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We present the results of 300 pc resolution Atacama Large Millimeter/submillimeter Array imaging of the [O iii ] 88 μm line and dust continuum emission from a z = 8.312 Lyman-break galaxy MACS0416_Y1. The velocity-integrated [O iii ] emission has three peaks that are likely associated with three young stellar clumps of MACS0416_Y1, while the channel map shows a complicated velocity structure with little indication of a global velocity gradient unlike what was found in [C ii ] 158 μm at a larger scale, suggesting random bulk motion of ionized gas clouds inside the galaxy. In contrast, dust emission appears as two individual clumps apparently separating or bridging the [O iii ]/stellar clumps. The cross-correlation coefficient between dust and ultraviolet-related emission (i.e., [O iii ] and ultraviolet continuum) is unity on a galactic scale, while it drops at <1 kpc, suggesting well-mixed geometry of multiphase interstellar media on subkiloparsec scales. If the cutoff scale characterizes different stages of star formation, the cutoff scale can be explained by gravitational instability of turbulent gas. We also report on a kiloparsec-scale off-center cavity embedded in the dust continuum image. This could be a superbubble producing galactic-scale outflows, since the energy injection from the 4 Myr starburst suggested by a spectral energy distribution analysis is large enough to push the surrounding media creating a kiloparsec-scale cavity. [ABSTRACT FROM AUTHOR]

Feedback from supernovae (SNe) is an essential mechanism that self-regulates the growth of galaxies. We build an SN feedback model based on high-resolution simulations of superbubble and SN-driven outflows for the physical understanding of the galaxy–CGM connection. Using an Eulerian hydrodynamic code Athena++ , we find universal scaling relations for the time evolution of superbubble momentum, when the momentum and time are scaled by those at the shell-formation time. We then develop an SN feedback model utilizing Voronoi tessellation, and implement it into the GADGET3-Osaka smoothed particle hydrodynamic code. We show that our stochastic thermal feedback model produces galactic outflow that carries the metals high above the galactic plane but with weak suppression of star formation. Additional mechanical feedback further suppresses star formation. Therefore, we argue that both thermal and mechanical feedback is necessary for the SN feedback model of galaxy evolution when an individual SN bubble is unresolved. [ABSTRACT FROM AUTHOR]

We present a suite of high-resolution cosmological zoom-in simulations to z = 4 of a 1012M⊙ halo at z = 0, obtained using seven contemporary astrophysical simulation codes (A rt-I , E nzo , R amses , C hanga , G adget-3 , G ear , and G izmo) widely used in the numerical galaxy formation community. The physics prescriptions for gas cooling and heating and star formation are the same as the ones used in our previous Assembling Galaxies of Resolved Anatomy (AGORA) disk comparison but now account for the effects of cosmological processes such as the expansion of the universe, intergalactic gas inflow, and the cosmic ultraviolet background radiation emitted by massive stars and quasars. In this work, we introduce the most careful comparison yet of galaxy formation simulations run by different code groups, together with a series of four calibration steps each of which is designed to reduce the number of tunable simulation parameters adopted in the final run. In the first two steps, we methodically calibrate the gas physics, such as cooling and heating, in simulations without star formation. In the third step, we seek agreement on the total stellar mass produced with the common star formation prescription used in the AGORA disk comparison, in stellar-feedback-free simulations. In the last calibration step, we activate stellar feedback, where each code group is asked to set the feedback prescription to as close to the most widely used one in its code community as possible, while aiming for convergence in the stellar mass at z = 4 to the values predicted by semiempirical models. After all the participating code groups successfully complete the calibration steps, we achieve a suite of cosmological simulations with similar mass assembly histories down to z = 4. With numerical accuracy that resolves the internal structure of a target halo (≲100 physical pc at z = 4), we find that the codes overall agree well with one another, e.g., in gas and stellar properties, but also show differences, e.g., in circumgalactic medium (CGM) properties. We argue that, if adequately tested in accordance with our proposed calibration steps and common parameters, high-resolution cosmological zoom-in simulations can have robust and reproducible results. New code groups are invited to join and enrich this comparison by generating equivalent models or to test the code's compatibility on their own, by adopting the common initial conditions, the common easy-to-implement physics package, and the proposed calibration steps. Further analyses of the zoom-in simulations presented here will be presented in forthcoming reports from the AGORA Collaboration, including studies of the CGM, simulations by additional codes, and results at lower redshift. [ABSTRACT FROM AUTHOR]

