Searching for z > 6.5 Analogs Near the Peak of Cosmic Star Formation

Abstract

Strong [OIII]$\lambda \lambda$4959,5007+H$\beta$ emission appears to be typical in star-forming galaxies at z > 6.5. As likely contributors to cosmic reionization, these galaxies and the physical conditions within them are of great interest. At z > 6.5, where Ly$\alpha$ is greatly attenuated by the intergalactic medium, rest-UV metal emission lines provide an alternative measure of redshift and also constraints on the physical properties of star-forming regions and massive stars. We present the first statistical sample of rest-UV line measurements in z $\sim$ 2 galaxies selected as analogs of those in the reionization era based on [OIII]$\lambda \lambda$4959,5007 EW or rest-frame U-B color. Our sample is drawn from the 3D-HST Survey and spans the redshift range 1.36 $⩽$ z $⩽$ 2.49. We find that the median Ly$\alpha$ and CIII]$\lambda \lambda$1907,1909 EWs of our sample are significantly greater than those of z $\sim$ 2 UV-continuum-selected star-forming galaxies. Measurements from both individual and composite spectra indicate a monotonic, positive correlation between CIII] and [OIII], while a lack of trend is observed between Ly$\alpha$ and [OIII] at [OIII] EW < 1000$\unicode{x212B}$. At higher [OIII] EW, extreme Ly$\alpha$ emission starts to emerge. Using stacked spectra, we find that Ly$\alpha$ and CIII] are significantly enhanced in galaxies with lower metallicity. Two objects in our sample appear comparable to z > 6.5 galaxies with exceptionally strong rest-UV metal line emission. These objects have significant CIV$\lambda \lambda$1548,1550, HeII$\lambda$1640, and OIII]$\lambda \lambda$1661,1665 emission in addition to intense Ly$\alpha$ or CIII]. Detailed characterization of these lower-redshift analogs provides unique insights into the physical conditions in z > 6.5 star-forming regions, motivating future observations of reionization-era analogs at lower redshifts.

22 pages, 9 figures, accepted for publication in ApJ

References in corpus (28)

• UV Luminosity Functions at redshifts z~4 to z~10: 10000 Galaxies from HST Legacy Fields
• 3D-HST WFC3-selected Photometric Catalogs in the Five CANDELS/3D-HST Fields: Photometry, Photometric Redshifts and Stellar Masses
• Strong Nebular Line Ratios in the Spectra of z~2-3 Star-forming Galaxies: First Results from KBSS-MOSFIRE
• The MOSFIRE Deep Evolution Field (MOSDEF) Survey: Rest-Frame Optical Spectroscopy for ~1500 H-Selected Galaxies at 1.37 < z < 3.8
• Modelling the nebular emission from primeval to present-day star-forming galaxies
• The Relation Between SFR and Stellar Mass for Galaxies at 3.5 $\le z\le$ 6.5 in CANDELS
• The Direct Detection of Lyman-Continuum Emission from Star-forming Galaxies at z~3
• Line Emitting Galaxies Beyond a Redshift of 7: An Improved Method for Estimating the Evolving Neutrality of the Intergalactic Medium
• New observations of z~7 galaxies: evidence for a patchy reionization
• Inferences on the Timeline of Reionization at z~8 From the KMOS Lens-Amplified Spectroscopic Survey
• A Spectroscopic Redshift Measurement for a Luminous Lyman Break Galaxy at z=7.730 using Keck/MOSFIRE
• Deriving model-based T${}_e$-consistent chemical abundances in ionised gaseous nebulae
• 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
• Constraining the neutral fraction of hydrogen in the IGM at redshift 7.5
• High-precision Photometric Redshifts from Spitzer/IRAC: Extreme [3.6]-[4.5] Colors Identify Galaxies in the Redshift Range z~6.6-6.9
• 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 Rest-Frame Optical Spectroscopic Properties of Ly$\alpha$-Emitters at $z\sim 2.5$: The Physical Origins of Strong Ly$\alpha$ Emission
• Intense CIV and HeII Emission in z~0 Galaxies: Probing High-Energy Ionizing Photons
• Near-Infrared Spectroscopy of Galaxies During Reionization: Measuring CIII] in a Galaxy at $\mathbf{z}=7.5$
• MMT & Magellan Infrared Spectrograph
• The MUSE Hubble Ultra Deep Field Survey: IV. Global properties of C III] emitters
• Data Reduction Pipeline for the MMT and Magellan Infrared Spectrograph
• Lyman-Alpha Emitter Galaxies at z ~ 2.8 in the Extended Chandra Deep Field-South: I. Tracing the Large-Scale Structure via Lyman-Alpha Imaging
• A Pilot Survey for CIII] Emission in the Reionization Era: Gravitationally-Lensed z$\sim 7-8$ Galaxies in the Frontier Fields Cluster Abell 2744

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• High star cluster formation efficiency in the strongly lensed Sunburst Lyman-continuum galaxy at z=2.37
• The X-SHOOTER Lyman-$\alpha$ survey at z=2 (XLS-z2) I: What makes a galaxy a Lyman-$\alpha$ emitter?
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• Low-redshift compact star-forming galaxies as analogues of high-redshift star-forming galaxies
• Strong Ly$\alpha$ Emission in an Overdense Region at $z=6.8$: A Very Large ($R\sim 3$ physical Mpc) Ionized Bubble in COSMOS?
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• The Lyman Continuum Escape Survey: Connecting Time-Dependent [OIII] and [OII] Line Emission with Lyman Continuum Escape Fraction in Simulations of Galaxy Formation
• JWST/NIRCam Observations of Stars and HII Regions in $z\simeq 6-8$ Galaxies: Properties of Star Forming Complexes on 150 pc Scales
• 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 $z>6$
• Rest-frame UV spectroscopy of extreme [OIII] emitters at $1.3<z<3.7$: Toward a high-redshift UV reference sample for JWST
• The [OIII]$\lambda 5007$ equivalent width distribution at z $\sim 2$: The redshift evolution of the extreme emission line galaxies
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• The MUSE Hubble Ultra Deep Field Survey. XV. The mean rest-UV spectra of Ly-alpha emitters at z>3
• Early results from GLASS-JWST. VI: Extreme rest-optical equivalent widths detected in NIRISS Wide Field Slitless Spectroscopy
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• CLEAR: Boosted Ly$\alpha$ Transmission of the Intergalactic Medium in UV bright Galaxies
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• Insights into the reionization epoch from cosmic-noon-CIV emitters in the VANDELS survey
• Spectroscopy of CASSOWARY gravitationally-lensed galaxies in SDSS: characterisation of an extremely bright reionization-era analog at $z=1.42$
• UNCOVERing the High-redshift AGN Population among Extreme UV Line Emitters
• MOSEL Survey: Extremely weak outflows in EoR analogues at z=3-4
• The high-redshift Universe with Spitzer
• Spectroscopy of an extreme [OIII] emitting active galactic nucleus at $z=3.212$: implications for the reionisation era
• The Physical Properties of Star-Forming Galaxies with Strong [O III] Lines at z=3.25
• On the dwarf irregular galaxy NGC 6822. I. Young, intermediate and old stellar populations
• The dwarf irregular galaxy NGC 6822. II. Young, intermediate and old stellar populations: comparison between theory and observations
• Extreme equivalent width-selected low-mass starbursts at $z=4-9$: insights into their role in cosmic reionization