Accurate redshift of the TDG candidate J15491758+214951179

Determine the accurate redshift of the tidal dwarf galaxy candidate J15491758+214951179, located at the tip of the tidal tail of PGC 56121 in the HCG 77 system.

Background

The HCG 77 system is dominated by two nearby dwarf galaxies, PGC 56121 and PGC 56125, at redshifts 0.006969 and 0.007505, respectively. UVIT/AstroSat far-UV imaging reveals multiple star-forming regions and a distinct tidal feature ending in a compact source identified as a candidate tidal dwarf galaxy (TDG), J15491758+214951179.

In the SED analysis, the redshift of J15491758+214951179 was assumed to be the same as PGC 56121 (z≈0.006969) based on the H I velocity field, but the authors emphasize that the accurate redshift of this TDG candidate is still unknown. A precise redshift measurement is necessary to establish its distance, refine derived physical parameters (e.g., stellar mass, SFR), and assess its physical association with the HCG 77 system.