We measure the scale dependence and redshift dependence of 21 cm line emitted from the neutral hydrogen gas at redshift 1 < |$z$| < 5 using full cosmological hydrodynamic simulations by taking the ratios between the power spectra of H  i –dark matter (DM) cross-correlation and DM autocorrelation. The neutral hydrogen distribution is computed in full cosmological hydrodynamic simulations including star formation and supernova feedback under a uniform ultraviolet background radiation. We find a significant scale dependence of H  i bias at |$z$| > 3 on scales of k ≳ 1 h  Mpc−1, but it is roughly constant at lower redshift |$z$| < 3. The redshift evolution of H  i bias is relatively slow compared to that of QSOs at similar redshift range. We also measure a redshift space distortion (RSD) of H  i gas to explore the properties of H  i clustering. Fitting to a widely applied theoretical prediction, we find that the constant bias is consistent with that measured directly from the real space power spectra, and the velocity dispersion is marginally consistent with the linear perturbation prediction. Finally, we compare the results obtained from our simulation and the Illustris simulation, and conclude that the detailed astrophysical effects do not affect the scale dependence of H  i bias very much, which implies that the cosmological analysis using 21 cm line of H  i will be robust against the uncertainties arising from small-scale astrophysical processes such as star formation and supernova feedback. [ABSTRACT FROM AUTHOR]

Recent observations with the Atacama Large Millimeter/submillimeter Array (ALMA) detected far-infrared emission lines such as the [O  iii ] |$88\,\mu \mathrm{ m}$| line from galaxies at z ∼ 7−9. We use a cosmological simulation of galaxy formation to study the physical properties of [O  iii ] |$88\,\mu \mathrm{ m}$| emitters. In a comoving volume of 50  h −1 Mpc on a side, we locate 34 galaxies with stellar masses greater than |$10^8\ \rm M_{\odot }$| at z = 9, and more than 270 such galaxies at z = 7. We calculate the [O  iii ] |$88\,\mu \mathrm{ m}$| luminosities (⁠|$L_{{\rm O\,{{\rm {\small{III}}}, 88}}}$|⁠) by combining a physical model of H  ii regions with emission line calculations using the photoionization code cloudy. We show that the resulting |$L_{{\rm O\,{{\rm {\small{III}}}, 88}}}$|⁠, for a given star formation rate, is slightly higher than predicted from the empirical relation for local galaxies, and is consistent with recent observations of galaxies at redshifts 7–9. Bright [O  iii ] emitters with |$L_{{\rm O\,{{\rm {\small{III}}}, 88}}}\gt 10^8\, \rm L_{\odot }$| have star formation rates higher than |$3\,\rm M_{\odot }\,{\rm yr}^{-1}$|⁠, and the typical metallicity is |${\sim } 0.1\, \rm Z_{\odot }$|⁠. The galaxies are hosted by dark matter haloes with masses greater than |$10^{11}\, \rm M_{\odot }$|⁠. We propose to use the [O  iii ] 5007 Å line, to be detected by James Webb Space Telescope, to study the properties of galaxies whose [O  iii ] |$88\,\mu \mathrm{ m}$| line emission has been already detected with ALMA. [ABSTRACT FROM AUTHOR]

ABSTRACT We use large cosmological smoothed particle hydrodynamics simulations to study the formation and evolution of submillimetre galaxies (SMGs). In our previous work, we studied the statistical properties of ultraviolet-selected star-forming galaxies at high redshifts. We populate the same cosmological simulations with SMGs by calculating the reprocessing of stellar light by dust grains into far-infrared to millimetre wavebands in a self-consistent manner. We generate light-cone outputs to compare directly the statistical properties of the simulated SMGs with available observations. Our model reproduces the submillimetre source number counts and the clustering amplitude. We show that bright SMGs with flux S > 1 mJy reside in haloes with masses of ∼1013 M⊙ and have stellar masses greater than 1011 M⊙. The angular cross-correlation between the SMGs and Lyman α emitters is significantly weaker than that between the SMGs and Lyman-break galaxies. The cross-correlation is also weaker than the autocorrelation of the SMGs. The redshift distribution of the SMGs shows a broad peak at z ∼ 2, where bright SMGs contribute significantly to the global cosmic star formation rate density. Our model predicts that there are hundreds of SMGs with S > 0.1 mJy at z > 5 per 1 deg2 field. Such SMGs can be detected by ALMA. [ABSTRACT FROM AUTHOR]

