The Web Epoch of Reionization Lyman-α\alpha Survey (WERLS) I. MOSFIRE Spectroscopy of z∼7−8\mathbf{z \sim 7-8} Lyman-α\alpha Emitters

We present the first results from the Web Epoch of Reionization Lyman-$\alpha$ Survey (WERLS), a spectroscopic survey of Lyman-$\alpha$ emission using Keck I/MOSFIRE and LRIS. WERLS targets bright ($J<26$) galaxy candidates with photometric redshifts of $5.5\lesssim z \lesssim 8$ selected from pre-JWST imaging embedded in the Epoch of Reionization (EoR) within three JWST deep fields: CEERS, PRIMER, and COSMOS-Web. Here, we report 11 $z\sim7-8$ Lyman-$\alpha$ emitters (LAEs; 3 secure and 8 tentative candidates) detected in the first five nights of WERLS MOSFIRE data. We estimate our observed LAE yield is $\sim13$%, broadly consistent with expectations assuming some loss from redshift uncertainty, contamination from sky OH lines, and that the Universe is approximately half-ionized at this epoch, whereby observable Lyman-$\alpha$ emission is unlikely for galaxies embedded in a neutral intergalactic medium. Our targets are selected to be UV-bright, and span a range of absolute UV magnitudes with $-23.1 < M_{\text{UV}} < -19.8$. With two LAEs detected at $z=7.68$, we also consider the possibility of an ionized bubble at this redshift. Future synergistic Keck+JWST efforts will provide a powerful tool for pinpointing beacons of reionization and mapping the large scale distribution of mass relative to the ionization state of the Universe.Comment: 27 pages, 8 figures; ApJ submitte

CEERS Key Paper. V. Galaxies at 4 &lt; z &lt; 9 Are Bluer than They Appear-Characterizing Galaxy Stellar Populations from Rest-frame ∼1 μm Imaging

We present results from the Cosmic Evolution Early Release Survey on the stellar population parameters for 28 galaxies with redshifts 4 &lt; z &lt; 9 using imaging data from the James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI) combined with data from the Hubble Space Telescope and the Spitzer Space Telescope. The JWST/MIRI 5.6 and 7.7 μm data extend the coverage of the rest-frame spectral energy distribution to nearly 1 μm for galaxies in this redshift range. By modeling the galaxies’ SEDs the MIRI data show that the galaxies have, on average, rest-frame UV (1600 Å)—I-band colors 0.4 mag bluer than derived when using photometry that lacks MIRI. Therefore, the galaxies have lower ratios of stellar mass to light. The MIRI data reduce the stellar masses by 〈 Δ log M * 〉 = 0.25 dex at 4 &lt; z &lt; 6 and 0.37 dex at 6 &lt; z &lt; 9. This also reduces the star formation rates (SFRs) by 〈ΔlogSFR〉 = 0.14 dex at 4 &lt; z &lt; 6 and 0.27 dex at 6 &lt; z &lt; 9. The MIRI data also improve constraints on the allowable stellar mass formed in early star formation. We model this using a star formation history that includes both a “burst” at z f = 100 and a slowly varying (“delayed-τ”) model. The MIRI data reduce the allowable stellar mass by 0.6 dex at 4 &lt; z &lt; 6 and by ≈1 dex at 6 &lt; z &lt; 9. Applying these results globally, this reduces the cosmic stellar-mass density by an order of magnitude in the early Universe (z ≈ 9). Therefore, observations of rest-frame ≳1 μm are paramount for constraining the stellar-mass buildup in galaxies at very high redshifts.</p

CEERS Key Paper IV: Galaxies at 4<z<94 < z < 9 are Bluer than They Appear -- Characterizing Galaxy Stellar Populations from Rest-Frame ∼1\sim 1 micron Imaging

