Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userFirst Light And Reionisation Epoch Simulations (FLARES) II: The Photometric Properties of High-Redshift Galaxies
74
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We present the photometric properties of galaxies in the First Light and Reionisation Epoch Simulations (FLARES). The simulations trace the evolution of galaxies in a range of overdensities through the Epoch of Reionistion (EoR). With a novel weighting scheme we combine these overdensities, extending significantly the dynamic range of observed composite distribution functions compared to periodic simulation boxes. FLARES predicts a significantly larger number of intrinsically bright galaxies, which can be explained through a simple model linking dust-attenuation to the metal content of the interstellar medium, using a line-of-sight (LOS) extinction model. With this model we present the photometric properties of the FLARES galaxies for $z in [5,10]$. We show that the ultraviolet (UV) luminosity function (LF) matches the observations at all redshifts. The function is fit by Schechter and double power-law forms, with the latter being favoured at these redshifts by the FLARES composite UV LF. We also present predictions for the UV continuum slope as well as the attenuation in the UV. The impact of environment on the UV LF is also explored, with the brightest galaxies forming in the densest environments. We then present the line luminosity and equivalent widths of some prominent nebular emission lines arising from the galaxies, finding rough agreement with available observations. We also look at the relative contribution of obscured and unobscured star formation, finding comparable contributions at these redshifts.
rate research
Read More
We introduce the First Light And Reionisation Epoch Simulations (FLARES), a suite of zoom simulations using the EAGLE model. We resimulate a range of overdensities during the Epoch of Reionisation (EoR) in order to build composite distribution functions, as well as explore the environmental dependence of galaxy formation and evolution during this critical period of galaxy assembly. The regions are selected from a large $(3.2 ;mathrm{cGpc})^{3}$ parent volume, based on their overdensity within a sphere of radius $14,h^{-1};mathrm{cMpc}$. We then resimulate with full hydrodynamics, and employ a novel weighting scheme that allows the construction of composite distribution functions that are representative of the full parent volume. This significantly extends the dynamic range compared to smaller volume periodic simulations. We present an analysis of the galaxy stellar mass function (GSMF), the star formation rate distribution function (SFRF) and the star forming sequence (SFS) predicted by flares, and compare to a number of observational and model constraints. We also analyse the environmental dependence over an unprecedented range of overdensity. Both the GSMF and the SFRF exhibit a clear double-Schechter form, up to the highest redshifts ($z = 10$). We also find no environmental dependence of the SFS normalisation. The increased dynamic range probed by FLARES will allow us to make predictions for a number of large area surveys that will probe the EoR in coming years, such as WFIRST and Euclid.
Using the First Light And Reionisation Epoch Simulations (textsc{Flares}) we explore the dust driven properties of massive high-redshift galaxies at $zin[5,10]$. 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-$beta$ 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 galaxies, which are extremely biased towards the most overdense regions. We see that the textsc{Flares} IRX-$beta$ relation (for $5le zle8$) predominantly follows the local starburst relation. The IRX shows an increase with stellar mass, plateauing at the high-mass end ($sim10^{10}$M$_{odot}$) and shows no evolution in the median normalisation with redshift. We also look at the dependence of the peak dust temperature (T$_{mathrm{peak}}$) on various galaxy properties including the stellar mass, IR luminosity and sSFR, finding the correlation to be strongest with sSFR. The luminosity-weighted dust temperatures increase towards higher redshifts, with the slope of the T$_{mathrm{peak}}$ - redshift relation showing a higher slope than the lower redshift relations obtained from previous observational and theoretical works. The results from textsc{Flares}, which is able to provide a better statistical sample of high-redshift galaxies compared to other simulations, provides a distinct vantage point for the high-redshift Universe.
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 the evolution of three galaxies and their ionising efficiency. We found that the variability of $f_{esc}$ follows that of the star formation rate. We then discuss the consequences of this variability on the observability of such galaxies by JWST.
We calculate the observable properties of the most massive high-redshift galaxies in the hierarchical formation scenario where stellar spheroid and supermassive black hole growth are fueled by gas-rich mergers. Combining high-resolution hydrodynamical simulations of the hierarchical formation of a z~6 quasar, stellar population synthesis models, template AGN spectra, prescriptions for interstellar and intergalactic absorption, and the response of modern telescopes, the photometric evolution of galaxies destined to host z~6 quasars are modeled at redshifts z~4-14. These massive galaxies, with enormous stellar masses of M_star ~10^11.5-10^12 M_sun. and star formation rates of SFR~10^3-10^4 M_sun yr^-1 at z>~7, satisfy a variety of photometric selection criteria based on Lyman-break techniques including V-band dropouts at z>~5, i-band dropouts at z>~6, and z-band dropouts at z>~7. The observability of the most massive high-redshift galaxies is assessed and compared with a wide range of existing and future photometric surveys including SDSS, GOODS/HUDF, NOAO WDFS, UKIDSS, the IRAC Shallow Survey, Pan-STARRS, LSST, and SNAP. Massive stellar spheroids descended from z~6 quasars will likely be detected at z~4 by existing surveys, but owing to their low number densities the discovery of quasar progenitor galaxies at z>7 will likely require future surveys of large portions of the sky (>~0.5%) at wavelengths lambda>1 micron. The detection of rare, star-bursting, massive galaxies at redshifts z>~6 would provide support for the hierarchical formation of the earliest quasars and characterize the primitive star-formation histories of the most luminous elliptical galaxies.
We present new deep ALMA and HST/WFC3 observations of MASOSA and VR7, two luminous Ly$alpha$ emitters (LAEs) at $z=6.5$, for which the UV continuum level differ by a factor four. No IR dust continuum emission is detected in either, indicating little amounts of obscured star formation and/or high dust temperatures. MASOSA, with a UV luminosity M$_{1500}=-20.9$, compact size and very high Ly$alpha$ EW$_{0}approx145$ A, is undetected in [CII] to a limit of L$_{rm [CII]}<2.2times10^7$ L$_{odot}$ implying a metallicity $Zlesssim0.07 Z_{odot}$. Intriguingly, our HST data indicates a red UV slope $beta=-1.1pm0.7$, at odds with the low dust content. VR7, which is a bright (M$_{1500}=-22.4$) galaxy with moderate color ($beta=-1.4pm0.3$) and Ly$alpha$ EW$_0 = 34$ A, is clearly detected in [CII] emission (S/N=15). VR7s rest-frame UV morphology can be described by two components separated by $approx1.5$ kpc and is globally more compact than the [CII] emission. The global [CII]-UV ratio indicates $Zapprox0.2 Z_{odot}$, but there are large variations in the UV-[CII] ratio on kpc scales. We also identify diffuse, possibly outflowing, [CII]-emitting gas at $approx 100$ km s$^{-1}$ with respect to the peak. VR7 appears assembling its components at a slightly more evolved stage than other luminous LAEs, with outflows already shaping its direct environment at $zsim7$. Our results further indicate that the global [CII]-UV relation steepens at SFR $<30$ M$_{odot}$ yr$^{-1}$, naturally explaining why the [CII]-UV ratio is anti-correlated with Ly$alpha$ EW in many, but not all, observed LAEs.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
