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Abstract We present a sample of 30 massive (log( M * / M ⊙ ) > 11) z = 3–5 quiescent galaxies selected from the Spitzer-HETDEX Exploratory Large Area (SHELA) Survey and observed at 1.1 mm with Atacama Large Millimeter/submillimeter Array (ALMA) Band 6 observations. These ALMA observations would detect even modest levels of dust-obscured star formation, on the order of ∼20 M ⊙ yr −1 at z ∼ 4 at the 1 σ level, allowing us to quantify the amount of contamination from dusty star-forming sources in our quiescent sample. Starting with a parent sample of candidate massive quiescent galaxies from the Stevans et al. v1 SHELA catalog, we use the Bayesian B agpipes spectral energy distribution fitting code to derive robust stellar masses ( M * ) and star formation rates (SFRs) for these sources, and select a conservative sample of 36 candidate massive ( M * > 10 11 M ⊙ ) quiescent galaxies, with specific SFRs >2 σ below the Salmon et al. star-forming main sequence at z ∼ 4. Based on the ALMA imaging, six of these candidate quiescent galaxies show the presence of significant dust-obscured star formation, and thus were removed from our final sample. This implies a ∼17% contamination rate from dusty star-forming galaxies with our selection criteria using the v1 SHELA catalog. This conservatively selected quiescent galaxy sample at z = 3–5 will provide excellent targets for future observations to constrain better how massive galaxies can both grow and shut down their star formation in a relatively short period. 

Abstract We used data from the Hobby–Eberly Telescope Dark Energy Experiment (HETDEX) to study the incidence of AGN in continuum-selected galaxies at z ∼ 3. From optical and infrared imaging in the 24 deg 2 Spitzer HETDEX Exploratory Large Area survey, we constructed a sample of photometric-redshift selected z ∼ 3 galaxies. We extracted HETDEX spectra at the position of 716 of these sources and used machine-learning methods to identify those which exhibited AGN-like features. The dimensionality of the spectra was reduced using an autoencoder, and the latent space was visualized through t-distributed stochastic neighbor embedding. Gaussian mixture models were employed to cluster the encoded data and a labeled data set was used to label each cluster as either AGN, stars, high-redshift galaxies, or low-redshift galaxies. Our photometric redshift (photo z ) sample was labeled with an estimated 92% overall accuracy, an AGN accuracy of 83%, and an AGN contamination of 5%. The number of identified AGN was used to measure an AGN fraction for different magnitude bins. The ultraviolet (UV) absolute magnitude where the AGN fraction reaches 50% is M UV = −23.8. When combined with results in the literature, our measurements of AGN fraction imply that the bright end of the galaxy luminosity function exhibits a power law rather than exponential decline, with a relatively shallow faint-end slope for the z ∼ 3 AGN luminosity function. 

ABSTRACT We define a new morphology metric called ‘patchiness’ (P) that is sensitive to deviations from the average of a resolved distribution, does not require the galaxy centre to be defined, and can be used on the spatially resolved distribution of any galaxy property. While the patchiness metric has a broad range of applications, we demonstrate its utility by investigating the distribution of dust in the interstellar medium (ISM) of 310 star-forming galaxies at spectroscopic redshifts 1.36 < z < 2.66 observed by the MOSFIRE Deep Evolution Field survey. The stellar continuum reddening distribution, derived from high-resolution multiwaveband CANDELS/3D-HST imaging, is quantified using the patchiness, Gini, and M20 coefficients. We find that the reddening maps of high-mass galaxies, which are dustier and more metal-rich on average, tend to exhibit patchier distributions (high P) with the reddest components concentrated within a single region (low M20). Our results support a picture where dust is uniformly distributed in low-mass galaxies (≲1010 M⊙), implying efficient mixing of dust throughout the ISM. On the other hand, the dust distribution is patchier in high-mass galaxies (≳1010 M⊙). Dust is concentrated near regions of active star formation and dust mixing time-scales are expected to be longer in high-mass galaxies, such that the outskirt regions of these physically larger galaxies remain relatively unenriched. This study presents direct evidence for patchy dust distributions on scales of a few kpc in high-redshift galaxies, which previously has only been suggested as a possible explanation for the observed differences between nebular and stellar continuum reddening, star formation rate indicators, and dust attenuation curves. 

ABSTRACT We analyse the completeness of the MOSDEF survey, in which z ∼ 2 galaxies were selected for rest-optical spectroscopy from well-studied HST extragalactic legacy fields down to a fixed rest-optical magnitude limit (HAB = 24.5). The subset of z ∼ 2 MOSDEF galaxies with high signal-to-noise (S/N) emission-line detections analysed in previous work represents a small minority (<10 per cent) of possible z ∼ 2 MOSDEF targets. It is therefore crucial to understand how representative this high S/N subsample is, while also more fully exploiting the MOSDEF spectroscopic sample. Using spectral-energy distribution (SED) models and rest-optical spectral stacking, we compare the MOSDEF z ∼ 2 high S/N subsample with the full MOSDEF sample of z ∼ 2 star-forming galaxies with redshifts, the latter representing an increase in sample size of more than a factor of three. We find that both samples have similar emission-line properties, in particular in terms of the magnitude of the offset from the local star-forming sequence on the [N ii] BPT diagram. There are small differences in median host galaxy properties, including the stellar mass (M*), star formation rate (SFR) and specific SFR (sSFR), and UVJ colours; however, these offsets are minor considering the wide spread of the distributions. Using SED modelling, we also demonstrate that the sample of z ∼ 2 star-forming galaxies observed by the MOSDEF survey is representative of the parent catalog of available such targets. We conclude that previous MOSDEF results on the evolution of star-forming galaxy emission-line properties were unbiased relative to the parent z ∼ 2 galaxy population. 

