scholarly journals An analytic model for [O iii] fine structure emission from high redshift galaxies

2020 ◽  
Vol 499 (3) ◽  
pp. 3417-3433 ◽  
Author(s):  
Shengqi Yang ◽  
Adam Lidz
Keyword(s):  
Fine Structure ◽  
High Redshift ◽  
Formation Rate ◽  
Line Emission ◽  
Relative Volume ◽  
H Ii Regions ◽  
Analytic Model ◽  
Free Electrons ◽  
High Redshift Galaxies ◽  
Better Than

ABSTRACT Recent ALMA measurements have revealed bright [O iii] 88 micron line emission from galaxies during the Epoch of Reionization (EoR) at redshifts as large as z ∼ 9. We introduce an analytic model to help interpret these and other upcoming [O iii] 88 micron measurements. Our approach sums over the emission from discrete Str$\ddot{\mathrm{o}}$mgren spheres and considers the total volume of ionized hydrogen in a galaxy of a given star-formation rate. We estimate the relative volume of doubly ionized oxygen and ionized hydrogen and its dependence on the spectrum of ionizing photons. We then calculate the level populations of O iii ions in different fine-structure states for H ii regions of specified parameters. In this simple model, a galaxy’s [O iii] 88 μm luminosity is determined by the typical number density of free electrons in H ii regions (ne), the average metallicity of these regions (Z), the rate of hydrogen ionizing photons emitted (QH i), and the shape of the ionizing spectrum. We cross-check our model by comparing it with detailed cloudy calculations, and find that it works to better than 15${{\ \rm per\ cent}}$ accuracy across a broad range of parameter space. Applying our model to existing ALMA data at z ∼ 6–9, we derive lower bounds on the gas metallicity and upper bounds on the gas density in the H ii regions of these galaxies. These limits vary considerably from galaxy to galaxy, with the tightest bounds indicating Z ≳ 0.5Z⊙ and nH ≲ 50 cm−3 at 2 − σ confidence.

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

2019 ◽  
Vol 487 (4) ◽  
pp. 5902-5921 ◽  
Author(s):  
Harley Katz ◽  
Thomas P Galligan ◽  
Taysun Kimm ◽  
Joakim Rosdahl ◽  
Martin G Haehnelt ◽  
...  
Keyword(s):  
High Redshift ◽  
Formation Rate ◽  
Line Emission ◽  
Emission Lines ◽  
Strong Line ◽  
Radiation Hydrodynamics ◽  
High Redshift Galaxies ◽  
Physical Conditions ◽  
Velocity Gradients ◽  
Ionization Parameter

ABSTRACT 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, ionization 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 discs that appear as velocity gradients in [C ii] 157.6 $\mu$m emission. Spatial and spectral offsets between [C ii] 157.6 $\mu$m and [O iii] 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 [C ii]–SFR relation, consistent with newer observations that question previously observed [C ii] 157.6 $\mu$m deficits. Our galaxies are consistent with the nebular line properties of observed z ∼ 2–3 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 α and [O ii] 3727$\, \mathring{\rm A}$ luminosity and galaxy SFR apply up to z > 10, as do the local relations between certain strong line diagnostics (R23 and [O iii] 5007$\, \mathring{\rm A}$/H β) 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).

scholarly journals The ‘Red Radio Ring’: ionized and molecular gas in a starburst/active galactic nucleus at z ∼ 2.55

2019 ◽  
Vol 488 (2) ◽  
pp. 1489-1500 ◽  
Author(s):  
Kevin C Harrington ◽  
A Vishwas ◽  
A Weiß ◽  
B Magnelli ◽  
L Grassitelli ◽  
...  
Keyword(s):  
Fine Structure ◽  
Spectral Energy Distribution ◽  
Formation Rate ◽  
Line Emission ◽  
Far Infrared ◽  
Spectral Energy ◽  
Molecular Gas ◽  
H Ii Regions ◽  
Galaxy Assembly ◽  
Dust Attenuation

