Diffuse Ionized Gas in Spiral Galaxies and the Disk-Halo Interaction

Reynolds, R. J.; Haffner, L. M.; Madsen, G. J.; Wood, Kenneth; Hill, Alex S.

doi:10.1051/eas/1256034

Cited by 3 publications

(4 citation statements)

References 26 publications

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“…These features reflect the complex motions of diffuse ionized gas (DIG) in the disk-halo interface (DHI) that is believed to be shaped by the on-going starformation in the Milky Way disk. Based on the derived gas densities and volume filling factors (Reynolds et al 2012;Haffner et al 2003), the total mass of ionized gas in the DHI of the Milky Way can be estimated to be ∼ 10 8 M ⊙ , in line with estimates for extra-planar ionized gas in other low-redshift disk galaxies (e.g., NGC 891 ;Dettmar 1990).…”

Section: Warm Ionized Gassupporting

confidence: 64%

Gas Accretion onto the Milky Way

Richter¹

2017

Gas Accretion Onto Galaxies

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The Milky Way is surrounded by large amounts of gaseous matter that are slowly being accreted over cosmic timescales to support star formation in the disk. The corresponding gas-accretion rate represents a key parameter for the past, present, and future evolution of the Milky Way. In this chapter, we discuss our current understanding of gas accretion processes in the Galaxy by reviewing past and recent observational and theoretical studies. The first part of this review deals with the spatial distribution of the different gas phases in the Milky Way halo, the origin of the gas, and its total mass. The second part discusses the gas dynamics and the physical processes that regulate the gas flow from the outer Galactic halo to the disk. From the most recent studies follows that the present-day gas accretion rate of the Milky Way is a few solar masses per year, which is sufficient to maintain the Galaxy's star-formation rate at its current level.

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Section: Warm Ionized Gassupporting

confidence: 64%

Gas Accretion onto the Milky Way

Richter¹

2017

Gas Accretion Onto Galaxies

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“…Second, DIG emission cannot be properly represented in photoionization models because the relative contributions of various ionization sources for DIG are still not agreed upon. The DIG ionization mechanism appears to be photoionization from some combination of leaking Lyman-continuum from O and B stars in H ii regions (Voges & Walterbos 2006;Haffner et al 2009;Reynolds et al 2012) and evolved intermediate-mass post-AGB stars (Flores-Fajardo et al 2011;Zhang et al 2017). Although O and B stars appear to provide most of the DIG ionization energy, there is an ongoing discussion about the importance of evolved stars.…”

Section: An Empirical Approach To Modeling Galaxy Spectramentioning

confidence: 99%

Biases in Metallicity Measurements from Global Galaxy Spectra: The Effects of Flux Weighting and Diffuse Ionized Gas Contamination

Sanders

Shapley

Zhang

et al. 2017

ApJ

142

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Galaxy metallicity scaling relations provide a powerful tool for understanding galaxy evolution, but obtaining unbiased global galaxy gas-phase oxygen abundances requires proper treatment of the various line-emitting sources within spectroscopic apertures. We present a model framework that treats galaxies as ensembles of H ii and diffuse ionized gas (DIG) regions of varying metallicities. These models are based upon empirical relations between line ratios and electron temperature for H ii regions, and DIG strong-line ratio relations from SDSS-IV MaNGA IFU data. Flux-weighting effects and DIG contamination can significantly affect properties inferred from global galaxy spectra, biasing metallicity estimates by more than 0.3 dex in some cases. We use observationally-motivated inputs to construct a model matched to typical local star-forming galaxies, and quantify the biases in strong-line ratios, electron temperatures, and direct-method metallicities as inferred from global galaxy spectra relative to the median values of the H ii region distributions in each galaxy. We also provide a generalized set of models that can be applied to individual galaxies or galaxy samples in atypical regions of parameter space. We use these models to correct for the effects of flux-weighting and DIG contamination in the local direct-method mass-metallicity and fundamental metallicity relations, and in the mass-metallicity relation based on strong-line metallicities. Future photoionization models of galaxy line emission need to include DIG emission and represent galaxies as ensembles of emitting regions with varying metallicity, instead of as single H ii regions with effective properties, in order to obtain unbiased estimates of key underlying physical properties.

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“…Almost all the spaxels of this system have line ratios in the Hii regime. Monnet 1971;Rand et al 1990;Rand 1997Rand , 1998Haffner et al 1999;Tüllmann et al 2000;Otte et al 2001Otte et al , 2002Collins & Rand 2001;Hoopes & Walterbos 2003;Wood & Mathis 2004;Voges & Walterbos 2006;Rand et al 2008;Haffner et al 2009;Reynolds et al 2012), which may be due to secondary ionization/heating sources (e.g., Reynolds & Cox 1992;Reynolds et al 1999). Thus comparing the line ratios of the Hα extension to that of Hii regions would constrain whether the Hα extension is DIG.…”

Section: Diffuse Ionized Gasmentioning

confidence: 99%

“…5a-c Voges & Walterbos 2006;Zhang et al 2016, submitted). This latter trend is particularly striking since [Nii]/Hα is sensitive to the temperature of the gas and has been used to infer that the DIG is about ∼ 2000 K hotter than Hii regions-a defining characteristic of DIG (Haffner et al 1999;Madsen et al 2006;Haffner et al 2009;Reynolds et al 2012). Another defining characteristic of DIG is its low density (∼ 10 −3 cm −3 ; e.g., Haffner et al 2009).…”

Section: Diffuse Ionized Gasmentioning

confidence: 99%

SDSS-IV MaNGA: A SERENDIPITOUS OBSERVATION OF A POTENTIAL GAS ACCRETION EVENT

Cheung

Stark

Huang

et al. 2016

ApJ

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The nature of warm, ionized gas outside of galaxies may illuminate several key galaxy evolutionary processes. A serendipitous observation by the MaNGA survey has revealed a large, asymmetric Hα complex with no optical counterpart that extends ≈ 8 ′′ (≈ 6.3 kpc) beyond the effective radius of a dusty, starbursting galaxy. This Hα extension is approximately three times the effective radius of the host galaxy and displays a tail-like morphology. We analyze its gas-phase metallicities, gaseous kinematics, and emission-line ratios, and discuss whether this Hα extension could be diffuse ionized gas, a gas accretion event, or something else. We find that this warm, ionized gas structure is most consistent with gas accretion through recycled wind material, which could be an important process that regulates the low-mass end of the galaxy stellar mass function.

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Diffuse Ionized Gas in Spiral Galaxies and the Disk-Halo Interaction

Cited by 3 publications

References 26 publications

Gas Accretion onto the Milky Way

Gas Accretion onto the Milky Way

Biases in Metallicity Measurements from Global Galaxy Spectra: The Effects of Flux Weighting and Diffuse Ionized Gas Contamination

SDSS-IV MaNGA: A SERENDIPITOUS OBSERVATION OF A POTENTIAL GAS ACCRETION EVENT

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