Probing cosmic dawn with emission lines: predicting infrared and nebular line emission for ALMA and JWST

Infrared and nebular lines provide some of our best probes of the physics regulating the properties of the interstellar medium (ISM) at high-redshift. However, interpreting the physical conditions of high-redshift galaxies directly from emission lines remains complicated due to inhomogeneities in temperature, density, metallicity, ionisation parameter, and spectral hardness. We present a new suite of cosmological, radiation-hydrodynamics simulations, each centred on a massive Lyman-break galaxy that resolves such properties in an inhomogeneous ISM. Many of the simulated systems exhibit transient but well defined gaseous disks that appear as velocity gradients in [CII]~158.6$\mu$m emission. Spatial and spectral offsets between [CII]~158.6$\mu$m and [OIII]~88.33$\mu$m are common, but not ubiquitous, as each line probes a different phase of the ISM. These systems fall on the local [CII]-SFR relation, consistent with newer observations that question previously observed [CII]~158.6$\mu$m deficits. Our galaxies are consistent with the nebular line properties of observed $z\sim2-3$ galaxies and reproduce offsets on the BPT and mass-excitation diagrams compared to local galaxies due to higher star formation rate (SFR), excitation, and specific-SFR, as well as harder spectra from young, metal-poor binaries. We predict that local calibrations between H$\alpha$ and [OII]~3727$\AA$ luminosity and galaxy SFR apply up to $z>10$, as do the local relations between certain strong line diagnostics (R23 and [OIII]~5007$\AA$/H$\beta$) and galaxy metallicity. Our new simulations are well suited to interpret the observations of line emission from current (ALMA and HST) and upcoming facilities (JWST and ngVLA)

New Methods for Identifying Lyman Continuum Leakers and Reionization-Epoch Analogues

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

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

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 $z\sim3$ and $z\sim0$. We find that the simulated galaxies with high LyC escape fractions ($f_{\rm esc}$) often exhibit high O32 and populate the same regions of the R23-O32 plane as $z\sim3$ LyC leakers. However, we show that viewing angle, metallicity, and ionisation parameter can all impact where a galaxy resides on the O32-$f_{\rm esc}$ plane. Based on emission line diagnostics and how they correlate with $f_{\rm esc}$, lower-metallicity LyC leakers at $z\sim3$ appear to be good analogues of reionization-era galaxies. In contrast, local [SII]-deficient galaxies do not overlap with the simulated high-redshift LyC leakers on the SII-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 IR and nebular emission lines. We show that our model using only [CII]$_{\rm 158\mu m}$ and [OIII]$_{\rm 88\mu m}$ 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 MACS1149_JD1 at $z=9.1$ is the most likely galaxy to be actively contributing to the reionization of the Universe

The nature of high [O III]88 μ m/[C II]158 μm galaxies in the epoch of reionization: Low carbon abundance and a top-heavy IMF?

ALMA observations of z > 6 galaxies have revealed abnormally high [O III]88 μm/[C II]158 μm ratios and [C II]158 μm deficits compared to local galaxies. The origin of this behaviour is unknown. Numerous solutions have been proposed including differences in C and O abundance ratios, observational bias, and differences in ISM properties, including ionization parameter, gas density, or photodissociation region (PDR) covering fraction. In order to elucidate the underlying physics that drives this high-redshift phenomenon, we employ SPHINX20, a state-of-the-art, cosmological radiation–hydrodynamics simulation, that resolves detailed ISM properties of thousands of galaxies in the epoch of reionization which has been post-processed with CLOUDY to predict emission lines. We find that the observed z > 6 [O III]88 μm–SFR and [C II]158 μm–SFR relations can only be reproduced when the C/O abundance ratio is ∼8 × lower than Solar and the total metal production is ∼4 × higher than that of a Kroupa IMF. This implies that high-redshift galaxies are potentially primarily enriched by low-metallicity core–collapse supernovae with a more top-heavy IMF. As AGB stars and type-Ia supernova begin to contribute to the galaxy metallicity, both the [C II]158 μm–SFR and [C II]158 μm luminosity functions are predicted to converge to observed values at z ∼ 4.5. While we demonstrate that ionization parameter, LyC escape fraction, ISM gas density, and CMB attenuation all drive galaxies towards higher [O III]88 μm/[C II]158 μm, observed values at z > 6 can only be reproduced with substantially lower C/O abundances compared to Solar. The combination of [C II]158 μm and [O III]88 μm can be used to predict the values of ionization parameter, ISM gas density, and LyC escape fraction and we provide estimates of these quantities for nine observed z > 6 galaxies. Finally, we demonstrate that [O I]63 μm can be used as a replacement for [C II]158 μ m in high-redshift galaxies where [C II]158 μ m is unobserved and argue that more observation time should be used to target [O I]63 μm at z > 6. Future simulations will be needed to self-consistently address the numerous uncertainties surrounding a varying IMF at high redshift and the associated metal returns

