Amanda A. Kepley

Resolving atomic gas at ≲100 pc physical resolution is currently feasible only for the very nearest galaxies. We combine 120 pc resolution H i data using the Karl G. Jansky Very Large Array (VLA) from the first data release of the Local Group L -Band Survey (LGLBS) with uniformly processed infrared, ultraviolet, H α , and CO maps. We analyze the radial profiles of gas, stars, and recent star formation for six local galaxies: M31, M33, IC 10, IC 1613, NGC 6822, and Wolf–Lundmark–Melotte. Across the sample, atomic-gas disks are the most extended component, reaching r _HI = 2.8–5.8 kpc in the dwarfs and 13–26 kpc in M33 and M31. Azimuthally averaged Σ _atom profiles are often flat or only slowly declining compared to the steeper decline of Σ _⋆ and Σ _SFR , with outer H i scale lengths of l HI outer ≈ 1.0 –8.5 kpc. The mass-weighted H i surface densities on a 120 pc scale generally exceed the azimuthally averaged values by 10%–70%, showing that localized high-column-density atomic structures persist even where azimuthally averaged profiles appear smooth. Atomic-gas depletion times rise from τ dep atom ≈ 0.8 –17 Gyr within the stellar half-mass–radius to tens to 100 Gyr in the outer disks. Molecular depletion times are shorter. We provide a public release of these multiwavelength data, which provide a valuable reference for the LGLBS targets and also form the basis for a companion paper that relates star formation, gas phases, and midplane pressure on 120 pc scales.

We present GBT-EDGE, a new CO (1–0) survey using the Green Bank Telescope to map 62 nearby (10–140 Mpc) galaxies spanning the star-forming main sequence (SFMS), green valley, and red sequence. The galaxy sample is selected from the Calar Alto Legacy Integral Field Area (CALIFA) survey with integral field spectroscopy (IFS), which provides a representative census of local galactic environments. Combining the CO data set with CALIFA’s optical IFS measurements, we derive molecular gas masses, star formation rates (SFR), metallicities, and stellar mass densities to measure star formation efficiency (SFE) and investigate the physical drivers of galaxy quenching. We obtain a median molecular gas depletion time of 2.1 0 − 1.31 + 2.35 , 6.9 0 − 3.67 + 17.00 , and 127 . 7 − 113.4 + 201.6 Gyr for our sample of main-sequence, green valley, and red galaxies, respectively, assuming a Galactic CO-to-H ₂ conversion factor. By applying various conversion factor prescriptions, we also confirm a systematic decrease of SFE with a galaxy’s offset below the SFMS, regardless of the adopted prescription. This suggests that the low SFR in some quenched galaxies is primarily driven by suppressed SFE rather than an absence of molecular gas. Our results provide evidence that galaxies below the main sequence can retain substantial molecular gas reservoirs comparable to star-forming galaxies, but they exhibit longer depletion times and form stars inefficiently, possibly due to the combined effects of low gas density and morphological quenching mechanisms.

The effect of supernovae (SNe) on star formation in the interstellar medium (ISM) depends sensitively on where SNe explode with respect to ISM clouds. Observationally, SN ISM environments characterized by spatially resolved gas maps can empirically guide the placement of SNe in subgrid models, but unfortunately such measurements remain scarce, as SNe are rare and often distant. Here we demonstrate a new approach—mapping the ISM around evolved massive stars that are soon to explode. These provide a substantially larger sample of “explosion sites” (than just historical SNe) in nearby galaxies that have high-resolution atomic and molecular ISM maps from the Jansky Very Large Array and Atacama Large Millimeter/submillimeter Array. We demonstrate this technique in the well-resolved Local Group spiral M33 by analyzing the 50 pc scale projected ISM densities around red supergiants (RSGs; 8–30 M _⊙ stars) Wolf–Rayet stars (W-Rs; >30 M _⊙ stars), and supernova remnants. We find a mass-dependent correlation between stars and gas clouds, with at least 45% of W-Rs and up to 77% of RSGs having no detectable H ₂ at their pixel locations. In the sample with H ₂ detections, we find that more-massive younger progenitors are coincident with denser gas. We show that the density distributions for stars >15 M _⊙ are statistically distinct from random alignment of stars and gas in M33. Our work provides the first observationally derived estimate of the fraction of the SN-producing stellar population correlated with ISM density peaks. We demonstrate how this can be compared with galaxy simulations, and advocate similar comparisons to the community for constraining subgrid models.

