J/ApJ/939/118 Deep view into Sagittarius dSph with MUSE. III. (Kacharov+, 2022)
A deep view into the nucleus of the Sagittarius dwarf spheroidal galaxy with
MUSE.
III. Discrete multicomponent population-dynamical models based on the Jeans
equations.
Kacharov N., Alfaro-Cuello M., Neumayer N., Lutzgendorf N., Watkins L.L.,
Mastrobuono-Battisti A., Kamann S., van de Ven G., Seth A.C., Voggel K.T.,
Georgiev I.Y., Leaman R., Bianchini P., Boker T., Mieske S.
<Astrophys. J., 939, 118 (2022)>
=2022ApJ...939..118K 2022ApJ...939..118K
ADC_Keywords: Galaxies, spectra; Optical; Radial velocities; Abundances, [Fe/H];
Photometry, HST
Keywords: Stellar kinematics ; Globular star clusters ; Galaxy dynamics ;
Ultracompact dwarf galaxies ; Stellar populations ; Galaxy nuclei
Abstract:
We present comprehensive multicomponent dynamical models of M54
(NGC6715), the nuclear star cluster of the Sagittarius (Sgr) dwarf
galaxy, which is undergoing a tidal disruption in the Milky Way halo.
Previous papers in this series used a large MUSE mosaic data set to
identify multiple stellar populations in the system and study their
kinematic differences. Here, we use Jeans-based dynamical models that
fit the population properties (mean age and metallicity), spatial
distributions, and kinematics simultaneously. They provide a solid
physical explanation for our previous findings. Population-dynamical
models deliver a comprehensive view of the whole system, and allow us
to disentangle the different stellar populations. We explore their
dynamical interplay and confirm our previous findings about the
build-up of Sgr's nuclear cluster via contributions from globular
cluster stars, Sgr inner field stars, and in situ star formation. We
explore various parameterizations of the gravitational potential and
show the importance of a radially varying mass-to-light ratio for the
proper treatment of the mass profile. We find a total dynamical mass
within M54's tidal radius (∼75pc) of 1.60±0.07x106M☉ in
excellent agreement with N-body simulations. Metal-poor globular
cluster stars contribute about 65% of the total mass or
1.04±0.05x106M☉. Metal-rich stars can be further divided
into young and intermediate-age populations, which contribute
0.32±0.02x106M☉ (20%) and 0.24±0.02x106M☉ (15%),
respectively. Our population-dynamical models successfully distinguish
the different stellar populations in Sgr's nucleus because of their
different spatial distributions, ages, metallicities, and kinematic
features.
Description:
In section 2, we present the three data sets from the Very Large
Telescope (VLT) Multi-Unit Spectroscopic Explorer (MUSE), which we use
to extract individual stellar spectra and create the M54 stellar
catalog. MUSE is located at UT 4 (Yepun) of the VLT at the Paranal
Observatory in Chile.
One part of the data set used to analyze the dynamical properties of
M54 consists of our MUSE mosaic observations of the system taken
between 2015 June 29 and September 19 during run 095.B-0585(A)
(P.I.: Lutzgendorf). These observations and the data reduction are
described in depth in Paper I (2019ApJ...886...57A 2019ApJ...886...57A) and Paper II
(2020ApJ...892...20A 2020ApJ...892...20A). See Section 2.1.
We observed adaptive optics (AO) corrected wide field mode (WFM)
pointing (WFM+AO), centered on M54 on 2017 August 8 with the MUSE AO
facility, which utilizes the GALACSI AO module for ground layer
atmospheric turbulence correction, as part of the MUSE WFM+AO science
verification program 60.A-9181(A) (PI: Alfaro-Cuello).
See Section 2.2.
We also include in this analysis a central narrow field mode (NFM+AO)
data cube in the very center of M54, taken during the MUSE/NFM science
verification observations on 2018 September 8 (program ID 60.A-9486(A),
P.I. Alfaro-Cuello, first results shown in
Leibundgut+ 2019Msngr.176...16L 2019Msngr.176...16L). See Section 2.3.
Our final stellar catalog in the field of view of M54 contains
8927 entries with measured radial velocities and metallicities from
spectra with signal-to-noise ratios better than 10px-1. Of these,
3008 sources are extracted from the WFM-AO cube and 627 from the NFM
cube. See Section 2.4.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
18 55 03.33 -30 28 47.4 M54 = NGC 6715
----------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table7.dat 162 8927 M54 complete dataset
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See also:
VII/195 : Globular Clusters in the Milky Way (Harris, 1996)
VII/202 : Globular Clusters in the Milky Way (Harris, 1997)
J/AJ/109/218 : Catalogue of globular cluster profiles (Trager+ 1995)
J/AJ/119/1760 : M54 and Sgr dSph VI photometry (Layden+, 2000)
J/ApJS/161/304 : Star clusters in the MW and satellites (McLaughlin+, 2005)
J/AJ/132/447 : Surface Brightness of Gal. Globular Clusters (Noyola+, 2006)
J/AJ/133/1658 : ACS survey of galactic globular clusters (Sarajedini+, 2007)
J/ApJ/678/116 : AGNs in nuclear star clusters (Seth+, 2008)
J/A+A/520/A95 : Abund. of red giants in M54 and Sgr dSph (Carretta+, 2010)
J/MNRAS/445/2385 : HST/ACS Coma Cluster Survey. X. (den Brok+, 2014)
J/A+A/588/A148 : NGC 6397 stars MUSE spectra (Husser+, 2016)
J/MNRAS/505/5978 : Gaia EDR3 view on Gal. globular clusters (Vasiliev+, 2021)
Byte-by-byte Description of file: table7.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 I6 --- Seq [6/389623] Sequential identifier for NGC 6715
from Sarajedini et al. (1)
8- 18 F11.7 deg RAdeg [283.7/283.8] Right Ascension (J2000) (1)
20- 31 F12.8 deg DEdeg [-30.51/-30.4] Declination (J2000) (1)
33- 54 F22.17 km/s RVel [-244.7/360.3] Radial velocity
56- 75 F20.17 km/s e_RVel [0.19/15] Uncertainty in RVel
77-101 F25.22 [-] FeH [-3.93/0.95]? Metallicity
103-125 F23.21 [-] e_FeH [1.4e-05/1.7]? Uncertainty in FeH
127-132 F6.3 mag F606W [12.31/24.31] HST/ACS WFC F606W Vega magnitude (1)
134-139 F6.3 mag F814W [11.46/22.94] HST/ACS WFC F814W Vega magnitude (1)
141-146 F6.4 mag e_F606W [0/2] Uncertainty in F606W (1)
148-153 F6.4 mag e_F814W [0/2.4] Uncertainty in F814W (1)
155-162 A8 --- Mode MUSE Mode ("WFM-noAO", "WFM-AO" or "NFM");
see the "Description" section
--------------------------------------------------------------------------------
Note (1): Sequential identifiers, positions, and magnitudes taken from the
catalog associated with Sarajedini+ 2007, J/AJ/133/1658
(<[SBC2007] NGC 6715 NNNNNN> in Simbad).
--------------------------------------------------------------------------------
History:
From electronic version of the journal
References:
Alfaro-Cuello et al. Paper I. 2019ApJ...886...57A 2019ApJ...886...57A
Alfaro-Cuello et al. Paper II. 2020ApJ...892...20A 2020ApJ...892...20A
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 12-Sep-2024