We probe the diffuse stellar mass in a sample of 1401 low redshift galaxy groups ( 10 ^ { 13 } - 10 ^ { 14 } h ^ { -1 } ~ { } M _ { \odot } ) by examining the rate of hostless Type Ia supernova ( SNe Ia ) within the groups .
We correlate the sample of confirmed SNe Ia from the SDSS supernova survey with the positions of our galaxy groups , as well as with the resolved galaxies within them .
We find that 19 of the 59 SNe Ia within the group sample have no detectable host galaxy , with another three ambiguous instances .
This gives a robust upper limit that a maximum of 2.69 ^ { +1.58 } _ { -1.34 } % percent of the group ’ s total mass arises from diffuse stars in the intragroup medium .
After correcting for a contribution from “ prompt ” SNe occurring within galaxies , and including a contribution from those which arise in dwarf galaxies below our photometric limit , we find that only 1.32 ^ { +0.78 } _ { -0.70 } \% of the group ’ s total mass is likely in the form of diffuse stellar mass .
Combining this result with the galaxy stellar mass functions of , we find that 47 ^ { +16 } _ { -15 } \% of the stellar mass in our groups is in the form of diffuse light , so that stars make up a fraction 0.028 ^ { +0.011 } _ { -0.010 } of the total group mass .
Galaxy groups appear to be very efficient in disrupting stellar mass into a diffuse component ; however , stars still make up a small fraction of the group mass , comparable to that seen in rich clusters .
This remains a challenge to galaxy formation models .