scholarly journals The Lyman Continuum Escape Fraction of Emission Line-selected z ∼ 2.5 Galaxies Is Less Than 15%

2017 ◽  
Vol 841 (2) ◽  
pp. L27 ◽  
Author(s):  
Michael J. Rutkowski ◽  
Claudia Scarlata ◽  
Alaina Henry ◽  
Matthew Hayes ◽  
Vihang Mehta ◽  
...  
Keyword(s):  
Emission Line ◽  
Lyman Continuum

scholarly journals New methods for identifying Lyman continuum leakers and reionization-epoch analogues

2020 ◽  
Vol 498 (1) ◽  
pp. 164-180 ◽  
Author(s):  
Harley Katz ◽  
Dominika Ďurovčíková ◽  
Taysun Kimm ◽  
Joki Rosdahl ◽  
Jeremy Blaizot ◽  
...  
Keyword(s):  
Emission Line ◽  
Galaxy Formation ◽  
Dwarf Galaxy ◽  
High Redshift ◽  
Indirect Methods ◽  
High Redshift Galaxies ◽  
Lyman Continuum ◽  
The Universe ◽  
Ionization Parameter ◽  
Redshift Galaxies

ABSTRACT Identifying low-redshift galaxies that emit Lyman continuum radiation (LyC leakers) is one of the primary, indirect methods of studying galaxy formation in the epoch of reionization. However, not only has it proved challenging to identify such systems, it also remains uncertain whether the low-redshift LyC leakers are truly ‘analogues’ of the sources that reionized the Universe. Here, we use high-resolution cosmological radiation hydrodynamics simulations to examine whether simulated galaxies in the epoch of reionization share similar emission line properties to observed LyC leakers at z ∼ 3 and z ∼ 0. We find that the simulated galaxies with high LyC escape fractions (fesc) often exhibit high O32 and populate the same regions of the R23–O32 plane as z ∼ 3 LyC leakers. However, we show that viewing angle, metallicity, and ionization parameter can all impact where a galaxy resides on the O32–fesc plane. Based on emission line diagnostics and how they correlate with fesc, lower metallicity LyC leakers at z ∼ 3 appear to be good analogues of reionization-era galaxies. In contrast, local [S ii]-deficient galaxies do not overlap with the simulated high-redshift LyC leakers on the S ii Baldwin–Phillips–Terlevich (BPT) diagram; however, this diagnostic may still be useful for identifying leakers. We use our simulated galaxies to develop multiple new diagnostics to identify LyC leakers using infrared and nebular emission lines. We show that our model using only [C ii]158 μm and [O iii]88 μm can identify potential leakers from non-leakers from the local Dwarf Galaxy Survey. Finally, we apply this diagnostic to known high-redshift galaxies and find that MACS 1149_JD1 at z = 9.1 is the most likely galaxy to be actively contributing to the reionization of the Universe.

scholarly journals The Ionization of Planetary Nebulae

1968 ◽  
Vol 34 ◽  
pp. 190-204 ◽  
Author(s):  
Robert E. Williams
Keyword(s):  
Ionizing Radiation ◽  
Emission Line ◽  
Radiation Field ◽  
Planetary Nebulae ◽  
Model Atmosphere ◽  
Evolutionary Sequence ◽  
Lyman Continuum ◽  
The Mean ◽  
Central Stars

The ionization of the most abundant elements in planetary nebulae has been determined for a number of models of nebulae at different epochs in their expansion. The values used for the temperatures and radii of the central stars and the sizes and densities of the shells have come from Seaton's evolutionary sequence. The ionizing radiation field has been taken from model atmosphere calculations of the central stars by Gebbie and Seaton, and Böhm and Deinzer. Emission-line fluxes have been calculated for the models and compared with observations of planetary nebulae by O'Dell, Osterbrock's group, and Aller and his collaborators. Results indicate that the central stars have strong He+ Lyman continuum excesses, similar to those predicted by Gebbie and Seaton. The mean abundance determinations for the nebulae made by Aller are confirmed, with the exception of nitrogen, which appears to be 3 or 4 times more abundant than his value. It is also seen that the electron temperatures of the nebulae are higher than previous theoretical determinations, providing better agreement with empirically derived values.

scholarly journals Emission-line Wings Driven by Lyman Continuum in the Green Pea Analog Mrk 71

2021 ◽  
Vol 920 (2) ◽  
pp. L39
Author(s):  
Lena Komarova ◽  
M. S. Oey ◽  
Mark R. Krumholz ◽  
Sergiy Silich ◽  
Nimisha Kumari ◽  
...  
Keyword(s):  
Emission Line ◽  
Lyman Continuum ◽  
Green Pea

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

2020 ◽  
Vol 644 ◽  
pp. A21
Author(s):  
L. Ramambason ◽  
D. Schaerer ◽  
G. Stasińska ◽  
Y. I. Izotov ◽  
N. G. Guseva ◽  
...  
Keyword(s):  
Emission Line ◽  
Column Density ◽  
Line Emission ◽  
Optical Emission ◽  
Emission Lines ◽  
Zone Model ◽  
High Hydrogen ◽  
Lyman Continuum ◽  
Hydrogen Column Density ◽  
Photoionization Model

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.

scholarly journals Testing an indirect method for identifying galaxies with high levels of Lyman continuum leakage

2020 ◽  
Vol 498 (3) ◽  
pp. 3095-3114 ◽  
Author(s):  
Satoshi Yamanaka ◽  
Akio K Inoue ◽  
Toru Yamada ◽  
Erik Zackrisson ◽  
Ikuru Iwata ◽  
...  
Keyword(s):  
Emission Line ◽  
Indirect Method ◽  
Direct Detection ◽  
Consistent Estimate ◽  
Photometric Redshifts ◽  
Indirect Methods ◽  
Lyman Break Galaxies ◽  
Lyman Continuum ◽  
Flux Measurements ◽  
Direct And Indirect Methods

