Near-Infrared Spectroscopy of Galaxies During Reionization: Measuring CIII] in a Galaxy at $\mathbf{z}=7.5$

Abstract

We present Keck/MOSFIRE $H$-band spectroscopy targeting CIII] $\lambda$1907,1909 in a $z=7.5056$ galaxy previously identified via Ly$\alpha$ emission. We detect strong line emission at $1.621\pm 0.002\mu$m with a line flux of ($2.63\pm 0.52$)$\times 10^{-18}$ erg s${}^{-1}$ cm${}^{-2}$. We tentatively identify this line as [CIII] $\lambda$1907, but we are unable to detect CIII] $\lambda$1909 owing to sky emission at the expected location. This gives a galaxy systemic redshift, $z_{sys}=7.5032\pm 0.0003$, with a velocity offset to Ly$\alpha$ of $\Delta$v${}_{Ly\alpha }$ = $88\pm 27$ km s${}^{-1}$. The ratio of combined CIII]/Ly$\alpha$ is 0.30-0.45, one of the highest values measured for any $z>2$ galaxy. We do not detect SiIII] $\lambda \lambda$1883, 1892, and place an upper limit on SiIII]/CIII] $<$ 0.35 ($2\sigma$). Comparing our results to photoionization models, the CIII] equivalent width (W${}_{\text{CIII]}}=16.23\pm 2.32$Å), low SiIII]/CIII] ratio, and high implied [OIII] equivalent width (from the $Spitzer$/IRAC [3.6]$-$[4.5]$\simeq$0.8 mag color) require sub-Solar metallicities ($Z\simeq 0.1-0.2Z_{\odot }$) and a high ionization parameter, logU $\gtrsim -1.5$. These results favor models that produce higher ionization, such as the BPASS models for the photospheres of high-mass stars, and that include both binary stellar populations and/or an IMF that extends to 300 M${}_{\odot }$. The combined CIII] equivalent width and [3.6]$-$[4.5] color are more consistent with ionization from young stars than AGN, however we cannot rule out ionization from a combination of an AGN and young stars. We make predictions for $JamesWebbSpaceTelescope$ spectroscopy using these different models, which will ultimately test the nature of the ionizing radiation in this source.

19 pages, 12 figures, accepted for publication in ApJ

References in corpus (33)

• A luminous quasar at a redshift of z = 7.085
• UV Luminosity Functions at redshifts z~4 to z~10: 10000 Galaxies from HST Legacy Fields
• Binary Population and Spectral Synthesis Version 2.1: construction, observational verification and new results
• Model-independent evidence in favor of an end to reionization by z~6
• 3D Lyman-alpha radiation transfer. I. Understanding Lyman-alpha line profile morphologies
• The Effects of Stellar Rotation. II. A Comprehensive Set of Starburst99 Models
• Modelling the nebular emission from primeval to present-day star-forming galaxies
• Dust in the reionization era: ALMA observations of a $z$=8.38 Galaxy
• Using Lyman-alpha to detect galaxies that leak Lyman continuum
• Lyman Alpha Emitting Galaxies as a Probe of Reionization
• Line Emitting Galaxies Beyond a Redshift of 7: An Improved Method for Estimating the Evolving Neutrality of the Intergalactic Medium
• Nebular Emission Line Ratios in z~2-3 Star-Forming Galaxies with KBSS-MOSFIRE: Exploring the Impact of Ionization, Excitation, and Nitrogen-to-Oxygen Ratio
• A Spectroscopic Redshift Measurement for a Luminous Lyman Break Galaxy at z=7.730 using Keck/MOSFIRE
• 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
• The Ly-alpha Properties of Faint Galaxies at z2-3 with Systemic Redshifts and Velocity Dispersions from Keck-MOSFIRE
• High-precision Photometric Redshifts from Spitzer/IRAC: Extreme [3.6]-[4.5] Colors Identify Galaxies in the Redshift Range z~6.6-6.9
• Star formation and the interstellar medium in z>6 UV-luminous Lyman-break galaxies
• Evidence for a Hard Ionizing Spectrum from a z=6.11 Stellar Population
• Lyman-alpha emitters gone missing: evidence for late reionization?
• A spectroscopic search for AGN activity in the reionization era
• Understanding the escape of LyC and Ly$\alpha$ photons from turbulent clouds
• Photoionization Models for the Semi-Forbidden C III] 1909 Emission in Star-Forming Galaxies
• The CALYMHA survey: Lya luminosity function and global escape fraction of Lya photons at z=2.23
• The HETDEX Pilot Survey V: The Physical Origin of Lyman-alpha Emitters Probed by Near-infrared Spectroscopy
• Lyman alpha Emitting Galaxies in the Nearby Universe
• Spectroscopic properties of luminous Lyman-α emitters at $z\approx 6-7$ and comparison to the Lyman-break population
• Interpreting high [O III]/Hbeta ratios with maturing starbursts
• The MUSE Hubble Ultra Deep Field Survey: IV. Global properties of C III] emitters
• FIGS -- Faint Infrared Grism Survey: Description and Data Reduction
• Texas Spectroscopic Search for Ly$\alpha$ Emission at the End of Reionization II. The Deepest Near-Infrared Spectroscopic Observation at $z\gtrsim 7$

Cited by in corpus (46)

