Galactic ionising photon budget during the Epoch of Reionisation in the Cosmic Dawn II simulation
Joseph S. W. Lewis, Pierre Ocvirk, Dominique Aubert, Jenny G. Sorce, Paul R. Shapiro, Nicolas Deparis, Taha Dawoodbhoy, Romain Teyssier, Gustavo Yepes, Stefan G… 展开作者
Joseph S. W. Lewis, Pierre Ocvirk, Dominique Aubert, Jenny G. Sorce, Paul R. Shapiro, Nicolas Deparis, Taha Dawoodbhoy, Romain Teyssier, Gustavo Yepes, Stefan Gottlöber, Kyungjin Ahn, Ilian T. Iliev, Jonathan Chardin
备注：
Submitted to MNRAS on 09/01/2020. Accepted on 12/06/2020
Cosmic Dawn ("CoDa") II yields the first statistically-meaningful determination of the relative contribution to reionization by galaxies of different halo mass, from a fully-coupled radiation-hydrodynamics simulation of the epoch of reionization large enough ($\sim$ 100 Mpc) to model global reionization while resolving the formation of all galactic halos above $\sim 10^8 M_\odot$. Cell transmission inside high-mass haloes is bi-modal -- ionized cells are transparent, while neutral cells absorb the photons their stars produce - and the halo escape fraction $f_{esc}$ reflects the balance of star formation rate ("SFR") between these modes. The latter is increasingly prevalent at higher halo mass, driving down $f_{esc}$ (we provide analytical fits to our results), whereas halo escape luminosity, proportional to $f_{esc} \times$SFR, increases with mass. Haloes with dark matter masses within $6.10^{8} M_\odot < M_h < 3.10^{10} M_\odot$ produce $\sim 80$% of the escaping photons at z=7, when the Universe is 50% ionized, making them the main drivers of cosmic reionization. Less massive haloes, though more numerous, have low SFRs and contribute less than 10% of the photon budget then, despite their high $f_{esc}$. High mass haloes are too few and too opaque, contributing $<10$% despite their high SFRs. The dominant mass range is lower (higher) at higher (lower) redshift, as mass function and reionization advance together (e.g. at z$=8.5$, x$_{\rm HI}=0.9$, $M_h < 5.10^9 M_\odot$ haloes contributed $\sim$80%). Galaxies with UV magnitudes $M_{AB1600}$ between $-12$ and $-19$ dominated reionization between z$=6$ and 8.
We report the discovery of a double-peaked Lyman-alpha profile in a galaxy at $z=6.803$, A370p\_z1, in the parallel Frontier Field of Abell 370. The velocity separation between the blue and red peaks of the Lyman-$α$ profile ($Δv=101_{-19}^{+38} (\pm48)\,\text{km s}^{-1}$) suggests an extremely high escape fraction of ionising photons $> 59(51)\% (2σ)$. The spectral energy distribution indicates a young ($50$ Myr), star-forming ($12\pm 6 \, \rm{M}_\odot \rm{yr}^{-1}$) galaxy with an IRAC excess implying strong [OIII]+H$β$ emission. On the basis of the high escape fraction measured, we demonstr…
Ionising properties of galaxies in JADES for a stellar mass complete sample: resolving the cosmic ionising photon budget crisis at the Epoch of Reionisation
Small galaxies are thought to be the main contributors to the ionising budget of the Universe before reionisation was complete. There have been a number of numerical studies trying to quantify their ionising efficiency through the escape fraction $f_{esc}$. While there is a clear trend that $f_{esc}$ is higher for smaller haloes, there is a large scatter in the distribution of $f_{esc}$ for a single halo mass. We propose that this is due to the intrinsic burstiness of star formation in low mass galaxies. We performed high resolution radiative hydrodynamics simulations with Ramses-RT to model t…
Using the First Light And Reionisation Epoch Simulations (\textsc{Flares}) we explore the dust driven properties of massive high-redshift galaxies at $z\in[5,10]$. By post-processing the galaxy sample using the radiative transfer code \textsc{skirt} we obtain the full spectral energy distribution. We explore the resultant luminosity functions, IRX-$β$ relations as well as the luminosity-weighted dust temperatures in the Epoch of Reionisation (EoR). We find that most of our results are in agreement with the current set of observations, but under-predict the number densities of bright IR galaxie…