ABSTRACT We report the detection of the far-infrared (FIR) fine-structure line of singly ionized nitrogen, [N ii] 205 $\mu$m , within the peak epoch of galaxy assembly, from a strongly lensed galaxy, hereafter ‘The Red Radio Ring’; the RRR, at z = 2.55. We combine new observations of the ground-state and mid-J transitions of CO (Jup = 1, 5, 8), and the FIR spectral energy distribution (SED), to explore the multiphase interstellar medium (ISM) properties of the RRR. All line profiles suggest that the H ii regions, traced by [N ii] 205 $\mu$m , and the (diffuse and dense) molecular gas, traced by CO, are cospatial when averaged over kpc-sized regions. Using its mid-IR-to-millimetre (mm) SED, we derive a non-negligible dust attenuation of the [N ii] 205 $\mu$m line emission. Assuming a uniform dust screen approximation results a mean molecular gas column density >1024 cm−2, with a molecular gas-to-dust mass ratio of 100. It is clear that dust attenuation corrections should be accounted for when studying FIR fine-structure lines in such systems. The attenuation corrected ratio of $L_{\rm N\,{\small II}205} / L_{\rm IR(8\!-\!1000\, \mu m)} = 2.7 \times 10^{-4}$ is consistent with the dispersion of local and z > 4 SFGs. We find that the lower limit, [N ii] 205 $\mu$m -based star formation rate (SFR) is less than the IR-derived SFR by a factor of 4. Finally, the dust SED, CO line SED, and $L_{\rm N\,{\small II}205}$ line-to-IR luminosity ratio of the RRR is consistent with a starburst-powered ISM.

scholarly journals The [CII] 158 μm line emission in high-redshift galaxies

2018 ◽  
Vol 609 ◽  
pp. A130 ◽  
Author(s):  
G. Lagache ◽  
M. Cousin ◽  
M. Chatzikos
Keyword(s):  
Galaxy Evolution ◽  
High Redshift ◽  
Formation Rate ◽  
Line Emission ◽  
Interstellar Gas ◽  
Structure Transition ◽  
High Redshift Galaxies ◽  
Star Forming ◽  
Crucial Component ◽  
Redshift Galaxies

Gas is a crucial component of galaxies, providing the fuel to form stars, and it is impossible to understand the evolution of galaxies without knowing their gas properties. The [CII] fine structure transition at 158 μm is the dominant cooling line of cool interstellar gas, and is the brightest of emission lines from star forming galaxies from FIR through metre wavelengths, almost unaffected by attenuation. With the advent of ALMA and NOEMA, capable of detecting [CII]-line emission in high-redshift galaxies, there has been a growing interest in using the [CII] line as a probe of the physical conditions of the gas in galaxies, and as a star formation rate (SFR) indicator at z ≥ 4. In this paper, we have used a semi-analytical model of galaxy evolution (G.A.S.) combined with the photoionisation code CLOUDY to predict the [CII] luminosity of a large number of galaxies (25 000 at z ≃ 5) at 4 ≤ z ≤ 8. We assumed that the [CII]-line emission originates from photo-dominated regions. At such high redshift, the CMB represents a strong background and we discuss its effects on the luminosity of the [CII] line. We studied the L[CII ]–SFR and L[ CII ]–Zg relations and show that they do not strongly evolve with redshift from z = 4 and to z = 8. Galaxies with higher [CII] luminosities tend to have higher metallicities and higher SFRs but the correlations are very broad, with a scatter of about 0.5 and 0.8 dex for L[ CII ]–SFR and L[ CII ]–Zg, respectively. Our model reproduces the L[ CII ]–SFR relations observed in high-redshift star-forming galaxies, with [CII] luminosities lower than expected from local L[ CII ]–SFR relations. Accordingly, the local observed L[ CII ]–SFR relation does not apply at high-z (z ≳ 5), even when CMB effects are ignored. Our model naturally produces the [CII] deficit (i.e. the decrease of L[ CII ]/LIR with LIR), which appears to be strongly correlated with the intensity of the radiation field in our simulated galaxies. We then predict the [CII] luminosity function, and show that it has a power law form in the range of L[ CII] probed by the model (1 × 107–2 × 109 L⊙ at z = 6) with a slope α = −1. The slope is not evolving from z = 4 to z = 8 but the number density of [CII]-emitters decreases by a factor of 20×. We discuss our predictions in the context of current observational estimates on both the differential and cumulative luminosity functions.

