astro-ph.GA Archives

Reaction mechanism for the CN + H2CS system computed at the CCSD(T)-F12a+ZPE//DSDPBEP86/aug-cc-pVTZ level. Relative energies are given in kcal mol−1 with respect to the separated reactants. - -astro-ph.GA

Reaction Mechanisms and Kinetics of CN and CCH with H2CS: Implications for Interstellar Sulfur Chemistry

by Keith CowingJune 24, 2026June 24, 2026

We report an ab initio and master-equation investigation of the gas-phase reactions of thioformaldehyde (H2CS) with CN and CCH radicals, motivated by the recent detection of the S-containing species HCSCN […]

ASPECS-6: Spectral fit using the full JWST/MIRI MRS wavelength coverage (light grey), together with the available photometric data (black crosses, see Sect. 3). The green line represents the total fit. The dark gray line shows the underlying continuum made of the cold dust (blue), cool dust (cyan), warm dust (orange), and hot dust component (not shown). The purple lines are the PAHs. -- astro-ph.GA

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

PAHSPECS: Polycyclic Aromatic Hydrocarbon Properties At Cosmic Noon With JWST/MIRI MRS

by Keith CowingJune 18, 2026June 18, 2026

Context. Cosmic noon (z ~ 1-3) marks the peak of the cosmic star-formation rate density, when dust-obscured star formation dominated galaxy growth. Mid-infrared spectroscopy probes the interstellar medium through PAH […]

PAH ratio maps for the five PAHSPECS galaxies. We only show pixels that have a > 3σ measurement of the ratio. The left column shows NIRCAM color images using the F090W, F200W, F444W filters (M. J. Rieke et al. 2023). The second column shows the PAH6.2/PAH7.7 ratio. The third column shows the PAH11.3/PAH7.7 ratios. The fourth column shows the PAH3.3/PAH11.3 ratios. The final column shows [ArII]/PAH6.2. -- astro-ph.GA

Astrochemistry, Astronomy & Telescopes, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Imaging & Spectroscopy, Status Report

PAHSPECS: Spatially Resolved PAH Spectroscopy At Cosmic Noon With JWST MIRI MRS

by Keith CowingJune 18, 2026June 18, 2026

We present spatially resolved spectroscopy with JWST/MIRI MRS of a representative sample of normal star-forming galaxies at z∼1.1 as part of the PAHSPECS program.

Hierarchical clustering of the molecular cores based on the abundance ratios HN13C/HC3N, H13CO+/HC3N, and HC17O+/HC3N. Top panel: dendrogram obtained using Ward’s method. The vertical axis represents the Ward distance, which quantifies the chemical dissimilarity between cores. The horizontal dashed line indicates the adopted linkage-distance cut. The x-axis labels denote the core numbering. Bottom panels: mean abundance ratios of HN13

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

Simple Cyanides and Formylium Ions Isotopologues in Early Star-forming Molecular Cores

by Keith CowingJune 8, 2026June 10, 2026

Understanding the chemistry related to the early stages of star formation is of great importance, as it is linked to the beginnings of the most complex chemistry in the interstellar […]

(Left) TPD curves of SO2 deposited at 80 K on c-ASW (circles) for different coverages (1 ML, blue; 0.72 ML, red; 0.48 ML, green; 0.16 ML, magenta; and 0.07 ML, orange) in the submonolayer regime, with corresponding first-order fits (black lines). (Right) Associated adsorption energy distribution for each TPD curve. -- astro-ph.GA

Astrochemistry, Astrogeology, Biosignatures & Paleobiology, Callisto, Enceladus, Europa, Ganymede, Icy Worlds, Imaging & Spectroscopy, Status Report

Temperature-programmed Desorption Of SO2 From Water Ice Surfaces: Adsorption Energy Distributions

by Keith CowingJune 5, 2026June 5, 2026

Context. Sulphur-bearing species play a key role in the chemical evolution of the interstellar medium and icy Solar System bodies such as the Jovian moons, yet the sulphur budget remains […]

Top row: molecular structures of 1,4-, 1,5-, and 2,3-dimethylnaphthalene cations (1,4-, 1,5, and 2,3-diMeNp.+). Bottom row: molecular structures of the three expected longlived isomers of C11H9+ cations: benzyltropylium (BzTr+ ), 1-, and 2-naphthylmethylium (1- and 2-NpCH2+ ). -- astro-ph.GA

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

Acenaphthene Derivatives As Signatures Of C11H9 Reactivity With Methylated Naphthalenes

by Keith CowingJune 4, 2026June 4, 2026

C11H+9 ion is the dominant fragment cation formed from methyl-naphthalene (MeNp) and dimethyl-naphthalene (diMeNp).