Recent results have suggested that active galactic nuclei (AGN) could provide enough photons to reionise the Universe. We assess the viability of this scenario using a semi-numerical framework for modeling reionisation, to which we add a quasar contribution by constructing a Quasar Halo Occupation Distribution (QHOD) based on Giallongo et al. observations. Assuming a constant QHOD, we find that an AGN-only model cannot simultaneously match observations of the optical depth $τ_e$, neutral fraction, and ionising emissivity. Such a model predicts $τ_e$ too low by $\sim 2σ$ relative to Planck cons…
The rapidly declining population of bright quasars at z~3 appears to make an increasingly small contribution to the ionising background at the HI Lyman limit. It is then generally though that massive stars in (pre-)galactic systems may provide the additional ionising flux needed to complete HI reionisation by z>6. A galaxy dominated background, however, may require that the escape fraction of Lyman continuum radiation from high redshift galaxies is as high as 10%, a value somewhat at odds with (admittedly scarce) observational constraints. High escape fractions from dwarf galaxies have been ad…
Context: Population III (Pop III) stars may be fast rotating. An expected consequence of fast rotation is strong internal mixing that deeply affects their evolutionary tracks in the Hertzsprung-Russell diagram and hence their ionising power. aims: We investigate the impact on the ionising power of Pop III stars in an extreme case of internal mixing, the one leading to chemically homogeneous evolution (CHE). In that situation, during the main sequence phase, the star keeps the same chemical composition from its center to its surface. Homogeneous stars have larger effective temperatures and lumi…
The recent low value of Planck (2016) integrated optical depth to Thomson scattering suggests that the reionization occurred fairly suddenly, disfavoring extended reionization scenarios. This will have a significant impact on the 21cm power spectrum. Using a semi-numerical framework, we improve our model from Hassan et al. (2016) to include time-integrated ionisation and recombination effects, and find that this leads to more sudden reionisation. It also yields larger HII bubbles which leads to an order of magnitude more 21cm power on large scales, while suppressing the small scale ionization …
The recent measurement of an ionising mean free path $λ_{\text{mfp}}<1$ pMpc at $z=6$ challenges our understanding of the small-scale structure of the intergalactic medium (IGM) at the end of reionisation. We introduce a new method to constrain \mfp at $z=6$ by using lower limits on the individual free paths of ionisation around quasars. Lyman-limit absorbers with a density sufficient to halt ionising photons produce strong absorption in the 6 lowest-energy Lyman transitions, in the absence of which a robust lower limit can be placed on the individual free path. Applying this method to a set o…
Hydrogen in the Universe was (re)ionised between redshifts $z \approx 10$ and $z \approx 6$. The nature of the sources of the ionising radiation is hotly debated, with faint galaxies below current detection limits regarded as prime candidates. Here we consider a scenario in which ionising photons escape through channels punctured in the interstellar medium by outflows powered by starbursts. We take account of the observation that strong outflows occur only when the star formation density is sufficiently high, and estimate the galaxy-averaged escape fraction as a function of redshift and lumino…
Starlight from galaxies plays a pivotal role throughout the process of cosmic reionisation. We present the statistics of dwarf galaxy properties at z > 7 in haloes with masses up to 10^9 solar masses, using a cosmological radiation hydrodynamics simulation that follows their buildup starting with their Population III progenitors. We find that metal-enriched star formation is not restricted to atomic cooling ($T_{\rm vir} \ge 10^4$ K) haloes, but can occur in haloes down to masses ~10^6 solar masses, especially in neutral regions. Even though these smallest galaxies only host up to 10^4 solar m…