scholarly journals Gone with the heat: a fundamental constraint on the imaging of dust and molecular gas in the early Universe

2016 ◽  
Vol 3 (6) ◽  
pp. 160025 ◽  
Author(s):  
Zhi-Yu Zhang ◽  
Padelis P. Papadopoulos ◽  
R. J. Ivison ◽  
Maud Galametz ◽  
M. W. L. Smith ◽  
...  
Keyword(s):  
Structural Characteristics ◽  
High Redshift ◽  
Line Emission ◽  
Velocity Fields ◽  
Molecular Gas ◽  
Gas Velocity ◽  
High Redshift Galaxies ◽  
Mass Distributions ◽  
Line Imaging ◽  
Cold Dust

Images of dust continuum and carbon monoxide (CO) line emission are powerful tools for deducing structural characteristics of galaxies, such as disc sizes, H 2 gas velocity fields and enclosed H 2 and dynamical masses. We report on a fundamental constraint set by the cosmic microwave background (CMB) on the observed structural and dynamical characteristics of galaxies, as deduced from dust continuum and CO-line imaging at high redshifts. As the CMB temperature rises in the distant Universe, the ensuing thermal equilibrium between the CMB and the cold dust and H 2 gas progressively erases all spatial and spectral contrasts between their brightness distributions and the CMB. For high-redshift galaxies, this strongly biases the recoverable H 2 gas and dust mass distributions, scale lengths, gas velocity fields and dynamical mass estimates. This limitation is unique to millimetre/submillimetre wavelengths and unlike its known effect on the global dust continuum and molecular line emission of galaxies, it cannot be addressed simply. We nevertheless identify a unique signature of CMB-affected continuum brightness distributions, namely an increasing rather than diminishing contrast between such brightness distributions and the CMB when the cold dust in distant galaxies is imaged at frequencies beyond the Raleigh–Jeans limit. For the molecular gas tracers, the same effect makes the atomic carbon lines maintain a larger contrast than the CO lines against the CMB.

Extreme variations in star formation activity in the first galaxies

2019 ◽  
Vol 15 (S341) ◽  
pp. 226-230
Author(s):  
Christian Binggeli ◽  
Erik Zackrisson ◽  
Xiangcheng Ma ◽  
Akio K. Inoue ◽  
Anton Vikaeus ◽  
...  
Keyword(s):  
Star Formation ◽  
Rest Frame ◽  
High Redshift ◽  
Formation Rate ◽  
High Redshift Galaxies ◽  
James Webb Space Telescope ◽  
Star Formation Activity ◽  
The Galaxy ◽  
First Galaxies ◽  
Star Formation Histories

AbstractRecently, spectroscopic detections of O[III] 88 μm and Ly-α emission lines from the z ≍ 9.1 galaxy MACS1149-JD1 have been presented, and with these, some interesting properties of this galaxy were uncovered. One such property is that MACS1149-JD1 exhibits a significant Balmer break at around rest-frame 4000 Å, which may indicate that the galaxy has experienced large variations in star formation rate prior to z ∼ 9, with a rather long period of low star formation activity. While some simulations predict large variations in star formation activity in high-redshift galaxies, it is unclear whether the simulations can reproduce the kind of variations seen in MACS1149-JD1. Here, we utilize synthetic spectra of simulated galaxies from two simulation suites in order to study to what extent these can accurately reproduce the spectral features (specifically the Balmer break) observed in MACS1149-JD1. We show that while the simulations used in this study produce galaxies with varying star formation histories, galaxies such as MACS1149-JD1 would be very rare in the simulations. In principle, future observations with the James Webb Space Telescope may tell us if MACS1149-JD1 represents something rare, or if such galaxies are more common than predicted by current simulations.

