J/ApJ/958/8 oMEGACat. I. MUSE sp. of stars in omega Cen (Nitschai+, 2023)
oMEGACat.
I. MUSE spectroscopy of 300000 stars within the half-light radius of
omega Centauri.
Nitschai M.S., Neumayer N., Clontz C., Haberle M., Seth A.C.,
Husser T.-O., Kamann S., Alfaro-Cuello M., Kacharov N., Bellini A.,
Dotter A., Dreizler S., Feldmeier-Krause A., Latour M., Libralato M.,
Milone A.P., Pechetti R., van de Ven G., Voggel K., Weisz D.R.
<Astrophys. J., 958, 8 (2023)>
=2023ApJ...958....8N 2023ApJ...958....8N
ADC_Keywords: Clusters, globular; Spectra, optical; Radial velocities;
Abundances; Effective temperatures; Photometry, HST
Keywords: Galaxy nuclei ; Globular star clusters ; Star clusters
Abstract:
Omega Centauri (ω Cen) is the most massive globular cluster of
the Milky Way and has been the focus of many studies that reveal the
complexity of its stellar populations and kinematics. However, most
previous studies have used photometric and spectroscopic data sets
with limited spatial or magnitude coverage, while we aim to
investigate it having full spatial coverage out to its half-light
radius and stars ranging from the main sequence to the tip of the red
giant branch. This is the first paper in a new survey of ω Cen
that combines uniform imaging and spectroscopic data out to its
half-light radius to study its stellar populations, kinematics, and
formation history. In this paper, we present an unprecedented MUSE
spectroscopic data set combining 87 new MUSE pointings with previous
observations collected from guaranteed time observations. We extract
spectra of more than 300,000 stars reaching more than 2 magnitudes
below the main-sequence turnoff. We use these spectra to derive
metallicity and line-of-sight velocity measurements and determine
robust uncertainties on these quantities using repeat measurements.
Applying quality cuts we achieve signal-to-noise ratios (S/Ns) of
16.47/73.51 and mean metallicity errors of 0.174/0.031dex for the
main-sequence stars (18mag<magF625W<22mag) and red giant branch
stars (16mag<magF625W<10mag), respectively. We correct the
metallicities for atomic diffusion and identify foreground stars. This
massive spectroscopic data set will enable future studies that will
transform our understanding of ω Cen, allowing us to investigate
the stellar populations, ages, and kinematics in great detail.
Description:
The data presented in this paper were acquired with MUSE, a
second-generation Very Large Telescope (VLT) instrument located at the
UT4 at the Paranal Observatory in Chile. Two sets of data are combined
in this paper; the first are existing data, part of the Multi-Unit
Spectroscopic Explorer (MUSE) guaranteed time observations ("GTO
data"), with program IDs: 094.D-0142, 095.D-0629, 096.D-0175,
097.D-0295, 098.D-0148, 099.D-0019, 0100.D-0161, 0101.D-0268,
0102.D-0270, 0103.D-0204, 0104.D-0257, 105.20CR, and 109.23DV. These
GTO data consist of 10 pointings with multiepoch data that have been
analyzed already in several papers (Kamann+ 2018MNRAS.473.5591K 2018MNRAS.473.5591K;
Husser+ 2020, J/A+A/635/A114; Latour+ 2021, J/A+A/653/L8) as well as
six central pointings using the MUSE narrow field adaptive optics mode
(NFM), presented in Pechetti+ 2024MNRAS.528.4941P 2024MNRAS.528.4941P
The second data set is from General Observer (GO) program 105.20CG.001
(PI: N. Neumayer); this includes 87 new MUSE pointings taken between
2021 February and 2022 September. We refer to this data set as the
"GO data" and describe this data set in more detail in Section 2.1.
To extract individual spectra for the stars in the MUSE fields we use
PAMPELMUSE (Kamann+ 2013A&A...549A..71K 2013A&A...549A..71K) and the Hubble Space
Telescope (HST) Wide-Field Channel (WFC) of the ACS catalog from
Anderson & van der Marel (2010, J/ApJ/710/1032).
After extracting the spectra, we use SPEXXY
(http://github.com/thusser/spexxy) version 2.5 to measure the physical
parameters of the stars.
See Section 3.