Time evolution of the fractional abundances of HCOOH, HC(O)SH, HC(S)SH, and CH3SH. Solid lines represent the fiducial model, including all grain-surface and gas-phase reactions. Dashed lines show the abundances obtained when grain-surface reactions 5 and 6 are switched off, adopting realistic rate coefficients for gas-phase reactions 1 and 2. Dotted lines correspond to models in which grain-surface reactions 5 and 6 are excluded and the upper limits of the rate coefficients for gas-phase reactions 1 and 2 are adopted. -- astro-ph.GA

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

Non-detection Of HC(S)SH: Estimating Upper Limits And Constraining Chemistry

by Keith CowingJune 3, 2026June 3, 2026

The search for dithioformic acid (t-HC(S)SH) in star-forming regions is crucial for understanding interstellar sulfur chemistry and addressing the ‘missing sulfur’ problem. Motivated by a recent claim of t-HC(S)SH detection […]

Cartoon illustration (not up to scale) of molecular distribution of detected N-bearing molecules towards NIRS3 based on estimated source sizes and temperatures. The direction of CO (J = 3–2) outflow is obtained from Zinchenko et al. (2020). -- astro-ph.GA

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

Digging Into The Massive Protostar S255IR NIRS3: A Study of Nitrogen-Bearing Molecules and Their Prebiotic Chemistry

by Keith CowingMay 28, 2026May 28, 2026

The study of complex nitrogen (N)-bearing molecules is essential for probing the physical and chemical evolution of star-forming regions.

Left: GO 2433’s F770W map of NGC 891, with the H2 S (1) maps for the four MRS pointings in our study, in colour. The contours in the background and inset images are F770W surface brightnesses. The white cross marks the centre of the galaxy. Right: Total intensity maps for a few key dust features in all observations. The maps are obtained by fitting a 1D model to each pixel independently, and summing the intensities of all sub-features belonging to the same complex. Because the 11.2 µm feature dominates the emission, each map is shown with its own scaling; we focus on the variations within each maps rather than the absolute intensity values. Non-fit pixels, skipped by PAHFIT, are shown in white. -- astro-ph.GA

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

Survival Of Very Small Carbonaceous Dust Grains In The Inner-CGM Of NGC 891 From JWST/MIRI MRS

by Keith CowingMay 28, 2026May 28, 2026

We present new spectroscopic observations of the inner circumgalactic medium (CGM) of NGC 891 taken with the Mid-Infrared Imager/Medium Resolution Spectroscopy instrument onboard JWST, in four positions: two near the […]

Transition between different accretion regimes as shown by the shading and top labels. From left to right the panels show central AGN masses of 109, 108 and 107 𝑀⊙. The top row shows 𝑣frag = 1m s−1 and the bottom row shows 𝑣frag = 10 m−1 . The symbol 𝑚p gives the characteristic planetesimal mass, 𝑀HB is the transition mass between the Hill and the Bondi accretion regime, 𝑀BG is the transition mass between the Bondi and the geometric accretion regimes, and 𝑀p,iso is the pebble isolation mass. The transition between 2D and 3D accretion is also shown. In general, the objects will accrete in the 3D regime right after formation, except in the 1–10 pc range in the case 𝑣frag = 10 m/s, 𝑀SMBH = 109 𝑀⊙ (lower left). Accretion is also more efficient in the inner disk than in the outer disk, with a progression from Hill, Hill/Bondi, Bondi, and Bondi/Geometric as the central mass object decreases. The horizontal dotted black line is the hydrogen burning limit. -- astro-ph.EP

Astrogeology, Astronomy & Telescopes, Exoplanets, -moons, -comets, Status Report

Active Galactic Nucleus Tori: Potential Birthplace to Millions of Planets

by Keith CowingMay 23, 2026May 23, 2026

The outer regions of AGN disks have temperatures similar to those of circumstellar disks, permitting dust condensation. Therefore, planet formation and growth could be active in these dust tori through […]

astro-ph.GA

Reaction Mechanisms and Kinetics of CN and CCH with H2CS: Implications for Interstellar Sulfur Chemistry

PAHSPECS: Polycyclic Aromatic Hydrocarbon Properties At Cosmic Noon With JWST/MIRI MRS

PAHSPECS: Spatially Resolved PAH Spectroscopy At Cosmic Noon With JWST MIRI MRS

Simple Cyanides and Formylium Ions Isotopologues in Early Star-forming Molecular Cores

Temperature-programmed Desorption Of SO2 From Water Ice Surfaces: Adsorption Energy Distributions

Acenaphthene Derivatives As Signatures Of C11H9 Reactivity With Methylated Naphthalenes

Non-detection Of HC(S)SH: Estimating Upper Limits And Constraining Chemistry

Digging Into The Massive Protostar S255IR NIRS3: A Study of Nitrogen-Bearing Molecules and Their Prebiotic Chemistry

Survival Of Very Small Carbonaceous Dust Grains In The Inner-CGM Of NGC 891 From JWST/MIRI MRS

Active Galactic Nucleus Tori: Potential Birthplace to Millions of Planets

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