Infrared line emission from high-redshift galaxies. 1: Calculations

1995 ◽  
Vol 442 ◽  
pp. 569 ◽  
Author(s):  
Filippo Mannucci ◽  
Steven V. W. Beckwith
Keyword(s):  
High Redshift ◽  
Line Emission ◽  
High Redshift Galaxies ◽  
Redshift Galaxies

scholarly journals Extremely metal-poor galaxies with HST/COS: laboratories for models of low-metallicity massive stars and high-redshift galaxies

2019 ◽  
Vol 488 (3) ◽  
pp. 3492-3506 ◽  
Author(s):  
Peter Senchyna ◽  
Daniel P Stark ◽  
Jacopo Chevallard ◽  
Stéphane Charlot ◽  
Tucker Jones ◽  
...  
Keyword(s):  
Massive Stars ◽  
High Redshift ◽  
Formation Rate ◽  
Uv Spectra ◽  
High Redshift Galaxies ◽  
Star Forming ◽  
High Ionization ◽  
Moderate Resolution ◽  
Low Metallicity ◽  
Nearby Galaxies

Abstract Ultraviolet (UV) observations of local star-forming galaxies have begun to establish an empirical baseline for interpreting the rest-UV spectra of reionization-era galaxies. However, existing high-ionization emission line measurements at z > 6 ($\rm W_{C\, {\scriptscriptstyle IV},0}{} \gtrsim 20$ Å) are uniformly stronger than observed locally ($\rm W_{C\, {\scriptscriptstyle IV},0}{} \lesssim 2$ Å), likely due to the relatively high metallicities (Z/Z$\odot$ > 0.1) typically probed by UV surveys of nearby galaxies. We present new HST/COS spectra of six nearby (z < 0.01) extremely metal-poor galaxies (XMPs, Z/Z$\odot$ ≲ 0.1) targeted to address this limitation and provide constraints on the highly uncertain ionizing spectra powered by low-metallicity massive stars. Our data reveal a range of spectral features, including one of the most prominent nebular C iv doublets yet observed in local star-forming systems and strong He ii emission. Using all published UV observations of local XMPs to date, we find that nebular C iv emission is ubiquitous in very high specific star formation rate systems at low metallicity, but still find equivalent widths smaller than those measured in individual lensed systems at z > 6. Our moderate-resolution HST/COS data allow us to conduct an analysis of the stellar winds in a local nebular C iv emitter, which suggests that some of the tension with z > 6 data may be due to existing local samples not yet probing sufficiently high α/Fe abundance ratios. Our results indicate that C iv emission can play a crucial role in the JWST and ELT era by acting as an accessible signpost of very low metallicity (Z/Z$\odot$ < 0.1) massive stars in assembling reionization-era systems.

scholarly journals High-redshift JWST predictions from IllustrisTNG: II. Galaxy line and continuum spectral indices and dust attenuation curves

2020 ◽  
Vol 495 (4) ◽  
pp. 4747-4768 ◽  
Author(s):  
Xuejian Shen ◽  
Mark Vogelsberger ◽  
Dylan Nelson ◽  
Annalisa Pillepich ◽  
Sandro Tacchella ◽  
...  
Keyword(s):  
High Redshift ◽  
Formation Rate ◽  
Spectral Indices ◽  
High Redshift Galaxies ◽  
Luminosity Functions ◽  
Galaxy Populations ◽  
Stellar Masses ◽  
Red Galaxies ◽  
Dust Attenuation ◽  
Rate Relation

