Investigating chemical variations between interstellar gas clouds in the Solar neighbourhood

Abstract

The interstellar medium (ISM) is a fundamental component of the Milky Way. Studying its chemical composition and the level of its chemical diversity gives us insight into the evolution of the Milky Way and the role of gas in the Galactic environment. In this paper, we use a novel simulation technique to model the distribution of total hydrogen between gas components, and therefore derive new constraints on the dust depletion and metallicity. We study individual gas components along the lines of sight towards eight bright O/B stars within 1.1 kpc of the Sun using high-resolution HST/STIS absorption spectra (R sim 114 000). We measure the level of dust depletion for these individual components and find components with higher levels of dust depletion compared to Milky Way sightlines in the literature. We find large ranges in the level of dust depletion among components along lines of sight, up to 1.19 dex. Although it is not possible to directly measure the metallicity of individual components due to the saturated and damped Ly-alpha line, we investigate possible metallicity ranges for individual gas components by exploring many different distributions of the total hydrogen gas between components. We select possible combinations of these gas fractions which produce the minimum metallicity difference between components, and for these cases we determine individual metallicities to accuracies that range between sim 0.1 to 0.4 dex. This work shows that full line-of-sight analyses wash out the level of diversity along lines of sight, and that component-by-component studies give a more in-depth understanding of the chemical intricacies of the interstellar medium.

Accepted for publication in A&A on 31 January 2025. Abstract edited for arXiv

References in corpus (28)

• The EAGLE project: Simulating the evolution and assembly of galaxies and their environments
• Interstellar Dust Grains
• The EAGLE simulations of galaxy formation: calibration of subgrid physics and model variations
• First Results from the TNG50 Simulation: Galactic outflows driven by supernovae and black hole feedback
• First Results from the TNG50 Simulation: The evolution of stellar and gaseous disks across cosmic time
• A Unified Representation of Gas-Phase Element Depletions in the Interstellar Medium
• The chemical make-up of the Sun: A 2020 vision
• The Role of Pressure in GMC Formation II: The H_2 - Pressure Relation
• Abundances of the elements in the solar system
• Star formation near the Sun is driven by expansion of the Local Bubble
• Ultraviolet Extinction Properties in the Milky Way
• Predictions for the Angular Dependence of Gas Mass Flow Rate and Metallicity in the Circumgalactic Medium
• The Galactic radial abundance gradients of C, N, O, Ne, S, Cl and Ar from deep spectra of H II regions
• High-Resolution Observations of Interstellar Ca I Absorption -- Implications for Depletions and Electron Densities in Diffuse Clouds
• CO-dark molecular gas at high redshift: very large H${}_2$ content and high pressure in a low metallicity damped Lyman-alpha system
• Large Metallicity Variations in the Galactic Interstellar Medium
• Cloud Structure and Physical Conditions in Star-forming Regions from Optical Observations. I. Data and Component Structure
• Interstellar Gas-phase Element Depletions in the Small Magellanic Cloud: A Guide to Correcting for Dust in QSO Absorption Line Systems
• The Mass Inflow and Outflow Rates of the Milky Way
• On the (in)variance of the dust-to-metals ratio in galaxies
• Atomic Data Revisions for Transitions Relevant to Observations of Interstellar, Circumgalactic, and Intergalactic Matter
• METAL: The Metal Evolution, Transport, and Abundance in the Large Magellanic Cloud Hubble program. II. Variations of interstellar depletions and dust-to-gas ratio within the LMC
• Dust depletion of metals from local to distant galaxies I: Peculiar nucleosynthesis effects and grain growth in the ISM
• Gas Accretion onto the Milky Way
• HD 62542: Probing the Bare, Dense Core of a Translucent Interstellar Cloud
• The Distribution of Metallicities in the Local Galactic Interstellar Medium
• Oscillator Strengths for Ultraviolet Transitions in P II -The Multiplet at 1308 Å
• Chemical diversity of gas in distant galaxies: The metal and dust enrichment and variations within absorbing galaxies

Cited by in corpus (2)

• Photometric Mapping of Carbonaceous/Siliceous Dust and Water Ice in the ISM with JWST: Applications to the Dense Sightlines
• Connecting the dusty dots: dust depletion and extinction of local interstellar clouds