J/A+A/664/A167 Fornax nuclear star clusters properties (Su+, 2022)
Photometric properties of nuclear star clusters and their host galaxies in the
Fornax cluster.
Su A.H., Salo H., Janz J., Venhola A., Peletier R.F.
<Astron. Astrophys. 664, A167 (2022)>
=2022A&A...664A.167S 2022A&A...664A.167S (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Galaxies, nearby ; Associations, stellar ;
Photometry, SDSS
Keywords: galaxies: nuclei - galaxies: clusters: individual: Fornax -
galaxies: groups: individual: Fornax A - galaxies: structure -
galaxies: dwarf - galaxies: photometry
Abstract:
We investigate the relations between nuclear star clusters (NSCs) and
their host galaxies, as well as conduct a comparison between the
structural properties of nucleated and non-nucleated galaxies. We also
address the environmental influences on the nucleation of galaxies in
the Fornax main cluster and the Fornax A group.
We select 557 galaxies (105.5M☉<M*,galaxy<1011.5M☉)
for which structural decomposition models and non-parametric
morphological measurements are available from our previous work. We
determine the nucleation of galaxies based on a combination of visual
inspection of galaxy images and residuals from multi-component
decomposition models, as well as use a model selection statistic, the
Bayesian information criterion (BIC), to avoid missing any faint
nuclei. We also test the BIC as an unsupervised method to determine
the nucleation of galaxies. We characterise the NSCs using the nucleus
components from the multi-component models conducted in the g', r',
and i' bands.
Overall, we find a dichotomy in the properties of nuclei which reside
in galaxies more or less massive than M*,galaxy∼108.5M☉. In
particular, we find that the nuclei tend to be bluer than their host
galaxies and follow a scaling relation of M*,nuc ∝
M*,galaxy0.5 for M*,galaxy<108.5M☉. In galaxies with
M*,galaxy>108.5M☉ we find redder nuclei compared to the host
galaxy which follow M*,nuc ∝ M*,galaxy. Comparing the
properties of nucleated and non-nuclated early-type galaxies, we find
that nucleated galaxies tend to be redder in global (g'-r') colour,
have redder outskirts relative to their own inner regions
(Δ(g'-r')), be less asymmetric (A) and exhibit less scatter in
the brightest second order moment of light (M20) than their
non-nucleated counterparts at a given stellar mass. However, with the
exception of Δ(g'-r') and the Gini coefficient (G), we do not
find any significant correlations with cluster-centric distance. Yet,
we find the nucleation fractions to be typically higher in the Fornax
main cluster than in the Fornax A group, and that the nucleation
fraction is highest towards the centre of their respective
environments. Additionally, we find that the observed ultra-compact
dwarf (UCD) fraction (i.e. the number of UCDs over the number of UCDs
and nucleated galaxies) in Fornax and Virgo peak at the cluster
centre, and is consistent with the predictions from simulations.
Lastly, we find that the BIC can recover our labels of nucleation up
to an accuracy of 97% without interventions.
The different trends in NSC properties suggests that different
processes are at play at different host stellar masses. A plausible
explanation is that the combination of globular cluster in-spiral and
in-situ star formation play a key role in the build-up of NSCs. In
addition, the environment is clearly another important factor in the
nucleation of galaxies, particularly at the centre of the cluster
where the nucleation and UCD fractions peak. Nevertheless, the lack of
significant correlations with the structures of the host galaxies is
intriguing. Finally, our exploration of the BIC as a potential method
of determining nucleation have applications for large scale future
surveys, such as Euclid.
Description:
We studied the properties of nucleated galaxies from the Fornax main
cluster and the Fornax A group, as well as the role that the
environment plays. From the Su et al. (2021A&A...647A.100S 2021A&A...647A.100S, Cat.
J/A+A/647/A100) compilation of dwarfs (from FDSDC, Venhola et al.
2018A&A...620A.165V 2018A&A...620A.165V, Cat. J/A+A/620/A165) and massive galaxies (from
Iodice et al. 2016ApJ...820...42I 2016ApJ...820...42I; Raj et al. 2019A&A...628A...4R 2019A&A...628A...4R,
2020A&A...640A.137R 2020A&A...640A.137R), we selected 557 galaxies that were labelled as
nucleated and non-nucleated based on visual inspection of the galaxy
and residual images from multi-component decompositions. To ensure we
did not miss any faint nuclei, we compiled an additional candidate
list of galaxies labelled as non-nucleated from Su et al.
(2021A&A...647A.100S 2021A&A...647A.100S, Cat. J/A+A/647/A100), which showed a better fit
with a Sersic+PSF model rather than a single Sersic when using the
model selection criterion BIC. This allowed us to find 20 additional
galaxies that indeed hosted faint nuclei.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 69 557 Table of galaxy properties
table2.dat 52 148 Table of nucleus properties
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See also:
J/A+A/647/A100 : Fornax Deep Survey with VST. XI. (Su+, 2021)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- FDS FDS identification (FDSNN_NNNNa)
14- 19 A6 --- FCC FCC identification (FCCNNN), if available
22- 28 F7.4 deg RAdeg [49.14/57.66] Right ascension (J2000)
30- 37 F8.4 deg DEdeg [-37.95/-32.99] Declination (J2000)
40- 43 F4.1 [Msun] logMstar [5.0/11.4] log10 of stellar mass
45- 50 F6.2 mag rMAG [-23.55/-8.98] Absolute r band magnitude
53- 56 F4.2 mag g-r [0.07/0.88] g-r colour
58- 62 F5.2 mag g-i [0.0/1.33] g-i colour
65- 69 A5 --- is_nuc [True False] Whether the galaxy hosts a nucleus
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- FDS FDS identification (FDSNN_NNNNa)
14- 19 A6 --- FCC FCC identification (FCCNNN), if available
22- 25 F4.1 [Msun] logMstargal [6.3/11.0] log10 of galaxy stellar mass
28- 30 F3.1 [Msun] logMstarnuc [4.5/8.7] log10 of nucleus stellar mass
33- 37 F5.2 mag (g-r)nuc [-1.13/12.22] Nucleus g-r colour
39- 44 F6.2 mag (g-i)nuc [-12.85/12.95] Nucleus g-i colour
47- 52 F6.4 --- nucff [0/1] Nucleus to total r band flux fraction
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Acknowledgements:
Alan Su, hung-shuo.su(at)oulu.fi
(End) Patricia Vannier [CDS] 03-Jun-2022