We find 9 nuclear cluster candidates in a sample of 14 edge-on , late-type galaxies observed with HST/ACS .
These clusters have magnitudes ( M _ { I } \sim - 11 ) and sizes ( r _ { eff } \sim 3 Â pc ) similar to those found in previous studies of face-on , late-type spirals and dE galaxies .
However , three of the nuclear clusters are significantly flattened and show evidence for multiple , coincident structural components .
The elongations of these three clusters are aligned to within \sim 10 ^ { \circ } of the galaxies ’ major axes .
Structurally , the flattened clusters are well fit by a combination of a spheroid and a disk or ring , with the disk preferred in two of three cases .
The nuclear cluster disks/rings have F606W-F814W ( \sim V-I ) colors 0.3-0.6 magnitudes bluer than the spheroid components , suggesting that the stars in these components have ages < 1Â Gyr .
In NGCÂ 4244 , the nearest of the nuclear clusters , we further constrain the stellar populations via spectroscopy and multi-band photometry .
This nuclear cluster is equally well fit by single-stellar populations with ages of either \sim 100Â Myr or \sim 1Â Gyr , and with masses of 2-5 \times 10 ^ { 6 } M _ { \odot } .
However , significantly better fits to the spectroscopy and photometry are obtained by combining two or more stellar populations .
Exploiting emission lines that appear to originate \sim 1″Â from the NGCÂ 4244 nucleus , we determine a lower limit on the dynamical mass of 2.5 ^ { +1.7 } _ { -1.2 } \times 10 ^ { 6 } M _ { \odot } within 19Â pc , typical of values found for other nuclear clusters .
We also present tentative evidence that another of the nuclear clusters ( in NGCÂ 4206 ) may also host a supermassive black hole .
Based on our observational results we propose an in situ formation mechanism for nuclear clusters in which stars form episodically in compact nuclear disks , and then lose angular momentum or heat vertically to form an older spheroidal structure .
We estimate the period between star formation episodes to be \sim 0.5 Gyr and discuss possible mechanisms for tranforming the disk-like components into spheroids .
We also note the connection between our objects and massive globular clusters ( e.g . \omega  Cen ) , ultra-compact dwarfs , and supermassive black holes .