We investigated the ultraviolet (UV) spectral properties of faint Lyman-α emitters (LAEs) in the redshift range 2.9 ≤ z ≤ 4.6, and we provide material to prepare future observations of the faint Universe. We used data from the MUSE Hubble Ultra Deep Survey to construct mean rest-frame spectra of continuum-faint (median M UV of −18 and down to M UV of −16), low stellar mass (median value of 10 8.4 M and down to 10 7 M) LAEs at redshift z 3. We computed various averaged spectra of LAEs, subsampled on the basis of their observational (e.g., Lyα strength, UV magnitude and spectral slope) and physical (e.g., stellar mass and starformation rate) properties. We searched for UV spectral features other than Lyα, such as higher ionization nebular emission lines and absorption features. We successfully observed the O iii]λ1666 and [C iii]λ1907+C iii]λ1909 collisionally excited emission lines and the He iiλ1640 recombination feature, as well as the resonant C ivλλ1548,1551 doublet either in emission or P-Cygni. We compared the observed spectral properties of the different mean spectra and find the emission lines to vary with the observational and physical properties of the LAEs. In particular, the mean spectra of LAEs with larger Lyα equivalent widths, fainter UV magnitudes, bluer UV spectral slopes, and lower stellar masses show the strongest nebular emission. The line ratios of these lines are similar to those measured in the spectra of local metal-poor galaxies, while their equivalent widths are weaker compared to the handful of extreme values detected in individual spectra of z > 2 galaxies. This suggests that weak UV features are likely ubiquitous in high z, lowmass, and faint LAEs. We publicly released the stacked spectra, as they can serve as empirical templates for the design of future observations, such as those with the James Webb Space Telescope and the Extremely Large Telescope.
We present an ultraviolet quasar absorption line analysis of metal lines associated with three strong intervening H I absorbers (with N(H I) > 10 16.5 cm −2 ) detected in the outskirts of Sunyaev-Zel'dovich (SZ) effect-selected galaxy clusters (z cl ∼ 0.4 − 0.5), within clustocentric impact parameters of ρ cl ∼ (1.6 − 4.7)r 500 . Discovered in a recent set of targeted far-UV HST/COS spectroscopic observations, these absorbers have the highest H I column densities ever observed in the outskirts of galaxy clusters, and are also rich in metal absorption lines. Photoionization models yield single phase solutions for the three absorbers with gas densities of n H ∼ 10 −3 − 10 −4 cm −3 and metallicities of [X/H] > -1.0 (from one-tenth solar to near-solar). The widths of detected absorption lines suggest gas temperatures of T ∼ 10 4 K. The inferred densities (temperatures) are significantly higher (lower) compared to the X-ray emitting intracluster medium in cluster cores. The absorbers are tracing a cool phase of the intracluster gas in the cluster outskirts, either associated with gas stripped from cluster galaxies via outflows, tidal streams or ram-pressure forces, or denser regions within the intracluster medium that were uniformly chemically enriched from an earlier epoch of enhanced supernova and AGN feedback.
The magnitude of spectral transmittance and reflectance is affected by the presence of inhomogeneity and interfacial roughness. Therefore, the methods, based on the magnitude of spectral transmittance and reflectance, are not adequate for the determination of thickness and optical constants of films with inhomogeneity and interfacial roughness. The present article proposes a method for the determination of thickness and refractive index using only the positions of the interference fringes in spectral transmittance and reflectance at two different angles of incidence. The proposed method is verified through numerical simulations, which result in <1% error for the film thickness. The complete parametrical dependence of spectral transmittance and reflectance of inhomogeneous film with rough interfaces on a substrate have been worked out for the film on transparent and opaque substrates, respectively. The spectrum envelopes have been solved simultaneously and the mathematical formulae are given for the determination of spectral scattering due to inhomogeneity and interfacial roughness for both transmittance and reflectance cases.
There have been many different models proposed for the luminescence in porous silicon (PS), yet it is believed that the quantum confinement effect persists at the absorption. However, from our investigation on both constant and pulsed electrochemically etched silicon (PS), the absence of quantum confinement effect at the absorption has been identified from the close correspondence of photoluminescence excitation (PLE) spectra of PS to the simulated absorption spectrum of an ultrathin silicon film with the bulk optical constants. In the simulation of absorption spectrum, the spectral dependence of reflectivity of the solid, which had been omitted in the traditional analysis of PLE, is considered. Further, although nanocrystallites of silicon are present in the PS matrix, the absence of quantum confinement is explained on the basis of structural characteristics of PS. Following that, many common observations in the luminescence of PS are attributed to the surface states. The blueshift of the PL peak with the increase in excitation energy is explained with the idea of quasithermal equilibrium and the probability of occupation of the carriers at the surface states.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.