Search

A limiting systematic effect in 21-cm interferometric experiments is the chromaticity due to the coupling between the sky and the instrument. This coupling is sourced by the instrument primary beam; therefore it is important to know the beam to extremely high precision. Here we demonstrate how known beam uncertainties can be characterized using databases of beam models. In this introductory work, we focus on beam errors arising from physically offset and/or broken antennas within a station. We use the public code OSKAR to generate an "ideal" SKA beam formed from 256 antennas regularly-spaced in a 35-m circle, as well as a large database of "perturbed" beams sampling distributions of broken/offset antennas. We decompose the beam errors ("ideal" minus "perturbed") using Principal Component Analysis (PCA) and Kernel PCA (KPCA). Using 20 components, we find that PCA/KPCA can reduce the residual of the beam in our datasets by 60-90% compared with the assumption of an ideal beam. Using a simulated observation of the cosmic signal plus foregrounds, we find that assuming the ideal beam can result in 1% error in the EoR window and 10% in the wedge of the 2D power spectrum. When PCA/KPCA is used to characterize the beam uncertainties, the error in the power spectrum shrinks to below 0.01% in the EoR window and, 12 pages, 9 main figures

The final phase of the reionization process can be probed by rest-frame UV absorption spectra of quasars at z>6, shedding light on the properties of the diffuse intergalactic medium within the first Gyr of the Universe. The ESO Large Programme "XQR-30: the ultimate XSHOOTER legacy survey of quasars at z~5.8-6.6" dedicated ~250 hours of observations at the VLT to create a homogeneous and high-quality sample of spectra of 30 luminous quasars at z~6, covering the rest wavelength range from the Lyman limit to beyond the MgII emission. Twelve quasar spectra of similar quality from the XSHOOTER archive were added to form the enlarged XQR-30 sample, corresponding to a total of ~350 hours of on-source exposure time. The median effective resolving power of the 42 spectra is R~11400 and 9800 in the VIS and NIR arm, respectively. The signal-to-noise ratio per 10 km/s pixel ranges from ~11 to 114 at $\lambda \simeq 1285$ \AA rest frame, with a median value of ~29. We describe the observations, data reduction and analysis of the spectra, together with some first results based on the E-XQR-30 sample. New photometry in the H and K bands are provided for the XQR-30 quasars, together with composite spectra whose characteristics reflect the large absolute magnitudes of the sample. The composite and the reduced spectra are released to the community through a public repository, and will enable a range of studies addressing outstanding questions regarding the first Gyr of the Universe., Comment: 21 pages, 10 figures. Final version accepted by MNRAS

We present new [O III] 88 ${\rm \mu}$m observations of five bright $z \sim 7$ Lyman-break galaxies spectroscopically confirmed by ALMA through the [C II] 158 ${\rm \mu}$m line, unlike recent [O III] detections where Lyman-${\rm \alpha}$ was used. This nearly doubles the sample of Epoch of Reionisation galaxies with robust ($5 \sigma$) detections of [C II] and [O III]. We perform a multi-wavelength comparison with new deep HST images of the rest-frame UV, whose compact morphology aligns well with [O III] tracing ionised gas. By contrast, we find more spatially extended [C II] emission likely produced in neutral gas, as indicated by a [N II] 205 ${\rm \mu}$m non-detection in one source. We find a positive correlation between the equivalent width of the optical [O III] and H${\rm \beta}$ lines and the [O III]/[C II] ratio, as seen in local metal-poor dwarf galaxies. Cloudy models of a nebula of typical density harbouring a young stellar population with a high ionisation parameter appear to adequately reproduce the far-infrared lines. Surprisingly, however, our models fail to reproduce the strength of [O III] 88 ${\rm \mu}$m, unless we assume an ${\rm \alpha}$/Fe enhancement and a near-solar nebular oxygen abundance. On spatially resolved scales, we find [O III]/[C II] shows a tentative anti-correlation with infrared excess, $L_{\rm IR}/L_{\rm UV}$, also seen on global scales in the local Universe. Finally, we introduce the far-infrared spectral energy distribution fitting code MERCURIUS to show that dust-continuum measurements of one source appear to favour a low dust temperature coupled with a high dust mass. This implies a high stellar metallicity yield and may point towards the need of dust production or grain-growth mechanisms beyond supernovae., Comment: 23 pages, 11 figures. Accepted for publication in Monthly Notices of the Royal Astronomical Society

Aims. We investigate the ionizing properties of the pair of bright Lyα emitting galaxies BDF521 and BDF2195 at z = 7.012 in order to constrain their contribution to the formation of the Bremer Deep Field (BDF) ‘reionized bubble’ in which they have been shown to reside. Methods. We obtain constraints on four UV emission lines (the CIVλ1548 doublet, HeIIλ1640, the OIII]λ1660 doublet, and the CIII]λ1909 doublet) from deep VLT X-shooter observations and compare them to those available for other high-redshift objects, and to models with mixed stellar and active galactic nucleus (AGN) emission. We use this spectroscopic information, together with the photometry available in the field, to constrain the physical properties of the two objects using the spectro-photometric fitting code BEAGLE. Results. We do not detect any significant emission at the expected position of the UV lines, with 3σ upper limits of equivalent width (EW) ≲2–7 Å rest-frame. We find that the two objects have a lower CIII] emission than expected on the basis of the correlation between the Lyα and CIII] EWs. The EW limits on CIV and HeII emission exclude pure AGN templates at ∼2 − 3σ significance, and only models with a ≲40% AGN contribution are compatible with the observations. The two objects are found to be relatively young (∼20–30 Myrs) and metal-poor (≲0.3 Z⊙), with stellar masses of a few 109 M⊙. Their production rate of hydrogen ionizing photons per intrinsic UV luminosity is log(ξion*/Hz erg−1) = 25.02–25.26, consistent with values typically found in high-redshift galaxies, but more than twice lower than values measured in z > 7 galaxies with strong CIII] and/or optical line emission (≃25.6–25.7). Conclusions. The two BDF emitters show no evidence of higher-than-average ionizing capabilities and are not capable of reionizing their surroundings by their own means, under realistic assumptions of the escape fraction of ionizing photons. Therefore, a dominant contribution to the formation of the reionized bubble must have been provided by fainter companion galaxies. The capabilities of the James Webb Space Telescope will be needed for spectroscopic confirmation of these objects.

