2013ApJ...778...91Y

With multiband photometric data in public archives, we detected four intracluster star-forming regions in the Virgo Cluster. Two of them were at a projected distance of 35 kpc from NGC 4388 and the other two were 66 kpc away. Our new spectroscopic observations revealed that their recessional velocities were comparable to the ram-pressure-stripped tail of NGC 4388 and confirmed the association. The stellar mass of the star-forming regions ranged from 10⁴ to 10^4.5 M_☉ except for that of the faintest one, which was <10³ M_☉. The metallicity was comparable to a solar abundance and the age of the stars was ∼10^6.8 yr. Their young stellar age meant that the star formation should have started after the gas was stripped from NGC 4388. This implied in situ condensation of the stripped gas. We also found that two star-forming regions were located near the leading edge of a filamentary dark cloud. The extinction of the filament was smaller than that derived from the Balmer decrement of the star-forming regions, implying that the dust in the filament would be locally dense around the star-forming regions.