interstellar medium Archives

Left panel: Pairs of [O/H] and [C/O] used in models. Blue circles correspond to models O0C0 and O0C1. Orange squares and green triangles correspond to models O1C0, O1C1, O1C2 according to the assumed D, which is the dust-to-gas ratio normalized to the solar value (see right panel). The horizontal dotted black line (‘Linear’) corresponds to the assumption of a constant [C/O] (equal to −0.07) and independent on [O/H]. The Sharda et al. (2023b,c) (Eqn. 2) cubic-fit, the Nicholls et al. (2017) (Eqn.3) best-fit, and the Garnett et al. (1995) (Eqn.4) best-fit are shown in dot-dashed, dashed, and solid lines, respectively. Small brown diamonds refer to Lyman-continuum leaking galaxies at 𝑧 ∼ 0.3 − 0.4 of Izotov et al. (2023), yellow and dark blue to metal-poor dwarf galaxies of Berg et al. (2016) and Berg et al. (2019), respectively and red to green pea galaxies of Ravindranath et al. (2020). The purple diamond refers to the Isobe et al. (2023) JWST observations of GN-z11. Right panel: Relation of [O/H] versus D. The big blue circle, orange square and green triangle correspond to the values used in our models while their colours are in tandem with those of the left panel. Blue and orange models follow an approximately linear decrease of D as a function of [O/H] and are labeled as ‘D0’. The green triangle has a sub-linear D and is labeled as ‘D1’. Black dotted line corresponds to a linear connection between [O/H] and D to guide the eye. Gray diamonds correspond to the KINGFISH observations of Rémy-Ruyer et al. (2014), while magenta diamonds to the Dwarf Galaxy Survey data of Rémy-Ruyer et al. (2013). -- astro-ph.GA

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

α-enhanced Astrochemistry: The Carbon Cycle In Extreme Galactic Conditions

by Keith CowingDecember 6, 2023December 6, 2023

Astrochemistry has been widely developed as a power tool to probe physical properties of the interstellar medium (ISM) in various conditions of the Milky Way (MW) Galaxy, and in near […]

NOEMA 3 mm-band spectral surveys of APM 08279+5255 and NCv1.143, shown as the blue and violet spectra, respectively. For visualization purposes, the spectrum of NCv1.143 has been shifted up by 2 mJy. Both spectra are binned to 50 MHz (about 150 km s−1) to highlight the line detection. Error bars are indicated by thin lines (the same color as the spectra) overlaid on the spectra. Black dashed lines identify the lines detected in both sources, while orange dashed lines highlight the lines that are only detected in one of the two sources. The line names are labeled above the dashed lines. The peak values indicated for CO(3–2), CO(4–3), and [C I](1-0) emission lines in NCv1.143 are the true peak values before the 2 mJy shift, and they are outside the box of the figure. A zoom-in version is provided in Fig. A.1 -- astro-ph.GA

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

SUNRISE: The Rich Molecular Inventory Of High-redshift Dusty Galaxies Revealed By Broadband Spectral Line Surveys

by Keith CowingNovember 17, 2023November 17, 2023

Understanding the nature of high-z dusty galaxies requires a comprehensive view of their ISM and molecular complexity. However, the molecular ISM at high-z is commonly studied using only a few […]

The purine nucleobases adenine and guanine

Astrochemistry, Astronomy & Telescopes, Biochemistry & Organic Chemistry, Biosignatures & Paleobiology, Genomics, Proteomics, Bioinformatics, Status Report

Infrared Spectral Signatures of Nucleobases in Interstellar Ices I: Purines

by Keith CowingNovember 16, 2023November 16, 2023

The purine nucleobases adenine and guanine are complex organic molecules that are essential for life. Despite their ubiquitous presence on Earth, purines have yet to be detected in observations of […]

Integrated intensity map of NH2CHO and CH13 3 CN in Sgr B2(N1). The integrated intensity map of NH2CHO at 103.525 GHz are shown in color scale. The integrated intensity map of CH13 3 CN at 91.94 GHz is shown in contours, which represent 30% to 90% percent of peak integrated intensity. The white crosses indicate the position of Sgr B2(N1E), Sgr B2(N1S), and the center of Sgr B2(N1). The white ellipse shows the size of the respective synthetic beam. -- astro-ph.GA

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

Tentative Detection Of Cyanoformamide NCCONH2 In Space

by Keith CowingNovember 7, 2023November 7, 2023

The peptide-like molecules, cyanoformamide (NCCONH2), is the cyano (CN) derivative of formamide (NH2CHO). It is known to play a role in the synthesis of nucleic acid precursors under prebiotic conditions.