Cosmic 21cm interferometry is set to revolutionize our understanding of the Epoch of Reionization (EoR) and the Cosmic Dawn (CD). However, the signal has structure on a huge range of scales, requiring large simulation boxes to statistically capture the relevant fields. In this work we quantify the minimum box size for simulating the power spectrum (PS) of the cosmic 21cm signal. We perform multiple realizations of the initial conditions, for a range of box sizes. We quantify convergence with respect to a mock observation of box length 1.1 Gpc, with thermal noise computed for a 1000h observation with SKA1-low. We find that simulations of box lengths 200-300 Mpc underestimate the large-scale power during the CD by ~7-9 % on average. We conclude that box lengths of $L\gtrsim250$ Mpc are needed to converge at the level of, Comment: 9 pages, 6 figures, published in MNRAS

The presence of excess scatter in the Ly-$\alpha$ forest at $z\sim 5.5$, together with the existence of sporadic extended opaque Gunn-Peterson troughs, has started to provide robust evidence for a late end of hydrogen reionisation. However, low data quality and systematic uncertainties complicate the use of Ly-$\alpha$ transmission as a precision probe of reionisation's end stages. In this paper, we assemble a sample of 67 quasar sightlines at $z>5.5$ with high signal-to-noise ratios of $>10$ per $\leq 15$ km s$^{-1}$ spectral pixel, relying largely on the new XQR-30 quasar sample. XQR-30 is a large program on VLT/X-Shooter which obtained deep (SNR $>20$ per pixel) spectra of 30 quasars at $z>5.7$. We carefully account for systematics in continuum reconstruction, instrumentation, and contamination by damped Ly-$\alpha$ systems. We present improved measurements of the mean Ly-$\alpha$ transmission over $4.93.5 \sigma$). Our results indicate that reionisation-related fluctuations, whether in the UVB, residual neutral hydrogen fraction, and/or IGM temperature, persist in the intergalactic medium until at least $z=5.3$ ($t=1.1$ Gyr after the Big Bang). This is further evidence for a late end to reionisation., Comment: Accepted for publication in MNRAS. Full measurement datasets are available on the first author's website

Bright, high-redshift (z > 6) QSOs are powerful probes of the ionization state of the intervening intergalactic medium (IGM). The detection of Ly α damping wing absorption imprinted in the spectrum of high-z QSOs can provide strong constraints on the epoch of reionization (EoR). In this work, we perform an independent Ly α damping wing analysis of two known z > 7 QSOs; DESJ0252−0503 at z= 7.00 (Wang etal.) and J1007+2115 at z= 7.51 (Yang etal.). For this, we utilize our existing Bayesian framework which simultaneously accounts for uncertainties in: (i) the intrinsic Ly α emission profile (reconstructed from a covariance matrix of measured emission lines; extended in this work to include N v) and (ii) the distribution of ionized (H ii) regions within the IGM using a 1.63 Gpc3 reionization simulation. This approach is complementary to that used in the aforementioned works as it focuses solely redward of Ly α (1218 < λ < 1230 Å) making it more robust to modelling uncertainties while also using a different methodology for (i) and (ii). We find, for an EoR morphology driven by galaxies within Mh ≳ 109 M⊙ haloes, x¯HI=0.64+0.19−0.23 (68per cent) at z= 7 and x¯HI=0.27+0.21−0.17 at z= 7.51 consistent within 1σ to the previous works above, though both are slightly lower in amplitude. Following the inclusion of N v into our reconstruction pipeline, we perform a reanalysis of ULASJ1120+0641 at z= 7.09 (Mortlock etal.) and ULASJ1342+0928 at z= 7.54 (Bañados etal.) finding x¯HI=0.44+0.23−0.24 at z= 7.09 and x¯HI=0.31+0.18−0.19 at z= 7.54. Finally, we combine the QSO damping wing constraints for all four z ≳ 7 QSOs to obtain a single, unified constraint of x¯HI=0.49+0.11−0.11 at z= 7.29.

Recent work has shown that UV-luminous reionization-era galaxies often exhibit strong Lyman-alpha emission despite being situated at redshifts where the IGM is thought to be substantially neutral. It has been argued that this enhanced Ly α transmission reflects the presence of massive galaxies in overdense regions which power large ionized bubbles. An alternative explanation is that massive galaxies shift more of their Ly α profile to large velocities (relative to the systemic redshift) where the IGM damping wing absorption is reduced. Such a mass-dependent trend is seen at lower redshifts, but whether one exists at z ∼ 7 remains unclear owing to the small number of existing systemic redshift measurements in the reionization era. This is now changing with the emergence of [C ii]-based redshifts from ALMA. Here, we report MMT/Binospec Ly α spectroscopy of eight UV-bright (MUV ∼ −22) galaxies at z ≃ 7 selected from the ALMA REBELS survey. We detect Ly α in four of eight galaxies and use the [C ii] systemic redshifts to investigate the Ly α velocity profiles. The Ly α lines are significantly redshifted from systemic (average velocity offset = 223 km s–1) and broad (FWHM ≈ 300–650 km s−1), with two sources showing emission extending to ≈750 km s−1. We find that the broadest Ly α profiles are associated with the largest [C ii] line widths, suggesting a potential link between the Ly α FWHM and the dynamical mass. Since Ly α photons at high velocities transmit efficiently through the z = 7 IGM, our data suggest that velocity profiles play a significant role in boosting the Ly α visibility of the most UV-luminous reionization-era galaxies.