We present the first localized detections of the cold neutral medium (CNM) in IC 10, offering a rare view of dense atomic gas in a low-metallicity ( Z / Z _⊙ ∼ 0.27) dwarf galaxy. As a low-metallicity starburst, IC 10’s interstellar medium conditions could reflect small scale physics conditions that mirror those of early galaxies, providing a unique window into the heating and cooling processes that shaped the interstellar medium in early-Universe environments. Leveraging the high angular (−1 ) resolution of the Local Group L -band Survey, we searched for H I absorption against nine continuum radio sources and detected absorption along three sightlines corresponding to internal radio emission sources within IC 10. Using Gaussian decomposition and radiative transfer, we characterize the CNM, deriving spin temperatures of ∼30–55 K, column densities of (0.6–3.0) × 10 ²¹ cm ⁻² , cold H I fractions of ∼21%–37%, and line widths of ∼5.6–13.6 km s ⁻¹ . For each individual detection of H I absorption, we find corresponding molecular emission from ¹² CO ( J = 1–0), HCO ⁺ ( J = 1–0), and HCN ( J = 1–0) at similar velocities and with comparable line widths, indicating a well-mixed cold atomic and molecular medium. In IC 10, the CNM shows a clear kinematic connection to the high-density ISM, implying a stronger dynamical coupling with molecular gas than in the Milky Way, in line with expectations for low-metallicity environments. At the ∼15 pc scales probed by slightly extended H II regions in IC 10, unresolved CNM clouds likely contribute to line blending, so the observed broad H I line widths may partly reflect spatial and kinematic averaging.

Dwarf galaxies, due to their shallow gravitational potentials, provide critical environments for studying feedback mechanisms from star formation and its impacts on dwarf galaxy evolution. In particular, radio continuum (RC) observations offer valuable insights into cosmic ray dynamics, which play a significant role in shaping these processes. This study investigates the detectability and spectral characteristics of RC emission in a sample of 15 dwarf galaxies (11 gas-rich, star forming dwarfs and 4 blue compact dwarfs) spanning a broad range of stellar masses and star formation histories. Using multi-band RC data (L/S-, C-, and X-band) from the Australia Telescope Compact Array, we analyse the physical conditions responsible for RC emission and explore the dominant emission mechanisms within these systems. RC emission is detected in 11 out of the 15 galaxies. Our results indicate that RC emission correlates strongly with star formation rate, far-infrared, and stellar mass, while dynamic parameters such as HI and rotational velocity exhibit no significant correlation with RC detectability. Spectral analysis reveals that the RC spectral energy distribution in these galaxies frequently deviate from a simple power-law behavior, instead displaying curvature that suggests more complex underlying physical processes. Statistical model comparison confirms that a single power-law model is inadequate to capture the observed spectral shapes, emphasising the necessity of more sophisticated approaches. Additionally, the observed radio-far-infrared correlation indicates that cosmic ray electrons in lower-mass dwarf galaxies cool more rapidly than they can escape (e.g. via galactic winds), resulting in a measurable RC deficit.

