Service interruption on Monday 11 July from 12:30 to 13:00: all the sites of the CCSD (HAL, EpiSciences, SciencesConf, AureHAL) will be inaccessible (network hardware connection).
Skip to Main content Skip to Navigation
Journal articles

The Multi-phase Cold Fountain in M82 Revealed by a Wide, Sensitive Map of the Molecular Interstellar Medium

Abstract : We present a wide area (≈8 × 8 kpc), sensitive map of CO (2-1) emission around the nearby starburst galaxy M82. Molecular gas extends far beyond the stellar disk, including emission associated with the well-known outflow as far as 3 kpc from M82's midplane. Kinematic signatures of the outflow are visible in both the CO and H i emission: both tracers show a minor axis velocity gradient and together they show double peaked profiles, consistent with a hot outflow bounded by a cone made of a mix of atomic and molecular gas. Combining our CO and H i data with observations of the dust continuum, we study the changing properties of the cold outflow as it leaves the disk. While H2 dominates the ISM near the disk, the dominant phase of the cool medium changes as it leaves the galaxy and becomes mostly atomic after about a kpc. Several arguments suggest that regardless of phase, the mass in the cold outflow does not make it far from the disk; the mass flux through surfaces above the disk appears to decline with a projected scale length of ≈1-2 kpc. The cool material must also end up distributed over a much wider angle than the hot outflow based on the nearly circular isophotes of dust and CO at low intensity and the declining rotation velocities as a function of height from the plane. The minor axis of M82 appears so striking at many wavelengths because the interface between the hot wind cavity and the cool gas produces Hα, hot dust, polycyclic aromatic hydrocarbon emission, and scattered UV light. We also show the level at which a face-on version of M82 would be detectable as an outflow based on unresolved spectroscopy. Finally, we consider multiple constraints on the CO-to-H2 conversion factor, which must change across the galaxy but appears to be only a factor of ≈2 lower than the Galactic value in the outflow.
Document type :
Journal articles
Complete list of metadata

https://hal-insu.archives-ouvertes.fr/insu-03644688
Contributor : Hal Sorbonne Université Gestionnaire Connect in order to contact the contributor
Submitted on : Tuesday, April 19, 2022 - 1:55:40 PM
Last modification on : Wednesday, April 20, 2022 - 3:40:04 AM

Links full text

Identifiers

Citation

Adam K. Leroy, Fabian Walter, Paul Martini, Hélène Roussel, Karin Sandstrom, et al.. The Multi-phase Cold Fountain in M82 Revealed by a Wide, Sensitive Map of the Molecular Interstellar Medium. The Astrophysical Journal, 2015, 814, ⟨10.1088/0004-637X/814/2/83⟩. ⟨insu-03644688⟩

Share

Metrics

Record views

3