Interferometry of the cosmic 21-cm signal is set to revolutionise our understanding of the Epoch of Reionisation (EoR) and the Cosmic Dawn (CD). The culmination of ongoing efforts will be the upcoming Square Kilometre Array (SKA), which will provide tomography of the 21-cm signal from the first billion years of our Universe. Using a galaxy formation model informed by high-$z$ luminosity functions, here we forecast the accuracy with which the first phase of SKA-low (SKA1-low) can constrain the properties of the unseen galaxies driving the astrophysics of the EoR and CD. We consider three observing strategies: (i) deep (1000h on a single field); (ii) medium-deep (100hr on 10 independent fields); and (iii) shallow (10hr on 100 independent fields). Using the 21-cm power spectrum as a summary statistic, and conservatively only using the 21-cm signal above the foreground wedge, we predict that all three observing strategies should recover astrophysical parameters to a fractional precision of $\sim 0.1$ -- 10 per cent. The reionisation history is recovered to an uncertainty of $\Delta z \lesssim 0.1$ (1$\sigma$) for the bulk of its duration. The medium-deep strategy, balancing thermal noise against cosmic variance, results in the tightest constraints, slightly outperforming the deep strategy. The shallow observational strategy performs the worst, with up to a $\sim 10$ -- 60 per cent increase in the recovered uncertainty. We note, however, that non-Gaussian summary statistics, tomography, as well as unbiased foreground removal would likely favour the deep strategy., Comment: 10 pages, 2 figures, submitted to MNRAS, comments welcome

We investigate the [CII] line intensity mapping (IM) signal from galaxies in the Epoch of Reionization (EoR) to assess its detectability, the possibility to constrain the $L_{\rm CII}-{\rm SFR}$ relation, and to recover the [CII] luminosity function (LF) from future experiments. By empirically assuming that ${\rm log}L_{\rm CII}={\rm log}A+\gamma {\rm SFR}\pm\sigma_L$, we derive the [CII] LF from the observed UV LF, and the [CII] IM power spectrum. We study the shot-noise and the full power spectrum separately. Although, in general, the shot-noise component has a much higher signal-to-noise ratio than the clustering one, it cannot be used to put independent constraints on log$A$ and $\gamma$. Full power spectrum measurements are crucial to break such degeneracy, and reconstruct the [CII] LF. In our fiducial survey S1 (inspired by CCAT-p/1000 hr) at $z \sim 6$, the shot-noise (clustering) signal is detectable for 2 (1) of the 5 considered $L_{\rm CII}-{\rm SFR}$ relations. The shot-noise is generally dominated by galaxies with $L_{\rm CII}\gtrsim 10^{8-9}~L_\odot$ ($M_{\rm UV}\sim-20$ to $-22$), already at reach of ALMA pointed observations. However, given the small field of view of such telescope, an IM experiment would provide unique information on the bright-end of the LF. The detection depth of an IM experiment crucially depends on the (poorly constrained) $L_{\rm CII}-{\rm SFR}$ relation in the EoR. If the $L_{\rm CII}-{\rm SFR}$ relation varies in a wide log$A - \gamma$ range, but still consistent with ALMA [CII] LF upper limits, even the signal from galaxies with $L_{\rm CII}$ as faint as $\sim 10^7~L_\odot$ could be detectable. Finally, we consider the contamination by continuum foregrounds (CIB, dust, CMB) and CO interloping lines, and derived the requirements on the residual contamination level to reliably extract the [CII] signal., Comment: 17 pages, 17 Figures. Accepted for publication in MNRAS. Comments welcome

Imaging the cosmic 21 cm signal will map out the first billion years of our Universe. The resulting 3D lightcone (LC) will encode the properties of the unseen first galaxies and physical cosmology. Here, we build on previous work using neural networks (NNs) to infer astrophysical parameters directly from 21 cm LC images. We introduce recurrent neural networks (RNNs), capable of efficiently characterizing the evolution along the redshift axis of 21 cm LC images. Using a large database of simulated cosmic 21 cm LCs, we compare the relative performance in parameter estimation of different network architectures. These including two types of RNNs, which differ in their complexity, as well as a more traditional convolutional neural network (CNN). For the ideal case of no instrumental effects, our simplest and easiest to train RNN performs the best, with a mean squared parameter estimation error (MSE) that is lower by a factor of $\ge 2$ compared with the other architectures studied here, and a factor of $\ge 8$ lower than the previously-studied CNN. We also corrupt the cosmic signal by adding noise expected from a 1000 h integration with the Square Kilometre Array, as well as excising a foreground-contaminated 'horizon wedge'. Parameter prediction errors increase when the NNs are trained on these contaminated LC images, though recovery is still good even in the most pessimistic case (with $R^2 \ge 0.5-0.95$). However, we find no notable differences in performance between network architectures on the contaminated images. We argue this is due to the size of our data set, highlighting the need for larger data sets and/or better data augmentation in order to maximize the potential of NNs in 21 cm parameter estimation., 15 pages, 11 figures, updated to match the version published in MNRAS, minor changes

We study radiation pressure due to Ly α line photons, obtaining and exploring analytical expressions for the force-multiplier, MF(NH, Z) = Fα/(Lα/c), as a function of gas column density, NH, and metallicity, Z, for both dust-free and dusty media, employing a WKB approach for the latter case. Solutions for frequency offset emission to emulate non-static media moving with a bulk velocity v have also been obtained. We find that, in static media, Ly α pressure dominates over both photoionization and dust-mediated UV radiation pressure in a very wide parameter range (16 < log NH < 23; −4 < log [Z/Z⊙] < 0). For example, it overwhelms the other two forces by $\lower.5ex\hbox{$\,\, \buildrel\gt \over \sim \,\,$}10$ (300) times in standard (low-Z) star-forming clouds. Thus, in agreement with previous studies, we conclude that Ly α pressure plays a dominant role in the initial acceleration of the gas around luminous sources, and must be implemented in galaxy formation, evolution and outflow models and simulations.

