Galactic winds and stellar populations in Lyman $\alpha$ emitting galaxies at z ~ 3.1

Abstract

We present a sample of 33 spectroscopically confirmed z ~ 3.1 Ly$\alpha$-emitting galaxies (LAEs) in the Cosmological Evolution Survey (COSMOS) field. This paper details the narrow-band survey we conducted to detect the LAE sample, the optical spectroscopy we performed to confirm the nature of these LAEs, and a new near-infrared spectroscopic detection of the [O III] 5007 Å line in one of these LAEs. This detection is in addition to two [O III] detections in two z ~ 3.1 LAEs we have reported on previously (McLinden et al 2011). The bulk of the paper then presents detailed constraints on the physical characteristics of the entire LAE sample from spectral energy distribution (SED) fitting. These characteristics include mass, age, star-formation history, dust content, and metallicity. We also detail an approach to account for nebular emission lines in the SED fitting process - wherein our models predict the strength of the [O III] line in an LAE spectrum. We are able to study the success of this prediction because we can compare the model predictions to our actual near-infrared observations both in galaxies that have [O III] detections and those that yielded non-detections. We find a median stellar mass of 6.9 $\times$ 10${}^8$ M${}_{\odot }$ and a median star formation rate weighted stellar population age of 4.5 $\times$ 10${}^6$ yr. In addition to SED fitting, we quantify the velocity offset between the [O III] and Ly$\alpha$ lines in the galaxy with the new [O III] detection, finding that the Ly$\alpha$ line is shifted 52 km s${}^{-1}$ redwards of the [O III] line, which defines the systemic velocity of the galaxy.

38 pages, 27 figures, 4 tables, Accepted for publication in MNRAS

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• The Ly-alpha Properties of Faint Galaxies at z2-3 with Systemic Redshifts and Velocity Dispersions from Keck-MOSFIRE
• Green Pea Galaxies Reveal Secrets of Ly$\alpha$ Escape
• Ly$\alpha$-Lyman Continuum connection in 3.5 < z < 4.3 star-forming galaxies from the VUDS survey
• Feedback in low-mass galaxies in the early Universe
• Near-Infrared Spectroscopy of Galaxies During Reionization: Measuring CIII] in a Galaxy at $\mathbf{z}=7.5$
• A Comprehensive Study of Ly$\alpha$ Emission in the High-redshift Galaxy Population
• A High Fraction of Ly-alpha-Emitters Among Galaxies with Extreme Emission Line Ratios at z ~ 2
• Spectral Energy Distribution Fitting of HETDEX Pilot Survey Lyman-alpha Emitters in COSMOS and GOODS-N
• 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 Lyman alpha reference sample: IV. Morphology at low and high redshift
• The VLT LBG Redshift Survey - V. Characterising the z = 3.1 Lyman Alpha Emitter Population
• MUSE integral-field spectroscopy towards the Frontier Fields cluster Abell S1063: II. Properties of low luminosity Lyman alpha emitters at z>3
• About AGN ionization echoes, thermal echoes, and ionization deficits in low redshift Lyman-alpha blobs
• Large-scale environment of $z\sim 5.7$ CIV absorption systems -II. Spectroscopy of Lyman-$\alpha$ emitters
• Lyman-Alpha Escape from Low-Mass, Compact, High-Redshift Galaxies
• Bright Lyman $\alpha$ emitters among Spitzer SMUVS galaxies in the MUSE/COSMOS field
• Similarities and uniqueness of Ly$\alpha$ emitters among star-forming galaxies at z=2.5
• The Lyman Alpha Spectral Database (LASD)