astro-ph.GA Archives

Molecular abundances as a function of the H2 column density. Each panel shows one molecule, with bars representing the derived abundances for the different cores and widths corresponding to half the uncertainty in N(H2). Hatched bars with a downward-facing triangle indicate upper limits (non-detections). Each panel also shows the Spearman rank correlation coefficient (ρ) and the corresponding p-value. -- astro-ph.GA

Astrochemistry, Astronomy & Telescopes, Biochemistry & Organic Chemistry, Biophysics, Biosignatures & Paleobiology, Imaging & Spectroscopy, Interstellar, Status Report

Tracing The Sulfur Depletion In Starless And Pre-stellar Cores

by Keith CowingMay 15, 2026May 15, 2026

Sulfur is one of the most abundant elements in the Universe, yet the sulfur budget inferred from the observed sulfur-bearing molecules in dense cores is significantly lower than expected.

Diagnostic band ratio diagrams extracted from the PAH diagnostic grids (Figure 4), illustrating the influence of varying aliphatic content (0%, 33.3%, 50%, and 100%) at five fixed ionization fractions (Neutral, N67C33, N50C50, N33C67, and Cation). Each panel presents data points representing individual PAH species or mixtures color-coded by their number of carbon atoms (Nc). Linear fits (solid and dashed lines) connect points within each ionization fraction to quantify trends in diagnostic ratios with increasing aliphatic content. The bottom-right panel summarizes these trends by showing the slope distribution histogram of the linear fits across different ionization states, highlighting the systematic increase in slope with aliphatic fraction for all cases except the fully ionized state. -- astro-ph.GA

Astrochemistry, Astronomy & Telescopes, Biochemistry & Organic Chemistry, Biophysics, Biosignatures & Paleobiology, Imaging & Spectroscopy, Interstellar, Status Report

The Influence of Aliphatic Components on the Aromatic Emission Characteristics of Polycyclic Aromatic Hydrocarbons

by Keith CowingMay 14, 2026May 14, 2026

Intensity ratios of aromatic emission features are widely used to diagnose the size and ionization state of polycyclic aromatic hydrocarbons (PAHs) in astronomical environments.

Velocity-integrated intensity maps and spatial averaged spectra

Astrochemistry, Astronomy & Telescopes, Biochemistry & Organic Chemistry, Biophysics, Biosignatures & Paleobiology, Imaging & Spectroscopy, Interstellar, Status Report

The Evolution Of C4H And c-C3H2 In Molecular Cores

by Keith CowingMay 13, 2026May 13, 2026

Linear C4H and cyclic c-C3H2, as small unsaturated hydrocarbons, are the key precursors to complex organic molecules and are critical components of the interstellar medium. We present on-the-fly mapping observations […]

Astrochemistry, Astronomy & Telescopes, Biochemistry & Organic Chemistry, Biophysics, Biosignatures & Paleobiology, Imaging & Spectroscopy, Interstellar, Status Report

First Interstellar Detection of Methyl Carbamate: A New Observational Anchor for Glycine Chemistry

by Keith CowingMay 12, 2026May 12, 2026

Glycine-the simplest amino acid-has remained undetected in the interstellar medium despite decades of sensitive searches, motivating alternative approaches to constrain its astrochemical origin.

PPV plot of the (sub)millimeter HCN-to-HCO+ flux ratios at J=2–1, J=3–2, and J=4–3, with a velocity resolution of 20 km s−1 and a pixel scale of 0. ′′02 pixel−1 for IRAS 00091−0738. The HCN-to-HCO+ flux ratios are calculated in brightness temperature (K). (This is virtually identical to the ratio in flux density (Jy ∝ K × ν 2 ), because the HCN and HCO+ frequencies differ only by a factor of ∼1.006 at the same J transition.) Only data with >3σ detections in emission for both the HCN and HCO+ lines are plotted. The color bar corresponds to 0.285 (blue) to 3.5 (pink) in the same way as Nishimura et al. (2024). Left: All >3σ-detected data. Center : Data with the top 10% ratios. Right: Data with ratios >1.5. East is to the left and west is to the right along the ∆α axis. North is farther and south is nearer along the ∆δ axis. -- astro-ph.GA

Astrochemistry, Astronomy & Telescopes, Biochemistry & Organic Chemistry, Imaging & Spectroscopy, Status Report

Spectrally And Spatially Resolved (sub)millimeter HCN-to-HCO+ Flux Ratios In Nearby Ultraluminous Infrared Galaxies

by Keith CowingMay 12, 2026May 12, 2026

We present the results of our investigations of spectrally and spatially resolved (sub)millimeter HCN-to-HCO+ flux ratios at J=2-1, J=3-2, and/or J=4-3 in 18 nearby (z< 0.15) ultraluminous infrared galaxies (ULIRGs), […]

Optical Hubble Space Telescope (HST) images of the targets NGC 4321 (top) and M51 (bottom) overlaid with CO, HCN and SFR contours (from left to right). The CO (HCN) contours are drawn at S/N≥ 10, 30, and 60 (1, 3, 10, 30). The SFR contours correspond to the 70th, 85th, and 95th percentiles of the data. The spiral arm masks are indicated as white contours. Background HST image credit: NGC 4321: PHANGS-HST (Lee et al. 2022); M51: NASA, ESA, S. Beckwith (STScI) and the Hubble Heritage Team (STScI/AURA). -- astro-ph.GA

Astrochemistry, Astronomy & Telescopes, Imaging & Spectroscopy, Interstellar, Status Report, Stellar Cartography

From Gas To Stars Along The Spiral Wave: CO, HCN, And Star Formation Variations Across The Spiral Arms In NGC 4321 And M51

by Keith CowingMay 9, 2026May 9, 2026

Molecular clouds form stars from the interstellar medium via gravitational collapse, following a sequence from low-density gas to high-density cores and eventually the formation of stars.

