The Survey for Ionization in Neutral Gas Galaxies. III. Diffuse, Warm Ionized Medium and Escape of Ionizing Radiation

By M. Oey, G. Meurer, S. Yelda, E. Furst, S. M. Caballero-Nieves, D. Hanish, Emily M. Levesque, D. Thilker, G. Walth, Joss Bland-Hawthorn and 18 more. 2007

132 citations recorded by the source corpus.

We use the first data release from the SINGG Hα survey of H I-selected galaxies to study the quantitative behavior of the diffuse, warm ionized medium (WIM) across the range of properties represented by these 109 galaxies. The mean fraction fWIM of diffuse ionized gas in this sample is 0.59 ± 0.19, slightly higher than found in previous samples. Since lower surface brightness galaxies tend to have higher fWIM, we believe that most of this difference is due to selection effects favoring large, optically bright, nearby galaxies with high star formation rates. As found in previous studies, there is no appreciable correlation with Hubble type or total star formation rate. However, we find that starburst galaxies, defined here by an Hα surface brightness >2.5 × 1039 erg s-1 kpc-2 within the Hα half-light radius, do show much lower fractions of diffuse Hα emission. The cause apparently is not dominated by a lower fraction of field OB stars. However, it is qualitatively consistent with an expected escape of ionizing radiation above a threshold star formation rate, predicted from our model in which the ISM is shredded by pressure-driven supernova feedback. The H I gas fractions in the starburst galaxies are also lower, suggesting that the starbursts are consuming and ionizing all the gas, and thus promoting regions of density-bounded ionization. If true, these effects imply that some amount of Lyman continuum radiation is escaping from most starburst galaxies, and that WIM properties and outflows from mechanical feedback are likely to be pressure-driven. However, in view of previous studies showing that the escape fraction of ionizing radiation is generally low, it is likely that other factors also drive the low fractions of diffuse ionized gas in starbursts.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/f7cb700c308796c3f0af28813f338d0f2b56fef4

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

Citations in the corpus

Evidence of Environmental Dependencies of Type Ia Supernovae from the Nearby Supernova Factory indicated by Local H$\alpha$ (2013, background): “This sample has been split in two at the median value log ΣHα = 38.35, which happens to correspond to the mean warm interstellar medium Hα surface brightness of galaxies (Oey et al. 2007) and to the mean Hα sensitivity level at our highest redshift.”
COMPARISON OF Hα AND UV STAR FORMATION RATES IN THE LOCAL VOLUME: SYSTEMATIC DISCREPANCIES FOR DWARF GALAXIES (2009, background): “…and there could be more leakage from the individual HII regions (the fraction of diffuse ionized gas appears to be nominally higher in dwarfs; e.g., Oey et al. 2007), star forming dwarf galaxies are often embedded in large envelopes of HI (e.g., Begum et al. 2008) which makes it unlikely that the…”
The lifecycle of molecular clouds in nearby star-forming disc galaxies (2019, background): “A large-scale reservoir of Hα emission tracing diffuse ionised gas is also commonly observed in galaxies (e.g. Monnet 1971; Dettmar 1990; Hoopes et al. 1996; Oey et al. 2007; Kreckel et al. 2016; Lacerda et al. 2018).”
A BUDGET AND ACCOUNTING OF METALS AT z ∼ 0: RESULTS FROM THE COS-HALOS SURVEY (2013, background): “However, systematic characterizations of the mass in this phase for galaxies other than our own are rare, and it is unclear how well the WIM mass scales with either H I or stellar mass (Oey et al. 2007).”
Star Formation in the Milky Way and Nearby Galaxies (2012, background): “By the same token, much of the Hα and dust emission in galaxies, typically 30–60%, is emitted by diffuse ionized gas and dust located hundreds of parsecs or more from any young stars (e.g., Oey et al. 2007; Dale et al. 2007).”
De re metallica: the cosmic chemical evolution of galaxies (2018, background): “The presence of diffuse ionized gas (DIG) in local and distant galaxies (e.g., Oey et al., 2007) can also affect the position of galaxies on the BPT diagrams and bias the measurements of metallicity, especially in galaxies with low sSFR and low surface brightness of Hα emission (Sanders et al.,…”
SDSS-IV MaNGA : the impact of diffuse ionized gas on emission-line ratios, interpretation of diagnostic diagrams and gas metallicity measurements (2016, background): “Contact e-mail: zkdtckk@gmail.com external galaxies both in extra-plannar halos (e.g., Dettmar 1990; Rand et al. 1990, 1996; Hoopes et al. 1999; Rossa & Dettmar 2003a,b) and in the disk (e.g., Monnet 1971; Zurita et al. 2000; Oey et al. 2007).”
SDSS IV MaNGA – spatially resolved diagnostic diagrams: a proof that many galaxies are LIERs (2016, background): “Diffuse ionised gas (DIG) with LINER-like emission is observed surrounding the plane of the Milky Way and other spiral galaxies (Hoopes & Walterbos 2003; Rossa & Dettmar 2003; Oey et al. 2007; Haffner et al. 2009; Blanc et al. 2009; Flores-Fajardo et al. 2011).”
THE NATURE OF STARBURSTS. I. THE STAR FORMATION HISTORIES OF EIGHTEEN NEARBY STARBURST DWARF GALAXIES (2010, background): “…over the past decade have used these different wavelength observations to study the properties of both nearby and distant actively bursting systems (e.g., Colless et al. 1994; Babul & Ferguson 1996; Meurer et al. 1997; Heckman et al. 2005; Oey et al. 2007; Lee et al. 2009, among many others).”
SDSS IV MaNGA – metallicity and nitrogen abundance gradients in local galaxies (2017, background): “Apart from classical, discrete HII regions, galaxies are observed to contain low surface brightness diffuse ionised gas (DIG), sometimes also referred to as warm ionised gas (Reynolds 1984; Hoopes & Walterbos 2003; Oey et al. 2007; Zhang et al. 2017).”
CONFIRMATION OF A STAR FORMATION BIAS IN TYPE Ia SUPERNOVA DISTANCES AND ITS EFFECT ON THE MEASUREMENT OF THE HUBBLE CONSTANT (2014, background): “Further information on the characteristics of the diffuse Hα can be found in Oey et al. (2007), Seon & Witt (2012) and references therein, and in Section 3 of R13.”
THE SPATIALLY RESOLVED STAR FORMATION LAW FROM INTEGRAL FIELD SPECTROSCOPY: VIRUS-P OBSERVATIONS OF NGC 5194 (2009, background): “Previous photometric measurements of the diffuse ionized fraction in nearby spiral galaxies, including NGC 5194, yield median diffuse fractions of ∼50% (e.g. Ferguson et al. 1996; Hoopes et al. 1996; Greenawalt et al. 1998; Thilker et al. 2002; Oey et al. 2007).”