arXiv subjects

Adam Ginsburg

Publications and source records attributed to Adam Ginsburg.

At least 19 recordsLinked to original sources

arXiv2026

Dust Seeding Molecules in a Massive Protostar -- Detection of TiO in Orion Source I

We report the first detection of TiO in star-forming regions based on Atacama Large Millimeter/submillimeter Array observations of Orion Source I, a well-characterized massive protostar. Multiple rotational transitions are identified, with emission spatially resolved within $\sim 50$ au, showing a compact distribution with a velocity structure consistent with the base of a rotating outflow. The spatial and velocity distributions of TiO are consistent with those of AlO, with both species being key dust seeding refractory molecules. The column density of TiO is derived to be $(3.0 \pm 0.4)\times10^{15}\ {\rm cm^{-2}}$, corresponding to $X_{\rm TiO/SiO} \sim 12.8 \pm 1.7 \times10^{-3}$, higher than CI chondrites and indicative of efficient dust-to-gas conversion near the protostar. The detection of TiO, a key dust seeding species, offers important constraints on refractory chemistry and the formation environments of primitive minerals, linking astrochemical processes in protostellar systems to the earliest stages of Solar System material formation.

astro-ph.GA↗

arXiv2026

ALMA Polarization Study of the Magnetic Fields in Two Massive Clumps in the 20 km s$^{-1}$ Cloud of the Central Molecular Zone

We present the Atacama Large Millimeter/submillimeter Array (ALMA) observations of linearly polarized 870 $μ$m continuum emission at a resolution of $\sim$0.2$^{\prime\prime}$ (2000 au) toward the two massive clumps, Clump 1 and Clump 4, in the 20 km s$^{-1}$ cloud. The derived magnetic field strengths for both clumps range from $\sim$0.3 to 3.1 mG using the Angular Dispersion Function (ADF) method. The magnetic field orientations across multiple scales suggests that the magnetic field dominates at the cloud scale, whereas gravity likely governs the structures at the core (0.01$-$0.1 pc) and condensation ($\le$ 0.01 pc) scales. Furthermore, the study on the angular difference between the orientations of the local gravity gradient and the magnetic field suggests that the gravity predominantly governs the dynamics in the diffuse regions, while both gravity and star formation feedback become increasingly significant within the dense regions. The ratio of the magnetic field tension force $F_\mathrm{B}$ to the gravitational force $F_\mathrm{G}$ suggests that the magnetic field may provide some support against gravity, but it is insufficient to prevent gas from infalling toward the dense cores.

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arXiv2026

ACES VIII: A Survey of Compact, High-Velocity Features Observed in CS(2-1)

The extreme kinematics of the Milky Way's Central Molecular Zone (CMZ) are influenced by processes such as dynamical shearing, cloud collisions, and stellar feedback. These events are visible in molecular data as vertically spiked features in position-velocity (PV) diagrams referred to as high velocity dispersion compact clouds (HVCCs). Using ALMA CMZ Exploration Survey (ACES) CS (2-1) molecular data, we identify a total of 235 HVCC candidates, 163 of which are visually identified, and an additional 72 identified via automated dendrogram methods. For each HVCC we catalog and report the physical and kinematic properties, explore line ratios of the cold dense gas tracer \HNCO with C-shock tracers, classify the morphology of their PV diagrams, and view their position-position-velocity distribution. The sample includes structures which are compact (d<5 pc) and have large velocity extents (20 km/s $<Δ\mathrm{V} <$ 140 km/s), with most structures showing thin, `spiked' PV morphologies. We highlight areas of high ratios between HNCO and C-shock tracers along the edge of known orbital streams, implying a buildup of bar lane gas accreting onto the CMZ. We also find a collection of HVCCs overlapping with the 50 km/s cloud and known circumnuclear disk features. This catalog will be used for future investigation of nuclear inflow and determining dominant mechanisms disrupting average CMZ gas flows.