Schematic for reactions in space occurring in the gas phase (top), and on the surface of grains (bottom). -- NASA

Astrochemistry, Biochemistry & Organic Chemistry, Biosignatures & Paleobiology, Interstellar, Status Report

Density Functional Theory Calculations on the Interstellar Formation of Biomolecules

by Keith CowingOctober 24, 2023October 24, 2023

The density functional theory (DFT) is the most versatile electronic structure method used in quantum chemical calculations, and is increasingly applied in astrochemical research.

Fractional abundances as a function of the kinetic temperature. Tk is derived from ammonia (Fontani et al. 2011). The four panels show sulphur-bearing molecules which contain: only carbon (top-left panel); carbon and hydrogen (top-right panel); only oxygen (bottom-left panel); anything else (bottom-right panel). The symbols without uncertainty are upper limits. The numbers below the label of each molecule is the Pearson’s ρ correlation coefficient. The curves represent linear fits to the data including upper limits plotted in logaritmic scale. -- astro-ph.GA

Astrochemistry, Astronomy & Telescopes, Biosignatures & Paleobiology, Imaging & Spectroscopy, Status Report

The Evolution Of Sulphur-bearing Molecules In High-mass Star-forming Cores

by Keith CowingOctober 22, 2023October 22, 2023

To understand the chemistry of sulphur (S) in the interstellar medium, models need to be tested by observations of S-bearing molecules in different physical conditions.

Continuum emission at 99 GHz in grey scale overlaid by contours of SO J = 23 − 12 at 99.3 GHz (top) and SiO J = 2 − 1 at 86.85 GHz (bottom) integrated intensities. The inner integration limits vary such that channels that contain deep absorption are excluded. The outer integration limits are fixed at 15 and 115 km s−1 for blue- and red-shifted SO emission, respectively, and 5 and 130 km s−1 for blue- and red-shifted SiO emission, respectively (see also Fig. 3). The blue and red contours start at 5σ and then increase by a factor of 2, where σ = 10.5 (SO, blue), 10.8 (SO, red), 4.5 (SiO, blue), and 5.8 K km s−1 (SiO, red) and corresponds to an average noise level that was measured in the respective map. The black contour indicates the 3σ level of the continuum emission (see Fig. 1). Based on the SO maps, we identify collimated features possibly tracing outflow axes that are shown as solid and dashed black arrows and labelled aB1, aR1, and aR2. The markers are the same as in Fig. 1. In addition to N2, the hot core N3 identified by Bonfand et al. (2017) is marked with a cyan tetragon. Blue and pink star markers indicate H2O maser spots (McGrath et al. 2004) with blue- and red-shifted velocities, respectively, with respect to 3sys ≡ 62 km s−1 . The HPBW is shown in the bottom-right corner of each panel. The position offsets are given with respect to the ReMoCA phase centre (black cross). The maps are not corrected for primary beam attenuation. -- astro-ph.GA

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

Shocking Sgr B2(N1) With Its Own Outflow: A New Perspective On Segregation Between O- and N-bearing Molecules

by Keith CowingOctober 21, 2023October 19, 2023

We want to investigate the influence of the powerful outflow driven by the hot core Sgr B2(N1) on the gas molecular inventory of the surrounding medium.

