Detection of the host galaxy of S5 0716+714

Understand

We have acquired a deep i-band image of the BL Lacertae object S5 0716+714 while the target was in an low optical state.

• Due to the faintness of the nucleus, we were able to detect the underlying host galaxy.
• The host galaxy is measured to have an I-band magnitude of 17.5 +- 0.5 and an effective radius of (2.7 +- 0.8) arcsec.
• Using the host galaxy as a ``standard candle'', we derive z = 0.31 +- 0.08 (1 sigma error) for the host galaxy of S5 0716+714.