We found an unusual complex of narrow blue filaments , bright blue knots , and H \alpha -emitting filaments and clouds , which morphologically resembled a complex of “ fireballs , ” extending up to 80 kpc south from an E+A galaxy RB199 in the Coma cluster .
The galaxy has a highly disturbed morphology indicative of a galaxy–galaxy merger remnant .
The narrow blue filaments extend in straight shapes toward the south from the galaxy , and several bright blue knots are located at the southern ends of the filaments .
The R _ { C } band absolute magnitudes , half light radii and estimated masses of the bright knots are \sim - 12 - -13 mag , \sim 200 - 300 pc and \sim 10 ^ { 6 - 7 } M _ { \odot } , respectively .
Long , narrow H \alpha -emitting filaments are connected at the south edge of the knots .
The average color of the fireballs is B - R _ { C } \approx 0.5 , which is bluer than RB199 ( B - R = 0.99 ) , suggesting that most of the stars in the fireballs were formed within several times 10 ^ { 8 } yr .
The narrow blue filaments exhibit almost no H \alpha emission .
Strong H \alpha and UV emission appear in the bright knots .
These characteristics indicate that star formation recently ceased in the blue filaments and now continues in the bright knots .
The gas stripped by some mechanism from the disk of RB199 may be traveling in the intergalactic space , forming stars left along its trajectory .
The most plausible fireball formation mechanism is ram pressure stripping by high-speed collision between the galaxy and the hot intra-cluster medium .
The fireballs may be a snapshot of diffuse intra-cluster population formation , or halo star population formation in a cluster galaxy .