The very first galaxies that started the cosmic dawn likely resided in so-called "minihaloes", with masses of $\sim10^5$-$10^8\mathrm{M}_\odot$, accreting their gas from the intergalactic medium through H$_2$ cooling. Such molecularly cooled galaxies (MCGs) mostly formed in pristine environments, hosted massive, metal-free stars, and were eventually sterilized by the build-up of a disassociating (Lyman-Werner; LW) background. Therefore, their properties might be very different from the galaxies we see in the later Universe. Although MCGs are probably too faint to be observed directly, we could nevertheless infer their properties from the imprint they leave in the cosmic 21-cm signal. Here we quantify this imprint by extending the public simulation code 21cmFAST to allow for a distinct population of MCGs. We allow MCGs to have different properties from other galaxies, including unique scaling relations for their stellar-to-halo mass ratios, ionizing escape fractions, and spectral energy distributions. We track inhomogeneous recombinations, disassociative LW feedback, and photoheating from reionization. After demonstrating how MCGs can shape the 21-cm signal, we explore to what extent current observations can already place constraints on their properties. The cosmic microwave background optical depth from Planck sets an upper limit on the product of the ionizing escape fraction and the stellar mass in MCGs. When including also the timing of the putative EDGES absorption signal, we find an additional strong degeneracy between the stellar mass and the X-ray luminosity of MCGs. If proven to be of cosmic origin, the timing of the EDGES signal would have been set by MCGs., 19 pages, 8 figures, 1 table; Updated to match the published version. Only minor changes

In the light of the recent Planck downward revision of the electron scattering optical depth, and of the discovery of a faint AGN population at $z > 4$, we reassess the actual contribution of quasars to cosmic reionization. To this aim, we extend our previous MCMC-based data-constrained semi-analytic reionization model and study the role of quasars on global reionization history. We find that, the quasars can alone reionize the Universe only for models with very high AGN emissivities at high redshift. These models are still allowed by the recent CMB data and most of the observations related to HI reionization. However, they predict an extended and early HeII reionization ending at $z\gtrsim4$ and a much slower evolution in the mean HeII Ly-$\alpha$ forest opacity than what the actual observation suggests. Thus when we further constrain our model against the HeII Ly-$\alpha$ forest data, this AGN-dominated scenario is found to be clearly ruled out at 2-$\sigma$ limits. The data seems to favour a standard two-component picture where quasar contributions become negligible at $z\gtrsim6$ and a non-zero escape fraction of $\sim10\%$ is needed from early-epoch galaxies. For such models, mean neutral hydrogen fraction decreases to $\sim10^{-4}$ at $z=6.2$ from $\sim0.8$ at $z=10.0$ and helium becomes doubly ionized at much later time, $z\sim3$. We find that, these models are as well in good agreement with the observed thermal evolution of IGM as opposed to models with very high AGN emissivities., Comment: 10 pages, MNRAS, accepted

Using a series of high-resolution hydrodynamical simulations we show that during the rapid growth of high-redshift (z > 5) galaxies, reserves of molecular gas are consumed over a time-scale of 300Myr, almost independent of feedback scheme. We find that there exists no such simple relation for the total gas fractions of these galaxies, with little correlation between gas fractions and specific star formation rates. The bottleneck or limiting factor in the growth of early galaxies is in converting infalling gas to cold star-forming gas. Thus, we find that the majority of high redshift dwarf galaxies are effectively in recession, with demand (of star formation) never rising to meet supply (of gas), irrespective of the baryonic feedback physics modelled. We conclude that the basic assumption of self-regulation in galaxies - that they can adjust total gas consumption within a Hubble time - does not apply for the dwarf galaxies thought to be responsible for providing most UV photons to reionize the high redshift Universe. We demonstrate how this rapid molecular time-scale improves agreement between semi-analytic model predictions of the early Universe and observed stellar mass functions., 17 pages, 27 figures, accepted for publication in MNRAS, minor updates to align with final published version

The transitional phase between the Middle and the Late Bronze Age in Northern Mesopotamia is difficult to define, both from a historical and an archaeological perspective. This paper seeks to address the main issues in the identification of diagnostic ceramic features for this phase, by comparing the evidence from the Erbil plain with the data gathered from surveys and excavations in the Middle and Upper Tigris region (i.e. Yorgan Tepe, Tell Rimah, Tell Billa) and in the Syrian Jazirah (i.e. Tell Brak, Tell Bderi and Tell Barri). Through the analysis of the ceramic assemblages coming from the Kurdistan Region of Iraq and their comparison with materials belonging to better known stratified sequences, I will focus on the diagnostic features characterizing the pottery repertoire during the Middle Bronze Age - Late Bronze Age transition.

We present a model for the formation of the first galaxies before and after the reionization of hydrogen in the early universe. In this model, galaxy formation can only take place in dark matter haloes whose mass exceeds a redshift-dependent critical value, which, before reionization, is equal (in the simplest case) to the mass at which atomic hydrogen cooling becomes effective and, after reionization, is equal to the mass above which gas cannot remain in hydrostatic equilibrium. We define the Halo Occupation Fraction (HOF) as the fraction of haloes that host a luminous galaxy as a function of halo mass. The HOF is established by the interplay between the evolution of the critical mass and the assembly history of haloes and depends on three factors: the minimum halo mass for galaxy formation before reionization, the redshift of reionization, and the intensity of the (evolving) external photoheating rate. Our fiducial model predicts a cutoff in the galaxy mass function at a present-day halo mass, $M_{200} \sim 3\times 10^{8} M_{\odot}$; 100\% occupation at $M_{200} > 5\times 10^9 M_{\odot}$; and a population of starless gaseous haloes of present-day mass in the range $10^{6} \lesssim M_{200} / M_{\odot}\lesssim 5\times 10^{9}$, in which the gas is in thermal equilibrium with the ultraviolet background radiation and in hydrostatic equilibrium in the gravitational potential of the halo. The transition between HOF = 0 and HOF=1 reflects the stochastic nature of halo mass growth. We explore how these characteristic masses vary with model assumptions and parameter values. The results of our model are in excellent agreement with cosmological hydrodynamic simulations of galaxy formation., Accepted for publication in MNRAS

