气候变化领域集成服务门户(CCPortal): The Semiforbidden C III λ1909 Emission in the Rest-ultraviolet Spectra of Green Pea Galaxies

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DOI	10.3847/1538-4357/ab91a5
	The Semiforbidden C III λ1909 Emission in the Rest-ultraviolet Spectra of Green Pea Galaxies
	Ravindranath S.; Monroe T.; Jaskot A.; Ferguson H.C.; Tumlinson J.
发表日期	2020
ISSN	0004637X
卷号	896 期号:2
英文摘要	We used the Space Telescope Imaging Spectrograph on the Hubble Space Telescope (HST) to observe the semiforbidden C iii] λλ1907, 1909 doublet emission in green pea galaxies at 0.13 ≤ z ≤ 0.3. We detect C iii] emission in 7/10 galaxies with C iii] equivalent widths (EWs) that range from 2 to 10 Å, confirming that C iii] emission is almost ubiquitous in low-mass, low-metallicity (12+log(O/H) < 8.4) galaxies that are characterized by strong optical [O iii] λ5007 emission. The composite UV spectrum shows evidence for the He ii λ1640 emission line and interstellar absorption features (e.g., C iv λλ1548, 1550, Al iii λλ1854, 1862). We do not detect the O iii] λλ1661, 1666 emission with >3σ significance. The observed C iii] emission line strengths are consistent with the predictions from photoionization models that incorporate the effects of binary stellar evolution with young stellar ages ≤3-5 Myr and high ionization parameters (log U > -2). The hard ionizing radiation from young massive stars and high nebular temperatures at low metallicities can account for the observed high EWs of C iii] λ1909 and [O iii] λ5007 emission lines. Some of the star-forming galaxies at high redshift and local blue compact dwarf galaxies show offsets from the EW(C iii]) versus EW([O iii]) model grids, indicating an additional contribution to the continuum emission from composite stellar populations or different C/O abundances, nebular temperatures, and electron densities than assumed in the photoionization models. The green pea galaxies do not show a significant correlation between the Lyα and C iii] EWs, and the observed scatter is likely due to the variations in the optical depth of Lyα to the neutral gas. Green pea galaxies are likely to be density-bounded, and we examined the dependence of C iii] emission on the Lyman continuum optical depth. The potential LyC leaker galaxies in our sample have high C iii] EWs that can only be reproduced by starburst ages as young as <3 Myr and harder ionizing spectra than the nonleakers. Among the galaxies with similar metallicities and ionization parameters, the C iii] EW appears to be stronger for those with higher optical depth to LyC, as expected from the photoionization models. There are various factors that affect the C iii] emission line strengths, and further investigation of a larger sample of C iii] emitters is necessary to calibrate the dependence of C iii] emission on the escape of LyC radiation and enable application of the C iii] diagnostics to galaxies in the reionization epoch. © 2020. The American Astronomical Society. All rights reserved.
来源期刊	Astrophysical Journal
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/176888
作者单位	Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218-2410, United States; Astronomy Department, Williams College, Williamstown, MA 01267, United States
推荐引用方式 GB/T 7714	Ravindranath S.,Monroe T.,Jaskot A.,et al. The Semiforbidden C III λ1909 Emission in the Rest-ultraviolet Spectra of Green Pea Galaxies[J],2020,896(2).
APA	Ravindranath S.,Monroe T.,Jaskot A.,Ferguson H.C.,&Tumlinson J..(2020).The Semiforbidden C III λ1909 Emission in the Rest-ultraviolet Spectra of Green Pea Galaxies.Astrophysical Journal,896(2).
MLA	Ravindranath S.,et al."The Semiforbidden C III λ1909 Emission in the Rest-ultraviolet Spectra of Green Pea Galaxies".Astrophysical Journal 896.2(2020).