Continuum emission image of high-mass star-formation region G358.93–0.03 at a wavelength of 988 µm. The synthesized beam size (white circle) of the continuum image is 0.412′′×0.363′′. The sub-millimeter continuum sources MM1–MM8 are located in the massive star-formation region G358.93–0.03. The contour (white colour) levels start at 3σ where σ is the RMS of the continuum emission image and the contour levels increase by a factor of √ 2. -- astro-ph.GA

Astrochemistry, Astronomy & Telescopes, Biosignatures & Paleobiology, Imaging & Spectroscopy, Interstellar, Status Report

Identification Of The Simplest Sugar-like Molecule Glycolaldehyde Towards The Hot Molecular Core G358.93-0.03 MM1

by Keith CowingAugust 30, 2023August 30, 2023

Glycolaldehyde (CH2OHCHO) is the simplest monosaccharide sugar in the interstellar medium, and it is directly involved in the origin of life via the ‘RNA world’ hypothesis.

Schematic illustration of the deuteration of PAHs in the Orion Bar PDR, from regions near the ionization front where the C–D bonds are mostly aromatic, to regions intermediate beteen the ionization front and the dissociation front where PAHs could be superhydrogenated and even superdeuterated. -- astro-ph.GA

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

Deuterated Polycyclic Aromatic Hydrocarbons In The Interstellar Medium: The Aliphatic C–D Band Strengths

by Keith CowingAugust 15, 2023August 15, 2023

Deuterium (D) was exclusively generated in the Big Bang and the standard Big Bang Nucleosynthesis (BBN) model predicts a primordial abundance of D/H~26ppm. As the Galaxy evolves, D/H gradually decreases […]

NGC 6946 with EMPIRE CO (1-0) contours overlaid on an optical image. The contours illustrate the IRAM-30m 12CO (1-0) integrated intensities. The millimeter observations have a resolution of 26′′(∼800 pc), indicated by the orange circle. The contours are drawn at arbitrary intervals between 5 and 200 K km s−1 to highlight the distribution of the molecular gas disk. The yellow circles indicate the locations of our pointed N2H + (1-0) and HCN (1-0) observations, covering a wide range of galactic environmental conditions: center (0), spiral arms (1 and 2), interarm (4), and outskirts (3). The size represents the 28′′ resolution of the IRAM-30m beam at ∼ 86 GHz. -- astro-ph.GA

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

A Constant N2H+(1-0)-to-HCN(1-0) Ratio On Kiloparsec Scales

by Keith CowingAugust 3, 2023August 3, 2023

Nitrogen hydrides such as NH3 and N2H+ are widely used by Galactic observers to trace the cold dense regions of the interstellar medium.

interstellar medium

α-enhanced Astrochemistry: The Carbon Cycle In Extreme Galactic Conditions

SUNRISE: The Rich Molecular Inventory Of High-redshift Dusty Galaxies Revealed By Broadband Spectral Line Surveys

Infrared Spectral Signatures of Nucleobases in Interstellar Ices I: Purines

Tentative Detection Of Cyanoformamide NCCONH2 In Space

Density Functional Theory Calculations on the Interstellar Formation of Biomolecules

The Evolution Of Sulphur-bearing Molecules In High-mass Star-forming Cores

Shocking Sgr B2(N1) With Its Own Outflow: A New Perspective On Segregation Between O- and N-bearing Molecules

Identification Of The Simplest Sugar-like Molecule Glycolaldehyde Towards The Hot Molecular Core G358.93-0.03 MM1

Deuterated Polycyclic Aromatic Hydrocarbons In The Interstellar Medium: The Aliphatic C–D Band Strengths

A Constant N2H+(1-0)-to-HCN(1-0) Ratio On Kiloparsec Scales

Ancient Layers On Mars Exposed By A Crater Within A Crater In Terra Sirenum

Send Your Name to Titan Aboard NASA’s Dragonfly Astrobiology Mission

Reconciling Giant Impacts with the Radius Valley: The Role of Silicate-Hydrogen Miscibility for Sub-Neptunes

Comprehensive Visible and Near-infrared Keck and Gemini Monitoring and Characterization of Interstellar Comet 3I/ATLAS during its Encounter with the Solar System

ExoVetter and a TESS Exoplanet Transit Search of Kepler Stars as Ground Truth