Using science verification observations obtained with ESPRESSO at the Very Large Telescope (VLT) in 4UT mode, we report the first bound on the carbon isotope ratio 12C/13C of a quiescent, near-pristine damped Ly-alpha (DLA) system at z=2.34. We recover a limit log10(12C/13C) > +0.37 (2 sigma). We use the abundance pattern of this DLA, combined with a stochastic chemical enrichment model, to infer the properties of the enriching stars, finding the total gas mass of this system to be log10(M_gas/M_sun)=6.3+1.4-0.9 and the total stellar mass to be log10(M_*/M_sun)=4.8+/-1.3. The current observations disfavour enrichment by metal-poor Asymptotic Giant Branch (AGB) stars with masses 1 Gyr after the cosmic reionization of hydrogen and, despite its very low metallicity (~1/1000 of solar), this DLA appears to have formed most of its stars in the past few hundred Myr. Combining the inferred star formation history with evidence that some of the most metal-poor DLAs display an elevated [C/O] ratio at redshift z, 13 pages, 8 figures, submitted to MNRAS

We present new HST/WFC3 observations and re-analyse VLT data to unveil the continuum, variability and rest-frame UV lines of the multiple UV clumps of the most luminous Ly$\alpha$ emitter at z=6.6, CR7. Our re-reduced, flux calibrated X-SHOOTER spectra of CR7 reveal a HeII emission line in observations obtained along the major axis of Lyman-alpha (Lya) emission with the best seeing conditions. HeII is spatially offset by +0.8'' from the peak of Lya emission, and it is found towards clump B. Our WFC3 grism spectra detects the UV continuum of CR7's clump A, yielding a power law with $\beta=-2.5^{+0.6}_{-0.7}$ and $M_{UV}=-21.87^{+0.25}_{-0.20}$. No significant variability is found for any of the UV clumps on their own, but there is tentative (~2.2$\sigma$) brightening of CR7 in F110W as a whole from 2012 to 2017. HST grism data fail to robustly detect rest-frame UV lines in any of the clumps, implying fluxes, Comment: 22 pages, 12 figures. Accepted for publication in MNRAS. Reduced data used in the paper will be available with the final published paper in MNRAS

We introduce 21CMMC: a parallelized, Monte Carlo Markov Chain analysis tool, incorporating the epoch of reionization (EoR) seminumerical simulation 21CMFAST. 21CMMC estimates astrophysical parameter constraints from 21 cm EoR experiments, accommodating a variety of EoR models, as well as priors on model parameters and the reionization history. To illustrate its utility, we consider two different EoR scenarios, one with a single population of galaxies (with a mass-independent ionizing efficiency) and a second, more general model with two different, feedback-regulated populations (each with mass-dependent ionizing efficiencies). As an example, combining three observations (z=8, 9 and 10) of the 21 cm power spectrum with a conservative noise estimate and uniform model priors, we find that interferometers with specifications like the Low Frequency Array/Hydrogen Epoch of Reionization Array (HERA)/Square Kilometre Array 1 (SKA1) can constrain common reionization parameters: the ionizing efficiency (or similarly the escape fraction), the mean free path of ionizing photons and the log of the minimum virial temperature of star-forming haloes to within 45.3/22.0/16.7, 33.5/18.4/17.8 and 6.3/3.3/2.4 per cent, ~$1\sigma$ fractional uncertainty, respectively. Instead, if we optimistically assume that we can perfectly characterize the EoR modelling uncertainties, we can improve on these constraints by up to a factor of ~few. Similarly, the fractional uncertainty on the average neutral fraction can be constrained to within $\lesssim10$ per cent for HERA and SKA1. By studying the resulting impact on astrophysical constraints, 21CMMC can be used to optimize (i) interferometer designs; (ii) foreground cleaning algorithms; (iii) observing strategies; (iv) alternative statistics characterizing the 21 cm signal; and (v) synergies with other observational programs., Comment: Accepted to MNRAS, matches online version. 20 pages, 4 tables, 11 colour figures

The properties of the first galaxies, expected to drive the Cosmic Dawn (CD) and the Epoch of Reionization (EoR), are encoded in the 3D structure of the cosmic 21-cm signal. Parameter inference from upcoming 21-cm observations promises to revolutionize our understanding of these unseen galaxies. However, prior inference was done using models with several simplifying assumptions. Here we introduce a flexible, physically-motivated parametrization for high-$z$ galaxy properties, implementing it in the public code 21cmFAST. In particular, we allow their star formation rates and ionizing escape fraction to scale with the masses of their host dark matter halos, and directly compute inhomogeneous, sub-grid recombinations in the intergalactic medium. Combining current Hubble observations of the rest-frame UV luminosity function (UV LFs) at high-$z$ with a mock 1000h 21-cm observation using the Hydrogen Epoch of Reionization Arrays (HERA), we constrain the parameters of our model using a Monte Carlo Markov Chain sampler of 3D simulations, 21CMMC. We show that the amplitude and scaling of the stellar mass with halo mass is strongly constrained by LF observations, while the remaining galaxy properties are constrained mainly by 21-cm observations. The two data sets compliment each other quite well, mitigating degeneracies intrinsic to each observation. All eight of our astrophysical parameters are able to be constrained at the level of $\sim 10\%$ or better. The updated versions of 21cmFAST and 21CMMC used in this work are publicly available., Comment: 16 pages, 8 figures and 2 tables. Associated movies are available at http://homepage.sns.it/mesinger/21CMMC.html. Updated to match the published version. All results and conclusions remain unchanged

