploration and use", centered in a Western worldview that attaches to a past history of colonialism. While that framework, articulated in the Outer Space Treaty (OST), claims to guarantee that outer space will remain "the province of all [hu]mankind," only entities with significant political power have to date decided the limits of the acceptable uses of space. This paper examines the historical record for clues about how states, private actors and Indigenous societies might interact in the future on matters of outer space governance to achieve more just ends. It analyzes a key case study: the dispute between the NASA and the Diné people of the American Southwest over the launches of human cremated remains to the Moon in 1998 and 2024, acts the Diné president called "deeply disturbing and unacceptable to our people and many other tribal nations." In a future in which space becomes increasingly commercialized and entities like NASA transform into mere contract-administering agencies, it is unclear how an impending, exploitative human presence on the Moon can simultaneously honor Indigenous rights and perspectives on lunar issues. The presentation concludes that best practices for future engagement with the Moon must transcend the mere "due regard" and "international consultations" required by the OST in favor of arrangements where participants co-create a human future in outer space.
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