ABSTRACT Using a sample of galaxies at z ≈ 3 with detected Lyman Continuum (LyC) leakage in the SSA22 field, we attempt to verify a proposed indirect method for identifying cases with high LyC escape fraction fesc based on measurements of the H β equivalent width (EW) and the β slope of the UV continuum. To this end, we present Keck/MOSFIRE H β emission line flux measurements of LyC galaxies (LCGs) at spectroscopic redshifts zspec ∼ 3.3, Lyman break galaxies (LBGs) at photometric redshifts zphot = 2.7–3.7, and Ly α emitters at zphot = 3.1. We also reconfirm the spectroscopic redshifts and measure the H β emission-line fluxes from two LCGs and six LBGs. For the LCG in our sample with the most extreme fesc, as revealed by the direct detection of LyC photons, we find that the EW(H β)–β method gives a broadly consistent estimate for fesc, although the error bars remain very large. We also discuss how a combination of fesc measurements based on direct and indirect methods can shed light on the LyC escape mechanism and the anisotropy of the leakage.

HII radiative transfer revealed by ionization parameter mapping

2012 ◽  
Vol 10 (H16) ◽  
pp. 587-589
Author(s):  
M. S. Oey ◽  
E. W. Pellegrini ◽  
P. F. Winkler ◽  
S. D. Points ◽  
R. C. Smith ◽  
...  
Keyword(s):  
Star Formation ◽  
Radiative Transfer ◽  
Emission Line ◽  
Column Density ◽  
Magellanic Clouds ◽  
Parameter Mapping ◽  
Lyman Continuum ◽  
Line Survey ◽  
Warm Ionized Medium ◽  
Ionization Parameter

AbstractWe develop the technique of ionization parameter mapping (IPM) to probe the optical depth of Hii regions, applying our method to the Magellanic Clouds. Our results dramatically clarify the radiative transfer in these galaxies. Based on Sii, Oiii, and Hα imaging from the Magellanic Clouds Emission Line Survey, we find that the frequency of optically thin objects correlates strongly with Hα luminosity and correlates inversely with Hi column density. The aggregate escape fraction for the Lyman continuum is sufficient to ionize the diffuse, warm ionized medium, but the galactic escape fraction is dominated by the few largest Hii regions. The quantitative trends are similar in both the LMC and SMC in spite of their different star formation and Hi properties.

FeXIV Line Emission Polarization of the July 11, 1991 Solar Corona

1994 ◽  
Vol 144 ◽  
pp. 541-547
Author(s):  
J. Sýkora ◽  
J. Rybák ◽  
P. Ambrož
Keyword(s):  
High Resolution ◽  
Solar Corona ◽  
Emission Line ◽  
Solar Eclipse ◽  
White Light ◽  
Preliminary Analysis ◽  
Line Emission ◽  
Total Solar Eclipse ◽  
Degree Of Polarization ◽  
High Resolution Images

AbstractHigh resolution images, obtained during July 11, 1991 total solar eclipse, allowed us to estimate the degree of solar corona polarization in the light of FeXIV 530.3 nm emission line and in the white light, as well. Very preliminary analysis reveals remarkable differences in the degree of polarization for both sets of data, particularly as for level of polarization and its distribution around the Sun’s limb.

Structuring, Motions and Shapes of Corona Emission Line Profiles

1994 ◽  
Vol 144 ◽  
pp. 421-426
Author(s):  
N. F. Tyagun
Keyword(s):  
Emission Line ◽  
Filling Factor ◽  
Direct Relationship ◽  
Coronal Plasma ◽  
Line Of Sight ◽  
Line Profiles ◽  
The Difference ◽  
Yellow Line ◽  
Red Line

AbstractThe interrelationship of half-widths and intensities for the red, green and yellow lines is considered. This is a direct relationship for the green and yellow line and an inverse one for the red line. The difference in the relationships of half-widths and intensities for different lines appears to be due to substantially dissimilar structuring and to a set of line-of-sight motions in ”hot“ and ”cold“ corona regions.When diagnosing the coronal plasma, one cannot neglect the filling factor - each line has such a factor of its own.

White-Light Coronal Structures: Streamers and CMEs

1994 ◽  
Vol 144 ◽  
pp. 82
Author(s):  
E. Hildner
Keyword(s):  
Emission Line ◽  
Electron Density ◽  
White Light ◽  
Coronal Mass Ejections ◽  
X Rays ◽  
Solar Cycles ◽  
Temperature Function ◽  
X Ray ◽  
Eclipse Observations ◽  
Coronal Structures

AbstractOver the last twenty years, orbiting coronagraphs have vastly increased the amount of observational material for the whitelight corona. Spanning almost two solar cycles, and augmented by ground-based K-coronameter, emission-line, and eclipse observations, these data allow us to assess,inter alia: the typical and atypical behavior of the corona; how the corona evolves on time scales from minutes to a decade; and (in some respects) the relation between photospheric, coronal, and interplanetary features. This talk will review recent results on these three topics. A remark or two will attempt to relate the whitelight corona between 1.5 and 6 R⊙to the corona seen at lower altitudes in soft X-rays (e.g., with Yohkoh). The whitelight emission depends only on integrated electron density independent of temperature, whereas the soft X-ray emission depends upon the integral of electron density squared times a temperature function. The properties of coronal mass ejections (CMEs) will be reviewed briefly and their relationships to other solar and interplanetary phenomena will be noted.

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