THESEUS is a space mission concept aimed at exploiting Gamma-Ray Bursts for investigating the early Universe and at providing a substantial advancement of multi-messenger and time-domain astrophysics. These goals will be achieved through a unique combination of instruments allowing GRB and X-ray transient detection over a broad field of view (more than 1sr) with 0.5¿1 arcmin localization, an energy band extending from several MeV down to 0.3¿keV and high sensitivity to transient sources in the soft X-ray domain, as well as on-board prompt (few minutes) follow-up with a 0.7¿m class IR telescope with both imaging and spectroscopic capabilities. THESEUS will be perfectly suited for addressing the main open issues in cosmology such as, e.g., star formation rate and metallicity evolution of the inter-stellar and intra-galactic medium up to redshift 10, signatures of Pop III stars, sources and physics of re-ionization, and the faint end of the galaxy luminosity function. In addition, it will provide unprecedented capability to monitor the X-ray variable sky, thus detecting, localizing, and identifying the electromagnetic counterparts to sources of gravitational radiation, which may be routinely detected in the late ¿20s/early ¿30s by next generation facilities like aLIGO/ aVirgo, eLISA, KAGRA, and Einstein Telescope. THESEUS will also provide powerful synergies with the next generation of multi-wavelength observatories (e.g., LSST, ELT, SKA, CTA, ATHENA).© 2018 COSPAR, S.E. acknowledges the financial support from contracts ASI-INAF 1/009/10/0, NARO15 ASI-INAF 1/037/12/0 and ASI 2015-046-R.0. R.H. acknowledges GACR grant 13-33324S. S.V. research leading to these results has received funding from the European Union's Seventh Framework Programme for research, technological development and demonstration under grant agreement no 606176. D.S. was supported by the Czech grant 1601116S GA CR. Maria Giovanna Dainotti acknowledges funding from the European Union through the Marie Curie Action FP7-PEOPLE-2013-IOF, under grant agreement No. 626267 (>Cosmological Candles>).

We study cross-correlations of the kinetic Sunyaev-Zel'dovich effect (kSZ) and 21 cm signals during the epoch of reionisation (EoR) to measure the effects of patchy reionisation. Since the kSZ effect is proportional to the line-of-sight velocity, the kSZ-21 cm cross correlation suffers from cancellation at small angular scales. We thus focus on the correlation between the kSZ-squared field (kSZ$^2$) and 21 cm signals. When the global ionisation fraction is low ($x_e\lesssim 0.7$), the kSZ$^2$ fluctuation is dominated by rare ionised bubbles which leads to an anti-correlation with the 21 cm signal. When $0.8\lesssim x_e, 7pages, 7 figures

We present first results from radio observations with the Murchison Widefield Array seeking to constrain the power spectrum of 21 cm brightness temperature fluctuations between the redshifts of 11.6 and 17.9 (113 and 75 MHz). 3 h of observations were conducted over two nights with significantly different levels of ionospheric activity. We use these data to assess the impact of systematic errors at low frequency, including the ionosphere and radio-frequency interference, on a power spectrum measurement. We find that after the 1–3 h of integration presented here, our measurements at the Murchison Radio Observatory are not limited by RFI, even within the FM band, and that the ionosphere does not appear to affect the level of power in the modes that we expect to be sensitive to cosmology. Power spectrum detections, inconsistent with noise, due to fine spectral structure imprinted on the foregrounds by reflections in the signal-chain, occupy the spatial Fourier modes where we would otherwise be most sensitive to the cosmological signal. We are able to reduce this contamination using calibration solutions derived from autocorrelations so that we achieve an sensitivity of 104 mK on comoving scales k ≲ 0.5 h Mpc[superscript −1]. This represents the first upper limits on the 21 cm power spectrum fluctuations at redshifts 12 ≲ z ≲ 18 but is still limited by calibration systematics. While calibration improvements may allow us to further remove this contamination, our results emphasize that future experiments should consider carefully the existence of and their ability to calibrate out any spectral structure within the EoR window., National Science Foundation (U.S.) (AST-0457585), National Science Foundation (U.S.) (AST-0821321), National Science Foundation (U.S.) (AST-1105835), National Science Foundation (U.S.) (AST-1410719), National Science Foundation (U.S.) (AST-1410484), National Science Foundation (U.S.) (AST-1411622), National Science Foundation (U.S.) (AST-1440343), National Science Foundation (U.S.) (1122374), National Science Foundation (U.S.) (PHY-0835713), National Science Foundation (U.S.) (CAREER-0847753), National Science Foundation (U.S.) (AST-0908884), United States. Air Force Office of Scientific Research (FA9550-0510247)

We investigate the clustering properties of Lyman-break galaxies (LBGs) at $z\sim6$ - $8$. Using the semi-analytical model {\scshape Meraxes} constructed as part of the Dark-ages Reionization And Galaxy-formation Observables from Numerical Simulation (DRAGONS) project, we predict the angular correlation function (ACF) of LBGs at $z\sim6$ - $8$. Overall, we find that the predicted ACFs are in good agreement with recent measurements at $z\sim 6$ and $z\sim 7.2$ from observations consisting of the Hubble eXtreme Deep Field (XDF), the Hubble Ultra-Deep Field (HUDF) and Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) field. We confirm the dependence of clustering on luminosity, with more massive dark matter haloes hosting brighter galaxies, remains valid at high redshift. The predicted galaxy bias at fixed luminosity is found to increase with redshift, in agreement with observations. We find that LBGs of magnitude $M_{\rm AB(1600)} < -19.4$ at $6\lesssim z \lesssim 8$ reside in dark matter haloes of mean mass $\sim 10^{11.0}$- $10^{11.5} M_{\rm \odot}$, and this dark matter halo mass does not evolve significantly during reionisation., 14 pages, 10 figures, published in MNRAS

