The contribution of N-rich stars to the Galactic stellar halo using
  APOGEE red giants
  The contribution of dissolved globular clusters (GCs) to the stellar content
of the Galactic halo is a key constraint on models for GC formation and
destruction, and the mass assembly history of the Milky Way. Earlier results
from APOGEE pointed to a large contribution of destroyed GCs to the stellar
content of the inner halo, by as much as 25$\%$, which is an order of magnitude
larger than previous estimates for more distant regions of the halo. We set out
to measure the ratio between N-rich and normal halo field stars, as a function
of distance, by performing density modelling of halo field populations in
APOGEE DR16. Our results show that at 1.5 kpc from the Galactic Centre, N-rich
stars contribute a much higher 16.8$^{+10.0}_{-7.0}$$\%$ fraction to the total
stellar halo mass budget than the 2.7$^{+1.0}_{-0.8}$$\%$ ratio contributed at
10 kpc. Under the assumption that N-rich stars are former GC members that now
reside in the stellar halo field, and assuming the ratio between first-and
second-population GC stars being 1:2, we estimate a total contribution from
disrupted GC stars of the order of 27.5$^{+15.4}_{-11.5}$$\%$ at r = 1.5 kpc
and 4.2$^{+1.5}_{-1.3}$$\%$ at r = 10 kpc. Furthermore, since our methodology
requires fitting a density model to the stellar halo, we integrate such density
within a spherical shell from 1.5-15 kpc in radius, and find a total stellar
mass arising from dissolved and/or evaporated GCs of $M_{\mathrm{GC,total}}$ =
9.6$^{+4.0}_{-2.6}$ $\times$ 10$^{7}$ M$\odot$.