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arXiv2026

A Novel Approach to 3D Dust Mapping of the Central Molecular Zone

The 3D distribution of dust and gas in the Milky Way's Central Molecular Zone (CMZ) is key to understanding gas inflows toward the Galactic Centre (GC), the process of star formation in this extreme environment, and the propagation of energetic cosmic rays originating from Sgr A*. However, while recent efforts have combined datasets in a Bayesian framework to estimate the near/far positions of individual molecular clouds in the CMZ, conflicts between different methodologies still remain and we are still lacking a comprehensive, model-independent map of all of the gas and dust in the CMZ, which is critical to address key science questions. Here we develop a new methodology to infer the 3D dust distribution of the CMZ. The key idea of the method is to use \emph{stellar} proper motions to get probabilistic information about the unknown stellar distances through a model of the distribution of star positions and velocities of the nuclear stellar disc (NSD), co-spatial to the CMZ. Taking \emph{stellar} proper motions and extinctions as input, the latter adopted as a proxy of the dust column density, the method returns the 3D dust distribution. It is non parametric, makes no a-priori assumption on the dust distribution, and is fundamentally distinct and largely independent of all existing methods. We show that the method can robustly and effectively reconstruct the mock 3D CMZ structure by testing it on a range of mock dust distributions, both analytically generated and taken from hydrodynamical simulations. Finally, we discuss the prospects for applying the method to real data.

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arXiv2026

ACES VII. Compact Continuum Source Catalog of the Central Molecular Zone

The Central Molecular Zone (CMZ) resides in the inner few hundred parsecs of our Galaxy, and despite being the largest reservoir of dense molecular gas in the Milky Way, it has a relatively low present-day star formation rate (SFR) of $\sim0.08~M_{\odot}~\text{yr}^{-1}$. Continuum and spectral line observations from the Atacama Large Millimeter/submillimeter Array (ALMA) CMZ Exploration Survey (ACES) provide the first full-coverage, high-resolution map of the inner 200 parsecs of the CMZ at 3 mm. In this paper we present the ACES catalog of compact continuum sources, the most complete catalog of potential sites of star formation in the CMZ to date. Using an automated dendrogram-based source extraction procedure in combination with a by-eye morphological classification scheme, we produce a `full' catalog of 1735 detections in total. Additionally, we use spectral index measurements to generate a `filtered' catalog of 567 sources with minimal contamination from non-thermal filaments and extended free-free emission. We find that 359 ($\sim63\%$) of the filtered catalog sources are located at column densities $< 10^{23}$ cm$^{-2}$, outside of the densest molecular cloud regions, 195 of which have not been identified in previous surveys. After cross-referencing with various catalogs generated from data at different wavelengths, we consider it likely that many of these newly discovered detections are produced by pre/protostellar sources or compact HII regions.

astro-ph.GA↗

arXiv2026

Electron temperature and emission measure of HII regions in the central molecular zone (CMZ) from H40 αrecombination line and continuum emissions by ALMA CMZ Exploration Survey - ACES -

Star formation activity in the Central Molecular Zone (CMZ) directly manifests itself as radio continuum free-free emission (Bremsstrahlung) and radio recombination line emission from HII regions surrounding newly formed massive stars. We derive the overall distribution of the HII regions and their fundamental properties: electron temperature ($\Te$) and emission measure ($EM$), and hence electron density in the form of two dimensional distribution maps over the CMZ by analyzing the ACES (ALMA CMZ Exploration Survey) \h40 (99.02 GHz) recombination line and 99.6 GHz continuum emission data with synthesized beam widths of $2''.45$ (0.097 pc at 8.2 kpc) and $2''.14$, respectively. We apply the 'TeEM' method ($\Te$--$EM$ mapping), which creates $\Te$ and $EM$ maps from input 2D maps of the continuum and integrated line intensity. The analysis covers the entire ACES field from $l\sim -0^\circ.6$ to $+0^\circ.8$ and from $b\sim -0^\circ.2$ to $+0^\circ.1$. The area analyzed is complete and includes previously known HII regions such as Sgr B2, Sgr B1, the Sickle, the Pistol, thermal filaments (Bridges), Sgr A HII regions, the Minispiral, and many other known HII regions. Sgr C is not included in the analysis due to the insufficient signal-to-noise ratio in the recombination line map. The mean electron temperature over the CMZ is determined to be $\Tcmz= 5872 \pm 78 ~{\rm (SE)} ~\pm 3682~{\rm (SD)}$ K (SE:standard error of the mean, SD: pixel-to-pixel standard deviation). Some HII regions, such as Sgr B2 Main and the Minispiral, exhibit large scatter and an internal $\Te$ gradient of several thousand K per parsec. The $EM$ distribution is more diverse, varying by orders of magnitude from $\sim 10^5$ to $\sim 3\times 10^8$ \emunit within the CMZ, as well as within individual HII regions.