In the last decade, numerous Lyman α (Lyα) emitters (LAEs) have been discovered with narrow-band filters at various redshifts. Recently, multiwavelength observations of LAEs have been performed and revealed that while many LAEs appear to be young and less massive, a noticeable fraction of LAEs possess much older populations of stars and larger stellar mass. How these two classes of LAEs are concordant with the hierarchical galaxy formation scenario has not been understood clearly so far. In this paper, we model LAEs by three-dimensional cosmological simulations of dark halo merger in a Λ cold dark matter (ΛCDM) universe. As a result, it is shown that the age of simulated LAEs can spread over a wide range from to yr. Furthermore, we find that there are two types of LAEs, in one of which the young half-mass age is comparable to the mean age of stellar component, and in the other of which the young half-mass age is appreciably shorter than the mean age. We define the former as Type 1 LAEs and the latter as Type 2 LAEs. A Type 1 LAE corresponds to early starburst in a young galaxy, whereas a Type 2 LAE does to delayed starburst in an evolved galaxy, as a consequence of delayed accretion of a subhalo on to a larger parent halo. Thus, the same halo can experience a Type 2 LAE phase as well as a Type 1 LAE phase in the merger history. Type 1 LAEs are expected to be younger than yr, less dusty and less massive with stellar mass , while Type 2 LAEs are older than yr, even dustier and as massive as . The fraction of Type 2s in all LAEs is a function of redshift, which is less than 2 per cent at , ∼30 per cent at redshift and ∼70 per cent at . Type 2 LAEs can be discriminated clearly from Type 1s in two-colour diagrams of versus . We find that the brightness distribution of Lyα in Type 2 LAEs is more extended than the main stellar component, in contrast to Type 1 LAEs. This is not only because delayed starbursts tend to occur in the outskirts of a parent galaxy, but also because Lyα photons are effectively absorbed by dust in an evolved galaxy. Hence, the extent of Lyα emission may be an additional measure to distinguish Type 2 LAEs from Type 1 LAEs. The sizes of Type 2 LAEs range from a few tens to a few hundreds kpc. At lower redshifts, the number of more extended, older Type 2 LAEs increases. Furthermore, it is anticipated that the amplitude of angular correlation function for Type 2 LAEs is significantly higher than that for Type 1 LAEs, but comparable to that for Lyman break galaxies (LBGs). This implies that LBGs with strong Lyα line may include Type 2 LAEs. [ABSTRACT FROM AUTHOR]

We present cosmological hydrodynamic simulations performed to study the evolution of galaxy population. The simulations follow timed release of mass, energy, and metals by stellar evolution and employ phenomenological treatments of supernova feedback, pre-supernova feedback modeled as feedback by radiation pressure from massive stars, and quenching of gas cooling in large halos. We construct the fiducial model so that it reproduces the observationally estimated galaxy stellar mass functions and the relationships between the galaxy stellar mass and the host halo mass from z = 4 to 0. We find that the fiducial model constructed this way naturally explains the cosmic star-formation history, the galaxy downsizing, and the star-formation rate and metallicity of the star-forming galaxies. The simulations without the quenching of the gas cooling in large halos overproduce massive galaxies at z < 2 and fail to reproduce galaxy downsizing. The simulations that do not employ the radiation pressure feedback from young stars predict too strong redshift evolution of the mass–metallicity relation. Furthermore, the slope of the relation becomes too steep at low redshift without the radiation pressure feedback. The metallicity dependence in the radiation pressure feedback is a key to explain the observed mass–metallicity relation. These facts indicate that these two processes in addition to supernova feedback are essential for galaxy evolution. Our simple phenomenological model is suitable to construct a mock galaxy sample to study physical properties of observed galaxy populations. [ABSTRACT FROM PUBLISHER]

Recently discovered large-scale structure of Lyman α emitters (LAEs) raises a novel challenge to the cold dark matter (CDM) cosmology. The structure is extended over more than 50 Mpc at redshift , and exhibits a considerably weak angular correlation. Such properties of LAE distributions appear to be incompatible with the standard biased galaxy formation scenario in the CDM cosmology. In this Letter, by considering the possibility that LAEs are short-lived events, we attempt to build up the picture of LAEs concordant with the CDM cosmology. We find that if the lifetime of LAEs is as short as , the distributions of simulated galaxies successfully match the extension and morphology of large-scale structure of LAEs at , and also the weak angular correlation function. This result implies that LAEs at do not necessarily reside in high density peaks, but tends to be located in less dense regions, in a different way from the expectation by the standard biased galaxy formation scenario. In addition, we make a prediction for the angular correlation function of LAEs at redshifts higher than 3. It is found that the prediction deviates from that made by the standard biased galaxy formation scenario even at redshifts . [ABSTRACT FROM AUTHOR]