The final catalog contains 342,797 unique individual stars with
physical parameters. We describe recommended quality cuts for using
this catalog further in Section 4.7.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table3.dat 278 342797 MUSE spectroscopic catalog
--------------------------------------------------------------------------------
See also:
VII/195 : Globular Clusters in the Milky Way (Harris, 1996)
VII/202 : Globular Clusters in the Milky Way (Harris, 1997)
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
J/AJ/113/634 : The survival of Sagittarius dwarf galaxy (Ibata+ 1997)
J/AJ/133/1658 : ACS survey of galactic globular clusters (Sarajedini+, 2007)
J/ApJ/663/296 : UBV(RI)c phot. of omega Cen subgiants (Villanova+, 2007)
J/ApJ/710/1032 : Proper motions in ω Cen (Anderson+, 2010)
J/AJ/140/631 : HST WFC3/UVIS photometry of omega Cen core (Bellini+, 2010)
J/ApJ/722/1373 : ω Centauri giants abundances (Johnson+, 2010)
J/MNRAS/441/3570 : Nuclear star clusters in spiral galaxies (Georgiev+, 2014)
J/ApJ/791/107 : Parameters of NGC 5139 SGBs stars (Villanova+, 2014)
J/AJ/149/53 : Radial velocities of 12 MW globular clusters (Kimmig+, 2015)
J/A+A/588/A148 : NGC 6397 stars MUSE spectra (Husser+, 2016)
J/ApJ/844/164 : HST astro-phot. analysis of NGC5139. III. (Bellini+, 2017)
J/MNRAS/478/1520 : Milky Way globular clusters data (Baumgardt+, 2018)
J/MNRAS/482/5138 : Gal. GC mean proper motions & velocities (Baumgardt+, 2019)
J/A+A/632/A3 : MUSE binaries in NGC 3201 (Giesers+, 2019)
J/other/NatAs/3.667 : Fimbulthul stream candidate stars (Ibata+, 2019)
J/ApJ/878/18 : NGVS. XXIII. Nuclear star clusters (Sanchez-Janssen+, 2019)
J/A+A/635/A114 : EW and [Fe/H] for globular cluster RGB stars (Husser+ 2020)
J/AJ/159/254 : Parameters for metal-poor stars in NGC5139 (Johnson+, 2020)
J/MNRAS/506/150 : The GALAH+ Survey DR3 (Buder+, 2021)
J/A+A/653/L8 : Metallicities on multiple MSs of Omega Cen (Latour+, 2021)
J/MNRAS/505/5978 : Gaia EDR3 view on Gal. globular clusters (Vasiliev+, 2021)
J/ApJ/939/118 : Sagittarius dSph with MUSE. III. (Kacharov+, 2022)
J/A+A/677/A86 : SHOTGLAS. II. BHB stars (Latour+, 2023)
http://pampelmuse.readthedocs.io/en/latest/about.html : PampelMuse doc
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 I6 --- Seq [1/342797] Identifier of stars in
MUSE spectroscopic catalog
8- 15 F8.2 km/s RVel [-1409/1374] Line-of-sight velocity
(vlos) measured with SPEXXY
17- 22 F6.2 km/s errRVel [0.15/273] SPEXXY uncertainty in RVel
(see Section 4.2)
24- 28 F5.3 --- sRVel [0.93/3.54] Scaling factor for SPEXXY
error line-of-sight velocity
(see Section 4.2)
30- 35 F6.2 km/s e_RVel [0.15/257] Scaled SPEXXY error in RVel
(see Section 4.2)
37- 41 F5.2 km/s prv [-0.34/0.35] Perspective rotation (1)
43- 50 F8.2 km/s prvRVel [-1408/1374] SPEXXY line-of-sight velocity
corrected for perspective rotation
52- 58 F7.1 K Teff [2760/12716] Effective temperature
measured with SPEXXY
60- 65 F6.1 K errTeff [0/4962] SPEXXY uncertainty in Teff
67- 71 F5.3 --- sTeff [0.86/1.7] Scaling factor for SPEXXY error
temperature (see Section 4.2)
73- 78 F6.1 K e_Teff [0/8279] Scaled SPEXXY error in Teff
(see Section 4.2)
80- 84 F5.3 [cm/s2] loggfix [0.2/6]? SPEXXY log of surface gravity,
fixed from isochrone (Section 3.3)
86- 90 F5.3 [cm/s2] loggfree [0.076/6]? SPEXXY log surface gravity,
free during fit
92- 98 F7.4 [Sun] [M/H] [-3.95/0.95] SPEXXY metallicity (MH)
100- 106 F7.4 [Sun] MHadc [-3.95/1.22]? SPEXXY metallicity with
Atomic Diffusion correction (Section 4.5)
108- 117 F10.4 [Sun] err[M/H] [0.0002/12767] SPEXXY uncertainty in [M/H]
119- 123 F5.3 --- s[M/H] [1.28/1.8] Scaling factor for SPEXXY error
metallicity (see Section 4.2)
125- 134 F10.4 [Sun] e_[M/H] [0.0002/17418] Scaled SPEXXY error in
[M/H] (see Section 4.2)
136- 141 F6.2 --- SNR [0.18/189] Signal-to-noise ratio of
spectrum from SPEXXY
143- 148 F6.1 --- ffit [-100/1] Fixed, 1, or free, 0, log(g) in
SPEXXY fit
150- 156 F7.2 pix edge [-3.97/158] Distance of star to OB edge,
PAMPELMUSE output (2)
158- 162 F5.3 --- Magacc [0.015/1]? Relative accuracy of recovered
magnitude from spectrum extraction,
PAMPELMUSE (2)
164- 167 F4.1 --- spFlag [0/11] Spectrum extraction quality flag,
PAMPELMUSE (0=best; see Section 3.1)