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arXiv2026

The IMF package: a toolkit implementing mass functions and statistical tools to analyze them

Mass functions are used in all areas of astrophysics. The stellar initial mass function (IMF), in particular, plays a central role in modeling stellar populations in galaxies. However, few dedicated tools for working directly with the IMF and its precursor functions are widely available. We present the $\texttt{imf}$ package, a Python library integrated into the wider scientific Python ecosystem that implements common and variant forms of mass functions, especially the IMF and its pre- and protostellar equivalents, as probability distribution functions based on SciPy's statistics architecture. This package enables the performance of operations such as sampling and integration on a wide array of highly customizable mass functions. $\texttt{imf}$ is publicly available on the Python package index $\texttt{pypi}$ under the project name $\texttt{initial_mass_function}$.

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arXiv2026

Mapping CO Ice in a Star-Forming Filament in the 3 kpc Arm with JWST

CO gas emission is a fundamental tool for measuring column density, but in cold, dark clouds, much of the CO is locked away in ice. We present JWST results from observations of a star forming filament (G0.342+0.024) that that appears to be associated with the 3 kpc arm. This filament is backlit by the Galactic Center, which has allowed us to construct a high-resolution extinction map (mean separation between stars of ~1" outside the filament, ~2" in the filament). ALMA Band 3 data reveals embedded star formation within the cloud. Using the CO ice feature covered by the F466N band, we map the CO ice column density of the filament. By combining the extinction map, CO ice column density map, and archival CO observations, we examine the efficacy of standard CO X-factor measurements of mass in star forming gas. We find that 50-88% of the CO is locked away in ice at large column densities ($N_{\rm \rm H_2} \gtrsim 10^{22} \rm ~cm^{-2}, 200 \rm ~M_{\odot} \rm ~pc^{-2}$) in the filament. The primary sources of uncertainty in this estimate are due to uncertainty in the ice composition and lab measurements of ice opacities. This shows that systematic corrections are needed for mass measurements in the Milky Way and nearby galaxies at high column densities.

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arXiv2026

IRIS: Deciphering Spectral-Line Imagery of the Galactic Center by Machine-Learning on Simulations

In understanding the 3D structure of the Milky Way's Central Molecular Zone (CMZ), we are limited by our edge-on perspective. Towards addressing this problem, we introduce Imagery Reversion Informed by Simulation (IRIS). IRIS is a novel machine-learning code base featuring a deep convolutional neural network (CNN), which we have designed to translate edge-on observations of our Milky Way Galaxy into top-down images by training on data generated from AREPO galaxy simulations and synthetic observations of those simulations. We develop a large custom dataset on which we train our bespoke model, and then test the trained model on synthetic data to probe the potential of this machine-learning method, which we call supervised reversion. We then apply our trained model to real observations from the SEDIGISM 13CO(2-1) survey, yielding new top-down views of our CMZ. Though our SEDIGISM reversions are not fully consistent across model training runs, we posit that this lack of convergence can be alleviated by expansion of the training dataset. We argue that these results represent a strong proof-of-concept for the use of supervised reversion to decipher our CMZ's 3D structure. Crucial in generating our training dataset's 100k synthetic observations, we introduce IRIS Synthetic Observation (IRIS-SO), a new GPU-accelerated and fully differentiable code implemented in PyTorch for the non-LTE synthetic observation of spectral lines and dust. We find that IRIS-SO provides up to 10,000x speedups in comparison to the synthetic-observation code RADMC-3D. We release all the IRIS code open-source at https://github.com/bldubois/IRIS.

