J/MNRAS/515/1903 Stars cluster and RGBs study in NGC362 (Vargas+, 2022)
Investigating a predicted metallicity [Fe/H] variation in the Type II globular
cluster NGC 362.
Vargas C., Villanova S., Geisler D., Munoz C., Monaco L., O'Connell J.,
Sarajedini A.
<Mon. Not. R. Astron. Soc. 515, 1903-1913 (2022)>
=2022MNRAS.515.1903V 2022MNRAS.515.1903V (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Stars, giant ; Photometry ; Optical ;
Ultraviolet ; Positional data ; Proper motions ; Photometry, HST ;
Radial velocities ; Spectroscopy ; Effective temperatures ;
Abundances, [Fe/H]
Keywords: stars: abundances - globular clusters: individual: NGC 362
Abstract:
NGC 362 is a non-common Type II Galactic globular cluster, showing a
complex pseudo two-colour diagram or 'chromosome map'. The clear
separation of its stellar populations in the colour-magnitude diagram
and the distribution of the giant stars in the chromosome map strongly
suggests that NGC 362 could host stars with both cluster-nominal, as
well as enhanced heavy-element abundances, and one of them could be
iron. However, despite previous spectroscopic observations of NGC 362,
no such iron variation has been detected. Our main goal is to confirm
or disprove this result by searching for any internal variation of
[Fe/H], which would give us insight into the formation and evolution
of this interesting globular cluster. In this paper, we present the
abundance analysis for a sample of 11 red giant branch members based
on high-resolution and high S/N spectra obtained with the MIKE echelle
spectrograph mounted at the Magellan- Clay telescope. HST and GAIA
photometry and astrometry has been used to determine atmospheric
parameters and membership. We obtained Teff, log(g), and vt for our
target stars and measured the mean iron content of the sample and its
dispersion with three different methods, which lead to
[Fe/H]1 = -1.10 ± 0.02, [Fe/H]2 = -1.09 ± 0.01, and
[Fe/H]3 = -1.10 ± 0.01, while the internal dispersion turned out
to be σ[Fe/H]1 = 0.06 ± 0.01,
σ[Fe/H]2 = 0.03 ± 0.01, and σ[Fe/H]3 = 0.05 ± 0.01,
respectively. The error analysis gives an internal dispersion due to
observational error of 0.05 dex. Comparing the observed dispersion
with the internal errors, we conclude that NGC 362 does not show any
trace of an internal iron spread.
Description:
To probe MSPs in the globular cluster NGC 362, we first reproduce its
chromosome map (as shown in figure 1 of the section 2) using
magnitudes in optical and UV bands of the HST UV Legacy Survey
(Nardiello et al. 2018MNRAS.481.3382N 2018MNRAS.481.3382N). We select (marked in red on
the figure 1 plot) stars presumably have a higher metallicity than the
bulk of the stars in order to optimize the possibility of detecting
any putative metallicity spread between them. These selected targets
include brightest anomalous stars from the chromosome map along with
bright normal stars chosen from the CMD which lay along the bluer and
brighter RGB. This selection maximize the possibility to detect any
variation in iron spread. Chromosome map parameters are presented in
table.dat with 1172 NGC0362 stars cluster.
Next, these 12 candidate NGC 362 members, six normal and six anomalous
stars, were observed during the nights of 2018 November 8 and 9 with
the MIKE high-resolution spectrograph. The spectra cover the range
3350-5000Å and 4850-9400Å in the blue and the red arms,
respectively. We confirmed the membership of our targets by
constraining GaiaEDR3 proper motions (see blue cyan points in figure 3
of section 3). We thus exclude the star number 12 which has proper
motion differs by by 3.3σ from the mean of the other stars. The
table1.dat lists the basic Gaia & HST photometric and astrometric
parameters of the eleven final members as well as the spectroscopic
observed RVhelio.
Hereafter, as fully exposed in section 4, we derive using three
different methods the atmospheric parameters Teff, log(g), vt and
[Fe/H]. Results are presented in three tables, the table2.dat refers
to isochrone fitting using GAIA and HST data, the table3.dat regroups
those from spectral synthesis method and the table4.dat are results
based on abundances estimates from EQW of FeI and FeII lines as
measured from the spectra.
Objects:
----------------------------------------------------------------------------
RA (2000) DE Designation(s)
----------------------------------------------------------------------------
01 03 14.25 -70 50 55.6 NGC 362 = C 0100-711
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File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table.dat 105 1172 *Chromosome map of NGC0362 with HST photometry
table1.dat 121 12 Gaia and HST astrometric and photometric data
for the 12 target stars
table2.dat 76 11 Atmospheric parameters for the 11 target stars
derived with isochrone fits
table3.dat 30 11 Atmospheric parameters for the 11 target stars
derived with Marino and Mott methods
table4.dat 25 11 Parameters and metallicities obtained
spectroscopically using the FeI and FeII lines
--------------------------------------------------------------------------------
Note on table.dat: The rows 1 to 11 correspond to 11 target stars.
