Luminosity functions of globular clusters in five nearby spiral galaxies
  using HST/ACS images
  We here present the luminosity function (LF) of globular clusters (GCs) in
five nearby spiral galaxies using the samples of GC candidates selected in
Hubble Space Telescope mosaic images in F435W, F555W and F814W filters. Our
search, which surpasses the fractional area covered by all previous searches in
these galaxies, has resulted in the detection of 158 GC candidates in M81, 1123
in M101, 226 in NGC4258, 293 in M51 and 173 in NGC628. The LFs constructed from
this dataset, after correcting for relatively small contamination from reddened
young clusters, are log-normal in nature, which was hitherto established only
for the Milky Way (MW) and Andromeda among spiral galaxies. The magnitude at
the turn-over (TO) corresponds to Mv(TO)=-7.41+/-0.14 in four of the galaxies
with Hubble types Sc or earlier, in excellent agreement with
Mv(TO)=-7.40+/-0.10 for the MW. The TO magnitude is equivalent to a mass of
~3x10^5 Msun for an old, metal-poor population. Mv(TO) is fainter by ~1.16
magnitude for the fifth galaxy, M101, which is of Hubble type Scd. The TO
dependence on Hubble type implies that the GCs in early-type spirals are
classical GCs, which have a universal TO, whereas the GC population in
late-type galaxies is dominated by old disk clusters, which are in general less
massive. The radial density distribution of GCs in our sample galaxies follows
the S\'ersic function with exponential power-law indices, and effective radii
of 4.0-9.5 kpc. GCs in the sample galaxies have a mean specific frequency of
1.10+/-0.24, after correcting for magnitude and radial incompleteness factors.
