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We present extensive optical photometric and spectroscopic observations ofthe high-velocity (HV) Type Ia supernova (SN Ia) 2017fgc, covering the phasefrom $\sim$ 12 d before to $\sim 389$ d after maximum brightness. SN 2017fgc issimilar to normal SNe Ia, with an absolute peak magnitude of $M_{\rm max}^{B}\approx$ $-19.32 \pm 0.13$ mag and a post-peak decline of ${\Delta}m_{15}(B)$ =$1.05 \pm 0.07$ mag. Its peak bolometric luminosity is derived as $1.32 \pm0.13) \times 10^{43} $erg s$^{-1}$, corresponding to a $^{56}$Ni mass of $0.51\pm 0.03 M_{\odot}$. The light curves of SN 2017fgc are found to exhibit excessemission in the $UBV$ bands in the early nebular phase and pronounced secondaryshoulder/maximum features in the $RrIi$ bands. Its spectral evolution issimilar to that of HV SNe Ia, with a maximum-light Si II velocity of $15,000\pm 150 $km s$^{-1}$ and a post-peak velocity gradient of $\sim$ $120 \pm 10$km s$^{-1} $d$^{-1}$. The Fe II and Mg II lines blended near 4300 {\AA} andthe Fe II, Si II, and Fe III lines blended near 4800 {\AA} are obviouslystronger than those of normal SNe Ia. Inspecting a large sample reveals thatthe strength of the two blends in the spectra, and the secondary peak in the$i/r$-band light curves, are found to be positively correlated with themaximum-light Si II velocity. Such correlations indicate that HV SNe~Ia mayexperience more complete burning in the ejecta and/or that their progenitorshave higher metallicity. Examining the birthplace environment of SN 2017fgcsuggests that it likely arose from a stellar environment with young andhigh-metallicity populations.

SN 2017fgc: A Fast-Expanding Type Ia Supernova Exploded in Massive Shell Galaxy NGC 474