We present results from the Cosmic Evolution Early Release Survey (CEERS) on the stellar-population parameters for 28 galaxies with redshifts $4<z<9$ using imaging data from the James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI) combined with data from the Hubble Space Telescope and the Spitzer Space Telescope. The JWST/MIRI 5.6 and 7.7 $\mu$m data extend the coverage of the rest-frame spectral-energy distribution (SED) to nearly 1 micron for galaxies in this redshift range. By modeling the galaxies' SEDs the MIRI data show that the galaxies have, on average, rest-frame UV (1600 \r{A}) $-$ $I$-band colors 0.4 mag bluer than derived when using photometry that lacks MIRI. Therefore, the galaxies have lower (stellar)-mass-to-light ratios. The MIRI data reduce the stellar masses by $\langle \Delta\log M_\ast\rangle=0.25$ dex at $4<z<6$ (a factor of 1.8) and 0.37 dex at $6<z<9$ (a factor of 2.3). This also reduces the star-formation rates (SFRs) by $\langle \Delta\log\mathrm{SFR} \rangle=0.14$ dex at $4<z<6$ and 0.27 dex at $6<z<9$. The MIRI data also improve constraints on the allowable stellar mass formed in early star-formation. We model this using a star-formation history that includes both a "burst' at $z_f=100$ and a slowly varying ("delayed-$\tau$") model. The MIRI data reduce the allowable stellar mass by 0.6 dex at $4<z< 6$ and by $\approx$1 dex at $6<z<9$. Applying these results globally, this reduces the cosmic stellar-mass density by an order of magnitude in the early universe ($z\approx9$). Therefore, observations of rest-frame $\gtrsim$1 $\mu$m are paramount for constraining the stellar-mass build-up in galaxies at very high-redshifts.Comment: Updated with accepted ApJ version. Part of the CEERS Focus Issue. 27 pages, many figures (4 Figure Sets, available upon reasonable request

On the Metallicities and Kinematics of the Circumgalactic Media of Damped Lyα Systems at z ∼ 2.5

We use medium- and high-resolution spectroscopy of close pairs of quasars to analyze the circumgalactic medium (CGM) surrounding 32 damped Ly α absorption systems (DLAs). The primary quasar sightline in each pair probes an intervening DLA in the redshift range 1.6 10 ^13 cm ^−2 within 100 kpc of DLAs are larger by 2 σ than those measured in the CGM of Lyman break galaxies (C _f ( N _C _II ) > 0.89 and ${{\rm{C}}}_{f}({N}_{\mathrm{Si}{\rm\small{II}}})={0.75}_{-0.17}^{+0.12}$ ). Metallicity constraints derived from ionic ratios for nine CGM systems with negligible ionization corrections and N _HI > 10 ^18.5 cm ^−2 show a significant degree of scatter (with metallicities/limits across the range $-2.06\lesssim \mathrm{log}Z/{Z}_{\odot }\lesssim -0.75$ ), suggesting inhomogeneity in the metal distribution in these environments. Velocity widths of C iv λ 1548 and low-ionization metal species in the DLA versus CGM sightlines are strongly (>2 σ ) correlated, suggesting that they trace the potential well of the host halo over R _⊥ ≲ 300 kpc scales. At the same time, velocity centroids for C iv λ 1548 differ in DLA versus CGM sightlines by >100 km s ^−1 for ∼50% of velocity components, but few components have velocities that would exceed the escape velocity assuming dark matter host halos of ≥10 ^12 M _⊙

Deeper than DEEP: A Spectroscopic Survey of z>3z>3 Lyman-α\alpha Emitters in the Extended Groth Strip

We present a spectroscopic survey of Ly$\alpha$ emitters in the Extended Groth Strip (EGS) field, targeting the regime near the Epoch of Reionization. Using Keck/DEIMOS, we observed 947 high-$z$ candidates with photometric redshifts from 3 $< z_\text{phot} <$ 7 and down to an $H$-band (HST/WFC3 F160W) magnitude limit of < 27.5. Observations were taken over the course of 8 nights, with integration times ranging from 4 to 7.8 hours. Our survey secured 137 unique redshifts, 126 of which are Ly$\alpha$ emitters at 2.8 $< z <$ 6.5 with a mean redshift of $\overline{z} = 4.3$. We provide a comprehensive redshift catalog for our targets, as well as the reduced one- and two- dimensional spectra for each object. These observations will provide an important auxiliary dataset for the JWST Directors Discretionary Early Release Science (DD-ERS) program the Cosmic Evolution Early Release Science Survey (CEERS), which recently completed near- and mid-IR imaging and spectroscopy of galaxies in the EGS field.Comment: 8 pages, 6 figures, 2 tables, submitted to MNRA