We present far-UV spectroscopy from the Cosmic Origins Spectrograph on the Hubble Space Telescope of a cool , star-forming filament in the core of Abell 1795 .
These data , which span 1025Å < \lambda _ { rest } < 1700Å , allow for the simultaneous modeling of the young stellar populations and the intermediate-temperature ( 10 ^ { 5.5 } K ) gas in this filament , which is far removed ( \sim 30 kpc ) from the direct influence of the central AGN .
Using a combination of UV absorption line indices and stellar population synthesis modeling , we find evidence for ongoing star formation , with the youngest stars having ages of 7.5 ^ { +2.5 } _ { -2.0 } Myr and metallicities of 0.4 ^ { +0.2 } _ { -0.1 } Z _ { \odot } .
The latter is consistent with the local metallicity of the intracluster medium .
We detect the O vi \lambda 1038 line , measuring a flux of f _ { \scriptsize \textrm { O } \tiny \textrm { VI } , 1038 } = 4.0 \pm 0.9 \times 10 ^ { -17 } erg s ^ { -1 } cm ^ { -2 } .
The O vi \lambda 1032 line is redshifted such that it is coincident with a strong Galactic H _ { 2 } absorption feature , and is not detected .
The measured O vi \lambda 1038 flux corresponds to a cooling rate of 0.85 \pm 0.2 ( stat ) \pm 0.15 ( sys ) M _ { \odot } yr ^ { -1 } at \sim 10 ^ { 5.5 } K , assuming that the cooling proceeds isochorically , which is consistent with the classical X-ray luminosity-derived cooling rate in the same region .
We measure a star formation rate of 0.11 \pm 0.02 M _ { \odot } yr ^ { -1 } from the UV continuum , suggesting that star formation is proceeding at 13 ^ { +3 } _ { -2 } % efficiency in this filament .
We propose that this inefficient star formation represents a significant contribution to the larger-scale cooling flow problem .