We present a size analysis of a sample of ∼49,000 galaxies from the Cosmic Assembly Near-infrared Deep Extragalactic Survey GOODS North and South fields, using redshift-independent relative ...surface-brightness metrics to determine an unbiased measure of the differential size evolution of galaxies at 1 ≤ z ≤ 7. We introduce a novel method of removing foreground objects from distant galaxy (z > 3) images that makes use of the Lyman break at 912 , in what we call "2D Lyman-break imaging." The images used are in the rest-frame optical at z < 3 and progressively bluer bands at z > 3. They are therefore subject to K-correction and cosmological dimming effects, which are tested and corrected for. We separately consider a mass-selected sample (with masses in the range 109M ≤ M* ≤ 1010.5M ) and a number-density-selected sample (using a constant number density of n = 1 × 10−4Mpc−3). Instead of utilizing the commonly used, but potentially biased, effective radii for size measurements, we measure the redshift-independent Petrosian radius, defined by the parameter , for each galaxy for three values of , and use this as a proxy for size. The evolution of the measured radii can be described by a power law of the form RPetr = (1+z)β kpc where β < 0. We find that the outer radius increases more rapidly, suggesting that as a galaxy grows, mass is added to its outer regions via an inside-out growth. This growth is stronger for the number-density-selected sample, with a growth rate of nearly three in the outer radii compared to the inner. We test and confirm these results using a series of image simulations.
ABSTRACT
We study the ionizing photon production efficiency at the end of the Epoch of Reionization (z ∼ 5.4 − 6.6) for a sample of 30 Ly α emitters. This is a crucial quantity to infer the ionizing ...photon budget of the universe. These objects were selected to have reliable spectroscopic redshifts, assigned based on the profile of their Ly α emission line, detected in the MUSE deep fields. We exploit medium-band observations from the JWST Extragalactic Medium-band Survey (JEMS) to find the flux excess corresponding to the redshifted Hα emission line. We estimate the ultraviolet (UV) luminosity by fitting the full JEMS photometry, along with several HST photometric points, with Prospector. We find a median UV continuum slope of $\beta = -2.09^{+0.23}_{-0.21}$, indicating young stellar populations with little-to-no dust attenuation. Supported by this, we derive ξion,0 with no dust attenuation and find a median value of log$\frac{\xi _{ion,0}}{\text{Hz erg}^{-1}} = 25.44^{+0.21}_{-0.15}$. If we perform dust attenuation corrections and assume a Calzetti attenuation law, our values are lowered by ∼0.1 dex. Our results suggest Ly α emitters at the Epoch of Reionization have slightly enhanced ξion,0 compared to previous estimations from literature, in particular, when compared to the non-Ly α emitting population. This initial study provides a promising outlook on the characterization of ionizing photon production in the early universe. In the future, a more extensive study will be performed on the entire data set provided by the JWST Advanced Deep Extragalactic Survey (JADES). Thus, for the first time, allowing us to place constraints on the wider galaxy populations driving reionization.
ABSTRACT
We use deep imaging from the JWST Advanced Deep Extragalactic Survey (JADES) to study the evolution of the ionizing photon production efficiency, ξion. We estimate ξion for a sample of 677 ...galaxies at z ∼ 4–9 using NIRCam (Near-Infrared Camera) photometry. Specifically, combinations of the medium and wide bands F335M–F356W and F410M–F444W to constrain emission lines that trace ξion: Hα and O iii. Additionally, we use the spectral energy distribution fitting code prospector to fit all available photometry and infer galaxy properties. The flux measurements obtained via photometry are consistent with FRESCO (First Reionisation Epoch Spectroscopic Complete Survey) and NIRSpec-derived fluxes. Moreover, the emission-line-inferred measurements are consistent with the prospector estimates. We also confirm the observed ξion trend with redshift and MUV, and find: log ξion(z, MUV) = (0.05 ± 0.02)z + (0.11 ± 0.02)MUV + (27.33 ± 0.37). We use prospector to investigate correlations of ξion with other galaxy properties. We see a clear correlation between ξion and burstiness in the star formation history of galaxies, given by the ratio of recent to older star formation, where burstiness is more prevalent at lower stellar masses. We also convolve our ξion relations with luminosity functions from the literature, and constant escape fractions of 10 per cent and 20 per cent, to place constraints on the cosmic ionizing photon budget. By combining our results, we find that if our sample is representative of the faint low-mass galaxy population, galaxies with bursty star formation are efficient enough in producing ionizing photons and could be responsible for the reionization of the Universe.
The Epoch of Reionization (EoR) began when galaxies grew in abundance and luminosity, so their escaping Lyman continuum (LyC) radiation started ionizing the surrounding neutral intergalactic medium ...(IGM). Despite significant recent progress, the nature and role of cosmic reionizers are still unclear: in order to define them, it would be necessary to directly measure their LyC escape fraction ( f esc ). However, this is impossible during the EoR due to the opacity of the IGM. Consequently, many efforts at low and intermediate redshift have been made to determine measurable indirect indicators in high-redshift galaxies so that their f esc can be predicted. This work presents the analysis of the indirect indicators of 62 spectroscopically confirmed star-forming galaxies at 6 ≤ z ≤ 9 from the Cosmic Evolution Early Release Science (CEERS) survey, combined with 12 sources with public data from other JWST-ERS campaigns. From the NIRCam and NIRSpec observations, we measured their physical and spectroscopic properties. We discovered that on average 6 < z < 9 star-forming galaxies are compact in the rest-frame UV ( r e ∼ 0.4 kpc), are blue sources (UV- β slope ∼ − 2.17), and have a predicted f esc of about 0.13. A comparison of our results to models and predictions as well as an estimation of the ionizing budget suggests that low-mass galaxies with UV magnitudes fainter than M 1500 = −18 that we currently do not characterize with JWST observations probably played a key role in the process of reionization.
