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A large population of ultra-diffuse galaxies (UDGs) was recently discovered in the Coma cluster. Here we present optical spectra of three such UDGs, DF7, DF44, and DF17, which have central surface brightnesses of μ g ≈24.4-25.1 mag arcsec −2 . The spectra were acquired as part of an ancillary program within the SDSS-IV MaNGA Survey. We stacked 19 fibers in the central regions from larger integral field units (IFUs) per source. With over 13.5 hr of on-source integration, we achieved a mean signal-to-noise ratio in the optical of 9.5 Å −1 , 7.9 Å −1 , and 5.0 Å −1 , respectively, for DF7, DF44, and DF17. Stellar population models applied to these spectra enable measurements of recession velocities, ages, and metallicities. respectively. Their stellar masses are (3-6)×10 8 M e . The UDGs in our sample are as old or older than galaxies at similar stellar mass or velocity dispersion (only DF 44 has an independently measured dispersion). They all follow the well-established stellar mass-stellar metallicity relation, while DF44 lies below the velocity dispersionmetallicity relation. These results, combined with the fact that UDGs are unusually large for their stellar masses, suggest that stellar mass plays a more important role in setting stellar population properties for these galaxies than either size or surface brightness.

The stellar content of the intracluster light (ICL) provides unique insight into the hierarchical assembly process of galaxy clusters. We present optical spectra of three ICL regions (μ g ≈25.3-26.2 magarcsec −2) in the Coma cluster, located between 100 and 180kpc from their nearest brightest cluster galaxies (BCGs): NGC4889 and NGC4874. Integralfield unit (IFU) spectroscopy with 13.5 hr on-source integration was acquired in an ancillary program within the Sloan Digital Sky Survey-IV MaNGA survey. We stacked the 127 individual fiber spectra in each IFU to achieve a 1σ limiting surface brightness of 27.9magarcsec −2 , corresponding to a mean signal-to-noise ratio in the optical of 21.7, 9.0, and 11.7 Å −1 , for each ICL region. We apply stellar population models to the stacked spectra. Our results show that the velocity dispersions of ICL regions are very high (σ∼630 km s −1), indicating the stars in these regions are tracing the gravitational potential of the cluster, instead of any individual galaxy. The line-of-sight velocities are different from each other by ∼700km s −1 , while the velocity of each region is similar to the closest BCG. This suggests that the ICL regions are associated with two distinct subclusters centered on NGC4889 and NGC4874. The stellar populations of these regions are old and metal-poor, with ages of-+ 12.7 3.4

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