astro-ph.GA↗

arXiv2026

The Colors of Ices: Measuring ice column density through photometry

Ices imprint strong absorption features in the near- and mid-infrared, but until recently they have been studied almost exclusively with spectroscopy toward small samples of bright sources. We show that JWST photometry alone can reveal and quantify interstellar ices, and we present a new open-source modeling tool, icemodels, to produce synthetic photometry of ices based on laboratory measurements. We provide reference tables indicating which filters are likely to be observably affected by ice absorption. Applying these models to NIRCam data of background stars behind several Galactic Center (GC) clouds (dust ridge clouds A [the Brick], C, and D), and validating against NIRSpec spectra of Galactic disk sources, we find clear signatures of CO, H$_2$O, and CO$_2$ ices and evidence for excess absorption in the F356W filter likely caused by CH-bearing species such as methanol. The ice ratios differ between the Galactic disk and Center, with GC clouds showing a higher H$_2$O fraction. A large ice abundance is observed in CO, H2O, and possibly complex molecules, which implies that there is substantial freezeout and therefore potential for ice-phase chemistry in non-star-forming gas. Accounting for all likely ices, we infer that $>25%$ of the total carbon is frozen into CO ice in the GC, which exceeds the entire solar-neighborhood carbon budget. By assuming the freezeout fraction is the same in GC and disk clouds, we obtain a metallicity measurement indicating that $Z_{GC}\gtrsim2.5Z_\odot$. These results demonstrate that photometric ice measurements are feasible with JWST and capable of probing the metallicity structure of the cold interstellar medium.

astro-ph.GA↗

arXiv2026

HOTDISK. Finding Massive Protostellar Disks with Water and Refractory Molecular Species

We present high-angular-resolution ($\sim0.05^{\prime\prime}$, $\sim 60-250$ au) ALMA Band~6 observations from the HOTDISK project (Hot-Origin Tracer survey of DISKs of massive protostars) aimed at investigating the "hot-disk" chemical pattern traced by vibrationally excited water, NaCl, SiS, and SiO in the innermost regions around massive protostars. Ten targets were selected based on strong CH$_3$CN emission exhibiting clear rotational signatures and centrally concentrated SiO emission from lower-resolution observations. We detect vibrationally excited water emission toward 7 of the 10 sources. In all detections, the blueshifted and redshifted components are compact and located on opposite sides of the 1.3 mm continuum peak, with velocity gradients approximately perpendicular to the outflow axes, consistent with rotation on disk scales. Emission from NaCl and SiS is detected toward 5 of these 7 sources and exhibits similar kinematics, further supporting the presence of compact rotating structures. In contrast, commonly used hot-core tracers (e.g., CH$_3$CN and SO$_2$) primarily probe larger-scale envelope gas. These results demonstrate that vibrationally excited water, NaCl, and SiS are powerful tracers of disk structures on $\sim$100 au scales, when observed at sufficient angular resolution and sensitivity. The high detection rate suggests that hot-disk chemical patterns -- and thus compact rotating disks -- are common in massive star-forming regions, at least among sources with well-developed rotating envelopes.

astro-ph.GA↗

arXiv2026

ALMA Central molecular zone Exploration Survey (ACES) VI: ALMA Large Program Reveals a Highly Filamentary Central Molecular Zone

