Detection of Extraplanar Diffuse Ionized Gas in M83

Journal Article · Sun Aug 20 04:00:00 EDT 2017 · Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/AA81CA· OSTI ID:22875889

Boettcher, Erin; Gallagher, III, J. S.

We present the first kinematic study of extraplanar diffuse ionized gas (eDIG) in the nearby, face-on disk galaxy M83 using optical emission-line spectroscopy from the Robert Stobie Spectrograph on the Southern African Large Telescope. We use a Markov Chain Monte Carlo method to decompose the [N ii]λλ 6548, 6583, Hα, and [S ii]λλ 6717, 6731 emission lines into H ii region and diffuse ionized gas emission. Extraplanar, diffuse gas is distinguished by its emission-line ratios ([N ii]λ6583/Hα ≳ 1.0) and its rotational velocity lag with respect to the disk (Δv=−24 km s{sup −1} in projection). With interesting implications for isotropy, the velocity dispersion of the diffuse gas, σ=96 km s{sup −1}, is a factor of a few higher in M83 than in the Milky Way and nearby, edge-on disk galaxies. The turbulent pressure gradient is sufficient to support the eDIG layer in dynamical equilibrium at an electron scale height of h{sub z}=1 kpc. However, this dynamical equilibrium model must be finely tuned to reproduce the rotational velocity lag. There is evidence of local bulk flows near star-forming regions in the disk, suggesting that the dynamical state of the gas may be intermediate between a dynamical equilibrium and a galactic fountain flow. As one of the first efforts to study eDIG kinematics in a face-on galaxy, this study demonstrates the feasibility of characterizing the radial distribution, bulk velocities, and vertical velocity dispersions in low-inclination systems.

• OSTI ID: 22875889
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 845; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
DETECTION
DISPERSIONS
ELECTRONS
EMISSION
EQUILIBRIUM
ISOTROPY
MARKOV PROCESS
MILKY WAY
MONTE CARLO METHOD
SCALE HEIGHT
SPATIAL DISTRIBUTION
SPECTROSCOPY
STARS
TELESCOPES
VELOCITY