NGC 147 Corroborates the Break in the Stellar Mass-Stellar Metallicity
  Relation for Galaxies
  The stellar mass-stellar metallicity relation (MZR) is an essential approach
to probe the chemical evolution of galaxies. It reflects the balance between
galactic feedback and gravitational potential as a function of stellar mass.
However, the current MZR of local dwarf satellite galaxies (M* <~ 10^8 Msun,
measured from resolved stellar spectroscopy) may not be reconcilable with that
of more massive galaxies (M* >~ 10^9.5 Msun, measured from integrated-light
spectroscopy). Such a discrepancy may result from a systematic difference
between the two methods, or it may indicate a break in the MZR around 10^9
Msun. To address this question, we measured the stellar metallicity of NGC 147
from integrated light using the Palomar Cosmic Web Imager (PCWI). We compared
the stellar metallicity estimates from integrated light with the measurements
from resolved stellar spectroscopy and found them to be consistent within 0.1
dex. On the other hand, the high-mass MZR overpredicts the metallicity by 0.6
dex at the mass of NGC 147. Therefore, our results tentatively suggest that the
discrepancy between the low-mass MZR and high-mass MZR should not be attributed
to a systematic difference in techniques. Instead, real physical processes
cause the transition in the MZR. In addition, we discovered a positive age
gradient in the innermost region and a negative metallicity gradient from the
resolved stars at larger radii, suggesting a possible outside-in formation of
NGC 147.
