Outlying Hα emitters in SDSS IV MaNGA

Abstract

We have carried out a systematic search for outlying Hα emitters in the entire Data Release 14 of the Sloan Digital Sky Survey (SDSS) IV Mapping Nearby Galaxies at APO (MaNGA) survey. We have discovered six outlying Hα emitters with no bright underlying optical continuum emission in the imaging Data Release 5 from the Dark Energy Camera Legacy Survey (DECaLS) and Data Release 6 of the Mayall z-band Legacy Survey (MzLS) + Beijing–Arizona Sky Survey (BASS). They also show a velocity field that is different from that of the host galaxy. These outlying Hα emitters all have extended structure in the Hα image. Their emission line ratios show that they are photoionized due to an active galactic nucleus (AGN) or a mixture of both an AGN and star formation. Some of them are very likely to be fainter counterparts of Hanny’s Voorwerp-like objects.