J/MNRAS/514/5570 Stellar population in GC NGC 5053 (Nikitha+, 2022)
Stellar populations of the globular cluster NGC 5053 investigated using
AstroSat-Ultra Violet Imaging Telescope.
Nikitha K.J., Vig S., Ghosh S.K.
<Mon. Not. R. Astron. Soc. 514, 5570-5582 (2022)>
=2022MNRAS.514.5570N 2022MNRAS.514.5570N (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Populations, stellar ; Positional data
Photometry, ultraviolet
Keywords: techniques: photometric - blue stragglers -
Hertzsprung-Russell and colour-magnitude diagrams -
stars: horizontal branch - globular clusters: individual: NGC 5053
Abstract:
Globular clusters (GCs), being old and densely packed, serve as ideal
laboratories to test stellar evolution theories. Although there is
enormous literature on GCs in optical bands, studies in the
ultraviolet (UV) regime are sparse. In this work, we study the stellar
populations of a metal-poor and a rather dispersed GC, NGC 5053, using
the UV instrument of AstroSat, namely the Ultra Violet Imaging
Telescope in three far-UV (F154W, F169M, F172M) and three near-UV
(N219M, N245M, N263M) filters. Photometry was carried out on these
images to construct a catalogue of UV stars, of which the cluster
members were identified using Gaia EDR3 catalogue. UV and optical
colour-magnitude diagrams (CMDs) help us locate known stellar
populations such as blue horizontal branch stars, RR-Lyrae stars, red
horizontal branch stars, blue straggler stars (BSSs), SX-Phe, red
giant branch, and AGB stars. Based on their locations in the CMDs, we
have identified eight new BSS candidates, six probable eBSSs, and an
extreme horizontal branch candidate. Their nature has been confirmed
by fitting their spectral energy distributions (SEDs) with stellar
atmospheric models. We believe the BSS population of this cluster is
likely to have a collisional origin based on our analyses of their
radial distribution and SEDs. BaSTI-IAC isochrones were generated to
characterize the cluster properties, and we find that the observed
brightness and colours of cluster members are best fit with a model
that is α-enhanced with Y = 0.247, [Fe/H] = -1.9, and
age = 12.5 ± 2.0 Gyr.
Description:
In this study, we examine the stellar populations of NGC 5053 using
the UVIT instrument on-board the AstroSat. AstroSat is India's first
space-based multi-wavelength mission that is capable of observing
simultaneously in UV, visible, and X-rays. One telescope observes in
the FUV (130-180 nm), while the other telescope observes in the
near-ultraviolet (NUV; 200-300 nm) and the visible (VIS; 320-550 nm),
the latter is made possible using a dichroic beam splitter. The
imaging of the GC through the FUV filters F154W and F172M, and the NUV
filters N219M, N245M, N263M were taken on 2017 June 14. Observations
through the FUV filter F169M were obtained on 2020 February 13. After
astrometry task were applied to UVIT images, we perfomed aperture
photometry on the UV images using daophot and sextractor. The AB
magntiudes of detected stars are corrected for reddening by applying
the extinction law. The total number of UV detected stars in the
catalogue is 1871.
Then, as explained along the section 3, we identified the stellar
populations in our UVIT catalogue from various photometric and
spectroscopic studies available in literature. Hereafter, we searched
for optical counterparts to the stars detected from the GaiaEDR3. We
found a total of 909 Gaia counterparts. We could extract PM data for
826 stars. We consider stars within a circle of radius 5 mas/yr about
the mean as probable cluster members. Photometric results are
available in tablea1.dat.
Objects:
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RA (2000) DE Designation(s)
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13 16 27.09 +17 42 00.9 NGC 5053 = C 1313+179
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 68 1871 UVIT photometric catalogue of NGC 5053 for
detected stars in images
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See also:
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
J/MNRAS/505/5978 : Gaia EDR3 view on Galactic globular clusters
(Vasiliev+, 2021)
J/AJ/143/121 : UV properties of Galactic globulars with GALEX.
(Schiavon+, 2012)
J/ApJS/237/18 : Cr, Co, and Ni abundances for metal-poor red giants
(Kirby+, 2018)
J/ApJ/819/135 : Lithium-rich giants in globular clusters (Kirby+, 2016)
J/ApJ/804/109 : Equivalent widths of RGB stars in NGC 5053 (Boberg+, 2015)
J/A+A/579/A104 : Abundances in NGC 5053 and NGC 5634 (Sbordone+, 2015)
B/gcvs : General Catalogue of Variable Stars (Samus+, 2007-2017)
II/349 : The Pan-STARRS release 1 (PS1) Survey - DR1 (Chambers+,2016)
II/312 : GALEX-DR5 (GR5) sources from AIS and MIS (Bianchi+ 2011)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- ID Identifier star number
6- 13 F8.4 deg RAdeg Right ascension (J2000) (RA)
15- 21 F7.4 deg DEdeg Declination (J2000) (Dec)
23- 27 F5.2 mag NUVB4mag ? AB magnitude corrected for reddening
in NUV B4 band centered on 263.2nm with
27.5nm bandwidth (N263M)
29- 33 F5.2 mag NUVB15mag ? AB magnitude corrected for reddening
in NUV B15 band centered on 219.6nm with
27.0nm bandwidth (N219M)
35- 39 F5.2 mag NUVB13mag ? AB magnitude corrected for reddening
in NUV B13 band centered on 244.7nm
with 28.0nm bandwidth (N245M)
41- 45 F5.2 mag F154Wmag ? AB magnitude corrected for reddening
in FUV F154W band centered on 154.1nm with
38.0nm bandwidth (F154W)
47- 51 F5.2 mag F169Mmag ? AB magnitude corrected for reddening
in FUV F169M band centered on 160.8nm with
29.0nm bandwidth (F169M)
53- 57 F5.2 mag F172Mmag ? AB magnitude corrected for reddening
in FUV F172M band centered on 171.7nm with
12.5nm bandwidth (F172M)
59- 61 F3.1 arcsec Delta ? Positional difference between the UVIT
source and the GaiaeDR3 counterpart
(Δ)
63- 68 A6 --- Type The nature of the source (Source) (1)
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Note (1): Star type are as follows:
RGB = red giant branch stars, 60 sources in our sample
BHB = blue horizontal branch stars, 35 sources in our sample
BSS = blue straggler stars, 16 sources in our sample
RR Lyr = RR Lyr variable stars, 10 sources in our sample
RHB = red horizontal branch stars, 8 sources in our sample
BSSc = blue straggler stars candidate, 8 sources in our sample
AGB = asymptotic giant branch stars, 5 sources in our sample
eBSS = evolved-BSS stars, 6 sources in our sample
SX Phe = SX Phoenicis variable stars, 4 sources in our sample
EHB = extreme horizontal branch stars, 1 source in our sample
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History:
From electronic version of the journal
(End) Luc Trabelsi [CDS] 04-Jun-2025