RUBIES. Spectroscopic census of little red dots

Photometric samples are constructed from varying selection criteria with limited spectroscopic follow-up available to test intrinsic spectral shapes and prevalence of broad emission lines. We use the RUBIES survey, a large spectroscopic program with wide color-morphology coverage and homogeneous data quality, to systematically analyze the emission-line kinematics, spectral shapes, and morphologies of ~1500 galaxies at z>3.1.

We identify broad Balmer lines via a novel fitting approach that simultaneously models NIRSpec/PRISM and G395M spectra, yielding 80 broad-line sources with 28 (35%) at z>6. A large subpopulation naturally emerges from the broad Balmer line sources, with 36 exhibiting 'v-shaped' UV-to-optical continua and a dominant point source component in the rest-optical; we define these as spectroscopic LRDs, constituting the largest such sample to date.