The Central Molecular Zone (CMZ) of the Milky Way is the way station that primarily controls how much gas flows from the disk of the Galaxy towards the central nucleus. While this region is well documented to have extreme gas properties that clearly distinguish it from the rest of the Galaxy, the properties of the bulk molecular gas at high angular resolution are relatively unexplored. Band 3 data from the ALMA (Atacama Large Millimeter/Submillimeter Array) large program ACES (ALMA CMZ Exploration Survey) reveal the highly filamentary nature of CMZ molecular gas at high resolution (3" or 0.1pc) across the entire CMZ. Visual inspection of these data suggests that there are at least two general classes of elongated structures, which we identify as: i) large-scale (10 pc) filamentary structures (LFs) and ii) a ubiquitous population of small-scale (about 1 pc) filamentary structures (SFs). We present detailed morphological and kinematic properties towards three structures in each category, as well as their association with magnetic fields and the correlation of HNCO 4(0,4)-3(0,3) with other molecular species. Our investigation reveals that these structures are largely coherent in position-position-velocity space. The alignment with the magnetic field structure is mixed, with some parallel, some perpendicular, and some intermediate alignments. We find that LFs likely trace pieces of contiguous CMZ orbital structures and are a manifestation of global CMZ dynamics. The second class, SFs, are pervasive and may be the result of complicated turbulence and shearing dynamics in the CMZ gas flows, as seen in numerical simulations.

astro-ph.GA↗

arXiv2026

Simulations of gas inflow in the Milky Way I. Stellar-Feedback-Regulated Transport from the Central Molecular Zone to the Circumnuclear disk

We perform hydrodynamical simulations with radially varying resolution to study the effects of stellar feedback on the radial inflow of gas from the Central Molecular Zone (CMZ, $R\sim200$ pc) to the Circumnuclear Disk (CND, $R\sim5$ pc) of the Milky Way. The simulations include a realistic Milky Way barred gravitational potential, a cooling function coupled to a non-equilibrium chemical network, gas self-gravity, star formation, supernova feedback, and radiation feedback from massive stars computed via on-the-fly radiative transfer. Our main findings are as follows: 1) Stellar feedback drives a radial inflow that decreases monotonically with decreasing Galactocentric radius. The time-averaged inflow rate in our fiducial SNRad simulation, which includes both supernova and radiation feedback, declines from $\langle \dot{M} \rangle\sim5\times10^{-3}$ Msun/yr at $R\sim100$ pc, to $\langle\dot{M}\rangle\sim10^{-4}$ Msun/yr at $R\sim10$ pc, to $\langle\dot{M}\rangle\sim10^{-6}$ Msun/yr at $R\sim1$ pc. 2) The total inflow rate can be broken down into two components driven by two distinct mechanisms. First, feedback-driven turbulence redistributes the angular momentum of gas clouds, producing a smooth (secular) transport of mass inward, similar to a Shakura-Sunyaev viscous accretion disk. This component contributes inflow rates that vary from $\dot{M}\sim5\times10^{-4}$ Msun/yr at $R\sim100$ pc to $\dot{M}\sim10^{-7}$ Msun/yr at $R\sim1$ pc. Second, episodic inflow events can transiently increase the inflow rate by several orders of magnitude, reaching $\dot{M}\sim10^{-3}$ Msun/yr over timescales of $Δt\sim3$-$5$ Myr at $R=10$ pc. 3) The stellar feedback model significantly affects the episodic inflow but has little impact on the smooth component. Simulations including radiation feedback produce substantially more episodic events than those with supernova feedback alone.

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arXiv2026

JWST's first view of the most vigorously star-forming cloud in the Galactic center -- Sagittarius B2

We report JWST NIRCAM and MIRI observations of Sgr B2, one of the most active sites of star formation in the Galaxy. These observations, using 14 filters spanning 1.5 to 25 microns, have revealed a multilayered and highly structured cloud that contains both a revealed, low-extinction and hidden, high-extinction population of massive stars. JWST has detected new candidate HII regions around massive stars previously missed by radio telescopes. MIRI has detected radiation escaping from the forming massive cluster Sgr B2 N along its outflow cavities, demonstrating that infrared radiation finds geometric escape routes even in the densest, most heavily embedded regions in the universe. JWST further highlights the gas asymmetry in the cloud, showing a sharp, straight cutoff along the eastern cloud edge. Despite the great sensitivity of these observations, no extended population of YSOs has been detected, placing a limit on their minimum extinction; this result hints that star formation has only just begun in the cloud. Together, these results suggest that, despite already holding the crown for one of the most actively star-forming clouds, we have underestimated the total star formation in Sgr B2. JWST unveils previously hidden massive stars and ionized structures, offering a clearest-yet view of how stars form under some of the most extreme Galactic conditions.

