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 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 Chemodynamics of green pea galaxies – I. Outflows and turbulence driving the escape of ionizing photons and chemical enrichment

2020 ◽  
Vol 494 (3) ◽  
pp. 3541-3561 ◽  
Author(s):  
L Hogarth ◽  
R Amorín ◽  
J M Vílchez ◽  
G F Hägele ◽  
M Cardaci ◽  
...  
Keyword(s):  
Emission Line ◽  
Indirect Evidence ◽  
Young Star ◽  
High Dispersion ◽  
H Ii Regions ◽  
Ionized Gas ◽  
Narrow Component ◽  
Radiation Fields ◽  
Hard Radiation ◽  
Green Pea

ABSTRACT We investigate the ionized gas kinematics, physical properties, and chemical abundances of Sloan Digital Sky Survey J142947, a Green Pea galaxy at redshift z∼ 0.17 with strong, double-peak Ly α emission and indirect evidence of Lyman continuum (LyC) leakage. Using high-dispersion spectroscopy, we perform a multicomponent analysis of emission-line profiles. Our model consistently fits all lines as a narrow component with intrinsic velocity dispersion σ ∼ 40 km s−1, and two broader blue-shifted components with σ ∼ 90 and ∼ 250 km s−1. We find electron densities and temperatures, ionization conditions, and direct O/H and N/O abundances for each component. A highly ionized, metal-poor, young and compact starburst dominates narrow emission, showing evidence of hard radiation fields and elevated N/O. The blue-shifted broader components are consistent with highly turbulent, possibly clumpy ionized gas at the base of a strong photoionized outflow, which accounts for ≳50 per cent of the integrated emission-line fluxes. The outflow is dense and metal-enriched compared to the H ii regions, with expansion velocities larger than those obtained from UV interstellar absorption lines under standard assumptions. Some of these metals may be able to escape, with outflows loading factors comparable to those found in high-z galaxies of similar SFR/Area. Our findings depict a two-stage starburst picture; hard radiation fields from young star clusters illuminate a turbulent and clumpy ISM that has been eroded by SNe feedback. Whilst UV data suggest an extended Ly α halo with high average H i column density, LyC photons could only escape from SDSS J142947 through low H i density channels or filaments in the ISM approaching density-bounded conditions, traced by outflowing gas.

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 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 The Green Peas: Searching for LyC Emitters at Low Redshift

2015 ◽  
Vol 11 (S319) ◽  
pp. 126-126
Author(s):  
Anne Jaskot ◽  
Sally Oey
Keyword(s):  
High Redshift ◽  
Optical Emission ◽  
Emission Lines ◽  
Gas Distribution ◽  
High Redshift Galaxies ◽  
Neutral Gas ◽  
Lyman Continuum ◽  
Green Pea ◽  
Green Peas ◽  
Redshift Galaxies

AbstractThe escape fraction of Lyman continuum (LyC) radiation from galaxies remains one of the primary uncertainties in studies of reionization. However, few LyC-emitting galaxies are known. The recently identified, low-redshift “Green Pea” (GP) galaxies exhibit a number of similarities with high-redshift galaxies, and their optical emission lines suggest they may be some of the elusive LyC emitters. Recent HST COS and ACS observations of four GPs suggest further evidence for LyC escape and give new insights into the origins of Lyα and low-ionization UV lines in high-redshift galaxies. The Lyα emission and low-ionization emission and absorption lines provide a coherent physical picture of the neutral gas distribution in the GPs and may identify LyC emitters at high redshift. The rare, low-redshift GPs hint at possible factors that may enable LyC and Lyα escape from high-redshift galaxies.

scholarly journals IFU investigation of possible Lyman continuum escape from Mrk 71/NGC 2366

2019 ◽  
Vol 623 ◽  
pp. A145 ◽  
Author(s):  
Genoveva Micheva ◽  
Edmund Christian Herenz ◽  
Martin M. Roth ◽  
Göran Östlin ◽  
Philipp Girichidis
Keyword(s):  
High Resolution ◽  
Velocity Dispersion ◽  
Physical Conditions ◽  
The North ◽  
Direct Observations ◽  
Lyman Continuum ◽  
High Ionization ◽  
Green Pea ◽  
Field Unit ◽  
Electron Density Map

Context. Mrk 71/NGC 2366 is the closest green pea (GP) analog and candidate Lyman Continuum (LyC) emitter. Recently, 11 LyC-leaking GPs have been detected through direct observations of the ionizing continuum, making this the most abundant class of confirmed LyC-emitters at any redshift. High resolution, multiwavelength studies of GPs can lead to an understanding of the method(s), through which LyC escapes from these galaxies. Aims. The proximity of Mrk 71/NCG 2366 offers unprecedented detail on the inner workings of a GP analog, and enables us to identify the mechanisms of LyC escape. Methods. We used 5825–7650 Å integral field unit PMAS observations to study the kinematics and physical conditions in Mrk 71. An electron density map was obtained from the [S II] ratio. A fortuitous second order contamination by the [O II] λ3727 doublet enabled the construction of an electron temperature map. Resolved maps of sound speed, thermal broadening, “true” velocity dispersion, and Mach number were obtained and compared to the high resolution magnetohydrodynamic SImulating the LifeCycle of molecular Clouds (SILCC) simulations. Results. Two regions of increased velocity dispersion indicative of outflows are detected to the north and south of the super star cluster, knot B, with redshifted and blueshifted velocities, respectively. We confirm the presence of a faint broad kinematical component, which is seemingly decoupled from the outflow regions, and is fainter and narrower than previously reported in the literature. Within uncertainties, the low- and high-ionization gasses move together. Outside of the core of Mrk 71, an increase in Mach numbers is detected, implying a decrease in gas density. Simulations suggest this drop in density can be as high as ∼4 dex, down to almost optically thin levels, which would imply a nonzero LyC escape fraction along the outflows even when assuming all of the detected H I gas is located in front of Mrk 71 in the line of sight. Conclusions. Our results strongly indicate that kinematical feedback is an important ingredient for LyC leakage in GPs.

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.

Sign in / Sign up

Export Citation Format

Share Document