ZFIRE: Measuring Electron Density with [O ii] as a Function of Environment at z=1.62
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AbstractThe global star formation rates (SFR) of galaxies at fixed stellar masses increase with redshift and are known to vary with environment up to z2. We explore here whether the changes in the SFRs also apply to the electron densities of the interstellar medium by measuring the [O ii] (, ) ratio for cluster and field galaxies at z2. We measure a median electron density of m{e}}}$?> =36684 cm for six galaxies (with 1 scatter=163 cm) in the Ultra-Deep Survey (UDS) protocluster at z=1.62. We find that the median electron density of galaxies in the UDS protocluster environment is three times higher compared to the median electron density of field galaxies ( m{e}}}$?> =11363 cm and 1 scatter=79 cm) at comparable redshifts, stellar mass, and SFR. However, we note that a sample of six protocluster galaxies is insufficient to reliably measure the electron density in the average protocluster environment at z2. We conclude that the electron density increases with redshift in both cluster and field environments up to z2 ( m{e}}}$?> =30 1 cm for z0 to m{e}}}$?> =25476 cm for z1.5). We find tentative evidence (2.6) for a possible dependence of electron density on environment, but the results require confirmation with larger sample sizes.