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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

3D CMZ V: A new orbital model of our Galaxy's Center, informed by data across the electromagnetic spectrum

The 3D structure of The Milky Way's Central Molecular Zone (CMZ) informs our understanding of star formation cycles, black hole accretion, and the evolution of galactic nuclei. However, a comprehensive 3D model has remained elusive, as no singular dataset nor theory contains the requisite information to describe the orbital motion of the gas. We implement a Bayesian framework to flexibly combine datasets across the electromagnetic spectrum for molecular clouds in our CMZ catalog. We develop near/far metrics for each dataset, including dust extinction, absorption, stellar densities, X-ray echoes, and proper motions; and report a posterior positional probability density function (PPDF) for each cloud. We then use the posterior PPDF distributions for all CMZ clouds to search for a best fitting x$_2$ orbit. We find that no single orbit is a perfect fit, but the structure can overall be represented by nested x$_2$ orbits, with major axes ranging from about $72 < a < 146$ pc. We also present projected line of sight distance estimates for all 31 clouds in the catalog. Our results highlight asymmetries along the line of sight, with most clouds lying on the near side of the Galactic Center, and agree overall with current near/far assumptions for most CMZ clouds, including those in the Sgr A region, which may be much closer to the center. We conclude that the CMZ can be well-described by x$_2$ orbital families, and that the overall gas distribution is more complex than a single closed or open elliptical orbit.

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arXiv2026

ALMA Central molecular zone Exploration Survey (ACES) V: CS(2-1), SO(2_3-1_2), CH3CHO(5_1,4-4_1,3), HC3N(11-10), and H40a lines data

We present data from the ALMA Central Molecular Zone Exploration Survey (ACES) Large Program, which provides broad spectral-line and 3 mm continuum coverage of the Central Molecular Zone (CMZ) at a spatial resolution of 0.1 pc. The survey delivers homogeneous, wide-field mosaics that enable direct comparisons of the physical and chemical conditions across diverse environments in the Galactic center. In this data release paper, we present the CS(2-1), SO(2_3-1_2), CH3CHO(5_1,4-4_1,3), HC3N(11-10), and H40a lines observed simultaneously within two broad spectral windows. These lines reveal pronounced spatial and chemical variations across the CMZ, tracing distinct components of molecular gas, shock-affected regions, and ionized structures. The high angular resolution and multi-line capability of the ACES dataset make it a powerful resource for future studies of gas dynamics, star formation activity, and the physical connection between the CMZ and Sgr A*.

astro-ph.GA↗

arXiv2026

Reconciling 3D Models for the Central 10 parsecs of the Milky Way

The construction of an accurate 3D model of the Milky Way center is necessary to understand inflow processes that drive its overall evolution, and to compare our Galactic nucleus to other galaxies' nuclei. A main point of contention is the line-of-sight location of sources observed toward the central 10 pc of the Galaxy, including recent star formation (the Sgr A East supernova remnant and Sgr A HII regions) and copious gas (the 50 and 20 km/s molecular clouds, the Circumnuclear Disk, and the Sgr A West ionized "minispiral" that encircles the central supermassive black hole, Sgr A*). Some models place all of these structures within a radius of 5 pc from Sgr A*, while others place the 20 and 50 km/s clouds at a distance of at least 30 - 50 pc away from Sgr A* along the line of sight. We present new radio and millimeter observations of the molecular gas toward the central ~10 pc, from which we have constructed an alternative 3D model that is consistent with both prior radio observations and orbital gas kinematics. Our model places the 20 km/s cloud, 50 km/s cloud, and Sgr A East more than 10 pc in front of Sgr A*. While this model does not conclusively rule out a connection between the 50 and 20 km/s clouds and the circumnuclear disk, we argue that prior evidence for these connections is tenuous, especially given the complex spatial and kinematic overlap of structures along the line of sight.

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