Optically unseen H I detections toward the Virgo cluster detected in the Arecibo Legacy Fast ALFA survey

Brian R. Kent, Riccardo Giovanelli, Martha P. Haynes, Amélie Saintonge, Sabrina Stierwalt, Thomas Balonek, Noah Brosch, Barbara Catinella, Rebecca A. Koopmann, Emmanuel Momjian, Kristine Spekkens

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39 Citations (Scopus)


We report the discovery by the Arecibo Legacy Fast ALFA (ALFALFA) survey of eight H i features not coincident with stellar counterparts in the Virgo Cluster region. All of the H i clouds have cz < 3000 km s-1 and, if at the Virgo distance, H i masses between 1.9 × 107 and 1.1 × 109 M⊙. Four of the eight objects were reported or hinted at by previous studies and "rediscovered" by ALFALFA. While some clouds appear to be associated with optical galaxies in their vicinity, others show no clear association with a stellar counterpart. Two of them are embedded in relatively dense regions of the cluster and are associated with M49 and M86; they were previously known. The others are mostly located in peripheral regions of the cluster. Especially notable are a concentration of objects toward the so-called M cloud, 3°-5° to the northwest of M87, and a complex of several clouds projected roughly halfway between M87 and M49. The object referred to as VIRGOHI 21 and proposed to be a "dark galaxy" is also detected and shown to be a tidal feature associated with NGC 4254.

Original languageEnglish
JournalThe Astrophysical Journal
Issue number1 PART 2
Publication statusPublished - 2007


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