Operation of the 8-T, 1-m-diameter test facility at Lawrence Livermore National Laboratory

The High-Field Test Facility (HFTF) being built at Lawrence Livermore National Laboratory (LLNL) consists of a set of four Nb-Ti coils, inside of which there is a pair of multifilamentary Nb/sub 3/Sn coils. The outer coils are designed to generate 8 T in the 1-m bore; the Nb/sub 3/Sn coils will boost this to 12 T in a 40-cm bore. This paper describes the first operation of the complete set of Nb-Ti coils and describes and gives results from the data acquisition and analysis system that was used during the test

Observational Diagnostics of Gas Flows: Insights from Cosmological Simulations

Galactic accretion interacts in complex ways with gaseous halos, including galactic winds. As a result, observational diagnostics typically probe a range of intertwined physical phenomena. Because of this complexity, cosmological hydrodynamic simulations have played a key role in developing observational diagnostics of galactic accretion. In this chapter, we review the status of different observational diagnostics of circumgalactic gas flows, in both absorption (galaxy pair and down-the-barrel observations in neutral hydrogen and metals; kinematic and azimuthal angle diagnostics; the cosmological column density distribution; and metallicity) and emission (Lya; UV metal lines; and diffuse X-rays). We conclude that there is no simple and robust way to identify galactic accretion in individual measurements. Rather, progress in testing galactic accretion models is likely to come from systematic, statistical comparisons of simulation predictions with observations. We discuss specific areas where progress is likely to be particularly fruitful over the next few years.Comment: Invited review to appear in Gas Accretion onto Galaxies, Astrophysics and Space Science Library, eds. A. J. Fox & R. Dave, to be published by Springer. Typos correcte

Gas Accretion and Giant Lyman-alpha Nebulae

Several decades of observations and discoveries have shown that high-redshift AGN and massive galaxies are often surrounded by giant Lyman-alpha nebulae extending in some cases up to 500 kpc in size. In this review, I discuss the properties of the such nebulae discovered at z>2 and their connection with gas flows in and around the galaxies and their halos. In particular, I show how current observations are used to constrain the physical properties and origin of the emitting gas in terms of the Lyman-alpha photon production processes and kinematical signatures. These studies suggest that recombination radiation is the most viable scenario to explain the observed Lyman-alpha luminosities and Surface Brightness for the large majority of the nebulae and imply that a significant amount of dense, ionized and cold clumps should be present within and around the halos of massive galaxies. Spectroscopic studies suggest that, among the giant Lyman-alpha nebulae, the one associated with radio-loud AGN should have kinematics dominated by strong, ionized outflows within at least the inner 30-50 kpc. Radio-quiet nebulae instead present more quiescent kinematics compatible with stationary situation and, in some cases, suggestive of rotating structures. However, definitive evidences for accretion onto galaxies of the gas associated with the giant Lyman-alpha emission are not unambiguously detected yet. Deep surveys currently ongoing using other bright, non-resonant lines such as Hydrogen H-alpha and HeII1640 will be crucial to search for clearer signatures of cosmological gas accretion onto galaxies and AGN.Comment: Invited review to appear in Gas Accretion onto Galaxies, Astrophysics and Space Science Library, eds. A. J. Fox & R. Dave', to be published by Springe

In vivo measurement of tumor estradiol and Vascular Endothelial Growth Factor in breast cancer patients

© 2008 Garvin and Dabrosin; licensee BioMed Central Ltd

Validity of sports watches when estimating energy expenditure during running

The aim of this study was to assess the accuracy of three different sport watches in estimating energy expenditure during aerobic and anaerobic running