The HETDEX Pilot Survey III: The Low Metallicities of High-Redshift Lyman Alpha Galaxies

Abstract

We present Keck/NIRSPEC spectroscopic observations of three Lyman alpha emitting galaxies (LAEs) at z ~ 2.3 discovered with the HETDEX pilot survey. We detect Halpha, [OIII], and Hbeta emission from two galaxies at z = 2.29 and 2.49, designated HPS194 and HPS256, respectively, representing the first detection of multiple rest-frame optical emission lines in galaxies at high-redshift selected on the basis of their Lyman alpha emission. The redshifts of the Lyman alpha emission from these galaxies are offset redward of the systemic redshifts by Delta_v = 162 +/- 37 (photometric) +/- 42 (systematic) km/s for HPS194, and Delta_v = 36 +/- 35 +/- 18 km/s for HPS256. An interpretation for HPS194 is that a large-scale outflow may be occurring in its interstellar medium. The emission line ratios imply that neither LAE hosts an active galactic nucleus. Using the upper limits on the [NII] emission we place meaningful constraints on the gas-phase metallicities in these two LAEs of Z < 0.17 and < 0.28 Zsol (1 sigma). Measuring the stellar masses of these objects via spectral energy distribution (SED) fitting (~ 10^10 and 6 x 10^8 Msol, respectively), we study the nature of LAEs in a mass-metallicity plane. At least one of these two LAEs appears to be more metal poor than continuum-selected star-forming galaxies at the same redshift and stellar mass, implying that objects exhibiting Lyman alpha emission may be systematically less chemically enriched than the general galaxy population. We use the SEDs of these two galaxies to show that neglecting the emission lines when fitting stellar population models to the observed photometry can result in overestimates of the population age by orders of magnitude, and the stellar mass by a factor of ~ 2. This effect is particularly important at z > 7, where similarly strong emission lines may masquerade in the photometry as a 4000 A break (abridged).

Replaced with the accepted (to ApJ) version

References in corpus (29)

• The Cosmic Evolution Survey (COSMOS) -- Overview
• The Structure and Kinematics of the Circum-Galactic Medium from Far-UV Spectra of z~2-3 Galaxies
• The Subaru/XMM-Newton Deep Survey (SXDS). IV. Evolution of Lya Emitters from z=3.1 to 5.7 in the 1 deg^2 Field: Luminosity Functions and AGN
• The Stellar, Gas and Dynamical Masses of Star-Forming Galaxies at z~2
• The Galaxy Mass Function up to z=4 in the GOODS-MUSIC sample: into the epoch of formation of massive galaxies
• Ly-alpha Emission-Line Galaxies at z = 3.1 in the Extended Chandra Deep Field South
• Physical Conditions in a Young, Unreddened, Low Metallicity Galaxy at High Redshift
• The Luminosity Function of X-ray Selected Active Galactic Nuclei: Evolution of Supermassive Black Holes at High Redshift
• New insights into the stellar content and physical conditions of star-forming galaxies at z = 2-3 from spectral modelling
• A Spectroscopic Survey of Redshift 1.4<z<3.0 Galaxies in the Goods-North Field: Survey Description, Catalogs, and Properties
• Spitzer's Contribution to the AGN Population
• On the physical properties of z~6-8 galaxies
• Metallicities and Physical Conditions in Star-forming Galaxies at z~1.0-1.5
• Escape of about five per cent of Lyman-alpha photons from high-redshift star-forming galaxies
• Stellar Populations of Lyman Alpha Emitters at z~6-7: Constraints on the Escape Fraction of Ionizing Photons from Galaxy Building Blocks
• Rest-Frame Optical Spectra of Three Strongly Lensed Galaxies at z~2
• HETDEX pilot survey for emission-line galaxies - I. Survey design, performance, and catalog
• Smoothly-Rising Star Formation Histories During the Reionization Epoch
• The Stellar Masses and Star Formation Histories of Galaxies at z ~ 6: Constraints from Spitzer Observations in the Great Observatories Origins Deep Survey
• The Stellar Mass Density at z~6 from Spitzer Imaging of i-drop Galaxies
• On the Detectability of Lyman-alpha Emission in Star-forming Galaxies: The Role of Dust
• Effects of Dust Geometry in Lyman Alpha Galaxies at z = 4.4
• The physical properties of Lyalpha emitting galaxies: not just primeval galaxies?
• Lyman Alpha Driven Outflows Around Star Forming Galaxies
• Turning Back the Clock: Inferring the History of the Eight O'clock Arc
• Evolution of Lyman Alpha Galaxies: Stellar Populations at z ~ 0.3
• Stellar Populations of Lyman-alpha Emitters at z=4.86: A Comparison to $z\sim 5$ LBGs
• A Plethora of AGN Among Lyman Alpha Galaxies at Low Redshift
• AEGIS: Infrared Spectroscopy of An Infrared Luminous Lyman Break Galaxy at z=3.01

