J/MNRAS/482/980 Runaway star cluster in the LMC's outer disc (Piatti+, 2019)
A likely runaway star cluster in the outer disc of the Large Magellanic Cloud.
Piatti A.E., Salinas R., Grebel E.K.
<Mon. Not. R. Astron. Soc., 482, 980-987 (2019)>
=2019MNRAS.482..980P 2019MNRAS.482..980P (SIMBAD/NED BibCode)
ADC_Keywords: Magellanic Clouds ; Associations, stellar ; Photometry, SDSS ;
Morphology
Keywords: galaxies: individual: LMC - galaxies: star clusters: general
Abstract:
We present results from photometric and spectroscopic data obtained
with SOAR and Gemini observatory facilities in the field of a recently
discovered star cluster. The cluster, projected towards the Eastern
side of the outer disc of the Large Magellanic Cloud (LMC), was
originally placed nearly 10kpc behind the LMC with an age and
metallicity typical of the innermost LMC star cluster population. We
assigned radial velocity (RV) memberships to stars observed
spectroscopically, and derived the cluster age and distance from
theoretical isochrone fitting to the cluster colour-magnitude diagram.
The new object turned out to be a 0.9Gyr old outer LMC disc cluster,
which possibly reached the present position after being scattered from
the innermost LMC regions where it might have been born. We arrived at
this conclusion by examining the spatial distribution of LMC star
clusters of similar age, by comparing the derived spectroscopic
metallicity with that expected for an outside-in galaxy formation
scenario, by considering the cluster internal dynamical stage as
inferred from its derived structural parameters and by estimating the
circular velocity of a disc that rotates with the corresponding star
cluster radial velocity at the cluster's deprojected distance, which
resulted to be nearly 60 per cent higher than that of most of the
outer LMC disc clusters.
Description:
The cluster was observed on 2018 January 3 with the SOAR Adaptive
Module (SAM) coupled with its Imager (SAMI), installed at the SOAR
4.1m telescope at Cerro Pachon, Chile. SAM is a ground-layer adaptive
optics system correcting atmospheric turbulence near the ground.
Technical details of the instrument can be found in Tokovinin et al.
(2016PASP..128l5003T 2016PASP..128l5003T). SAMI provides a field of view (FOV) of
3x3arcmin2 with a pixel scale of 0.091arcsec when used with a 2x2
binning. Observations were taken in the SDSS g and i filters, with
3x300s and 3x200s exposures, at mean-corrected full width at
half-maximums of the stellar images of 0.54arcsec in g and 0.41arcsec
in i, respectively.
The images were not combined. Instead the photometry was done in each
of them separately with the DAOPHOT/ALLSTAR suite of programs (Stetson
1987PASP...99..191S 1987PASP...99..191S).
Table 1 shows the resulting photometric data set.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 81 1505 gi data of stars in the field of the new star
cluster
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- ID Star ID
6- 16 F11.8 deg RAdeg Right ascension (J2000)
18- 29 F12.8 deg DEdeg Declination (J2000)
31- 36 F6.3 mag gmag SDSS g-band magnitude
38- 42 F5.3 mag e_gmag Error on gmag
44- 49 F6.3 mag imag SDSS i-band magnitude
51- 55 F5.3 mag e_imag Error on imag
57- 61 F5.3 --- Chi2gmag Reduced chi-squared of g-band measurements
63- 68 F6.3 --- sharpg g-band sharpness parameter
70- 74 F5.3 --- Chi2imag Reduced chi-squared of i-band measurements
76- 81 F6.3 --- sharpi i-band sharpness parameter
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 24-Jun-2022