Distant luminous Lyman-alpha emitters (LAEs) are excellent targets for spectroscopic observations of galaxies in the epoch of reionisation (EoR). We present deep high-resolution (R=5000) VLT/X-SHOOTER observations, along with an extensive collection of photometric data of `COLA1', a proposed double peaked LAE at z=6.6 (Hu et al. 2016). We rule out that COLA1's emission line is an [OII] doublet at z=1.475 on the basis of i) the asymmetric red line-profile and flux ratio of the peaks (blue/red=$0.31\pm0.03$) and ii) an unphysical [OII]/Ha ratio ([OII]/Ha > 22). We show that COLA1's observed B-ba…
GLIMPSE-D: Metallicity Decline in Faint Galaxies: Implications for [O III]+Hb Luminosity Function and Reionisation Budget
University of Geneva（日内瓦大学）；CNRS, IRAP（法国国家科学研究中心，天体物理研究所）；Stockholm University（斯德哥尔摩大学）；Univ Lyon1（里昂第一大学）；The University of Texas at Austin（得克萨斯大学奥斯汀分校）；Space Telescope Science Institute（太空望远镜科学研究所）；Rutgers University（罗格斯大学）；Institut d’Astrophysique de Paris（巴黎天体物理研究所）
We examine various implications from a dynamical and chemical model of globular clusters (GCs), which successfully reproduces the observed abundance patterns and the multiple populations of stars in these systems assuming chemical enrichment from fast rotating massive stars. Using the model of Decressin et al. (2007) we determine the ratio between the observed, present-day mass of globular clusters and their initial stellar mass as a function of the stellar initial mass function (IMF). We also compute the mass of low-mass stars ejected, and the amount of hydrogen ionising photons emitted by th…
We present a detailed spectroscopic analysis of a galaxy at $z \simeq 4.88$ that is, by chance, magnified $\sim 30 \times$ by gravitational lensing. Only three sources at $z \gtrsim 5$ are known with such high magnification. This particular source has been shown to exhibit widespread, high equivalent width CIV $λ$ 1549 Å emission, implying it is a unique example of a metal-poor galaxy with a hard radiation field, likely representing the galaxy population responsible for cosmic reionisation. Using UV nebular line ratio diagnostics, VLT/X-shooter observations rule out strong AGN activity, indica…
The cosmic 21 cm signal is set to revolutionise our understanding of the early Universe, allowing us to probe the 3D temperature and ionisation structure of the intergalactic medium (IGM). It will open a window onto the unseen first galaxies, showing us how their UV and X-ray photons drove the cosmic milestones of the epoch of reionisation (EoR) and epoch of heating (EoH). To facilitate parameter inference from the 21 cm signal, we previously developed 21CMMC: a Monte Carlo Markov Chain sampler of 3D EoR simulations. Here we extend 21CMMC to include simultaneous modelling of the EoH, resulting…
Unveiling the Cosmic Dawn with SHARP: Probing extended Lyman-$α$ nebulae in a Universe less than 600 Myr old
INAF-IASF Milano（意大利国家天体物理研究所米兰天文物理研究所）；INAF – Osservatorio Astronomico di Roma（意大利国家天体物理研究所罗马天文台）；Department of Mathematics and Physics, Roma Tre University（罗马三大大学数学与物理系）；INAF–OAT, Osservatorio Astronomico di Trieste（意大利国家天体物理研究所的里雅斯特天文台）
Prior to the epoch of reionisation, the 21-cm signal of the cosmic dawn is dominated by the Lyman-$α$ coupling and gas temperature fluctuations caused by the first sources of radiation. While early efforts to model this epoch relied on analytical techniques, the community quickly transitioned to more expensive semi-numerical models. Here, we re-assess the viability of simpler approaches that allow for rapid explorations of the vast astrophysical parameter space. We propose a new analytical method to calculate the 21-cm power spectrum based on the framework of the halo model. Both the Lyman-$α$…
Investigating ionising sources and the complex interstellar medium of GHZ2 at $z=12.3$
INAF Osservatorio Astronomico di Roma（意大利国家天体物理研究所罗马天文台）；Università di Firenze, Dipartimento di Fisica e Astronomia（佛罗伦萨大学物理与天文学系）；INAF – Arcetri Astrophysical Observatory（意大利国家天体物理研究所阿切特里天文台）；European Southern Observatory（欧洲南方天文台）；Niels Bohr Institute, University of Copenhagen（哥本哈根大学尼尔斯·玻尔研究所）；Department of Space, Earth, & Environment, Chalmers University of Technology（查尔姆斯理工大学空间、地球与环境系）；NSF’s NOIRLab（美国国家科学基金会NOIR实验室）；Institute of Science and Technology Austria (ISTA)（奥地利科学与技术研究所）；IPAC, California Institute of Technology（加州理工学院IPAC）；Centre for Astrophysics and Supercomputing, Swinburne University of Technology（斯威本科技大学天体物理学与超级计算中心）