Cited by in corpus (97)

• The Evolution of the Galaxy Rest-Frame Ultraviolet Luminosity Function Over the First Two Billion Years
• De Re Metallica: The cosmic chemical evolution of galaxies
• Evidence for PopIII-like stellar populations in the most luminous Lyman-$\alpha$ emitters at the epoch of re-ionisation: spectroscopic confirmation
• The Relation Between SFR and Stellar Mass for Galaxies at 3.5 $\le z\le$ 6.5 in CANDELS
• Rest-frame ultraviolet-to-optical spectral characteristics of extremely metal-poor and metal-free galaxies
• Very Strong Emission-Line Galaxies in the WISP Survey and Implications for High-Redshift Galaxies
• Observations of the Lyman-$\alpha$ Universe
• A robust sample of galaxies at redshifts 6.0<z<8.7: stellar populations, star-formation rates and stellar masses
• The Ly-alpha Properties of Faint Galaxies at z2-3 with Systemic Redshifts and Velocity Dispersions from Keck-MOSFIRE
• A Refined Estimate of the Ionizing Emissivity from Galaxies at z~3: Spectroscopic Follow-up in the SSA22a Field
• Extreme Emission Line Galaxies in CANDELS: Broad-Band Selected, Star-Bursting Dwarf Galaxies at z>1
• Diffuse Lyman-alpha Halos around Galaxies at z=2.2-6.6: Implications for Galaxy Formation and Cosmic Reionization
• What is the physical origin of strong Lya emission? II. Gas Kinematics and Distribution of Lya Emitters
• Observational Searches for Galaxies at z > 6
• The Lyman alpha Reference Sample: II. HST imaging results, integrated properties and trends
• ISM excitation and metallicity of star-forming galaxies at z~3.3 from near-IR spectroscopy
• The star formation history and metal content of the "Green Peas". New detailed GTC-OSIRIS spectrophotometry of three galaxies
• Average Metallicity and Star Formation Rate of Lya Emitters Probed by a Triple Narrow-Band Survey
• First Spectroscopic Evidence for High Ionization State and Low Oxygen Abundance in Lya Emitters
• Line Transfer through Clumpy, Large-Scale Outflows: Lyman Alpha Absorption and Halos around Starforming Galaxies
• Gas Motion Study of Lya Emitters at z~2 Using UV and Optical Spectral Lines
• The Evolution of Ly-alpha Emitting Galaxies Between z = 2.1 and z = 3.1
• Photoionization Models for the Semi-Forbidden C III] 1909 Emission in Star-Forming Galaxies
• A Close Comparison between Observed and Modeled Lyα Lines for z ~ 2.2 Lyman Alpha Emitters
• The Stellar Halos of Massive Elliptical Galaxies II: Detailed Abundance Ratios at Large Radius
• The HETDEX Pilot Survey V: The Physical Origin of Lyman-alpha Emitters Probed by Near-infrared Spectroscopy
• The Rest-Frame Optical Spectroscopic Properties of Ly$\alpha$-Emitters at $z\sim 2.5$: The Physical Origins of Strong Ly$\alpha$ Emission
• SED fitting with Markov Chain Monte Carlo: Methodology and Application to z=3.1 Lyman Alpha Emitting Galaxies
• Surveying Galaxy Proto-clusters in Emission: A Large-scale Structure at z=2.44 and the Outlook for HETDEX
• The Spitzer-HETDEX Exploratory Large-Area Survey
• Statistical Properties of Diffuse Lyman-alpha Halos around Star-forming Galaxies at z~2
• Sizing up Lyman-alpha and Lyman Break Galaxies
