The Semi-forbidden CIII]$\lambda$1909Å~ Emission in the Rest-Ultraviolet Spectra of Green Pea Galaxies

Abstract

We used the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST) to observe the semi-forbidden CIII] emission in Green Pea galaxies at 0.13 < z < 0.3. We detect CIII] emission in 7/10 galaxies with CIII] equivalent widths that range from 2-10Å~. The observed CIII] emission line strengths are consistent with the predictions from photoionization models which incorporate the effects of binary stellar evolution with young stellar ages < 3-5 Myrs, and high ionization parameters (logU > -2). The hard ionizing radiation from young massive stars, and high nebular temperatures at low-metallicities can account for the observed high equivalent widths of CIII] and [OIII] emission lines. The Green Pea galaxies do not show a significant correlation between the Ly$\alpha$ and CIII] equivalent widths, and the observed scatter is likely due to the variations in the optical depth of Ly$\alpha$ to the neutral gas. Green Pea galaxies are likely to be density-bounded, and we examined the dependence of CIII] emission on the Lyman continuum optical depth. The potential LyC leaker galaxies in our sample have high CIII] equivalent widths that can only be reproduced by starburst ages as young as < 3 Myrs and harder ionizing spectra than the non-leakers. Among the galaxies with similar metallicities and ionization parameters, the CIII] equivalent width appears to be stronger for those with higher optical depth to LyC, as expected from the photoionization models. Further investigation of a larger sample of CIII]-emitters is necessary to calibrate the dependence of CIII] emission on the escape of LyC radiation, and to enable application of the CIII] diagnostics to galaxies in the reionization epoch.

27 pages, 9 figures, accepted for publication in the Astrophysical Journal. Revised references and corrected typos

References in corpus (24)

• Binary Population and Spectral Synthesis Version 2.1: construction, observational verification and new results
• Strong Nebular Line Ratios in the Spectra of z~2-3 Star-forming Galaxies: First Results from KBSS-MOSFIRE
• Modelling the nebular emission from primeval to present-day star-forming galaxies
• Using Lyman-alpha to detect galaxies that leak Lyman continuum
• The MOSDEF Survey: Excitation Properties of $z\sim 2.3$ Star-forming Galaxies
• Lyman-alpha spectral properties of five newly discovered Lyman continuum emitters
• Ultraviolet Emission Lines in Young Low Mass Galaxies at z~2: Physical Properties and Implications for Studies at z>7
• Spectroscopic detections of CIII]1909 at z~6-7: A new probe of early star forming galaxies and cosmic reionisation
• Ultraviolet spectra of extreme nearby star-forming regions --- approaching a local reference sample for JWST
• Rapid Decline of Lyman-alpha Emission Toward the Reionization Era
• High-precision Photometric Redshifts from Spitzer/IRAC: Extreme [3.6]-[4.5] Colors Identify Galaxies in the Redshift Range z~6.6-6.9
• Accelerated Evolution of Ly$\alpha$ Luminosity Function at $\text{z}\gtrsim 7$ Revealed by the Subaru Ultra-Deep Survey for Ly$\alpha$ Emitters at $\text{z}=7.3$
• The Chemical Evolution of Carbon, Nitrogen, and Oxygen in Metal-Poor Dwarf Galaxies
• Evidence for a Hard Ionizing Spectrum from a z=6.11 Stellar Population
• The Nature of Extreme Emission Line Galaxies at z=1-2: Kinematics and Metallicities from Near-Infrared Spectroscopy
• A spectroscopic search for AGN activity in the reionization era
• Photoionization Models for the Semi-Forbidden C III] 1909 Emission in Star-Forming Galaxies
• A Hard Ionizing Spectrum in z=3-4 Ly-alpha Emitters with Intense [OIII] Emission: Analogs of Galaxies in the Reionization Era?
• Excitation properties of galaxies with the highest [OIII]/[OII] ratios: No evidence for massive escape of ionizing photons
• Linking Ly-alpha and Low-Ionization Transitions at Low Optical Depth
• Near-Infrared Spectroscopy of Galaxies During Reionization: Measuring CIII] in a Galaxy at $\mathbf{z}=7.5$
• Kinematics and Optical Depth in the Green Peas: Suppressed Superwinds in Candidate LyC Emitters
• The MUSE Hubble Ultra Deep Field Survey: IV. Global properties of C III] emitters
• Neutral Gas Properties and Ly$\alpha$ Escape in Extreme Green Pea Galaxies

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