First detection of dust emission in a High-Velocity Cloud

Abstract

By comparing sensitive Spitzer Space Telescope (SST) infrared and Green Bank Telescope 21 cm observations, we are able to report the first detection of dust emission in Complex C, the largest High Velocity Cloud in the sky. Dust in the region of Complex C studied here has a colder temperature ($T=10.7_{-0.8}^{+0.9}$ K - 1$\sigma$) than the local interstellar medium ($T=17.5$ K), in accordance with its great distance from the Galactic plane. Based on the metallicity measurements and assuming diffuse Galactic interstellar medium dust properties and dust/metals ratio, this detection could imply gas column densities more than 5 times higher than observed in HI. We suggest that the dust emission detected here comes from small molecular clumps, spatially correlated with the HI but with a low surface filling factor. Our findings imply that the HVCs' mass would be much larger than inferred from HI observations and that most of the gas falling on the Milky Way would be in cold and dense clumps rather than in a diffuse phase.

arXiv commentAccepted for publication in the Astrophysical Journal Letter, 5 pages, 4 figures

References in corpus (13)

• IRIS: A new generation of IRAS maps
• Highly-Ionized High-Velocity Gas in the Vicinity of the Galaxy
• Distances and Metallicities of High- and Intermediate-Velocity Clouds
• Modelling the infrared galaxy evolution using a phenomenological approach
• Complex C: A Low-Metallicity High-Velocity Cloud Plunging into the Milky Way
• WHAM Observations of H-alpha Emission from High Velocity Clouds in the M, A, and C Complexes
• FUSE Observations of Atomic Abundances and Molecular Hydrogen in the Leading Arm of the Magellanic Stream
• Power spectrum of the cosmic infrared background at 60 and 100 microns with IRAS
• Molecular Hydrogen in High-Velocity Clouds
• The Deuterium-to-Hydrogen Ratio in a Low-Metallicity Cloud Falling onto the Milky Way
• The Spitzer Space Telescope First-Look Survey: Neutral Hydrogen Emission
• Molecular hydrogen as baryonic dark matter
• The First Measurements of Galaxy Clustering from IRAC Data of the Spitzer First Look Survey

Cited by in corpus (26)

• Gaseous Galaxy Halos
• Filaments and ridges in Vela C revealed by Herschel: from low-mass to high-mass star-forming sites
• Planck Early Results XXIV: Dust in the diffuse interstellar medium and the Galactic halo
• A new all-sky map of Galactic high-velocity clouds from the 21-cm HI4PI survey
• GHIGLS: HI mapping at intermediate Galactic latitude using the Green Bank Telescope
• Ongoing Galactic Accretion: Simulations and Observations of Condensed Gas in Hot Halos
• The Mass Inflow and Outflow Rates of the Milky Way
• An accurate measurement of the anisotropies and mean level of the Cosmic Infrared Background at 100 and 160 um
• Low-Velocity Halo Clouds
• A new probe of line-of-sight magnetic field tangling
• HI filaments are cold and associated with dark molecular gas. HI4PI based estimates of the local diffuse CO-dark H2 distribution
• Gas Accretion onto the Milky Way
• Chandra Detection of Local Warm-Hot Gas Toward Markarian 279
• All-sky census of Galactic high-latitude molecular intermediate-velocity clouds
• Observations of Diffuse Ultraviolet Emission from Draco
• Serendipity observations of far infrared cirrus emission in the Spitzer Infrared Nearby Galaxies Survey: Analysis of far-infrared correlations
• A peculiar HI cloud near the distant globular cluster Pal 4
• Dust in a compact, cold, high-velocity cloud: A new approach to removing foreground emission
• Detection of Dust in High-Velocity Cloud Complex C -- Enriched Gas Accreting onto the Milky Way
• Dust-to-Gas Ratios of the GALFA-HI Compact Cloud Catalog
• Astrophysics in 2006
• La Freccia Rossa: An IR-dark cloud hosting the Milky Way intermediate-mass black hole candidate
• Dense gas tracing the collisional past of Andromeda. An atypical inner region?
• Molecular gas in high-velocity clouds: revisited scenario
• A Spitzer-MIPS search for dust in compact high-velocity HI clouds
• Galactic HCO+ Absorption toward Compact Extragalactic Radio Sources