We present the Local Group L-Band Survey, a Karl G. Jansky Very Large Array (VLA) survey producing the highest-quality 21 cm and 1–2 GHz radio continuum images to date, for the six VLA-accessible, star-forming, Local Group galaxies. Leveraging the VLA’s spectral multiplexing power, we simultaneously survey the 21 cm line at high 0.4 km s⁻¹ velocity resolution, the 1–2 GHz polarized continuum, and four OH lines. For the massive spiral M31, the dwarf spiral M33, and the dwarf irregular galaxies NGC 6822, IC 10, IC 1613, and the Wolf–Lundmark–Melotte Galaxy, we use all four VLA configurations and the Green Bank Telescope to reach angular resolutions of 20 cm⁻² column density sensitivity, and even sharper views (D ≲ 1 Mpc) reveals a sharp, resolved view of the atomic gas, including 21 cm absorption, and continuum emission from supernova remnants and H ii regions. These data sets can be used to test theories of the abundance and formation of cold clouds, the driving and dissipation of interstellar turbulence, and the impact of feedback from massive stars and supernovae. Here, we describe the survey design and execution, scientific motivation, data processing, and quality assurance. We provide a first look at and publicly release the wide-field 21 cm H i data products for M31, M33, and four dwarf irregular targets in the survey, which represent some of the highest-physical-resolution 21 cm observations of any external galaxies beyond the LMC and SMC.

We report observations of the ground state transitions of ¹²CO, ¹³CO, C¹⁸O, HCN, and HCO⁺ at 88–115 GHz in the inner region of the nearby galaxy IC 342. These data were obtained with the 16 pixel spectroscopic focal plane array Argus on the 100 m Robert C. Byrd Green Bank Telescope (GBT) at 6″–9″ resolution. In the nuclear bar region, the intensity distributions of ¹²CO(1–0) and ¹³CO(1–0) emission trace moderate densities, and differ from the dense gas distributions sampled in C¹⁸O(1–0), HCN(1–0), and HCO⁺(1–0). We observe a constant HCN(1–0)-to-HCO⁺(1–0) ratio of 1.2 ± 0.1 across the whole ∼1 kpc bar. This indicates that the HCN(1–0) and HCO⁺(1–0) lines have intermediate optical depth, and that the corresponding n H 2 of the gas producing the emission is of order 10^4.5−6 cm⁻³. We show that HCO⁺(1–0) is thermalized and HCN(1–0) is close to thermalization. The very tight correlation between the HCN(1–0) and HCO⁺(1–0) intensities across the 1 kpc bar suggests that this ratio is more sensitive to the relative abundance of the two species than to the gas density. We confirm an angular offset (∼10″) between the spatial distribution of molecular gas and the star formation sites. Finally, we find a breakdown of the L _IR– L HCN correlation at high spatial resolution due to the effect of incomplete sampling of star-forming regions by HCN emission in IC 342. The scatter of the L _IR– L HCN relation decreases as the spatial scale increases from 10″ to 30″ (170–510 pc), and is comparable to the scatter of the global relation at a scale of 340 pc.

We describe the calibration and imaging heuristics developed and deployed in the ALMA interferometric data processing pipeline, as of ALMA Cycle 9. The pipeline software framework is written in Python, with each data reduction stage layered on top of tasks and toolkit functions provided by the Common Astronomy Software Applications package. This framework supports a variety of tasks for observatory operations, including science data quality assurance, observing mode commissioning, and user reprocessing. It supports ALMA and VLA interferometric data along with ALMA and NRO45m single dish data, via different stages and heuristics. In addition to producing calibration tables, calibrated measurement sets, and cleaned images, the pipeline creates a WebLog which serves as the primary interface for verifying the data quality assurance by the observatory and for examining the contents of the data by the user. Following the adoption of the pipeline by ALMA Operations in 2014, the heuristics have been refined through annual development cycles, culminating in a new pipeline release aligned with the start of each ALMA Cycle of observations. Initial development focused on basic calibration and flagging heuristics (Cycles 2-3), followed by imaging heuristics (Cycles 4-5), refinement of the flagging and imaging heuristics with parallel processing (Cycles 6-7), addition of the moment difference analysis to improve continuum channel identification (2020 release), addition of a spectral renormalization stage (Cycle 8), and improvement in low SNR calibration heuristics (Cycle 9). In the two most recent Cycles, 97% of ALMA datasets were calibrated and imaged with the pipeline, ensuring long-term automated reproducibility. We conclude with a brief description of plans for future additions, including self-calibration, multi-configuration imaging, and calibration and imaging of full polarization data.