The properties of He II 1640 emitters at z ~ 2.5-5 from the VANDELS survey

Abstract

Strong He II emission is produced by low-metallicity stellar populations. Here, we aim to identify and study a sample of He II $\lambda 1640$-emitting galaxies at redshifts of $z\sim 2.5-5$ in the deep VANDELS spectroscopic survey.. We identified a total of 33 Bright He II emitters (S/N > 2.5) and 17 Faint emitters (S/N < 2.5) in the VANDELS survey and used the available deep multi-wavelength data to study their physical properties. After identifying seven potential AGNs in our sample and discarding them from further analysis, we divided the sample of \emph{Bright} emitters into 20 \emph{Narrow} (FWHM < 1000 km s${}^{-1}$) and 6 \emph{Broad} (FWHM > 1000 km s${}^{-1}$) He II emitters. We created stacks of Faint, Narrow, and Broad emitters and measured other rest-frame UV lines such as O III] and C III] in both individual galaxies and stacks. We then compared the UV line ratios with the output of stellar population-synthesis models to study the ionising properties of He II emitters. We do not see a significant difference between the stellar masses, star-formation rates, and rest-frame UV magnitudes of galaxies with He II and no He II emission. The stellar population models reproduce the observed UV line ratios from metals in a consistent manner, however they under-predict the total number of \heii ionising photons, confirming earlier studies and suggesting that additional mechanisms capable of producing He II are needed, such as X-ray binaries or stripped stars. The models favour subsolar metallicities ($\sim 0.1Z_{\odot }$) and young stellar ages ($10^6-10^7$ years) for the He II emitters. However, the metallicity measured for He II emitters is comparable to that of non-He II emitters at similar redshifts. We argue that galaxies with He II emission may have undergone a recent star-formation event, or may be powered by additional sources of He II ionisation.

arXiv comment21 pages, 11 figures (including appendix), Accepted for publication in A&A

References in corpus (67)

