The Diffuse Ionized Gas Halo of the Small Magellanic Cloud

Abstract

Observations with the Wisconsin H-alpha Mapper (WHAM) reveal a large, diffuse ionized halo that surrounds the Small Magellanic Cloud (SMC). We present the first kinematic H-alpha survey of an extended region around the galaxy, from (l,b) = (289.5,-35.0) to (315.1,-5.3) and covering +90 <= vLSR <= +210 km s-1. The ionized gas emission extends far beyond the central stellar component of the galaxy, reaching similar distances to that of the diffuse neutral halo traced by 21 cm observations. H-alpha emission extends several degrees beyond the sensitivity of current H I surveys toward smaller Galactic longitudes and more negative Galactic latitudes. The velocity field of the ionized gas near the SMC appears similar to to the neutral halo of the galaxy. Using the observed emission measure as a guide, we estimate the mass of this newly revealed ionized component to be roughly (0.8 - 1.0) x 10^9 M_sun, which is comparable to the total neutral mass in the same region of (0.9 - 1.1) x 10^9 M_sun. We find ratios of the total ionized gas mass divided by the total neutral plus ionized gas mass in three distinct subregions to be: (1) 46%-54% throughout the SMC and its extended halo, (2) 12%-32% in the SMC Tail that extends toward the Magellanic Bridge, and (3) 65%-79% in a filament that extends away from the SMC toward the Magellanic Stream. This newly discovered, coherent H-alpha filament does not appear to have a well-structured neutral component and is also not coincident with two previously identified filaments traced by 21 cm emission within the Stream.

arXiv comment16 pages, 8 figures, 3 tables

References in corpus (45)

• The Leiden/Argentine/Bonn (LAB) Survey of Galactic HI: Final data release of the combined LDS and IAR surveys with improved stray-radiation corrections
• HI4PI: A full-sky HI survey based on EBHIS and GASS
• A Quantitative Comparison of SMC, LMC, and Milky Way UV to NIR Extinction Curves
• Are the Magellanic Clouds on their First Passage about the Milky Way?
• Third-Epoch Magellanic Cloud Proper Motions I: HST/WFC3 data and Orbit Implications
• The Star Formation History of the Small Magellanic Cloud
• The Wisconsin H-Alpha Mapper Northern Sky Survey
• The warm ionized medium in spiral galaxies
• N-body Simulations of the Small Magellanic Cloud and the Magellanic Stream
• The cold gaseous halo of NGC 891
• The Vertical Structure of Warm Ionised Gas in the Milky Way
• The Magellanic Stream, High-Velocity Clouds and the Sculptor Group
• A New Look at the Kinematics of Neutral Hydrogen in the Small Magellanic Cloud
• The Origin of the Magellanic Stream and Its Leading Arm
• The Parkes HI Survey of the Magellanic System
• Chemical Evolution of the Magellanic Clouds: analytical models
• The Survey for Ionization in Neutral-Gas Galaxies: III. Diffuse, Warm Ionized Medium and Escape of Ionizing Radiation
• The 200 Degree-Long Magellanic Stream System
• The gravitational and hydrodynamical interaction between the LMC and the Galaxy
• The COS/UVES Absorption Survey of the Magellanic Stream. III: Ionization, Total Mass, and Inflow Rate onto the Milky Way
• Ram Pressure Stripping of the Large Magellanic Cloud's Disk as a Probe of the Milky Way's Circumgalactic Medium
• The Carnegie Hubble Program: The Distance and Structure of the SMC as Revealed by Mid-infrared Observations of Cepheids
• The 3D structure of the Small Magellanic Cloud
• Depth estimation of the Large and Small Magellanic Clouds
• The VMC Survey. XXV. The 3D structure of the Small Magellanic Cloud from Classical Cepheids
• Diffuse Ionized Gas in Three Sculptor Group Galaxies
• An H-alpha survey aiming at the detection of extraplanar diffuse ionized gas in halos of edge-on spiral galaxies. I. How common are gaseous halos among non-starburst galaxies?
• The Source of Ionization along the Magellanic Stream
• An H-alpha survey aiming at the detection of extraplanar diffuse ionized gas in halos of edge-on spiral galaxies II. The H-alpha survey atlas and catalog
• WHAM Observations of H-alpha Emission from High Velocity Clouds in the M, A, and C Complexes
• Exploring the Origin and Fate of the Magellanic Stream with Ultraviolet and Optical Absorption
• The Extension of the Transition Temperature Plasma into the Lower Galactic Halo
• On the dynamics of the Small Magellanic Cloud through high-resolution ASKAP HI observations
• Toward a Complete Understanding of the Magellanic Stream Formation
• Cold gas outflows from the Small Magellanic Cloud traced with ASKAP
• Ionized Gas in the Smith Cloud
• Warm Ionized Gas Revealed in the Magellanic Bridge Tidal Remnant: Constraining the Baryon Content and the Escaping Ionizing Photons around Dwarf Galaxies
• Interstellar H-Alpha Line Profiles toward HD 93521 and the Lockman Window
• Revealing the Ionization Properties of the Magellanic Stream using Optical Emission
• Measurements of He I λ5876 Recombination Line Radiation from the Diffuse, Warm Ionized Medium in Irregular Galaxies
• The Effect of Drag from the Galactic Hot Halo on the Magellanic Stream and Leading Arm
• Present-day Galactic Evolution: Low-metallicity, Warm, Ionized Gas Inflow Associated with High-Velocity Cloud Complex A
• On the Structure and Morphology of the `Diffuse Ionized Medium' in Star-Forming Galaxies
• Warm Ionized Medium Throughout the Sagittarius-Carina Arm
• Halpha and [S II] emission from warm ionized gas in the Scutum-Centaurus Arm

Cited by in corpus (9)

• Rotation measure structure functions with higher-order stencils as a probe of small-scale magnetic fluctuations and its application to the Small and Large Magellanic Clouds
• A Radio Polarisation Study of Magnetic Fields in the Small Magellanic Cloud
• Disentangling the Faraday rotation sky
• Mapping the Supernovae Driven Winds of the Large Magellanic Cloud in H$\alpha$ Emission I
• Cold HI ejected into the Magellanic Stream
• HI filaments as potential compass needles? Comparing the magnetic field structure of the Small Magellanic Cloud to the orientation of GASKAP-HI filaments
• The Diffuse Ionized Gas of the Large Magellanic Cloud
• Ionization and Star Formation in the Giant HII Region SMC-N66
• SILCC -- IX. The multi-phase interstellar medium at low metallicity