The MOSDEF Survey: [S iii] as a New Probe of Evolving Interstellar Medium Conditions*

Jones, Tucker; Shapley, Alice E.; Reddy, Naveen A.; Kriek, Mariska; Coil, Alison L.; Siana, Brian; Mobasher, Bahram; Shivaei, Irene; Price, Sedona H.; Freeman, William R.; Azadi, Mojegan; Leung, Gene C. K.; Fetherolf, Tara; Zick, Tom; Groot, Laura de; Barro, Guillermo; Fornasini, Francesca M.

doi:10.3847/2041-8213/ab5d40

Cited by 32 publications

(28 citation statements)

References 39 publications

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“…Finally, the low ionization lines are also affected by diffuse ionized gas (DIG) in galaxies, as recently discussed by Mingozzi et al (2020), Shapley et al (2019), Sanders et al (2020), and others. In the LyC emitters studied here, the contribution of the DIG would presumably be low, if we adopt the observed scaling of the DIG contribution with surface density of star-formation (e.g., Oey et al 2007;Shapley et al 2019), since the LyC emitters are compact by selection, and have a very high SFR surface density (Izotov et al 2018b).…”

Section: Low Ionization Line Diagnostics: Progress and Caveatsmentioning

confidence: 74%

“…shown on the right panel of this figure, the deficiency of the models is even more striking, as they fail to reproduce the bulk of the observations. The two discrepancies might arise from the fact that the models do not take into account a DIG component, which can significantly contribute to the emission of [O i] and [S ii] (Sanders et al 2017(Sanders et al , 2020. Alternatively, these discrepancies could also be attributed to the presence of shocks, which are not included in our models (see, e.g., Plat et al 2019) because of problems with atomic data for sulfur (Izotov et al 2006;Kewley & Dopita 2002;Kewley et al 2019), or others.…”

Section: Diagnostics Of the Low-ionization Regionsmentioning

confidence: 99%

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Reconciling escape fractions and observed line emission in Lyman-continuum-leaking galaxies

Ramambason

Schaerer

Stasińska

et al. 2020

A&A

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Context. Finding and elucidating the properties of Lyman-continuum(LyC)-emitting galaxies is an important step in improving our understanding of cosmic reionization. Aims. Although the z ∼ 0.3 − 0.4 LyC emitters found recently show strong optical emission lines, no consistent quantitative photoionization model taking into account the escape of ionizing photons and inhomogenous interstellar medium (ISM) geometry of these galaxies has yet been constructed. Furthermore, it is unclear to what extent these emission lines can be used to distinguish LyC emitters. Methods. To address these questions we construct one- and two-zone photoionization models accounting for the observed LyC escape, which we compare to the observed emission line measurements. The main diagnostics used include lines of [O III], [O II], and [O I] plus sulfur lines ([S II], [S III]) and a nitrogen line ([N II]), which probe regions of different ionization in the ISM. Results. We find that single (one-zone) density-bounded photoionization models cannot reproduce the emission lines of the LyC leakers, as pointed out by earlier studies, because they systematically underpredict the lines of species of low ionization potential, such as [O I] and [S II]. Introducing a two-zone model, with differing ionization parameter and a variable covering fraction and where one of the zones is density-bounded, we show that the observed emission line ratios of the LyC emitters are well reproduced. Furthermore, our model yields LyC escape fractions, which are in fair agreement with the observations and independent measurements. The [O I] λ6300 excess, which is observed in some LyC leakers, can be naturally explained in this model, for example by emission from low-ionization and low-filling-factor gas. LyC emitters with a high escape fraction (fesc ≳ 38%) are deficient both in [O I] λ6300 and in [S II] λλ6716,6731. We also confirm that a [S II] λλ6716,6731 deficiency can be used to select LyC emitter candidates, as suggested earlier. Finally, we find indications for a possible dichotomy in terms of escape mechanisms for LyC photons between galaxies with relatively low (fesc ≲ 10%) and higher escape fractions. Conclusions. We conclude that two-zone photoionization models are sufficient and required to explain the observed emission line properties of z ∼ 0.3 − 0.4 LyC emitters. This is in agreement with UV absorption line studies, which also show the co-existence of regions with high hydrogen column density (i.e., no escape of ionizing photons) and density-bounded or very low column density regions responsible for the observed escape of LyC radiation. These simple but consistent models provide a first step towards the use of optical emission lines and their ratios as quantitative diagnostics of LyC escape from galaxies.