ABSTRACT We present predictions for high redshift (z = 2−10) galaxy populations based on the IllustrisTNG simulation suite and a full Monte Carlo dust radiative transfer post-processing. Specifically, we discuss the H α and H β + $[\rm O \,{\small III}]$ luminosity functions up to z = 8. The predicted H β + $[\rm O \,{\small III}]$ luminosity functions are consistent with present observations at z ≲ 3 with ${\lesssim} 0.1\, {\rm dex}$ differences in luminosities. However, the predicted H α luminosity function is ${\sim }0.3\, {\rm dex}$ dimmer than the observed one at z ≃ 2. Furthermore, we explore continuum spectral indices, the Balmer break at 4000 Å; (D4000) and the UV continuum slope β. The median D4000 versus specific star formation rate relation predicted at z = 2 is in agreement with the local calibration despite a different distribution pattern of galaxies in this plane. In addition, we reproduce the observed AUV versus β relation and explore its dependence on galaxy stellar mass, providing an explanation for the observed complexity of this relation. We also find a deficiency in heavily attenuated, UV red galaxies in the simulations. Finally, we provide predictions for the dust attenuation curves of galaxies at z = 2−6 and investigate their dependence on galaxy colours and stellar masses. The attenuation curves are steeper in galaxies at higher redshifts, with bluer colours, or with lower stellar masses. We attribute these predicted trends to dust geometry. Overall, our results are consistent with present observations of high-redshift galaxies. Future James Webb Space Telecope observations will further test these predictions.

scholarly journals Planck’s Dusty GEMS

2019 ◽  
Vol 624 ◽  
pp. A23 ◽  
Author(s):  
N. P. H. Nesvadba ◽  
R. Cañameras ◽  
R. Kneissl ◽  
S. Koenig ◽  
C. Yang ◽  
...  
Keyword(s):  
High Redshift ◽  
Starburst Galaxies ◽  
Molecular Gas ◽  
Atomic Carbon ◽  
High Redshift Galaxies ◽  
Neutral Gas ◽  
The Common ◽  
The Masses ◽  
Better Than ◽  
Good Agreement

The bright 3P1–3P0 ([CI] 1–0) and 3P2–3P1 ([CI] 2–1) lines of atomic carbon are becoming more and more widely employed as tracers of the cold neutral gas in high-redshift galaxies. Here we present observations of these lines in the 11 galaxies of the set of Planck’s Dusty GEMS, the brightest gravitationally lensed galaxies on the extragalactic submillimeter sky probed by the Planck satellite. We have [CI] 1–0 and [CI] 2–1 measurements for seven and eight of these galaxies, respectively, including four galaxies where both lines have been measured. We use our observations to constrain the gas excitation mechanism, excitation temperatures, optical depths, atomic carbon and molecular gas masses, and carbon abundances. Ratios of LCI/LFIR are similar to those found in the local universe, and suggest that the total cooling budget through atomic carbon has not significantly changed in the last 12 Gyr. Both lines are optically thin and trace 1 − 6 × 107 M⊙ of atomic carbon. Carbon abundances, XCI, are between 2.5 and 4 × 10−5, for an ultra-luminous infrared galaxy (ULIRG) CO-to-H2 conversion factor of αCO = 0.8 M⊙ / [K km s−1 pc2]. Ratios of molecular gas masses derived from [CI] 1–0 and CO agree within the measurement uncertainties for five galaxies, and agree to better than a factor of two for another two with [CI] 1–0 measurements, after carefully taking CO excitation into account. This does not support the idea that intense, high-redshift starburst galaxies host large quantities of “CO-dark” gas. These results support the common assumptions underlying most molecular gas mass estimates made for massive, dusty, high-redshift starburst galaxies, although the good agreement between the masses obtained with both tracers cannot be taken as independent confirmation of either αCO or XCI.

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