We present environmental analyses for 13 KPNO International Spectroscopic Survey Green Pea (GP) galaxies. These galaxies were discovered via their strong [O
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Abstract iii ] emission in the redshift range 0.29 <z < 0.42, and they are undergoing a major burst of star formation. A primary goal of this study is to understand what role the environment plays in driving the current star formation activity. By studying the environments around these extreme star-forming galaxies, we can learn more about what triggers their star formation processes and how they fit into the narrative of galaxy evolution. Using the Hydra multifiber spectrograph on the WIYN 3.5 m telescope, we mapped out the galaxy distribution around each of the GPs (out to ∼15 Mpc at the redshifts of the targets). Using three density analysis methodologies chosen for their compatibility with the geometry of our redshift survey, we categorized the galaxian densities of the GPs into different density regimes. We find that the GPs in our sample tend to be located in low-density environments. We find no correlation between the density and the SFRs seen in the GPs. We conclude that the environments the GPs are found in are likely not the driving factor behind their extreme star formation activity. -
Abstract We present rest-frame optical emission-line flux ratio measurements for five
z > 5 galaxies observed by the James Webb Space Telescope Near-Infared Spectrograph (NIRSpec) in the SMACS 0723 Early Release Observations. We add several quality-control and post-processing steps to the NIRSpec pipeline reduction products in order to ensure reliablerelative flux calibration of emission lines that are closely separated in wavelength, despite the uncertainabsolute spectrophotometry of the current version of the reductions. Compared toz ∼ 3 galaxies in the literature, thez > 5 galaxies have similar [Oiii ]λ 5008/Hβ ratios, similar [Oiii ]λ 4364/Hγ ratios, and higher (∼0.5 dex) [NeIII ]λ 3870/[OII ]λ 3728 ratios. We compare the observations to MAPPINGS V photoionization models and find that the measured [NeIII ]λ 3870/[OII ]λ 3728, [Oiii ]λ 4364/Hγ , and [Oiii ]λ 5008/Hβ emission-line ratios are consistent with an interstellar medium (ISM) that has very high ionization ( , units of cm s−1), low metallicity (Z /Z ⊙≲ 0.2), and very high pressure ( , units of cm−3). The combination of [Oiii ]λ 4364/Hγ and [Oiii ]λ (4960 + 5008)/Hβ line ratios indicate very high electron temperatures of , further implying metallicities ofZ /Z ⊙≲ 0.2 with the application of low-redshift calibrations for “T e -based” metallicities. These observations represent a tantalizing new view of the physical conditions of the ISM in galaxies at cosmic dawn.