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1. Revealing Hidden Cosmic Flows through the Zone of Avoidance with Deep Learning

   https://doi.org/10.3847/1538-4357/ae21d0  

   Dupuy, Alexandra; Jeong, Donghui; Hong, Sungwook E; Hwang, Ho Seong; Kim, Juhan; Courtois, Hélène M (January 2026, The Astrophysical Journal)

   Abstract We present a refined deep-learning-based method to reconstruct the 3D dark matter density, gravitational potential, and peculiar velocity fields in the Zone of Avoidance (ZOA), a region near the Galactic plane with limited observational data. Using a convolutional neural network (V-Net) trained on A-SIM simulation data, our approach reconstructs density or potential fields from galaxy positions and radial peculiar velocities. The full 3D peculiar velocity field is then derived from the reconstructed potential. We validate the method with mocks that mimic the spatial distribution of the Cosmicflows-4 (CF4) catalog and apply it to actual data. Given CF4’s significant observational uncertainties and since our model does not yet account for them, we use peculiar velocities corrected via an existing Hamiltonian Monte Carlo reconstruction, rather than raw catalog distances. Our results demonstrate that the reconstructed density field recovers known galaxy clusters detected in an Hisurvey of the ZOA, despite this dataset not being used in the reconstruction. This agreement underscores the potential of our method to reveal structures in data-sparse regions. Most notably, streamline convergence and watershed analysis identify a mass concentration consistent with the Great Attractor, at (l,b) = (308 $\stackrel{\text{°}}{.}$ 4 ± 2 $\stackrel{\text{°}}{.}$ 4, 29 $\stackrel{\text{°}}{.}$ 0 ± 1 $\stackrel{\text{°}}{.}$ 9) andcz= 4960.1 ± 404.4 km s⁻¹, for 64% of realizations. Our method is particularly valuable as it does not rely on data point density, enabling accurate reconstruction in data-sparse regions and offering strong potential for future surveys with more extensive galaxy datasets. 

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2. Chemodynamics of Boötes I with S ⁵ : Revised Velocity Gradient, Dark Matter Density, and Galactic Chemical Evolution Constraints

   https://doi.org/10.3847/1538-4357/ae2fe5  

   Sandford, Nathan R; Li, Ting S; Koposov, Sergey E; Hayashi, Kohei; Pace, Andrew B; Erkal, Denis; Bovy, Jo; Da_Costa, Gary S; Cullinane, Lara R; Ji, Alexander P; et al (February 2026, The Astrophysical Journal)

   Abstract We combine new spectroscopic observations of the ultrafaint dwarf (UFD) galaxy Boötes I (Boo I) from the Southern Stellar Stream Spectroscopic Survey (S⁵) with ∼15 yr of archival spectroscopic data to create the largest sample of stellar kinematics and metallicities to date for any Milky Way UFD. Our combined sample includes 148 members extending out to ∼7 half-light radii (r_h), including 24 newly confirmed members, 18 binary candidates, 15 RR Lyrae stars, and 92 [Fe/H] measurements. Using this larger and more spatially extended sample, we provide updated constraints on Boo I’s systemic properties, including its radial population gradients. Properly accounting for perspective rotation effects in a UFD for the first time, we detect a 4σline-of-sight velocity gradient of 1.2 ± 0.3 km s⁻¹ $r_h^{-1}$ aligned along Boo I’s orbit and discuss its potential tidal origins. We also infer a metallicity gradient of −0.10 ± 0.02 dex $r_h^{-1}$ in agreement with previous studies. Using an axisymmetric Jeans model, we provide updated constraints on Boo I’s dark matter density profile, which weakly favors a cusped ( $\gamma =1.0_{-0.6}^{+0.5}$ ) dark matter profile. Lastly, we reanalyze Boo I’s metallicity distribution function with a one-zone galactic chemical evolution model and place new constraints on its rapid, inefficient star formation and strong galactic outflows. 

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3. A Uniform Analysis of Gas-phase Metallicity Evolution with 1–3 Gyr Time Sampling over the Past 12 Gyr

   https://doi.org/10.3847/1538-4357/ae4590  

   Jain, Shweta; Sanders, Ryan L; Khostovan, Ali Ahmad; Jones, Tucker; Shapley, Alice E; Reddy, Naveen A; Garcia, Alex M; Torrey, Paul; Coil, Alison (March 2026, The Astrophysical Journal)