• 3D-HST Grism Spectroscopy of a Gravitationally Lensed, Low-metallicity Starburst Galaxy at z=1.847
• The Lyman-alpha signature of the first galaxies
• The X-SHOOTER Lyman-$\alpha$ survey at z=2 (XLS-z2) I: What makes a galaxy a Lyman-$\alpha$ emitter?
• The Stellar Halos of Massive Elliptical Galaxies
• Constraints on the low-mass end of the mass-metallicity relation at z=1-2 from lensed galaxies
• Contamination of Broad-Band Photometry by Nebular Emission in High Redshift Galaxies: Investigations with Keck's MOSFIRE Near-Infrared Spectrograph
• ART^2 : Coupling Lyman-alpha Line and Multi-wavelength Continuum Radiative Transfer
• A CANDELS WFC3 Grism Study of Emission-Line Galaxies at z~2: A Mix of Nuclear Activity and Low-Metallicity Star Formation
• Hubble Space Telescope Grism Spectroscopy of Extreme Starbursts Across Cosmic Time: The Role of Dwarf Galaxies in the Star Formation History of the Universe
• HST Emission Line Galaxies at z ~ 2: Comparing Physical Properties of Lyman Alpha and Optical Emission Line Selected Galaxies
• Exploring the Galaxy Mass-Metallicity Relation at z~3-5
• Turbulent Diffusion in the Photosphere as Derived from Photospheric Bright Point Motion
• Orbital Motion of HR 8799 b,c, d using Hubble Space Telescope data from 1998: Constraints on Inclination, Eccentricity and Stability
• The UV, Lyman-alpha, and dark matter halo properties of high redshift galaxies
• On the influence of physical galaxy properties on Lyman-alpha escape in star-forming galaxies
• A Ly-alpha Emitter with an Extremely Large Rest-frame Equivalent Width of ~900A at z=6.5: A Candidate of Population III-dominated Galaxy?
• Spectral Energy Distribution Fitting of HETDEX Pilot Survey Lyman-alpha Emitters in COSMOS and GOODS-N
• Searching for Neutral Hydrogen Halos around z ~ 2.1 and z ~ 3.1 Ly-alpha Emitting Galaxies
• The ages, masses and star-formation rates of spectroscopically confirmed z~6 galaxies in CANDELS
• Formation of Metal-Poor Globular Clusters in Lyman alpha Emitting Galaxies in the Early Universe
• The UV-brightest Lyman continuum emitting star-forming galaxy
• Lyman-alpha spectroscopy of extreme [OIII] emitting galaxies at $z\simeq 2-3$: Implications for Ly$\alpha$ visibility and LyC leakage at $z>6$
• The Spectrally Resolved Lyman-alpha Emission of Three Lyman-alpha Selected Field Galaxies at z~2.4 from the HETDEX Pilot Survey
• NIR spectroscopic observation of massive galaxies in the protocluster at z = 3.09
• Dust Extinction and Metallicities of Star-Forming Lyman Alpha Emitting Galaxies at Low Redshift
• The VIMOS Ultra Deep Survey: Ly$\alpha$ Emission and Stellar Populations of Star-Forming Galaxies at 2<z<2.5
• The Lyman alpha reference sample: IV. Morphology at low and high redshift
• Spectroscopic observations of PHz G237.01+42.50: A galaxy protocluster at z=2.16 in the Cosmos field
• How Do Galaxies trace a large scale structure?: A case study around a massive protocluster at $z=3.13$
• Kinematics of Gas in Lyman Alpha Nebulae
• The Properties of Lyman Alpha Nebulae: Gas Kinematics from Non-resonant Lines
• Molecular gas and star formation in an absorption-selected galaxy: Hitting the bull's eye at z = 2.46
