We present a detection of 89 candidates of ultra-diffuse galaxies ( UDGs ) in a 4.9 degree ^ { 2 } field centered on the Hickson Compact Group 95 ( HCG 95 ) using deep g - and r -band images taken with the Chinese Near Object Survey Telescope .
This field contains one rich galaxy cluster ( Abell 2588 at z =0.199 ) and two poor clusters ( Pegasus I at z =0.013 and Pegasus II at z =0.040 ) .
The 89 candidates are likely associated with the two poor clusters , giving about 50 - 60 true UDGs with a half-light radius r _ { e } > 1.5 kpc and a central surface brightness \mu ( g, 0 ) > 24.0 mag arcsec ^ { -2 } .
Deep z \arcmin -band images are available for 84 of the 89 galaxies from the Dark Energy Camera Legacy Survey ( DECaLS ) , confirming that these galaxies have an extremely low central surface brightness .
Moreover , our UDG candidates are spread over a wide range in g - r color , and \sim 26 % are as blue as normal star-forming galaxies , which is suggestive of young UDGs that are still in formation .
Interestingly , we find that one UDG linked with HCG 95 is a gas-rich galaxy with H I mass 1.1 \times 10 ^ { 9 } M _ { \odot } detected by the Very Large Array , and has a stellar mass of M _ { \star } \sim 1.8 \times 10 ^ { 8 } M _ { \odot } .
This indicates that UDGs at least partially overlap with the population of nearly dark galaxies found in deep H I surveys .
Our results show that the high abundance of blue UDGs in the HCG 95 field is favored by the environment of poor galaxy clusters residing in H I -rich large-scale structures .