--------------------------------------------------------------------------------
See also:
J/MNRAS/482/5138 : Galactic GC mean proper motions & velocities
(Baumgardt+, 2019)
J/MNRAS/478/1520 : Milky Way globular clusters data (Baumgardt+, 2018)
J/MNRAS/492/1641 : APOGEE southern GCs with the BACCHUS code (Meszaros+, 2020)
J/MNRAS/450/815 : Red giants in NGC 5286 (Marino+, 2015)
J/MNRAS/492/1641 : APOGEE southern GCs with the BACCHUS code (Meszaros+, 2020)
J/MNRAS/505/5978 : Gaia EDR3 view on Galactic globular clusters
(Vasiliev+, 2021)
J/ApJ/722/1373 : ω Centauri giants abundances (Johnson+, 2010)
J/ApJS/245/5 : Globular cluster intrinsic iron abundance spreads
(Bailin, 2019)
J/A+A/557/A138 : Detailed chemical abundances in the GlC NGC 362
(Carretta+ 2013)
J/A+A/520/A95 : Abundances of red giants in M54 and Sgr dSph
(Carretta+, 2010)
J/A+A/659/A122 : Metallicity of NGC 6388 (Carretta+, 2022)
J/A+A/505/117 : Abundances of red giants in 15 globular clusters
(Carretta+, 2009)
J/A+A/490/625 : Abundances of NGC 6121 red giants (Marino+, 2008)
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
VII/202 : Globular Clusters in the Milky Way (Harris, 1997)
VII/195 : Globular Clusters in the Milky Way (Harris, 1996)
Byte-by-byte Description of file: table.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 F7.1 --- ID Star identifier number (ID)
9- 17 F9.6 deg RAdeg Right ascension (J2000) at Ep=2015.0 from
HUGS Catalog (2015AJ....149...91P 2015AJ....149...91P) (RA)
19- 28 F10.6 deg DEdeg Declination (J2000) at Ep=2015.0 from
HUGS Catalog (2015AJ....149...91P 2015AJ....149...91P) (DEC)
30- 36 F7.4 mag F275Wmag Apparent magnitude in F275W HST filter
from UV Legacy Survey Nardiello et al.
(2018MNRAS.481.3382N 2018MNRAS.481.3382N) (F275W)
38- 44 F7.4 mag F336Wmag Apparent magnitude in F336W HST filter
from UV Legacy Survey Nardiello et al.
(2018MNRAS.481.3382N 2018MNRAS.481.3382N) (F336W)
46- 52 F7.4 mag F438Wmag Apparent magnitude in F438W HST filter
from UV Legacy Survey Nardiello et al.
(2018MNRAS.481.3382N 2018MNRAS.481.3382N) (F438W)
54- 60 F7.4 mag F814Wmag Apparent magnitude in F814W HST filter
from UV Legacy Survey Nardiello et al.
(2018MNRAS.481.3382N 2018MNRAS.481.3382N) (F814W)
62- 82 F21.18 mag F275W-F814W Delta(F275W,F814W) pseudo-colour
(|F275W-F814W|)
84-105 F22.19 mag C Delta(CF275W,F336W,F438W) pseudo-colours
as (F275W-F336W) - (F336W-F438W)
(DeltaCF275W,F336W,F438W)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- ID Star identifier number (ID)
4- 20 F17.14 deg RAdeg Right ascension (J2000) at Ep=2015.0 (RA)
22- 39 F18.14 deg DEdeg Declination (J2000) at Ep=2015.0 (DEC)
41- 45 F5.3 mas/yr pmRA Proper motions in right ascension direction
(pmRA*cosDE) from Gaia eDR3 (pmRA)
47- 52 F6.3 mas/yr pmDE Proper motion in declination direction from
Gaia eDR3 (pmDEC)
54- 58 F5.2 mag Vmag Apparent magnitude in optical V band based
on F438W, F606W and F814W HST filters (V)
60- 65 F6.3 mag Gmag G-band mean magnitude (Vega) from Gaia DR2
(G)
67- 72 F6.3 mag BPmag Integrated BP mean magnitude (Vega) from
Gaia DR2 (Bp)
74- 79 F6.3 mag RPmag Integrated RP mean magnitude (Vega) from
Gaia DR2 (Rp)
81- 86 F6.3 mag F275Wmag Apparent magnitude in F275W HST filter
from UV Legacy Survey Nardiello et al.
(2018MNRAS.481.3382N 2018MNRAS.481.3382N) (F275W)
88- 93 F6.3 mag F336Wmag Apparent magnitude in F336W HST filter
from UV Legacy Survey Nardiello et al.
