J/A+A/694/A231 NGC5018 galaxy group globular cluster population (Lonare+, 2025)
VEGAS-SSS: An intra-group component in the globular cluster system of NGC 5018
group of galaxies using VST data.
Lonare P., Cantiello M., Mirabile M., Spavone M., Rejkuba M., Hilker M.,
Habas R., Iodice E., Hazra N., Riccio G.
<Astron. Astrophys. 694, A231 (2025)>
=2025A&A...694A.231L 2025A&A...694A.231L (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Galaxies ; Clusters, globular ; Photometry, SDSS
Keywords: galaxies: evolution - galaxies: interactions -
galaxies: groups: individual: NGC 5018 - galaxies: peculiar -
galaxies: star clusters: general - galaxies: structure
Abstract:
Globular clusters (GCs) represent a valuable tool as a fossil tracer
of the formation and evolution of galaxies and their environment. As
such, studying the properties of these stellar systems provides
crucial insights into the past formation and interaction events of the
galaxies, especially in galaxy group and cluster environments.
We study the properties of globular cluster (GC) candidates in an area
of 1.25x1.03 sq. degrees centred on the NGC 5018 group of galaxies
using the deep, wide field and multi-passband (ugr) observations
obtained with the VLT Survey Telescope (VST) as part of the VST
Elliptical Galaxy Survey (VEGAS). With a focus on studying small
stellar systems (SSS) associated with bright galaxies, this paper is a
continuation of the VEGAS-SSS series to investigate the GCs in the NGC
5018 group.
We derived photometric catalogues of compact and extended sources in
the area and identified GC candidates using a set of photometric and
morphometric selection parameters. A GC candidates catalogue is
provided and is inspected using a statistical background
decontamination technique, benefiting from the wide area coverage of
the data.
The 2D distribution map of GC candidates reveals an overdensity of
sources on the brightest member of the group, NGC 5018. No significant
GC overdensities are observed in the other bright galaxies of the
group. We report the discovery of a candidate local nucleated LSB
dwarf galaxy that is possibly in tidal interaction with NGC 5018. The
2D map also reveals an intra-group GC population aligning with the
bright galaxies and along the intra-group light (IGL) component of the
group. The radial density profile of GC candidates in NGC 5018 follows
the galaxy surface brightness profile. The (g-r) colour profile of GC
candidates centred on this galaxy shows no evidence of the well-known
colour bimodality, which is instead observed in the intra-group
population. From the GC luminosity function (GCLF) analysis, we find a
low specific frequency SN=0.59±0.27 for NGC 5018, consistent with
previous results based on less deep optical data over a smaller area.
This relatively low S_N and the lack of colour bimodality might be due
to a combination of observational data limitations and the post-merger
status of NGC 5018, which might host a population of relatively young
GCs. For the intra-group GC population, we obtain a lower limit of
SN,gr∼0.6. Using the GCLF as a distance indicator, we estimate that
NGC 5018 is located 38.0±7.9Mpc away, consistent with values in
the literature.
Description:
The observational dataset used in this work is a part of the VEGAS
survey (P.I. E. Iodice; Capaccioli et al. 2015A&A...581A..10C 2015A&A...581A..10C, Cat.
J/A+A/581/A10; Iodice et al. 2021Msngr.183...25I 2021Msngr.183...25I). It is a deep,
multi-passband (u, g, r, i) imaging survey carried out using the VST
telescope, an Istituto Nazionale di Astrofisica (INAF) facility,
located at the Paranal Observatory in Chile.
Catalogue associated with our study on the GC population in the group
of galaxies around NGC 5018. Our analysis is based on multi-wavelength
u, g, r data. The catalogue contains the photometric and morphometric
properties of all the sources across the field. The reported
magnitudes are extinction corrected using Schlafly & Finkbeiner
(2011ApJ...737..103S 2011ApJ...737..103S).