Air overpressure is a critical negative effect of blasting in construction or production sites and projects. So far, many attempts have been made to prevent or reduce this negative effect on the ...nearby construction, equipment, or people. While various experiential equations have been proposed to forecast the air overpressure value for determining the blasting area, these models are typically inaccurate and impractical. Due to the recent efforts to predict the air overpressure by employing artificial intelligence techniques, this study developed five support vector machine-based models optimized by some praised optimization techniques, including the moth flame optimization, particle swarm optimization, grey wolf optimization, cuckoo optimization algorithm, and whale optimization algorithm. These algorithms optimize the most important parameters of the support vector machine, including “C” and “gamma”, and improve the performance of this model for air overpressure prediction. The findings showed that the moth flame optimization algorithm is the best optimizer for support vector machine and is suitable for air overpressure prediction. The support vector machine–moth flame optimization model achieved the best
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2
(train: 0.9939; test: 0.9941) and comprehensive score (34). On the other hand, the worst model was the support vector machine–particle swarm optimization, which achieved the lowest comprehensive score (13). In addition, all optimization techniques improved the performance of the single support vector machine model. The findings of this study imply that all optimization techniques successfully enhanced the performance of the support vector machine model; however, the moth flame optimization optimizer was the most effective one. The support vector machine–moth flame optimization technique can be employed to solve other mining-related issues.
The resonant scattering interaction between photons and neutral hydrogen implies that a partially neutral intergalactic medium has the ability to significantly impact the detectability of emission in ...galaxies. Thus, the redshift evolution of the equivalent width distribution of galaxies offers a key observational probe of the degree of ionization during the Epoch of Reionization (EoR). Previous in-depth investigations at $z$ geq 7 were limited by ground-based instrument capabilities. We present an extensive study of the evolution of emission from galaxies at 4.5 < $z$ < 8.5, observed as part of the CEERS and JADES surveys in the JWST NIRSpec/PRISM configuration. The sample consists of 235 galaxies in the redshift range of 4.1 < $z$ < 9.9. We identified 65 of them as emitters. We first measured the escape fractions from to Balmer line flux ratios and explored the correlations with the inferred galaxies' physical properties, which are similar to those found at lower redshift. We also investigated the possible connection between the escape of photons and the inferred escape fractions of LyC photons obtained from indirect indicators, finding no secure correlation. We then analyzed the redshift evolution of the emitter fraction, finding lower average values at $z$ = 5 and 6 compared to previous ground-based observations. At $z$ = 7, the GOODS-S results are aligned with previous findings, whereas the visibility in the EGS field appears to be enhanced. This discrepancy in visibility between the two fields could potentially be attributed to the presence of early reionized regions in the EGS. Such a broad variance is also expected in the Cosmic Dawn II radiation-hydrodynamical simulation. The average emitter fraction obtained from the CEERS+JADES data continues to increase from $z$ = 5 to 7, ultimately declining at $z$ = 8. This suggests a scenario in which the ending phase of the EoR is characterized by sim 1 pMpc ionized bubbles around a high fraction of moderately bright galaxies. Finally, we characterize such two ionized regions found in the EGS at $z$ = 7.18 and $z$ = 7.49 by estimating the radius of the ionized bubble that each of the spectroscopically-confirmed members could have created.
The resonant scattering interaction between Ly$\alpha$ photons and neutral
hydrogen implies that a partially neutral IGM can significantly impact the
detectability of Ly$\alpha$ emission in galaxies. ...The redshift evolution of the
Ly$\alpha$ equivalent width distribution of galaxies thus offers a key probe of
the degree of ionization during the Epoch of Reionization (EoR). Previous
in-depth investigations at $z$ $\geq$ 7 were limited by ground-based instrument
capabilities. We present an extensive study of Ly$\alpha$ emission from
galaxies at 4 < $z$ < 8.5, observed from the CEERS and JADES surveys in the
JWST NIRSpec/PRISM configuration. The sample consists of 235 galaxies, among
which we identify 65 as Ly$\alpha$ emitters. We first measure Ly$\alpha$ escape
fractions from Balmer lines, and explore the correlations with the inferred
galaxies' physical properties, which are similar to those found at lower
redshift. We also investigate the possible connection between the escape of
Ly$\alpha$ photons and the inferred escape fractions of LyC photons obtained
from indirect indicators. We then analyze the redshift evolution of the
Ly$\alpha$ emitter fraction, finding lower average values at $z$ = 5 and 6
compared to ground-based observations. At $z$ = 7 we find a very large
difference in Ly$\alpha$ visibility between the EGS and GOODS-South fields,
possibly due to the presence of early reionized regions in the EGS. Such large
variance is also expected in the Cosmic Dawn II radiation-hydrodynamical
simulation. Our findings suggest a scenario in which the ending phase of the
EoR is characterized by $\sim$ 1 pMpc ionized bubbles around a high fraction of
moderately bright galaxies. Finally, we characterize such two ionized regions
found in the EGS at $z$ = 7.18 and $z$ = 7.49 by estimating the radius of the
ionized bubble that each of the spectroscopically-confirmed members could have
created.
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