Nuclear Star Cluster Research Articles

Nuclei of Nearby Disk Galaxies.I.A Hubble Space Telescope Imaging Survey

view Abstract Citations (117) References (36) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Nuclei of Nearby Disk Galaxies.I.A Hubble Space Telescope Imaging Survey Phillips, Andrew C. ; Illingworth, Garth D. ; MacKenty, John W. ; Franx, Marijn Abstract We present deconvolved images of the central regions of 20 nearby disk galaxies, obtained with the original Planetary Camera of the Hubble Space Telescope. The galaxies span a range in Hubble type from S0 to Sm. We have measured surface brightness profiles, and inverted these to estimate luminosity-density profiles. Surface brightness profiles in the central regions show a variety of forms, sometimes clearly affected by heavy dust obscuration. All galaxies in the sample earlier than type Sc show a continuing rise in surface brightness up to the resolution limit in the deconvolved images. Later types show shallower slopes, consistent with exponential disks either continuing into the center or else flattening in the central regions. These galaxies often, but not always, exhibit an unresolved nucleus which is likely a dense nuclear star cluster. Luminosity densities in the earlier-type galaxies reach or exceed 10^4^ L_sun_,V_ pc^-3^, and the nuclei of the later-type galaxies occasionally approach the same level. The dS0 galaxies in our sample have central characteristics most closely resembling the late-type galaxies. A comparison of the central luminosity and central surface brightness of our galaxies with elliptical galaxies and nucleated dwarfs supports an association of late-type disks systems and such dwarfs. Publication: The Astronomical Journal Pub Date: April 1996 DOI: 10.1086/117896 Bibcode: 1996AJ....111.1566P Keywords: GALAXIES: NUCLEI; GALAXIES: LUMINOSITY FUNCTION; SURVEYS; GALAXIES: IRREGULAR full text sources ADS | data products SIMBAD (25) NED (20) MAST (1) ESA (1)

The Nuclear Star Cluster of the Milky Way: Star Formation, Stellar Collisions and Central Dark Mass

High resolution near-infrared imaging and spectroscopy now gives detailed information about the structure, evolution and mass distribution in the nuclear star cluster of the Milky Way. The central parsec is powered by a cluster of luminous and helium rich, blue supergiants/Wolf-Rayet stars. The most likely scenario for the formation of the massive stars is a star formation burst a few million years ago at which time a dense gas cloud may have fallen into the center. The stellar density in the ∼ 0.3 pc radius central core is high enough that collisions with main sequence stars destroy the largest late type giant stars. Radial velocity measurements for about 300 early and late type stars between 0.1 and 5pc radius from the dynamic center now strongly favor the existence of a central dark mass of 2.5 − 3.3 × 106M⊙ (density (109M⊙pc−3, M/L2μm) ∼ 100M⊙/L⊙) within 0.1pc of the dynamic center. This central dark mass cannot be a cluster of neutron stars. It is either a compact cluster of stellar black holes or, most likely, a single massive black hole.