Identifying and characterising reionised bubbles enables us to track both their size distribution, which depends on the primary ionising sources, and the relationship between reionisation and galaxy evolution. We demonstrate that spectrally resolved $z\gtrsim6$ Lyman-alpha (Ly$α$) emission can constrain properties of reionised regions. Specifically, the distant from a source to a neutral region sets the minimum observable Ly$α$ velocity offset from systemic. Detection of flux on the blue side of the Ly$α$ resonance implies the source resides in a large, sufficiently ionised region that photons…
Nebular emission lines associated with galactic HII regions carry information about both physical properties of the ionised gas and the source of ionising photons as well as providing the opportunity of measuring accurate redshifts and thus distances once a cosmological model is assumed. While nebular line emission has been extensively studied at lower redshift there are currently only few constraints within the epoch of reionisation (EoR, $z>6$), chiefly due to the lack of sensitive near-IR spectrographs. However, this will soon change with the arrival of the Webb Telescope providing sensitiv…
A GLIMPSE into the very faint-end of the H$β$+[OIII]$λλ$4960,5008 luminosity function at z=7-9 behind Abell S1063
Observatoire de Genève, Université de Genève（日内瓦天文台，日内瓦大学）；Institut d’Astrophysique de Paris, CNRS, Sorbonne Université（巴黎天体物理研究所，法国国家科学研究中心，索邦大学）；Department of Physics, Ben-Gurion University of the Negev（内盖夫本-古里安大学物理系）；Department of Astronomy, The University of Texas at Austin（德克萨斯大学奥斯汀分校天文学系）；CNRS, IRAP（法国国家科学研究中心，天体物理研究所）；Department of Astronomy, Oskar Klein Centre, Stockholm University（斯德哥尔摩大学奥斯卡·克莱因中心天文学系）
Life After the Quasar: Overmassive Black Holes and Remnant Ionised Bubbles in and Around Two z~6.6 Galaxies
University of Geneva（日内瓦大学）；Niels Bohr Institute, University of Copenhagen（哥本哈根大学尼尔斯·玻尔研究所）；University College London（伦敦大学学院）；Heidelberg University（海德堡大学）；Max Planck Institut für Astronomie（马克斯·普朗克天文学研究所）；University of Hertfordshire（赫特福德大学）；Aix Marseille Université（艾克斯-马赛大学）；Institute of Science and Technology Austria (ISTA)（奥地利科学和技术研究所）
Quasar Impostors: Two Extremely UV-Bright ($M_{\rm UV}\approx-23.5$) Reionisation-Epoch Galaxies Powered by Very Massive Stars
Leiden University（莱顿大学）；University of California, Santa Barbara（加州大学圣塔芭芭拉分校）；Heidelberg University（海德堡大学）；Max-Planck-Institut für Astronomie（马克斯·普朗克天文学研究所）；University of California, Los Angeles（加州大学洛杉矶分校）
The epochs of cosmic dawn and reionisation present promising avenues for understanding the role of dark matter (DM) in our cosmos. The first galaxies that populated the Universe during these eras resided in DM halos that were much less massive than their counterparts today. Consequently, observations of such galaxies can provide us with a handle on the clustering of DM in an otherwise currently inaccessible regime. In this work, we use high-redshift UV galaxy luminosity-function (UV LF) data from the Hubble Space Telescope to study the clustering properties of DM at small scales. In particular…
21cmEMUv3: a hybrid diffusion-LSTM emulator of 21cmFAST summary observables
Research Center for the Early Universe, Graduate School of Science, The University of Tokyo（早期宇宙研究中心，东京大学研究生院）；Department of Physics, Graduate School of Science, The University of Tokyo（东京大学研究生院物理系）；Scuola Normale Superiore (SNS), Piazza dei Cavalieri 7, Pisa（普拉蒂亚学院（SNS），比萨）；Physics Department, Stellenbosch University（斯坦福博斯奇大学物理系）；Cosmic Dawn Center (DAWN)（黎明宇宙中心（DAWN））；Niels Bohr Institute, University of Copenhagen（哥本哈根大学尼尔斯·波尔研究所）；SISSA, Via Bonomea 265, 34136 Trieste（SISSA，特里斯特）；INFN Sezione di Trieste（INFN特里埃斯特分部）；Centro Nazionale di Ricerca in High Performance Computing, Big Data e Quantum Computing（高性能计算、大数据和量子计算国家研究中心）；Physics Department, Blackett Lab, Imperial College London（伦敦帝国理工学院布莱特实验室物理系）