Correlations of crystallization metrics with cluster mass, Galactocentric distance, and a dynamical-age proxy. Top row: Cindex versus log(Mcl/M⊙), RGC, and log10(tage/trh). Bottom row: the N⋆-corrected residual index Cresid versus the same quantities. Spearman rank coefficients and two-sided p-values are printed in each panel. Star symbols mark Tier 1 clusters. -- astro-ph.GA

AI - Data - Apps - Cybernetics, Astronomy & Telescopes, SETI & Technosignatures, Status Report

Phase-Space Crystallization in Galactic Globular Clusters: A Gaia-Based Metric and Implications for Technosignature Searches

by Keith CowingMay 9, 2026May 9, 2026

We develop a model-independent framework to quantify phase-space “crystallization”, the degree of ordered radial and kinematic substructure, in 79 Galactic globular clusters using the Gaia EDR3-based membership catalogue of E. […]

As Fig. 3 in the main text, but showing results for different monolayer thicknesses of the active surface (as indicated on top of each panel). For clarity, only those species with a relative abundance of over 1% are labeled on the pie charts. The fiducial 100 ML model is also included for reference.-- astro-ph.GA

Astrochemistry, Astronomy & Telescopes, Biochemistry & Organic Chemistry, Biophysics, Biosignatures & Paleobiology, Icy Worlds, Imaging & Spectroscopy, Interstellar, Status Report

Modeling The UV-photon Irradiation Of CS2-bearing Ices In The Laboratory With The pyRate Gas-grain Astrochemical Code. New Insights Into The Missing Sulfur Problem

by Keith CowingMay 7, 2026May 7, 2026

Observations indicate that the total abundance of S-bearing species in dense clouds is orders of magnitude lower than the cosmic sulfur abundance.

IRAS 15398 JWST NIRSpec spectrum (Program ID 1854, PI: M. McClure), NIRSpec Prism spectrum (Program ID 6161, PI: K. Slavicinska), and MIRI-MRS spectrum (Program ID 2151, PI: Y.-L. Yang) with the radiative transfer model spectrum extracted in a 1” diameter overlaid in black. Data points which hit the noise floor from the G395H and Prism data were removed. A spectrum zoomed in to the NIR CO2 and CO absorption is shown in Appendix E. -- astro-ph.SR

Astrochemistry, Astronomy & Telescopes, Biochemistry & Organic Chemistry, Biophysics, Biosignatures & Paleobiology, Icy Worlds, Imaging & Spectroscopy, Interstellar, Status Report

CORINOS V: Radiative Transfer Effects In Protostellar Ice Observations

by Keith CowingMay 2, 2026May 2, 2026

Recent observations of protostars with the James Webb Space Telescope have revealed unprecedented chemical complexity from their ice absorption features.

Integrated intensity between 5.3 and 6.5 kms−1 of different molecular transitions (colors) compared with that of C6H5CN (black contours; first contour and step are 0.75 mK kms−1 )

Astrochemistry, Astronomy & Telescopes, Biochemistry & Organic Chemistry, Biophysics, Biosignatures & Paleobiology, Imaging & Spectroscopy, Status Report

TMC-1: Probing The Onset Of Chemical Complexity In Space

by Keith CowingApril 30, 2026April 30, 2026

In recent years, the obsessive interest in the observation of TMC-1 has brought a boost in our knowledge of the chemistry of cold dark clouds. The number of molecules detected […]

astro-ph.GA

Tracing The Sulfur Depletion In Starless And Pre-stellar Cores

The Influence of Aliphatic Components on the Aromatic Emission Characteristics of Polycyclic Aromatic Hydrocarbons

The Evolution Of C4H And c-C3H2 In Molecular Cores

First Interstellar Detection of Methyl Carbamate: A New Observational Anchor for Glycine Chemistry

Spectrally And Spatially Resolved (sub)millimeter HCN-to-HCO+ Flux Ratios In Nearby Ultraluminous Infrared Galaxies

From Gas To Stars Along The Spiral Wave: CO, HCN, And Star Formation Variations Across The Spiral Arms In NGC 4321 And M51

Phase-Space Crystallization in Galactic Globular Clusters: A Gaia-Based Metric and Implications for Technosignature Searches

Modeling The UV-photon Irradiation Of CS2-bearing Ices In The Laboratory With The pyRate Gas-grain Astrochemical Code. New Insights Into The Missing Sulfur Problem

CORINOS V: Radiative Transfer Effects In Protostellar Ice Observations

TMC-1: Probing The Onset Of Chemical Complexity In Space

Tricorder Tech: New Handheld Device Maps Chemical Composition Using Infrared Light

No Statistically Significant Evidence For A Correlation Between Stellar And planetary Composition

Water Planet Recon: How Accurately Can We Measure Earth Ocean’s Deepest Point?

Webb Reveals A Stunning Panorama Of Star Formation

Deep Learning of SHERLOC Raman Spectra For Facilitating Mars Astromaterial Identification