Detection of Extraplanar Diffuse Ionized Gas in M83*

Boettcher, Erin; Gallagher, John S.; Zweibel, Ellen G.

doi:10.3847/1538-4357/aa81ca

Cited by 17 publications

(20 citation statements)

References 46 publications

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“…Finally, it is clear that edge-on galaxies alone will not fully illuminate the vertical structure, support, and kinematics of eDIG layers. Ongoing efforts to study the vertical bulk velocities and velocity dispersions in lowinclination galaxies will be a powerful complement to the high-inclination perspective (e.g., Boettcher et al 2017), allowing more rigorous testing of the ideas discussed here.…”

Section: Discussionmentioning

confidence: 99%

A Dynamical Study of Extraplanar Diffuse Ionized Gas in NGC 5775*

Boettcher¹,

Gallagher²,

Zweibel³

2019

ApJ

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The structure and kinematics of gaseous, disk-halo interfaces are imprinted with the processes that transfer mass, metals, and energy between galactic disks and their environments. We study the extraplanar diffuse ionized gas (eDIG) layer in the interacting, star-forming galaxy NGC 5775 to better understand the consequences of star-formation feedback on the dynamical state of the thick-disk interstellar medium (ISM). Combining emission-line spectroscopy from the Robert Stobie Spectrograph on the Southern African Large Telescope with radio continuum observations from Continuum Halos in Nearby Galaxies -an EVLA Survey, we ask whether thermal, turbulent, magnetic field, and cosmicray pressure gradients can stably support the eDIG layer in dynamical equilibrium. This model fails to reproduce the observed exponential electron scale heights of the eDIG thick disk and halo on the northeast (h z,e = 0.6, 7.5 kpc) and southwest (h z,e = 0.8, 3.6 kpc) sides of the galaxy at R < 11 kpc. We report the first definitive detection of an increasing eDIG velocity dispersion as a function of height above the disk. Blueshifted gas along the minor axis at large distances from the midplane hints at a disk-halo circulation and/or ram pressure effects caused by the ongoing interaction with NGC 5774. This work motivates further integral field unit and/or Fabry-Perot spectroscopy of galaxies with a range of star-formation rates to develop a spatially-resolved understanding of the role of star-formation feedback in shaping the kinematics of the disk-halo interface.

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Section: Discussionmentioning

confidence: 99%

A Dynamical Study of Extraplanar Diffuse Ionized Gas in NGC 5775*

Boettcher¹,

Gallagher²,

Zweibel³

2019

ApJ

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“…The presence of extra-planar diffuse ionized gas (eDIG) in M83 was detected by Boettcher et al (2017) using Markov Chain Monte Carlo methods to decompose the Hii regions from the eDIG using high spectral resolution observations from the South African Large Telescope (SALT). Due to the relatively low (R∼ 850) spectral resolution of TYPHOON, we are unable to spectrally decompose the emission line fluxes into multiple components and separate the eDIG from the planar DIG.…”

Section: Previous Researchmentioning

confidence: 99%

The effects of diffuse ionized gas and spatial resolution on metallicity gradients: TYPHOON two-dimensional spectrophotometry of M83

Poetrodjojo

D'Agostino

Groves

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We present a systematic study of the diffuse ionized gas (DIG) in M83 and its effects on the measurement of metallicity gradients at varying resolution scales. Using spectrophotometric data cubes of M83 obtained at the 2.5m duPont telescope at Las Campanas Observatory as part of the TYPHOON program, we separate the Hii regions from the DIG using the [SII]/Hα ratio, HIIphot (Hii finding algorithm) and the Hα surface brightness. We find that the contribution to the overall Hα luminosity is approximately equal for the Hii and DIG regions. The data is then rebinned to simulate low-resolution observations at varying resolution scales from 41 pc up to 1005 pc. Metallicity gradients are measured using five different metallicity diagnostics at each resolution. We find that all metallicity diagnostics used are affected by the inclusion of DIG to varying degrees. We discuss the reasons of why the metallicity gradients are significantly affected by DIG using the Hii dominance and emission line ratio radial profiles. We find that applying the [SII]/Hα cut will provide a closer estimate of the true metallicity gradient up to a resolution of 1005 pc for all metallicity diagnostics used in this study.

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“…At high Galactic latitudes, typical Milky Way disk gas should have low line-of sight velocities, since the bulk of its motion is in the transverse direction. However, any extraplanar gas moving at |v| < 25 km/s cannot be easily disentangled from disk gas (Boettcher et al 2017;). Table 2 lists best-fit values for column density N , radial velocity v, and Doppler b parameter b D , which we combine with spatial coordinates from the SEGUE catalog to provide a characterization of IV gas in the halo.…”

Section: Isolating Absorption Signatures Of the Galacticmentioning

confidence: 99%

Galactic Gas Flows from Halo to Disk: Tomography and Kinematics at the Milky Way’s Disk–Halo Interface

Bish

Werk

Prochaska

et al. 2019

ApJ

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We present a novel absorption line survey using 54 blue horizontal branch stars (BHBs) in the Milky Way halo as background sources for detecting gas flows at the disk-halo interface. Distance measurements to high-latitude (b > 60 • ) background stars at 3.1 -13.4 kpc, combined with unprecedented spatial sampling and spectral resolution, allow us to examine the 3-dimensional spatial distribution and kinematics of gas flows near the disk. We detect absorption signatures of extraplanar CaII and NaI in Keck HIRES spectra and find that their column densities exhibit no trend with distance to the background sources, indicating that these clouds lie within 3.1 kpc of the disk. We calculate covering fractions of f CaII = 63%, f NaI = 26%, and f HI = 52%, consistent with a picture of the CGM that includes multi-phase clouds containing small clumps of cool gas within hotter, more diffuse gas. Our measurements constrain the scale of any substructure within these cool clouds to < 0.5 kpc. CaII and NaI absorption features exhibit an intermediate-velocity (IV) component inflowing at velocities of −75 km/s < v < −25 km/s relative to the local standard of rest, consistent with previously-studied HI structures in this region. We report the new detection of an inflow velocity gradient ∆v z ∼ 6 − 9 km/s/kpc across the Galactic plane. These findings place constraints on the physical and kinematic properties of CGM gas flows through the disk-halo interface, and support a galactic fountain model in which cold gas rains back onto the disk.

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Detection of Extraplanar Diffuse Ionized Gas in M83*

Cited by 17 publications

References 46 publications

A Dynamical Study of Extraplanar Diffuse Ionized Gas in NGC 5775*

A Dynamical Study of Extraplanar Diffuse Ionized Gas in NGC 5775*

The effects of diffuse ionized gas and spatial resolution on metallicity gradients: TYPHOON two-dimensional spectrophotometry of M83

Galactic Gas Flows from Halo to Disk: Tomography and Kinematics at the Milky Way’s Disk–Halo Interface

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