PAH Archives

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 […]

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).

Schematic drawing of the modified 22-pole radio frequency ion trap setup. The ions are produced between the first two plates of the ion guide by electron impact ionization and repelled towards the QMS-1. Mass-selected ions are injected into the 22-pole trap. The trap is equipped with neutral and pulsed buffer gas input ports. A neutral density measurement gauge (Pfeiffer CMR 375) is also connected to the trap volume. After a specified trapping time, the ions are mass-analyzed by QMS-2 and counted in the CEM detector. -- astro-ph.GA

Analog Studies, Astrochemistry, Astronomy & Telescopes, Biochemistry & Organic Chemistry, Biophysics, Biosignatures & Paleobiology, Icy Worlds, Imaging & Spectroscopy, Interstellar, Press Release, Titan

Observation Of Spontaneous N-bearing PAH Formation Using Ion Trap: A New Formation Pathway In The Interstellar Medium

by Keith CowingMay 16, 2026May 16, 2026

Nitrogen-bearing polycyclic aromatic hydrocarbons (N-PAHs) are key precursors to complex organic molecules in both the interstellar medium and the nitrogen-rich planetary atmospheres.

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.

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 […]

Astrochemistry, Astronomy & Telescopes, Biophysics, Icy Worlds, Imaging & Spectroscopy, Interstellar, Status Report, Water/Hycean Worlds & Oceanography

Cluster Anions of Hydrated Polycyclic Aromatic Hydrocarbons: “Magic” Water Tetramer

by Keith CowingApril 17, 2026April 17, 2026

The PAH-water (PAH = polycyclic aromatic hydrocarbon) interactions occur in interstellar ice grains and in atmospheres of planets and can serve as models for the interaction between water and graphite-like […]

2D color map as a function of Teq and [M/H]

Astrochemistry, Astrogeology, Atmospheres, Climate, Weather, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report

Sub-Neptunes As Soot Factories: Deep Atmosphere Hydrocarbon Formation and Quenching as the Origin of Sub-Neptune Aerosol Trends

by Keith CowingApril 16, 2026June 10, 2026

Recent population-level studies of sub-Neptune atmospheres have identified a parabolic trend in transmission spectrum amplitude for planets with Teq ~ 500-800 K. While the trend has been commonly attributed to […]

A three-color image of the CygX region constructed from SPHEREx mosaics. In this image, blue is 1.13–1.19 μm, green is 2.9–3.20 μm (containing the H2O ice absorption feature), and red is 4.75–5.1 μm. Continuum emission from warm dust extends across the image, as evidenced by the extended orange clouds. Dark lanes are seen where the dust and H2O ice absorption are the strongest. Red sources appear in these dark lanes where there are background sources or embedded young stars shining through the dust. Blue stars are seen in regions with lower extinction or are foreground objects. -- The Astrophysical Journal

Astrochemistry, Astronomy & Telescopes, Biochemistry & Organic Chemistry, Biophysics, Biosignatures & Paleobiology, Imaging & Spectroscopy, Interstellar, Press Release

Astrochemistry Update: SPHEREx Maps Vast Galactic Ice Regions

by Keith CowingApril 15, 2026April 15, 2026

NASA’s SPHEREx (Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer) mission has mapped interstellar ice at an unprecedented scale.

Nuclear dust and molecular structure, with a sketch summarizing grain and PAH processing in IRAS 07251−0248

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

Abundant Hydrocarbons In A Buried Galactic Nucleus With Signs Of Carbonaceous Grain And Polycyclic Aromatic Hydrocarbon Processing

by Keith CowingFebruary 6, 2026February 6, 2026

Hydrocarbons play a key role in shaping the chemistry of the interstellar medium (ISM), but their enrichment and relationship with carbonaceous grains and polycyclic aromatic hydrocarbons (PAHs) still lack clear […]

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

Millimeter And Submillimeter Spectroscopy Of Methylallene, CH3CHCCH2

by Keith CowingFebruary 5, 2026February 5, 2026

Small polycyclic aromatic hydrocarbons and somewhat larger cyano derivatives were detected in the cold dark cloud TMC-1 recently. Their formation from smaller hydrocarbons is not well understood, in part because […]

PAH

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

Acenaphthene Derivatives As Signatures Of C11H9 Reactivity With Methylated Naphthalenes

Observation Of Spontaneous N-bearing PAH Formation Using Ion Trap: A New Formation Pathway In The Interstellar Medium

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

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

Cluster Anions of Hydrated Polycyclic Aromatic Hydrocarbons: “Magic” Water Tetramer

Sub-Neptunes As Soot Factories: Deep Atmosphere Hydrocarbon Formation and Quenching as the Origin of Sub-Neptune Aerosol Trends

Astrochemistry Update: SPHEREx Maps Vast Galactic Ice Regions

Abundant Hydrocarbons In A Buried Galactic Nucleus With Signs Of Carbonaceous Grain And Polycyclic Aromatic Hydrocarbon Processing

Millimeter And Submillimeter Spectroscopy Of Methylallene, CH3CHCCH2

A Search For Narrowband Technosignatures From LTT 3780 With The Allen Telescope Array And The Karl G. Jansky Very Large Array

Tricorder Tech: Identifying Proteins, Molecule By Molecule

First Completed Rocky Worlds Program Observations Open New Era in Exoplanet Studies

Pioneer 10/11 Telemetry Explanatory Almanac

Diverse Organic Molecules Discovered Surrounding A Newly Formed Star