   Abstract We present a systematic investigation of the evolution of the mass–metallicity relation (MZR) and fundamental metallicity relation (FMR) using uniform metallicity diagnostics across redshiftsz∼ 0 toz∼ 3.3. We present new Keck/Deep Imaging Multi-Object Spectrograph measurements of the [OII]λλ3726, 3729 emission line doublet for star-forming galaxies atz∼ 1.5 with existing measurements of redder rest-optical lines from the MOSFIRE Deep Evolution Field survey. These new observations enable uniform estimation of the gas-phase oxygen abundance using ratios of the [OII], Hβ, and [OIII] lines for mass-binned samples of star-forming galaxies in six redshift bins, employing strong line calibrations that account for the distinct interstellar medium ionization conditions atz< 1 andz> 1. We find that the low-mass power-law slope of the MZR remains constant over this redshift range with a value ofγ= 0.28 ± 0.01, implying the outflow metal loading factor ( ${\zeta }_{\text{out}}=\frac{Z_{\text{out}}}{Z_{\text{ISM}}}\frac{{\dot{M}}_{\text{out}}}{\text{SFR}}$ ) scales approximately as ${\zeta }_{\mathrm{out}}\propto M_{*}^{-0.3}$ out to at leastz∼ 3.3. The normalization of the MZR at 10¹⁰M_⊙decreases with increasing redshift at a rate of $d\log \left(\text{O/H}\right)/dz=-0.11\pm 0.01$ across the full redshift range. We find that any evolution of the FMR is smaller than 0.1 dex out toz∼ 3.3. We compare to cosmological galaxy formation simulations, and find that IllustrisTNG matches our measured combination of a nearly-invariant MZR slope, rate of MZR normalization decrease, and constant or very weakly evolving FMR. This work provides the most detailed view of MZR and FMR evolution from the present day through Cosmic Noon with a fine time sampling of 1−3 Gyr, setting a robust baseline for metallicity evolution studies atz> 4 with JWST. 

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4. Molecular Outflows in the Nucleus of the Nearby Compton-thick AGN NGC 3079

   https://doi.org/10.3847/1538-4357/ae6654  

   Lin, Ming-Yi; Medling, Anne M; Davies, Richard I; Krips, Melanie; Barcos-Muñoz, L; Genzel, R; González-Alfonso, E; Gracia-Carpio, J; Lutz, D; Neri, R; et al (June 2026, The Astrophysical Journal)

   Abstract We present Northern Extended Millimeter Array observations of the CO (2–1) molecular gas kinematics in the nearby Compton-thick Seyfert 2 galaxy NGC 3079, with an angular resolution of 0 $\stackrel{\text{″}}{.}$ 5 (∼40 pc). To interpret the observed CO (2–1) kinematics, we model the rotating disk using two software tools, 3D-Barolo and DysmalPy, to generate mock 3D data cubes. Both models indicate, in addition to the rotating disk, the presence of a spatially unresolved nuclear component characterized by high velocity dispersion. Analysis of the visibility data reveals that the blueshifted, high-velocity component is spatially offset from the continuum peak by 0 $\stackrel{\text{″}}{.}$ 17 (∼14 pc) and exhibits line-of-sight velocities ofv−v_sys= −350 to −450 km s⁻¹, which we interpret as a nuclear molecular outflow. We calculate a molecular gas mass outflow rate of 8.82M_⊙yr⁻¹, with a kinetic power ( ${\dot{E}}_{\text{out}}$ ) of 3.8 ×10⁴¹erg s⁻¹and a momentum rate ( ${\dot{p}}_{\text{out}}$ ) of 2.05 × 10³⁴Dyne. The momentum rate exceeds the AGN radiation momentum rate by a factor of ∼15, suggesting an energy-driven outflow. Furthermore, we argue that the derived kinetic power of the nuclear molecular outflow favors a jet-powered scenario that explains the slowdown and brightening of the parsec-scale radio source observed with the Very Long Baseline Array. 

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5. A Large Molecular Gas Reservoir in the Protocluster SPT2349−56 at z  = 4.3

   https://doi.org/10.3847/2041-8213/adb8d8  

   Zhou, Dazhi; Chapman, Scott C; Sulzenauer, Nikolaus; Hill, Ryley; Aravena, Manuel; Araya-Araya, Pablo; Cathey, Jared; Marrone, Daniel P; Phadke, Kedar A; Reuter, Cassie; et al (March 2025, The Astrophysical Journal Letters)

   Abstract We present Atacama Compact Array (ACA) Band-3 observations of the protocluster SPT2349−56, an extreme system hosting >10 ultraluminous infrared galaxies (ULIRGs;L_IR ≳  10¹²L_⊙) in a 200 kpc diameter region atz =  4.3, to study its integrated molecular gas content via CO(4–3) and the long-wavelength dust continuum. The ∼30 hr integration represents one of the longest exposures yet taken on a single pointing with the ACA 7 m. The low-resolution ACA data (21 $\stackrel{\text{″}}{.}$ 0  ×  12 $\stackrel{\text{″}}{.}$ 2) reveal a 75% excess CO(4–3) flux compared to the sum of individual sources detected in higher-resolution Atacama Large Millimeter/submillimeter Array (ALMA) data (1 $\stackrel{\text{″}}{.}$ 0  ×  0 $\stackrel{\text{″}}{.}$ 8). Our work also reveals a similar result by tapering the ALMA data to 10″. In contrast, the 3.2 mm dust continuum shows little discrepancy between ACA and ALMA. A single-dish [Cii] spectrum obtained by APEX/FLASH supports the ACA CO(4–3) result, revealing a large excess in [Cii] emission relative to ALMA. The missing flux is unlikely due to undetected faint sources but instead suggests that high-resolution ALMA observations might miss extended and low-surface-brightness gas. Such emission could originate from the circumgalactic medium or the preheated protointracluster medium (proto-ICM). If this molecular gas reservoir replenishes the star formation fuel, the overall depletion timescale will exceed 400 Myr, reducing the requirement for the simultaneous ULIRG activity in SPT2349−56. Our results highlight the role of an extended gas reservoir in sustaining a high star formation rate in SPT2349−56 and potentially establishing the ICM during the transition phase to a mature cluster. 

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