ABSTRACT We perform an aperture-matched analysis of dust-corrected H α and UV star formation rates (SFRs) using 303 star-forming galaxies with spectroscopic redshifts 1.36 < zspec < 2.66 from the MOSFIRE Deep Evolution Field survey. By combining H α and H β emission line measurements with multiwaveband resolved Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey/3D-HST imaging, we directly compare dust-corrected H α and UV SFRs, inferred assuming a fixed attenuation curve shape and constant SFHs, within the spectroscopic aperture. Previous studies have found that H α and UV SFRs inferred with these assumptions generally agree for typical star-forming galaxies, but become increasingly discrepant for galaxies with higher SFRs (≳100 M⊙ yr−1), with H α-to-UV SFR ratios being larger for these galaxies. Our analysis shows that this trend persists even after carefully accounting for the apertures over which H α and UV-based SFRs (and the nebular and stellar continuum reddening) are derived. Furthermore, our results imply that H α SFRs may be higher in the centres of large galaxies (i.e. where there is coverage by the spectroscopic aperture) compared to their outskirts, which could be indicative of inside-out galaxy growth. Overall, we suggest that the persistent difference between nebular and stellar continuum reddening and high H α-to-UV SFR ratios at the centres of large galaxies may be indicative of a patchier distribution of dust in galaxies with high SFRs. 

Abstract We present the Texas Euclid Survey for Lyα(TESLA), a spectroscopic survey in the 10 deg²of the Euclid North Ecliptic Pole (NEP) field. Using TESLA, we study how the physical properties of Lyαemitters (LAEs) correlate with Lyαemission to understand the escape of Lyαemission from galaxies at redshifts of 2–3.5. We present an analysis of 43 LAEs performed in the NEP field using early data from the TESLA survey. We use Subaru Hyper Suprime-Cam imaging in thegrizybands, Spitzer/IRAC channels 1 and 2 from the Hawaii 20 deg²(H20) survey, and spectra acquired by the Visible Integral-Field Replicable Unit Spectrograph (VIRUS) on the Hobby–Eberly Telescope. We perform spectral energy distribution (SED) fitting to compute the galaxy properties of 43 LAEs, and study correlations between stellar mass, star formation rate (SFR), and dust to the Lyαrest-frame equivalent width (W_Lyα). We uncover marginal (1σsignificance) correlations between stellar mass andW_Lyα, and SFR andW_Lyα, with a Spearman correlation coefficient of −0. ${34}_{-.14}^{+.17}$and −0. ${37}_{-.14}^{+.16}$, respectively. We show that theW_Lyαdistribution of the 43 LAEs is consistent with being drawn from an exponential distribution with an e-folding scale ofW₀= 150 Å. Once complete the TESLA survey will enable the study of ≳50,000 LAEs to explore more correlations between galaxy properties andW_Lyα. The large sample size will allow the construction of a predictive model forW_Lyαas a function of SED-derived galaxy properties, which could be used to improve Lyα-based constraints on reionization. 

ABSTRACT We analyse the rest-optical emission-line ratios of z ∼ 1.5 galaxies drawn from the Multi-Object Spectrometer for Infra-Red Exploration Deep Evolution Field (MOSDEF) survey. Using composite spectra, we investigate the mass–metallicity relation (MZR) at z ∼ 1.5 and measure its evolution to z = 0. When using gas-phase metallicities based on the N2 line ratio, we find that the MZR evolution from z ∼ 1.5 to z = 0 depends on stellar mass, evolving by $$\Delta \rm log(\rm O/H) \sim 0.25$$ dex at M*< $$10^{9.75}\, \mathrm{M}_{\odot }$$ down to $$\Delta \rm log(\rm O/H) \sim 0.05$$ at M* ≳ $$10^{10.5}\, \mathrm{M}_{\odot }$$. In contrast, the O3N2-based MZR shows a constant offset of $$\Delta \rm log(\rm O/H) \sim 0.30$$ across all masses, consistent with previous MOSDEF results based on independent metallicity indicators, and suggesting that O3N2 provides a more robust metallicity calibration for our z ∼ 1.5 sample. We investigated the secondary dependence of the MZR on star formation rate (SFR) by measuring correlated scatter about the mean M*-specific SFR and M*−$$\log (\rm O3N2)$$ relations. We find an anticorrelation between $$\log (\rm O/H)$$ and sSFR offsets, indicating the presence of a M*−SFR−Z relation, though with limited significance. Additionally, we find that our z ∼ 1.5 stacks lie along the z = 0 metallicity sequence at fixed μ = log (M*/M⊙) − 0.6 × $$\log (\rm SFR / M_{\odot } \, yr^{-1})$$ suggesting that the z ∼ 1.5 stacks can be described by the z = 0 fundamental metallicity relation (FMR). However, using different calibrations can shift the calculated metallicities off of the local FMR, indicating that appropriate calibrations are essential for understanding metallicity evolution with redshift. Finally, understanding how [N ii]/H α scales with galaxy properties is crucial to accurately describe the effects of blended [N ii] and H α on redshift and H α fiux measurements in future large surveys utilizing low-resolution spectra such as with Euclid and the Roman Space Telescope.