• Were progenitors of local L* galaxies Lyman-alpha emitters at high redshift?
• Predicting Ly$\alpha$ Emission from Galaxies via Empirical Markers of Production and Escape in the KBSS
• To Stack or Not to Stack: Spectral Energy Distribution Properties of Lya-Emitting Galaxies at z=2.1
• Lyα Equivalent Width Distribution of Lyα Emitting Galaxies at Redshift z $\sim$ 4.5
• Growth of First Galaxies: Impacts of Star Formation and Stellar Feedback
• The clustering of typical Ly$\alpha$ emitters from $z\sim 2.5-6$: host halo masses depend on Ly$\alpha$ and UV luminosities
• The Stellar Haloes of Massive Elliptical Galaxies III: Kinematics at Large Radius
• Stellar Populations of Lyman Break Galaxies at z=1-3 in the HST/WFC3 Early Release Science Observations
• Hubble Space Telescope Imaging of Lyman Alpha Emission at z=4.4
• The VANDELS survey: A strong correlation between Ly$\alpha$ equivalent width and stellar metallicity at $3\le \mathbf{z}\le 5$
• Environmental Dependence of Galactic Properties Traced by Ly$\alpha$ Forest Absorption: Diversity among Galaxy Populations
• Long GRBs are metallicity-biased tracers of star formation: evidence from host galaxies and redshift distribution
• Lyman alpha Luminosity Functions at Redshift z = 4.5
• Texas Spectroscopic Search for Ly$\alpha$ Emission at the End of Reionization I. Constraining the Ly$\alpha$ Equivalent Width Distribution at 6.0 < $z$ < 7.0
• The MOSDEF Survey: Environmental dependence of the gas-phase metallicity of galaxies at $1.4\le z\le 2.6$
• Ly$\alpha$ Emitters with Very Large Ly$\alpha$ Equivalent Widths, EW${}_0$(Ly$\alpha$) $\simeq 200-400$ Å, at $z\sim 2$
• Lyman Alpha and MgII as Probes of Galaxies and their Environments
• Constraining the Lyman Alpha Escape Fraction with Far-Infrared Observations of Lyman Alpha Emitters
• Magellan/MMIRS near-infrared multi-object spectroscopy of nebular emission from star forming galaxies at 2<z<3
• Large-scale environment of $z\sim 5.7$ CIV absorption systems -II. Spectroscopy of Lyman-$\alpha$ emitters
• Galactic winds and stellar populations in Lyman $\alpha$ emitting galaxies at z ~ 3.1
• The VIMOS Ultra Deep Survey: The role of HI kinematics and HI column density on the escape of Lyalpha photons in star-forming galaxies at 2<z<4
• Rest-frame UV Properties of Luminous Strong Gravitationally Lensed Ly$\alpha$ Emitters from the BELLS GALLERY Survey
• The Curious Case of Lyman Alpha Emitters: Growing Younger from z ~ 3 to z ~ 2?
• Probing the Physical Properties of z=4.5 Lyman Alpha Emitters with Spitzer
• The Dynamical Masses, Densities, and Star Formation Scaling Relations of Lyman Alpha Galaxies
• Scrutiny of a very young, metal-poor star-forming Lyα-emitter at z ~ 3.7
• A deep search for CO J=2-1 emission from a Lyman-Alpha blob at z~6.595
• A magnified view of star formation at redshift 0.9 from two lensed galaxies
• Observations of Ly$\alpha$ Emitters at High Redshift
• A z ~ 5.7 Lyα Emission Line with an Ultra Broad Red Wing
• Effects of photon trapping on the Lyman-alpha properties of star-forming galaxies
• Unveiling an old disk around a massive young leaking blueberry in SDSS-IV MaNGA