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Section: Low Ionization Line Diagnostics: Progress and Caveatsmentioning

confidence: 74%

Section: Diagnostics Of the Low-ionization Regionsmentioning

confidence: 99%

Reconciling escape fractions and observed line emission in Lyman-continuum-leaking galaxies

Ramambason

Schaerer

Stasińska

et al. 2020

A&A

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“…BPASS is extensively used for interpretation of massive star populations (e.g. Pahl et al 2021;Cullen et al 2021;Vijayan et al 2021;Neugent 2021;Marshall et al 2020;Stevance et al 2020b;Neugent et al 2020;Shivaei et al 2020;Topping et al 2020;Dorn-Wallenstein & Levesque 2020;Wilkins et al 2020;Chrimes et al 2020;Sanders et al 2020). Its accuracy and capabilities in the low mass regime have been explored through the white dwarf progenitor initial to final mass ratio (Eldridge et al 2017), the impact of low mass binary stars on understanding ages of globular clusters and elliptical galaxies (Stanway & Eldridge 2018) and consideration of the type Ia supernova rate (Tang et al 2020), producing good matches to the data in each case.…”

Section: Bpassmentioning

confidence: 99%

Binary evolution pathways of blue large-amplitude pulsators

Byrne

Stanway

Eldridge

2021

Monthly Notices of the Royal Astronomical Society

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Blue Large-Amplitude Pulsators (BLAPs) are a recently discovered class of pulsating star, believed to be proto-white dwarfs, produced by mass stripping of a red giant when it has a small helium core. An outstanding question is why the stars in this class of pulsator seem to form two distinct groups by surface gravity, despite predictions that stars in the gap between them should also pulsate. We use a binary population synthesis model to identify potential evolutionary pathways that a star can take to become a BLAP. We find that BLAPs can be produced either through common envelope evolution or Roche lobe overflow, with a Main Sequence star or an evolved compact object being responsible for the envelope stripping. The mass distribution of the inferred population indicates that fewer stars would be expected in the range of masses intermediate to the two known groups of pulsators, suggesting that the lack of observational discoveries in this region may be a result of the underlying population of pre-white dwarf stars. We also consider metallicity variation and find evidence that BLAPs at Z = 0.010 (half-Solar) would be pulsationally unstable and may also be more common. Based on this analysis, we expect the Milky Way to host around 12000 BLAPs and we predict the number density of sources expected in future observations such as the Legacy Survey of Space and Time at the Vera Rubin Observatory.

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“…5 (Law et al 2015), which corresponds to 1 ∼ 2 kpc at the typical redshifts of MaNGA galaxies. As suggested by Sanders et al (2020) and Mannucci in prep, the observed line ratios from H ii regions could change considerably if individual H ii regions are resolved. There are two effects involved.…”

Section: Sample Selection Effectmentioning

confidence: 76%

Correlation between the gas-phase metallicity and ionization parameter in extragalactic HII regions

Ji,

Yan

2021

Preprint

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The variations of the metallicity and ionization parameter in H ii regions are usually thought to be the dominant factors that produce the variations we see in the observed emission line spectra. There is an increasing amount of evidence that these two quantities are physically correlated, although the exact form of this correlation is debatable in the literature. Simulated emission line spectra from photoionized clouds provide important clues about the physical conditions of H ii regions and are frequently used for deriving metallicities and ionization parameters. Through a systematic investigation on the assumptions and methodology used in applying photoionization models, we find that the derived correlation has a strong dependence on the choice of model parameters. On the one hand, models that give consistent predictions over multiple emission-line ratios would yield a positive correlation between metallicity and ionization parameter for the general population of H ii regions or star-forming (SF) galaxies. On the other hand, models that are inconsistent with the data locus in high-dimensional line ratio space would yield discrepant correlations when different subsets of line ratios are used in the derivation. The correlation between metallicity and ionization parameter has a secondary dependence on the star formation rate (SFR) surface density, with the higher SFR regions showing higher ionization parameter but weaker correlations. The existence of the positive correlation contradicts the analytical wind-driven bubble model for H ii regions. We explore assumptions in both dynamical models and photoionization models, and conclude that there is a potential bias associated with the geometry. However, this is still insufficient to explain the correlation. Mechanisms that suppress the dynamical influence of stellar winds in realistic H ii regions might be the key to solve this puzzle, which require more sophisticated combinations of dynamical models and photoionization models to test.

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The MOSDEF Survey: [S iii] as a New Probe of Evolving Interstellar Medium Conditions*

Cited by 32 publications

References 39 publications

Reconciling escape fractions and observed line emission in Lyman-continuum-leaking galaxies

Reconciling escape fractions and observed line emission in Lyman-continuum-leaking galaxies

Binary evolution pathways of blue large-amplitude pulsators

Correlation between the gas-phase metallicity and ionization parameter in extragalactic HII regions

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