学术文献库

Based on the Sloan Digital Sky Survey Data Release 16, we have detected the large-scale structure of Ly$α$ emission in the Universe at redshifts $z = 2$--3.5 by cross-correlating quasar positions and Ly$α$ emission imprinted in the residual spectra of luminous red galaxies. We apply an analytical model to fit the corresponding Ly$α$ surface brightness profile and multipoles of the redshift-space quasar-Ly$α$ emission cross-correlation function. The model suggests an average cosmic Ly$α$ luminosity density of ${6.6_{-3.1}^{+3.3}}\times 10^{40} {\rm erg\, s^{-1} cMpc^{-3}}$, a $\sim 2σ$ detection with a median value about 8--9 times those estimated from deep narrowband surveys of Ly$α$ emitters at similar redshifts. Although the low signal-to-noise ratio prevents us from a significant detection of the Ly$α$ forest-Ly$α$ emission cross-correlation, the measurement is consistent with the prediction of our best-fit model from quasar-Ly$α$ emission cross-correlation within current uncertainties. We rule out the scenario that these Ly$α$ photons mainly originate from quasars. We find that Ly$α$ emission from star-forming galaxies, including contributions from that concentrated around the galaxy centers and that in the diffuse Ly$α$ emitting halos, is able to explain the bulk of the the Ly$α$ luminosity density inferred from our measurements. Ongoing and future surveys can further improve the measurements and advance our understanding of the cosmic Ly$α$ emission field.