ﻻ يوجد ملخص باللغة العربية
We present observations with the Cosmic Origins Spectrograph onboard the Hubble Space Telescope of eight compact star-forming galaxies at redshifts z=0.02811-0.06540, with low oxygen abundances 12+log(O/H)=7.43-7.82 and extremely high emission-line flux ratios O32=[OIII]5007/[OII]3727~22-39, aiming to study the properties of Ly-alpha emission in such conditions. We find a diversity in Ly-alpha properties. In five galaxies Ly-alpha emission line is strong, with equivalent width (EW) in the range 45-190A. In the remaining galaxies, weak Ly-alpha emission with EW(Ly-alpha)~2-7A is superposed on a broad Ly-alpha absorption line, indicating a high neutral hydrogen column density N(HI)~(1-3)x10^21 cm^-2. We examine the relation between the Ly-alpha escape fraction fesc(Ly-alpha) and the Lyman continuum escape fraction fesc(LyC), using direct measures of the latter in eleven low-redshift LyC leakers, to verify whether fesc(Ly-alpha) can be an indirect measure of escaping LyC radiation. The usefulness of O32, of the Ly-alpha equivalent width EW(Ly-alpha) and of the Ly-alpha peak separation Vsep as indirect indicators of Ly-alpha leakage is also discussed. It is shown that there is no correlation between O32 and fesc(Ly-alpha). We find an increase of fesc(Ly-alpha) with increasing EW(Ly-alpha) for EW(Ly-alpha)<100A, but for higher EW(Ly-alpha)>150A the fesc(Ly-alpha) is nearly constant attaining the value of ~0.25. We find an anticorrelation between fesc(Ly-alpha) and Vsep, though not as tight as the one found earlier between fesc(LyC) and Vsep. This finding makes Vsep a promising indirect indicator of both the Ly-alpha and ionizing radiation leakage.
We present Large Binocular Telescope spectrophotometric observations of five low-redshift (z<0.070) compact star-forming galaxies (CSFGs) with extremely high emission-line ratios O32 = [OIII]5007/[OII]3727, ranging from 23 to 43. Galaxies with such h
We present observations with the Cosmic Origins Spectrograph onboard the Hubble Space Telescope of five star-forming galaxies at redshifts z in the range 0.2993-0.4317 and with high emission-line flux ratios O32=[OIII]5007/[OII]3727 ~ 8-27 aiming to
We present a study of the [OIII]5007/[OII]3727 (O32) ratios of star-forming galaxies drawn from MUSE data spanning a redshift range 0.28<z<0.85. Recently discovered Lyman continuum (LyC) emitters have extremely high oxygen line ratios: O32>4. Here we
We compare the relations among various integrated characteristics of ~25,000 low-redshift (z<1.0) compact star-forming galaxies (CSFGs) from Data Release 16 (DR16) of the Sloan Digital Sky Survey (SDSS) and of high-redshift (z>1.5) star-forming galax
Using the Large Binocular Telescope (LBT)/Multi-Object Dual Spectrograph (MODS), we have obtained optical spectroscopy of one of the most metal-poor dwarf star-forming galaxies (SFG) in the local Universe, J2229+2725. This galaxy with a redshift z=0.