J/MNRAS/443/1151 AIMSS Project. I. Compact Stellar Systems (Norris+, 2014)
The AIMSS Project. I. Bridging the star cluster-galaxy divide.
Norris M.A., Kannappan S.J., Forbes D.A., Romanowsky A.J., Brodie J.P.,
Faifer F.R., Huxor A., Maraston C., Moffett A.J., Penny S.J., Pota V.,
Smith-Castelli A., Strader J., Bradley D., Eckert K.D., Fohring D.,
Mcbride J., Stark D.V., Vaduvescu O.
<Mon. Not. R. Astron. Soc., 443, 1151-1172 (2014)>
=2014MNRAS.443.1151N 2014MNRAS.443.1151N
ADC_Keywords: Clusters, globular ; Galaxies, optical ; Morphology ;
Velocity dispersion
Keywords: galaxies: dwarf - galaxies: evolution - galaxies: formation -
galaxies: kinematics and dynamics
Abstract:
We describe the structural and kinematic properties of the first
compact stellar systems discovered by the Archive of Intermediate Mass
Stellar Systems project. These spectroscopically confirmed objects
have sizes (∼6<Re[pc]<500) and masses (∼2x106<M*/M☉<6x109)
spanning the range of massive globular clusters, ultracompact dwarfs
(UCDs) and compact elliptical galaxies (cEs), completely filling the
gap between star clusters and galaxies. Several objects are close
analogues to the prototypical cE, M32. These objects, which are more
massive than previously discovered UCDs of the same size, further call
into question the existence of a tight mass-size trend for compact
stellar systems, while simultaneously strengthening the case for a
universal 'zone of avoidance' for dynamically hot stellar systems in
the mass-size plane. Overall, we argue that there are two classes of
compact stellar systems (1) massive star clusters and (2) a population
closely related to galaxies. Our data provide indications for a
further division of the galaxy-type UCD/cE population into two groups,
one population that we associate with objects formed by the stripping
of nucleated dwarf galaxies, and a second population that formed
through the stripping of bulged galaxies or are lower mass analogues
of classical ellipticals. We find compact stellar systems around
galaxies in low- to high-density environments, demonstrating that the
physical processes responsible for forming them do not only operate in
the densest clusters.
Description:
The majority of our southern spectroscopic observations to date have
been obtained using the Southern Astrophysical Research (SOAR)
Telescope and the Goodman spectrograph in longslit and MOS modes.
We used the South African Large Telescope (SALT) to observe fainter
targets requiring exposure times impractically long to be used as
filler targets for SOAR observing and which cannot be observed with
Keck.
As part of a study examining the GCs and UCDs of the shell elliptical
NGC 3923 we obtained deep Gemini/GMOS spectroscopy of three UCDs (see
Norris et al., 2012MNRAS.421.1485N 2012MNRAS.421.1485N, Cat. J/MNRAS/421/1485 for further
details). The observations were made in MOS mode.
The majority of our Northern hemisphere candidates were
spectroscopically confirmed using the DEIMOS and ESI instruments on
the Keck telescope .
We also obtained spectra of NGC 4649 UCD1 with the IDS instrument on
the Isaac Newton Telescope.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 116 902 Catalogue of Compact Stellar Systems (CSS)
and comparison sample
refs.dat 72 56 References
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See also:
J/MNRAS/421/1485 : NGC 3923 globular clusters (Norris+, 2012)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 31 A31 --- Name Name
33 I1 --- Type [1/7] Type of object (1)
36- 45 F10.6 deg RAdeg Right ascension (J2000)
47- 56 F10.6 deg DEdeg Declination (J2000)
58- 62 F5.1 mag VMAG Absolute V magnitude
64- 72 E9.4 Msun M* [340/2.8e+12] Stellar mass
74- 80 F7.1 pc Re [0.7/30620] Effective radius
82- 87 F6.1 km/s sigma [0.4/382]?=-999.9 Velocity dispersion σ
90-115 A26 --- Refs References (see "refs.dat" file)
116 A1 --- n_M* [*] M* derived with our method (2)
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Note (1): Type code as follows
1 = galaxy of type E or S0
2 = dwarf galaxy dE or dS0
3 = dwarf spheroidal (dSph)
4 = Nuclear Star Cluster
5 = globular cluster (GC), ultra-compact dwarf galaxy (UCD),
compact elliptical (cE), as found in the literature
6 = GC, UCD or cE newly found in AIMSS
7 = Young Massive Cluster (YMC)
Note (2): Stellar masses are from the literature sources listed in "Refs",
except for types 2, 5, 6, and 7 (indicated with an *) where the stellar
masses were computed following the approach outlined in Section 3.6.
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Ref Reference code
4- 22 A19 --- BibCode BibCode
24- 44 A21 --- Aut Author's name
46- 72 A27 --- Com Comments
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History:
From electronic version of the journal
References:
Forbes et al., Paper II 2014MNRAS.444.2993F 2014MNRAS.444.2993F
(End) Patricia Vannier [CDS] 14-Apr-2015