In the conventional traditional literature the life of ancient polis demonstrates its last of the antique city-characteristics during the late antique and/or early Byzantine periods. This period came to an end in the seventh century first by the Persian attacks, later by the Arab invasions. The uniterraupted warfare and consequently a growing need for defence and security turned polis into a small, fortified units, i.e. the so-called medieval kastron. Although this common view has some truth and legitimacy, it still provides a quite simplified and incomplete model about the transformation of the Byzantine cities. Therefore this pioneer study analyses causes and factors which effect this transformation of polis and in the meantime it also epitomizes related topics from a political, social and economic point of views stretching from the late antique to the end of early Middle Ages. In this context the ancient city of Amorium as the model of medieval urban city and its urbanite topographies and its architecture provide the perfect example illustrating this phenomenon. Suna&İnan Kıraç Akdeniz Medeniyetleri Araştırma Merkezi, AKMED İÇİNDEKİLER: KABUL VE ONAY……………………………………………………...………..i BİLDİRİM……………………………………………………………...…………ii YAYIMLAMA VE FİKRİ MÜLKİYET HAKLARI BEYANI…………..……..iii ETİK BEYAN………………………………………….………………………....iv TEŞEKKÜR…………………………………………………………..…………...v ÖZET……………………………………………………………………………..vi ABSTRACT……………………………………………………………………..vii İÇİNDEKİLER …………………………………………………………...…….viii KISALTMALAR DİZİNİ………………………………………………………....x İTHAF……………………………………………………………………..…..….xi GİRİŞ…………………………………………………………………………….1 1. GEÇ ANTİK DÖNEMDE ROMA İMPARATORLUĞU…………………….4 1.1. ÜÇÜNCÜ YÜZYIL KRİZİ……………………………………………….5 1.2. GEÇ ROMA İDARESİ…………………………………………………....7 1.3. EKONOMİ………………………………………………………………...9 1.3.1. Toprak Yönetimi…………………………………………………...16 1.3.2. Mali Organizasyon………………………………………………....23 1.3.3. Geç Antik Dönemde Vergi Organizasyonu………………………..25 1.4. POLİS……………………………………………………………………………….29 1.4.1. Polis İdaresi………………………………………………………..31 1.4.2. Polis Organizasyonunun Çözülmesi……………………………….33 1.4.3. Geç Antik Dönemde Polis…………………………………………36 1.4.4. Geç Antik Dönem Kentinin Sonu………………………………….38 1.5. DEĞERLENDİRME ve SONUÇ…………………………………………41 2. KARANLIK ÇAĞDA BİZANS İMPARATORLUĞU……………………....44 2.1. TARİHSEL ve EKONOMİK GELİŞMELER…………………………....45 2.2. THEMA SİSTEMİ………………………………………………………....49 2.2.1. Themanın Gelişimi………………………………………………....51 2.2.2. Thema Organizasyonu……………………………………………...58 2.2.3. Thema Sisteminin Sonu………………………………………….....61 2.3. EKONOMİ………………………………………………………………...63 2.3.1. Toprak Yönetimi…………………………………………………....71 2.3.2. Vergi Sistemi……………………………………………………….75 2.4. DÖNÜŞEN KENT: ORTAÇAĞ BİZANS KENTLEŞMESİ ve KENTSEL CANLANMA……………………………………………..………..…..…..79 2.5. DEĞERLENDİRME ve SONUÇ……………………………..…………...87 3. AMORİUM……………………………………………………….……………90 3.1. GEÇ ANTİK DÖNEMDE AMORİUM…………………………..……….93 3.2. KARANLIK ÇAĞDA AMORİUM…………………………….…………96 3.3. ÜST KENT…………………………………………………………….....102 3.4. ALT KENT………………………………………………………….…....105 3.4.1. Alt Kent Surları…………………………………………………...108 3.4.2. Hamam……………………………………………………………112 3.4.3. Kapalı Alan……………………………………………………….119 3.4.4. Bazilikal Kilise……………………………………………………125 3.5. DEĞERLENDİRME ve SONUÇ………………………………………..136 SEÇİLMİŞ BİBLİOGRAFYA……………………………………………….141 AMORİUM İÇİN BİBLİOGRAFYA………………………………………..150 EK 1. ORJİNALLİK RAPORU EK 2. ETİK KURUL İZİN MUAFİYET FORMU Geleneksel literatürde geç antik dönem ve/veya erken Bizans dönemi antik kent yaşamı ve özelliklerinin son dönemi sayılmaktadır. Genel anlayışa göre yedinci yüzyılda ilk olarak Pers ve ardından Arap akınları nedeniyle antik kent yaşamı sona ermiştir. Sürekli savaş durumu ve artan savunma ihtiyacı antik polisi küçük, surlu, kastron denilen Ortaçağ kent tipine dönüştürmüştür. Bu genel görüş kısmen doğru ve geçerli olmasına rağmen, Bizans kentlerinin dönüşümü konusunda halen oldukça basitleştirilmiş ve eksik bir model sunmaktadır. Buradan hareket ederek tez çalışması, antik kentlerin dönüşümüne etki eden faktörleri analiz etmeye çalışmıştır. Aynı zamanda geç antik dönemden erken Ortaçağ’ın sonuna kadar olan evreyi politik, sosyal ve ekonomik yönlerini de ele alarak değerlendirmiştir. Konuyla ilgili öncü bir çalışma sayılabilecek olan tez bu bağlamda, bir Ortaçağ kent modeli olarak antik Amorium’un topografyası ve mimari yapılarını söz konusu kentsel dönüşüme örnek olarak ele almıştır.

Direct detection of regions of ionized hydrogen (HII) has been suggested as a promising probe of cosmic reionization. Observing the redshifted 21-cm signal of hydrogen from the epoch of reionization (EoR) is a key scientific driver behind new-generation, low-frequency radio interferometers. We investigate the feasibility of combining low-frequency observations with the Square Kilometre Array and near infra-red survey data of the Wide-Field Infrared Survey Telescope to detect cosmic reionization by imaging HII bubbles surrounding massive galaxies during the cosmic dawn. While individual bubbles will be too small to be detected, we find that by stacking redshifted 21-cm spectra centred on known galaxies, it will be possible to directly detect the EoR at $z \sim 9-12$, and to place qualitative constraints on the evolution of the spin temperature of the intergalactic medium (IGM) at $z \geq 9$. In particular, given a detection of ionized bubbles using this technique, it is possible to determine if the IGM surrounding them is typically in absorption or emission. Determining the globally-averaged neutral fraction of the IGM using this method will prove more difficult due to degeneracy with the average size of HII regions., Comment: 14 pages, 11 figures, 2 tables, published in MNRAS. Updated to match published version. Additional results and comments added from previous version. All other results and conclusions remain unchanged

