The FLASHES Survey I: Integral Field Spectroscopy of the CGM around 48 $z=2.3-3.1$ QSOs

Abstract

We present the pilot study component of the Fluorescent Lyman-Alpha Structures in High-z Environments (FLASHES) Survey; the largest integral-field spectroscopy survey to date of the circumgalactic medium at $z=2.3-3.1$. We observed 48 quasar fields between 2015 and 2018 with the Palomar Cosmic Web Imager (Matuszewski et al. 2010). Extended HI Lyman-$\hat{\mathrm{I}}\pm$ emission is discovered around 42/48 of the observed quasars, ranging in projected, flux-weighted radius from 21-71 proper kiloparsecs (pkpc), with 26 nebulae exceeding $100\mathrm{pkpc}$ in effective diameter. The circularly averaged surface brightness radial profile peaks at a maximum of $1\times 10^{-17}\mathrm{erg}{\mathrm{s}}^{-1}\mathrm{c}{\mathrm{m}}^{-2}\mathrm{arcse}{\mathrm{c}}^{-2}$ ($2\times 10^{-15}\mathrm{erg}{\mathrm{s}}^{-1}\mathrm{c}{\mathrm{m}}^{-2}\mathrm{arcse}{\mathrm{c}}^{-2}$ adjusted for cosmological dimming) and luminosities range from $1.9\times 10^{43}\mathrm{erg}{\mathrm{s}}^{-1}$ to $-14.1\times 10^{43}\mathrm{erg}{\mathrm{s}}^{-1}$. The emission appears to have a highly eccentric morphology and a maximum covering factor of $50\%$ ($60\%$ for giant nebulae). On average, the nebular spectra are red-shifted with respect to both the systemic redshift and Ly$\hat{I}\pm$ peak of the quasar spectrum. The integrated spectra of the nebulae mostly have single or double-peaked line shapes with global dispersions ranging from $167\mathrm{km}{\mathrm{s}}^{-1}$ to $690\mathrm{km}{\mathrm{s}}^{-1}$, though the individual (Gaussian) components of lines with complex shapes mostly appear to have dispersions $\le 400$ $\mathrm{km}{\mathrm{s}}^{-1}$, and the flux-weighted velocity centroids of the lines vary by thousands of $\mathrm{km}{\mathrm{s}}^{-1}$ with respect to the systemic QSO redshifts. Finally, the root-mean-square velocities of the nebulae are found to be consistent with gravitational motions expected in dark matter halos of mass ${\mathrm{M}}_{\mathrm{h}}\simeq 10^{12.5}{\mathrm{M}}_{\odot }$. We compare these results to existing surveys at both higher and lower redshift.