(SpecFlag) (2)
169- 173 F5.3 --- Rel [0.087/1] Reliability Parameter
(Section 4.1) (2)
175- 176 I2 --- Nobs [1/66] Number of times the star was
observed (Section 4.3) (Num)
178- 183 A6 --- Data Observing program (GO, GTO or "GO_GTO"
(both)) the star belongs to
185- 194 E10.3 deg Rad [8.8e-5/0.12] Radius from cluster center
(3)
195- 205 F11.7 deg RAdeg [201.5/201.9] HST Right Ascension (J2000)
(4)
207- 217 F11.7 deg DEdeg [-47.6/-47.3] HST Declination (J2000) (4)
219- 224 F6.3 mag F435Wmag [11.7/32.1]? Magnitude in the HST/WFC
F435W filter (B-band) from Anderson+ 2010,
J/ApJ/710/1032
226- 231 F6.3 mag F625Wmag [10.3/32]? Magnitude in the HST/WFC F625W
filter (R-band) from Anderson+ 2010,
J/ApJ/710/1032
233- 238 F6.3 mag F435Wmagc [11.2/31.6]? The F435Wmag with Av and RV
correction
240- 245 F6.3 mag F625Wmagc [9.99/31.7]? The F625Wmag with Av and RV
correction
247- 251 F5.3 mag e_F435Wmag [0/9.9]? RMS scatter of single-exposure
F435W observation
253- 257 F5.3 mag e_F625Wmag [0/9.9]? RMS scatter of single-exposure
F625W observation
259- 260 I2 --- NBf [0/9]? Number of F435W images where star
was found from Anderson+ 2010,
J/ApJ/710/1032
262- 263 I2 --- NRf [0/9]? Number of F625W images where star
was found from Anderson+ 2010,
J/ApJ/710/1032
265- 268 F4.2 --- PMmRV [0/1]? Membership probability using radius
and velocity (Section 4.4) (probRV)
270- 273 F4.2 --- PMmRVM [0/1]? Membership probability using
radius, velocity and metallicity (probRVM)
275 I1 --- Q [0/1] Quality Flag
(Section 4.7; 1=True, 156871 occurrences)
(Flag)
277- 278 I2 --- HFlag [0/1]? HST Quality Flag (1=reliable)
(HST10Flag) (5)
--------------------------------------------------------------------------------
Note (1): omega Cen takes up a large angle on the plane of the sky. Therefore,
there is a non-negligible apparent rotation caused by the different
projections of the space motion at different positions on the sky.
This is known as perspective rotation (van de Ven+ 2006A&A...445..513V 2006A&A...445..513V).
To correct for it we need to subtract from the line-of-sight velocity
the perspective rotation term:
vpr[km/s]=1.3790x10-3D*
(-ΔRAcosDEC*muRAsys+ΔDEC*muDECsys)
with the distance to the center ΔRA,ΔDEC in units of
arcmin, distance to the cluster D=(5.43±0.05)kpc (Baumgardt &
Vasiliev 2021MNRAS.505.5957B 2021MNRAS.505.5957B), proper motion in RA
muRAsys=(3.25±0.022)mas/yr and proper motion in DEC
muDECsys=(-6.746±0.022)mas/yr from Vasiliev & Baumgardt
(2021, J/MNRAS/505/5978).
See Section 4.6.
Note (2): For the parameters edge, Magacc, SpecFlag, and Rel we provide the
minimum (maximum for SpecFlag) value when combining multiple measures,
see Section 4.3.
Note (3): Where Rad=(((RA-RAc)cos(Dec))2+(Dec-Decc)2)0.5 with
RAc=13:26:47.24 and Decc=-47:28:46.45
(Anderson & van der Marel 2010, J/ApJ/710/1032).
Note (4): For our final catalog, we combine both the GO and GTO data sets.
As described in Section 3, the GO analysis followed that of the GTO
data with three main differences:
(1) the GTO data have multiple epochs of observations as opposed to a
single epoch for the GO data,
(2) the GTO uses two HST catalogs for source positions, the catalog
created by Anderson+ 2008AJ....135.2055A 2008AJ....135.2055A for the Advanced Camera for
Surveys (ACS) survey of Galactic GCs (Sarajedini+ 2007, J/AJ/133/1658)
and the Anderson & van der Marel (2010, J/ApJ/710/1032) catalog, and
(3) during spexxy fits the log(g) for the BSS in the GTO data set was
kept fixed to 4.2dex, while we fit for log(g) for these stars.
Note (5): Flag "0": unreliable photometry/astrometry from
Anderson & van der Marel 2010R, J/ApJ/710/1032
--------------------------------------------------------------------------------
History:
From electronic version of the journal
References:
Haberle et al. Paper II. 2024ApJ...970..192H 2024ApJ...970..192H
Nitschai et al. Paper III. 2024ApJ...970..152N 2024ApJ...970..152N
Clontz et al. Paper IV. 2024ApJ...977...14C 2024ApJ...977...14C
Clontz et al. Paper V. 2025ApJ...984..162C 2025ApJ...984..162C
Haberle et al. Paper VI. 2025ApJ...983...95H 2025ApJ...983...95H
Wang et al. Paper VII. 2025ApJ...994..143W 2025ApJ...994..143W
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 20-Jan-2026