Objects:
-------------------------------------------
RA (2000) DE Designation(s)
-------------------------------------------
13 13 01.03 -19 31 05.50 NGC 5018 Group
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
catalog.dat 152 50682 Catalogue of globular cluster candidates
in the observed field (table B1)
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See also:
II/336 : AAVSO Photometric All Sky Survey (APASS) DR9 (Henden+, 2016)
Byte-by-byte Description of file: catalog.dat
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Bytes Format Units Label Explanations
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1- 11 F11.7 deg RAdeg Right Ascension (J2000)
13- 23 F11.7 deg DEdeg Declination (J2000)
25- 42 F18.15 mag umag ? Apparent magnitude in u-band within 19.04
pixels diameter
44- 49 F6.4 mag e_umag ? Error in magnitude in u-band
51- 68 F18.15 mag gmag Apparent magnitude in g-band within 19.04
pixels diameter
70- 75 F6.4 mag e_gmag Error in magnitude in g-band
77- 94 F18.15 mag rmag Apparent magnitude in r-band within 19.04
pixels diameter
96-101 F6.4 mag e_rmag Error in magnitude in r-band
103-112 F10.8 mag CIu ? Concentration index in u-band (Difference
between apparent magnitude within 8 and
19.04 pixels diameter)
114-123 F10.8 mag CIg Concentration index in g-band (Difference
between apparent magnitude within 8 and
19.04 pixels diameter)
125-134 F10.8 mag CIr Concentration index in r-band (Difference
between apparent magnitude within 8 and
19.04 pixels diameter)
136-140 F5.3 --- Elongu ? Elongation in u-band (major/minor axis)
142-146 F5.3 --- Elongg Elongation in g-band (major/minor axis)
148-152 F5.3 --- Elongr Elongation in r-band (major/minor axis)
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History:
From Pratik Lonare, pratik.lonare(at)inaf.it
Acknowledgements:
This work is based on visitor mode observations taken at the European
Southern Observatory (ESO) La Silla Paranal Observatory within the VST
Guaranteed Time Observations; Programme IDs 096.B-0582(B),
097.B-0806(A), and 099.B-0560(A). M.S. wishes to thank the ESO staff
of the Paranal Observatory for their support during the observations
at VST. PL acknowledges financial support from the Astronomical
Observatory of Abruzzo of the Italian National Institute for
Astrophysics (INAF-OAAb) and University of Rome Tor Vergata. EI, MS
and MC acknowledge the support by the Italian Ministry for Education
University and Research (MIUR) grant PRIN 2022 2022383WFT
"SUNRISE", CUP C53D23000850006 and by VST funds. EI, MS, MC and RH
acknowledge funding from the INAF through the large grant PRIN 12-2022
"INAF-EDGE" (PI L. Hunt). This research has made use of the NASA/IPAC
Extragalactic Database (NED), which is funded by the National
Aeronautics and Space Administration (NASA) and operated by the
California Institute of Technology. We also acknowledge the usage of
the HyperLeda database (http://leda.univ-lyon1.fr) and the the
Extragalactic Distance Database (EDD, https://edd.ifa.hawaii.edu/). We
made extensive use of the softwares SExtractor and Topcat
(https://www.star.bris.ac.uk/~mbt/topcat/). This research has made use
of the AAVSO Photometric All Sky Survey (APASS) database, located at
the AAVSO web site (https://www.aavso.org). Funding for APASS has been
provided by the Robert Martin Ayers Sciences Fund. This research has
made use of the VizieR catalogue access tool, Strasbourg Astronomical
Data Center (CDS), Strasbourg, France. This research has made use of
the Sloan Digital Sky Survey (SDSS) database (www.sdss.org). Funding
for the SDSS V has been provided by the Alfred P. Sloan Foundation,
the Heising-Simons Foundation, the National Science Foundation, and
the Participating Institutions. SDSS acknowledges support and
resources from the Center for High- Performance Computing at the
University of Utah. SDSS telescopes are located at Apache Point
Observatory, funded by the Astrophysical Research Consortium and
operated by New Mexico State University, and at Las Campanas
Observatory, operated by the Carnegie Institution for Science. This
work made use of Astropy (http://www.astropy.org) a
community-developed core Python package and an ecosystem of tools and
resources for astronomy. This research made use of Photutils, an
Astropy package for detection and photometry of astronomical sources.
(End) Patricia Vannier [CDS] 07-Jan-2025