Far-infrared excess emission as a tracer of disk-halo interaction

Abstract

Given the current and past star-formation in the Milky Way in combination with the limited gas supply, the re-fuelling of the reservoir of cool gas is an important aspect of Galactic astrophysics. The infall of \ion{H}{i} halo clouds can, among other mechanisms, contribute to solving this problem. We study the intermediate-velocity cloud IVC135+54 and its spatially associated high-velocity counterpart to look for signs of a past or ongoing interaction. Using the Effelsberg-Bonn \ion{H}{i} Survey data, we investigated the interplay of gas at different velocities. In combination with far-infrared Planck and IRIS data, we extended this study to interstellar dust and used the correlation of the data sets to infer information on the dark gas. The velocity structure indicates a strong compression and deceleration of the infalling high-velocity cloud (HVC), associated with far-infrared excess emission in the intermediate-velocity cloud. This excess emission traces molecular hydrogen, confirming that IVC135+54 is one of the very few molecular halo clouds. The high dust emissivity of IVC135+54 with respect to the local gas implies that it consists of disk material and does not, unlike the HVC, have an extragalactic origin. Based on the velocity structure of the HVC and the dust content of the IVC, a physical connection between them appears to be the logical conclusion. Since this is not compatible with the distance difference between the two objects, we conclude that this particular HVC might be much closer to us than complex C. Alternatively, the indicators for an interaction are misleading and have another origin.

arXiv comment11 pages, 10 figures, accepted for publication in A&A

References in corpus (39)

• HEALPix -- a Framework for High Resolution Discretization, and Fast Analysis of Data Distributed on the Sphere
• The Leiden/Argentine/Bonn (LAB) Survey of Galactic HI: Final data release of the combined LDS and IAR surveys with improved stray-radiation corrections
• Dust Masses, PAH Abundances, and Starlight Intensities in the SINGS Galaxy Sample
• Planck 2013 results. XI. All-sky model of thermal dust emission
• Chemical evolution with radial mixing
• Cold gas accretion in galaxies
• IRIS: A new generation of IRAS maps
• Gaseous Galaxy Halos
• Representations of celestial coordinates in FITS
• The Wisconsin H-Alpha Mapper Northern Sky Survey
• A General Model for the CO-H2 Conversion Factor in Galaxies with Applications to the Star Formation Law
• Toward a Unification of Star Formation Rate Determinations in the Milky Way and Other Galaxies
• Distances and Metallicities of High- and Intermediate-Velocity Clouds
• Accretion of gas onto nearby spiral galaxies
• Planck Early Results XXIV: Dust in the diffuse interstellar medium and the Galactic halo
• Fuel Efficient Galaxies: Sustaining Star Formation with Stellar Mass Loss
• Distances to Galactic high-velocity clouds. Complex C
• The Fate of High-Velocity Clouds: Warm or Cold Cosmic Rain?
• An Accurate Distance to High-Velocity Cloud Complex C
• Cosmological evolution of atomic gas and implications for 21 cm HI absorption
• Planck 2013 results. VI. High Frequency Instrument data processing
• Highly Ionized Gas Surrounding High Velocity Cloud Complex C
• H2 formation and excitation in the Stephan's Quintet galaxy-wide collision
• The Diversity of High- and Intermediate-Velocity Clouds: Complex C versus IV Arch
• The Effelsberg-Bonn HI Survey (EBHIS)
• Galactic chemical abundance evolution in the solar neighborhood up to the Iron peak
• Smith's Cloud: A High-velocity Cloud Colliding with the Milky Way
• Infrared Excess and Molecular Clouds: A comparison of new suerveys of far-infrared and H I 21-cm emission at high galactic latitudes
• A Survey of O VI, C III, and H I in Highly Ionized High-Velocity Clouds
• The Effelsberg-Bonn HI Survey: Data reduction
• Ongoing Galactic Accretion: Simulations and Observations of Condensed Gas in Hot Halos
• Ionized absorbers as evidence for supernova-driven cooling of the lower Galactic corona
• Cold gas accretion by high-velocity clouds and their connection to QSO absorption-line systems
• Low-Velocity Halo Clouds
• On the origin of the warm-hot absorbers in the Milky Way's halo
• An absorption-selected survey of neutral gas in the Milky Way halo
• A Low Metallicity Molecular Cloud In The Lower Galactic Halo
• Present-day Galactic Evolution: Low-metallicity, Warm, Ionized Gas Inflow Associated with High-Velocity Cloud Complex A
• A dynamical transition from atomic to molecular intermediate-velocity clouds

Cited by in corpus (6)

• HI4PI: A full-sky HI survey based on EBHIS and GASS
• Understanding star formation in molecular clouds IV. Column density PDFs from quiescent to massive molecular clouds
• All-sky census of Galactic high-latitude molecular intermediate-velocity clouds
• Maps of the number of HI clouds along the line of sight at high galactic latitude
• High-resolution HI and CO observations of high-latitude intermediate-velocity clouds
• Star formation in a diffuse high-altitude cloud?