We present the results of ALMA spectroscopic follow-up of a z = 6.766 Lyα emitting galaxy behind the cluster RX J1347.1-1145. We report the detection of [C II] 158 μm line fully consistent with the Lyα redshift and with the peak of the optical emission. Given the magnification of μ = 5.0 ± 0.3, the intrinsic (corrected for lensing) luminosity of the [C II] line is L [C II] = {1.4}-0.3+0.2× {10}7 {L}☉ , roughly ∼5 times fainter than other detections of z ∼ 7 galaxies. The result indicates that low L [C II] in z ∼ 7 galaxies compared to the local counterparts might be caused by their low metallicities and/or feedback. The small velocity offset ({{∆ }}v={20}-40+140 {km} {{{s}}}-1) between the Lyα and [C II] line is unusual, and may be indicative of ionizing photons escaping. These observations are based on the following ALMA data: ADS/JAO.ALMA#2015.1.00091.S. They are also associated with programs Spitzer #90009, 60034, 00083, 50610, 03550, 40593, and HST # GO10492, GO11591, GO12104, and GO13459. Furthermore based on multi-year KECK programs.

The Hydrogen Epoch of Reionization Array (HERA) is a staged experiment to measure 21 cm emission from the primordial intergalactic medium (IGM) throughout cosmic reionization ($z=6-12$), and to explore earlier epochs of our Cosmic Dawn ($z\sim30$). During these epochs, early stars and black holes heated and ionized the IGM, introducing fluctuations in 21 cm emission. HERA is designed to characterize the evolution of the 21 cm power spectrum to constrain the timing and morphology of reionization, the properties of the first galaxies, the evolution of large-scale structure, and the early sources of heating. The full HERA instrument will be a 350-element interferometer in South Africa consisting of 14-m parabolic dishes observing from 50 to 250 MHz. Currently, 19 dishes have been deployed on site and the next 18 are under construction. HERA has been designated as an SKA Precursor instrument. In this paper, we summarize HERA's scientific context and provide forecasts for its key science results. After reviewing the current state of the art in foreground mitigation, we use the delay-spectrum technique to motivate high-level performance requirements for the HERA instrument. Next, we present the HERA instrument design, along with the subsystem specifications that ensure that HERA meets its performance requirements. Finally, we summarize the schedule and status of the project. We conclude by suggesting that, given the realities of foreground contamination, current-generation 21 cm instruments are approaching their sensitivity limits. HERA is designed to bring both the sensitivity and the precision to deliver its primary science on the basis of proven foreground filtering techniques, while developing new subtraction techniques to unlock new capabilities. The result will be a major step toward realizing the widely recognized scientific potential of 21 cm cosmology., Comment: 26 pages, 24 figures, 2 tables

QSO near-zones are an important probe of the the ionization state of the IGM at z ~ 6-7, at the end of reionization. We present here high-resolution cosmological 3D radiative transfer simulations of QSO environments for a wide range of host halo masses, 10$^{10-12.5}$ M_sun. Our simulated near-zones reproduce both the overall decrease of observed near-zone sizes at 6 < z < 7 and their scatter. The observable near-zone properties in our simulations depend only very weakly on the mass of the host halo. The size of the H II region expanding into the IGM is generally limited by (super-)Lyman Limit systems loosely associated with (low-mass) dark matter haloes. This leads to a strong dependence of near-zone size on direction and drives the large observed scatter. In the simulation centred on our most massive host halo, many sightlines show strong red damping wings even for initial volume averaged neutral hydrogen fractions as low as ~ 10$^{-3}$. For QSO lifetimes long enough to allow growth of the central supermassive black hole while optically bright, we can reproduce the observed near-zone of ULAS J1120+0641 only with an IGM that is initially neutral. Our results suggest that larger samples of z > 7 QSOs will provide important constraints on the evolution of the neutral hydrogen fraction and thus on how late reionization ends., Comment: This is a pre-copyedited, author-produced PDF of an article accepted for publication in MNRAS following peer review. 19 pages, 17 figures and 3 tables

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved, We use a compilation of star formation histories (SFHs) and cosmological simulations to explore the impact of cosmic reionization on nearby isolated dwarf galaxies. Nearby dwarfs show a wide diversity of SFHs; from ancient systems that completed their star formation (SF) ~10 Gyr ago to young dwarfs that formed themajority of their stars in the past~5Gyr to 'twocomponent' systems characterized by the overlap of old and young stars. As an ensemble, SF in nearby dwarfs dips to lower-than-average rates at intermediate times (4, This work was supported in part by the National Science Foundation under Grant No. PHYS-1066293. Our collaboration has been supported by DFG grants GO 563/21-1 and GO 563/24-1 as well as by CONICET. ABL, JFN and MGA aknowledge support from ANPCyT grant PICT2012-1137. GY acknowledges financial support from MINECO under research grants AYA2012-31101. FPA2012-34694 and MultiDark CSD2009-00064. YH has been partially supported by the Israel Science Foundation (13/08)

How does a society assimilate a foreign religious tradition, transforming it while simultaneously being transformed by it? My project explores the process of assimilation of Buddhism in Tibet during the so-called Dark Age period (842-978 CE) with this central question in mind. While traditional Tibetan historiography considers this era as one of intellectual decline that witnessed the almost complete disappearance of Buddhism from Tibet, my research will argue that the Dark Age was, instead, one of the most creative and transformational periods for the assimilation of Buddhism in the region. At the center of this creative process of assimilation during this period we find the emergence of the Great Perfection tradition, a Tibetan reinterpretation of Buddhist doctrine and practice that rejected the complex and antinomian tantric practices that were so popular during the early introduction of Buddhism in Tibet (7th-9th centuries). I will use as evidence for my research the single largest philosophical treatise written by a Tibetan scholar that has survived from this period, The Lamp for the Eye in Meditation (Tib. bsam gtan mig sgron), a doxography authored by the 10th century scholar, Nupchen Sangyé Yeshé (Tib. gNubs chen sangs rgyas ye shes), which contradicts many traditional assumptions about this period