Michael Jones, Steward Observatory
Young, blue, and isolated stellar systems in the Virgo cluster
Wide area surveys of neutral gas (HI) have a history of identifying nearby, extreme gas-to-stellar mass ratio objects, with 10s or 100s of times more gas than stars, pushing the boundaries of what we consider to be "galaxies." One such enigmatic object is SECCO1, a very blue, extremely low mass (M* ~ 10^5 Msol), high metallicity (12 + log O/H = 8.38), gas rich (MHI/M* ~ 100), actively star-forming, and isolated stellar system embedded deep in the Virgo galaxy cluster. In this talk I will discuss 4 analogous objects in Virgo, which were identified through their optical/UV morphology, rather than their HI emission. Based on follow-up HST, VLT/MUSE, VLA and GBT observations we have found that these objects are universally blue, high metallicity (12 + log O/H > 8.3), extremely low-mass (M* ~ 10^5 Msol), and surprisingly isolated. Despite the abundance of HII regions identified in all these objects, only one is detected in neutral gas, having an enormous gas-to-stellar mass ratio (MHI/M* ~ 800). Based on these results we propose that the most plausible formation mechanism for these objects is from extreme ram pressure stripping events in recent cluster members. However, this means that the stripped clouds must remain intact as they travel hundreds of kpc through the intracluster medium. Together these objects appear to represent a new class of stellar system, related to both "fireballs" and "tidal dwarf galaxies", but distinct from both.