A Survey of FUSE and HST Sightlines through High-Velocity Cloud Complex C

Abstract

Using archival Far Ultraviolet Spectroscopic Explorer (FUSE) and Hubble Space Telescope (HST) data, we have assembled a survey of eight sightlines through high-velocity cloud Complex C. Abundances of the observed ion species vary significantly for these sightlines, indicating that Complex C is not well characterized by a single metallicity. Reliable metallicities based on [OI/HI] range from 0.1-0.25 solar. Metallicities based on [SII/HI] range from 0.1-0.6 solar, but the trend of decreasing abundance with HI column density indicates that photoionization corrections may affect the conversion to [S/H]. We present models of the dependence of the ionization correction on HI column density; these ionization corrections are significant when converting ion abundances to elemental abundances for S, Si, and Fe. The measured abundances in this survey indicate that parts of the cloud have a higher metallicity than previously thought and that Complex C may represent a mixture of ``Galactic fountain'' gas with infalling low-metallicity gas. We find that [S/O] and [Si/O] have a solar ratio, suggesting little dust depletion. Further, the measured abundances suggest an over-abundance of O, S, and Si relative to N and Fe. The enhancement of these alpha-elements suggests that the bulk of the metals in Complex C were produced by Type II supernovae and then removed from the star-forming region, possibly via supernovae-driven winds or tidal stripping, before the ISM could be enriched by N and Fe.

50 pages, 17 figures. Accepted to ApJ. Previous version was the first submitted manuscript

Cited by in corpus (58)

• A Unified Representation of Gas-Phase Element Depletions in the Interstellar Medium
• The COS-Halos Survey: Rationale, Design, and A Census of Circumgalactic Neutral Hydrogen
• What is the Total Deuterium Abundance in the Local Galactic Disk?
• The Low-z Intergalactic Medium. III. HI and Metal Absorbers at z<0.4
• Planck Early Results XXIV: Dust in the diffuse interstellar medium and the Galactic halo
• Complex C: A Low-Metallicity High-Velocity Cloud Plunging into the Milky Way
• A FUSE Survey of Interstellar Molecular Hydrogen toward High-Latitude AGN
• An Accurate Distance to High-Velocity Cloud Complex C
• Highly Ionized Gas Surrounding High Velocity Cloud Complex C
• A Large Reservoir of Ionized Gas in the Galactic Halo: Ionized Silicon in High-Velocity and Intermediate-Velocity Clouds
• High-velocity clouds as streams of ionized and neutral gas in the halo of the Milky Way
• FUSE and STIS Observations of the Warm-Hot Intergalactic Medium towards PG1259+593
• Intergalactic HII Regions Discovered in SINGG
• The Deuterium-to-Hydrogen Ratio in a Low-Metallicity Cloud Falling onto the Milky Way
• Highly Ionized High-Velocity Clouds: Hot Intergalactic Medium or Galactic Halo?
• Highly Ionized High-Velocity Clouds toward PKS 2155-304 and Markarian 509
• Discovery of a Primitive Damped Lyman alpha Absorber Near an X-ray Bright Galaxy Group in the Virgo Cluster
• Metallicity and Ionization in High Velocity Cloud Complex C
• The Abundance Gradient in the Extremely Faint Outer Disk of NGC 300
• Simulations of High-Velocity Clouds. I. Hydrodynamics and High-Velocity High Ions
• Does the Milky Way Produce a Nuclear Galactic Wind?
• Hubble Space Telescope Survey of Interstellar High-Velocity Si III
• Highly Ionized Gas in the Galactic Halo and the High Velocity Clouds Toward PG 1116+215
• The Mass Inflow and Outflow Rates of the Milky Way
• Head-Tail Clouds: Drops to Probe the Diffuse Galactic Halo
• A population of weak metal-line absorbers surrounding the Milky Way
• C II Radiative Cooling of the Diffuse Gas in the Milky Way
• The Connection between a Lyman Limit System, a very strong OVI Absorber, and Galaxies at z~0.203
• Metal-Ion Absorption in Conductively Evaporating Clouds
• High Metallicity, Photoionised Gas in Intergalactic Large-Scale Filaments
• Intermediate- and high-velocity clouds in the Milky Way I: covering factors and vertical heights
• Hubble-COS Observations of Galactic High-Velocity Clouds: Four AGN Sight Lines through Complex C
• HST/COS Spectra of Three QSOs That Probe The Circumgalactic Medium of a Single Spiral Galaxy: Evidence for Gas Recycling and Outflow
• On the origin of the warm-hot absorbers in the Milky Way's halo
• OVI, NV and CIV in the Galactic Halo: II. Velocity-Resolved Observations with Hubble and FUSE
• Intermediate- and high-velocity clouds in the Milky Way II: evidence for a Galactic fountain with collimated outflows and diffuse inflows
• Physical Properties of Complex C Halo Clouds
• Intrinsic Absorption in the Spectrum of Mrk 279: Simultaneous Chandra, FUSE, and STIS Observations
• High-Velocity Clouds and the Local Intergalactic Medium
• The Circumgalactic Medium of Milky Way-like Galaxies in the TNG50 Simulation -- II: Cold, Dense Gas Clouds and High-Velocity Cloud Analogs
• Gas Accretion onto the Milky Way
• Potential Condensed Fuel for the Milky Way
• Absorption Line Study of Halo Gas in NGC 3067 Toward the Background Quasar 3C 232
• The Milky Way halo as a QSO absorption-line system. New results from an HST/STIS absorption-line catalogue of Galactic high-velocity clouds
• The Surprisingly Constant Strength of O VI Absorbers over Cosmic Time
• Mass, Morphing, Metallicities: The Evolution of Infalling High Velocity Clouds
• Ultraviolet and X-ray Variability of the Seyfert 1.5 Galaxy Markarian 817
• The contribution of halo red giant mass loss to the high-velocity gas falling onto the Milky Way disk
• The HI Column Density Distribution of the Galactic Disk and Halo
• Detection of Dust in High-Velocity Cloud Complex C -- Enriched Gas Accreting onto the Milky Way
• A High-Metallicity High Velocity Cloud along the MRK 421 Sight Line: A Tracer of Complex M?
• Caught in the Act: A Metal-Rich High-Velocity Cloud in the Inner Galaxy
• Molecular gas in high-velocity clouds: revisited scenario
• Zooming in on the Circumgalactic Medium with GIBLE: Tracing the Origin and Evolution of Cold Clouds
• Is High-Velocity Cloud Complex C Associated with the Galactic Warp?
• Solar-Metallicity Gas in the Extended Halo of a Galaxy at $z\sim 0.12$
• Resolving the formation of cold HI filaments in the high velocity cloud complex C
• Absorption Line Studies in the Halo