Wolf-Rayet Galaxies in SDSS-IV MaNGA. I. Catalog Construction and Sample Properties

Wolf-Rayet (WR) galaxies are a rare galaxy type that hosts living high-mass stars during the WR phase (i.e., WR stars) and can thus provide constraints on the stellar initial mass function, massive star formation, stellar evolution models, etc. Spatially resolved spectroscopy should in principle identify WR galaxies more efficiently than single-fiber surveys of galactic centers, as WR stars should be more preferentially found in disks. Using integral field unit data from the ongoing SDSS-IV MaNGA survey, we have performed a thorough search for WR galaxies. We first identify H ii regions in each datacube and carry out full spectral fitting to the stacked spectra. We then visually inspect the residual spectrum of each H ii region and identify significant WR "blue bumps" at 4600-4750 Å. The WR catalog includes 267 WR regions of ∼500 pc (radius) sizes, distributed in 90 galaxies from MaNGA Product Launch-7. We find that WR regions are exclusively found in galaxies with the bluest colors and highest star formation rates. Most WR galaxies have late-type morphologies and show relatively large asymmetry in their images, implying WR regions exist more in interacting galaxies. We estimate the stellar mass function of WR galaxies and the mass-dependent detection rate (typically ∼2%). This rate is about 40 times higher than that in catalogs from SDSS single-fiber surveys and half that of the CALIFA-based catalog. The difference in detection rates can be explained mainly by three factors: spatial coverage, spectral signal-to-noise ratio, and redshift ranges of parent samples. We tabulate WR galaxy properties for future studies.