(2018MNRAS.481.3382N 2018MNRAS.481.3382N) (F336W)
95-100 F6.3 mag F438Wmag Apparent magnitude in F438W HST filter
from UV Legacy Survey Nardiello et al.
(2018MNRAS.481.3382N 2018MNRAS.481.3382N) (F438W)
102-107 F6.3 mag F606Wmag Apparent magnitude in F606W HST filter
from UV Legacy Survey Nardiello et al.
(2018MNRAS.481.3382N 2018MNRAS.481.3382N) (F606W)
109-114 F6.3 mag F814Wmag Apparent magnitude in F814W HST filter
from UV Legacy Survey Nardiello et al.
(2018MNRAS.481.3382N 2018MNRAS.481.3382N) (F814W)
116-121 F6.2 km/s RV Spectroscopic heliocentric radial velocity
from MIKE spectrograph as explained in the
section 3 (RVhelio)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- ID Star identifier number (ID)
4- 7 I4 K TeffGaiam11 Effective temperature obtained via 11 Gyr
isochrone fitting using Gaia data
(TGAIAm11)
9- 12 F4.2 [cm/s2] loggGaiam11 Logarithm of the surface gravity
obtained via 11 Gyr isochrone fitting
using Gaia data (gGAIAm11)
14- 17 I4 K TeffGaiam09 Effective temperature obtained via 9 Gyr
isochrone fitting using Gaia data
(TGAIAm09)
19- 22 F4.2 [cm/s2] loggGaiam09 Logarithm of the surface gravity
obtained via 9 Gyr isochrone fitting
using Gaia data (gGAIAm09)
24- 27 I4 K TeffHSTm11 Effective temperature obtained via 11 Gyr
isochrone fitting using HST data
(THSTm11)
29- 32 F4.2 [cm/s2] loggHSTm11 Logarithm of the surface gravity
obtained via 11 Gyr isochrone fitting
using HST data (gHSTm11)
34- 37 I4 K TeffHSTm09 Effective temperature obtained via 9 Gyr
isochrone fitting using HST data
(THSTm09)
39- 42 F4.2 [cm/s2] loggHSTm09 Logarithm of the surface gravity
obtained via 9 Gyr isochrone fitting
using HST data (gHSTm09)
44- 47 F4.2 [cm/s2] loggphot Logarithm of the surface gravity
obtained with the canonical relation as
the described in section 4 (loggphot)
49- 52 I4 K Teff Effective temperature used to compute
vt and [Fe/H] (Teff)
54- 57 F4.2 [cm/s2] logg Logarithm of the surface gravity used to
compute vt and [Fe/H] (logg)
59- 62 F4.2 km/s Vt Microturbulent velocity obtained
assuming Teff, log(g) and FeI line
spectra (vt)
64- 68 F5.2 [Sun] [Fe/H] Iron to hydrogen abundance ratio assuming
Teff, log(g) and FeI line spectra
([Fe/H])
70- 74 F5.2 [Sun] [FeII/H] Derived ionic iron FeII to hydrogen
abundance ratio ([FeII/H])
76 A1 --- Class [a/n] Star classification a for anomalous
and n for normal (Class)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- ID Star identifier number (ID)
4- 7 I4 K Teff Effective temperature used to compute vt
and [Fe/H] (Teff)
9- 12 F4.2 [cm/s2] logg Logarithm of the surface gravity used to
compute vt and [Fe/H] (logg)
14- 17 F4.2 km/s VtMott Microturbulence velocity (vtMott) (1)
19- 23 F5.2 [Sun] [Fe/H] Iron to hydrogen obtained using spectral
synthesis of FeI lines and considering
vtMott ([Fe/H])
25- 28 F4.2 km/s VtMarino Microturbulence obtained from empirical
relation in Marino et al.
2008A&A...490..625M 2008A&A...490..625M, Cat. J/A+A/490/625
(vtMarino)
30 A1 --- Class [a/n] Star classification a for anomalous and
n for normal (Class)
--------------------------------------------------------------------------------
Note (1): Obtained from theoretical relation Mott et al. (2020A&A...638A..58M 2020A&A...638A..58M)
that was derived from 3D-NLTE models and relates log(g) and Teff with
vt.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- ID Star identifier number (ID)
4- 7 I4 K Teff Effective temperature (Teff)
9- 12 F4.2 [cm/s2] logg Logarithm of the surface gravity (logg)
14- 17 F4.2 km/s Vt Microturbulent velocity (vt)
19- 23 F5.2 [Sun] [Fe/H] Iron to hydrogen abundance ratio ([Fe/H])
25 A1 --- Class [a/n] Star classification a for anomalous and n
for normal (Class)
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Luc Trabelsi [CDS] 19-Jun-2025