• The GLASS James Webb Space Telescope Early Release Science Program. I. Survey Design and Release Plans
• Galaxy Formation and Reionization: Key Unknowns and Expected Breakthroughs by the James Webb Space Telescope
• Reionization Era Bright Emission Line Survey: Selection and Characterization of Luminous Interstellar Medium Reservoirs in the z>6.5 Universe
• CEERS Spectroscopic Confirmation of NIRCam-Selected z > 8 Galaxy Candidates with JWST/NIRSpec: Initial Characterization of their Properties
• The Far-Ultraviolet Continuum Slope as a Lyman Continuum Escape Estimator at High-redshift
• The [OIII]$+$H$\beta$ Equivalent Width Distribution at z$\simeq$7: Implications for the Contribution of Galaxies to Reionization
• Texas Spectroscopic Search for Ly$\alpha$ Emission at the End of Reionization III. the Ly$\alpha$ Equivalent-width Distribution and Ionized Structures at $z>7$
• A First Look at the Abundance Pattern -- O/H, C/O, and Ne/O -- in $z>7$ Galaxies with JWST/NIRSpec
• The Physical Conditions of Emission-Line Galaxies at Cosmic Dawn from JWST/NIRSpec Spectroscopy in the SMACS 0723 Early Release Observations
• Star formation histories of UV-luminous galaxies at $z\simeq 6.8$: implications for stellar mass assembly at early cosmic times
• EMPRESS. V. Metallicity Diagnostics of Galaxies over 12+log(O/H)=~6.9-8.9 Established by a Local Galaxy Census: Preparing for JWST Spectroscopy
• Characterizing Extreme Emission Line Galaxies I: A Four-Zone Ionization Model for Very-High-Ionization Emission
• First Light And Reionisation Epoch Simulations (FLARES) II: The Photometric Properties of High-Redshift Galaxies
• Spectral Templates Optimal for Selecting Galaxies at z > 8 with JWST
• On the ages of bright galaxies $\sim 500$ Myr after the Big Bang: insights into star formation activity at $z\gtrsim 15$ with JWST
• CEERS Key Paper IV: Galaxies at $4<z<9$ are Bluer than They Appear -- Characterizing Galaxy Stellar Populations from Rest-Frame $\sim 1$ micron Imaging
• The Effects of Stellar Population and Gas Covering Fraction on the Emergent Lyman Alpha Emission of High-Redshift Galaxies
• Interpreting the Spitzer/IRAC Colours of 7<z<9 Galaxies: Distinguishing Between Line Emission and Starlight Using ALMA
• JWST/NIRCam Observations of Stars and HII Regions in $z\simeq 6-8$ Galaxies: Properties of Star Forming Complexes on 150 pc Scales
• Early Results from GLASS-JWST. XXI: Rapid assembly of a galaxy at z=6.23 revealed by its C/O abundance
• Ultraviolet spectra of extreme nearby star-forming regions: evidence for an overabundance of very massive stars
• Lyman-alpha spectroscopy of extreme [OIII] emitting galaxies at $z\simeq 2-3$: Implications for Ly$\alpha$ visibility and LyC leakage at $z>6$
• Seven wonders of Cosmic Dawn: JWST confirms a high abundance of galaxies and AGNs at z $\simeq$ 9-11 in the GLASS field
• JADES: The star-formation and chemical enrichment history of a luminous galaxy at z~9.43 probed by ultra-deep JWST/NIRSpec spectroscopy
• Rest-frame UV spectroscopy of extreme [OIII] emitters at $1.3<z<3.7$: Toward a high-redshift UV reference sample for JWST
• Searching for z > 6.5 Analogs Near the Peak of Cosmic Star Formation
• Assessing the sources of reionisation: a spectroscopic case study of a 30$\times$ lensed galaxy at $z\sim 5$ with Lyα, CIV, MgII, and [NeIII]
• The [OIII]$\lambda 5007$ equivalent width distribution at z $\sim 2$: The redshift evolution of the extreme emission line galaxies
• Ionized gas kinematics and chemical abundances of low-mass star-forming galaxies at $z\sim 3$
• The Semi-forbidden CIII]$\lambda$1909Å~ Emission in the Rest-Ultraviolet Spectra of Green Pea Galaxies
• The MUSE Hubble Ultra Deep Field Survey. XV. The mean rest-UV spectra of Ly-alpha emitters at z>3
• SuperBoRG: Exploration of point sources at $z\sim 8$ in HST parallel fields
• Star formation law in the EoR from [CII] and CIII] lines
• Recovery and analysis of rest-frame UV emission lines in 2052 galaxies observed with MUSE at $1.5<z<6.4$
• Physical properties of extreme emission-line galaxies at $z\sim 4-9$ from the JWST CEERS survey
• RELICS: Properties of z>5.5 Galaxies Inferred from Spitzer and Hubble Imaging Including A Candidate z~6.8 Strong [OIII] Emitter
• The Ionizing Spectra of Extremely Metal-Poor O Stars: Constraints from the Only HII Region in Leo P
• CLEAR: Boosted Ly$\alpha$ Transmission of the Intergalactic Medium in UV bright Galaxies
• The Detection of Ionized Carbon Emission at z~8
• The ALPINE-ALMA [CII] Survey: Investigation of 10 Galaxies at $z\sim 4.5$ with [OII] and [CII] Line Emission $-$ ISM Properties and [OII]$-$SFR Relation
• The interstellar medium of high-redshift galaxies: Gathering clues from C III] and [C II] lines
• MOSEL Survey: Extremely weak outflows in EoR analogues at z=3-4
• Feedback and dynamical masses in high-$z$ galaxies: the advent of high-resolution NIRSpec spectroscopy
• Flexure updates to MOSFIRE on the Keck I telescope
• Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). XIV. A Candidate Type-II Quasar at z=6.1292
• Ciii]$\lambda 1909$ emission as an alternative to Ly$\alpha$ in the reionization era: the dependence of Ciii] and Ly$\alpha$ at $3<z<4$ from the VANDELS survey