• Astropy: A Community Python Package for Astronomy
• Planck 2015 results. XIII. Cosmological parameters
• Stellar population synthesis at the resolution of 2003
• The Dust Content and Opacity of Actively Star-Forming Galaxies
• CANDELS: The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey
• CANDELS: The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey - The Hubble Space Telescope Observations, Imaging Data Products and Mosaics
• In the Beginning: The First Sources of Light and the Reionization of the Universe
• Rest-Frame Ultraviolet Spectra of z~3 Lyman Break Galaxies
• The First Stars
• Binary Population and Spectral Synthesis Version 2.1: construction, observational verification and new results
• Cosmic Reionization and Early Star-Forming Galaxies: A Joint Analysis of New Constraints from Planck and Hubble Space Telescope
• On the properties of massive Population III stars and metal-free stellar populations
• Strong Nebular Line Ratios in the Spectra of z~2-3 Star-forming Galaxies: First Results from KBSS-MOSFIRE
• Reevaluating Old Stellar Populations
• The transition from Population III to normal galaxies: Ly-a and HeII 1640 emission and the ionising properties of high redshift starburst galaxies
• The Chandra Deep Field-South Survey: 7 Ms Source Catalogs
• Understanding Galaxy Evolution through Emission Lines
• The First Galaxies
• The Birth of a Galaxy: Primordial Metal Enrichment and Stellar Populations
• Reionization after Planck: The Derived Growth of the Cosmic Ionizing Emissivity now matches the Growth of the Galaxy UV Luminosity Density
• Reconciling the Stellar and Nebular Spectra of High Redshift Galaxies
• Stellar Population Effects on the Inferred Photon Density at Reionization
• Early star-forming galaxies and the reionization of the Universe
• Conditions for Reionizing the Universe with A Low Galaxy Ionizing Photon Escape Fraction
• Modelling the nebular emission from primeval to present-day star-forming galaxies
• Evidence for PopIII-like stellar populations in the most luminous Lyman-$\alpha$ emitters at the epoch of re-ionisation: spectroscopic confirmation
• Nuclear activity versus star formation: emission-line diagnostics at ultraviolet and optical wavelengths
• Systematic effects and a new determination of the primordial abundance of 4He and dY/dZ from observations of blue compact galaxies
• Physical Conditions in a Young, Unreddened, Low Metallicity Galaxy at High Redshift
• X-ray Binary Evolution Across Cosmic Time
• Zero-Metallicity Stars and the Effects of the First Stars on Reionization
• Strongly star forming galaxies in the local Universe with nebular He II 4686 emission
• Galaxies with Wolf-Rayet signatures in the low-redshift Universe - A survey using the Sloan Digital Sky Survey
• A Spectroscopic Study of a Large Sample of Wolf-Rayet Galaxies
• Energy Feedback from X-ray Binaries in the Early Universe
• Spectral models for binary products: Unifying Subdwarfs and Wolf-Rayet stars as a sequence of stripped-envelope stars
• Ultraviolet spectra of extreme nearby star-forming regions --- approaching a local reference sample for JWST
• The Dust-to-Gas and Dust-to-Metals Ratio in Galaxies from z=0-6
• Carbon and Oxygen Abundances in Low Metallicity Dwarf Galaxies
• Cosmic Reionisation by Stellar Sources: Population III Stars
• Low-metallicity massive single stars with rotation. Evolutionary models applicable to I Zwicky 18
• The VIMOS Ultra Deep Survey: Nature, ISM properties, and ionizing spectra of CIII]1909 emitters at z=2-4
• The MOSDEF survey: a stellar mass-SFR-metallicity relation exists at $z\sim 2.3$
• Emission-line diagnostics of nearby HII regions including interacting binary populations
• The VANDELS ESO public spectroscopic survey: observations and first data release
• A Window On The Earliest Star Formation: Extreme Photoionization Conditions of a High-Ionization, Low-Metallicity Lensed Galaxy at z~2
• X-ray binaries as the origin of nebular HeII emission in low-metallicity star-forming galaxies
• Low Masses and High Redshifts: The Evolution of the Mass-Metallicity Relation
• The VANDELS survey: the stellar metallicities of star-forming galaxies at 2.5 < z < 5.0
• Enhanced X-ray emission from Lyman Break Analogues and a Possible $L_{\mathrm{X}}$--SFR--Metallicity Plane
• A young star-forming galaxy at z = 3.5 with an extended Ly\,$\alpha$ halo seen with MUSE
• The Mass-Metallicity-SFR Relation at z >~ 2 with 3D-HST
• The impact of stars stripped in binaries on the integrated spectra of stellar populations
• The extended HeII4686-emitting region in IZw18 unveiled: clues for peculiar ionizing sources
• Evolution of Dust-to-Metal Ratio in Galaxies
• X-UDS: The Chandra Legacy Survey of the UKIDSS Ultra Deep Survey Field
• Intense CIV and HeII Emission in z~0 Galaxies: Probing High-Energy Ionizing Photons
• HeII emitters in the VIMOS VLT Deep Survey: PopIII star formation or peculiar stellar populations in galaxies at 2<z<4.6?
• About the initial mass function and HeII emission in young starbursts
• Extremely metal-poor galaxies with HST/COS: laboratories for models of low-metallicity massive stars and high-redshift galaxies
• Metallicity dependence of HMXB populations
• Ly$\alpha$-Lyman Continuum connection in 3.5 < z < 4.3 star-forming galaxies from the VUDS survey
• High-mass X-ray binaries in nearby metal-poor galaxies: on the contribution to nebular HeII emission
• Initial Mass Function Variations Cannot Explain the Ionizing Spectrum of Low Metallicity Starbursts
• Exploring HeII$\lambda$1640 emission line properties at $z\sim 2-4$
• The MOSDEF Survey: The Metallicity Dependence of X-ray Binary Populations at $z\sim 2$
• Easylife: the data reduction and survey handling system for VIPERS

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