J/A+A/683/A8 NGC 3311 globular cluster source spectra (Grasser+, 2024)
Ages, metallicity and alpha-enhancement of the globular cluster populations in
NGC 3311. A stellar population analysis of MUSE co-added 1D spectra.
Grasser N., Arnaboldi M., Barbosa C.E., Spiniello C., Coccato L.,
Mendel J.T.
<Astron. Astrophys. 683, A8 (2024)>
=2024A&A...683A...8G 2024A&A...683A...8G (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Clusters, globular ; Spectra, optical ;
Spectra, infrared
Keywords: galaxies: elliptical and lenticular, cD -
galaxies: individual: NGC 3311 - galaxies: stellar content
Abstract:
We aim to investigate the stellar population properties, ages, and
metal content of the globular clusters (GCs) in NGC 3311, the central
galaxy of the Hydra I cluster, to better constrain its evolution
history.
We used integral-field spectroscopic data from the Multi-Unit
Spectroscopic Explorer (MUSE) to identify 680 sources in the central
region of NGC 3311 and extract their 1D spectra. An analysis of these
sources in terms of morphologies, radial velocities, and emission
lines allowed us to narrow down our selection to 49 bona fide GC
candidates. We split these candidates into two groups depending on
their projected distance to the galaxy center (R), namely inner
(R≤20°) and outer (R>20°) GCs. We stacked the extracted 1D
spectra of the inner and outer GC populations to increase the
signal-to-noise ratios (S/Ns) of the resulting spectra and hence allow
full-spectrum fitting. In addition, we also created a stacked spectrum
of all GCs in NGC 3311 and one of the two most central GC candidates.
Using the code pPXF, we performed a stellar population analysis on the
four stacked 1D spectra, obtaining mass-weighted integrated ages,
metallicities, and [alpha/Fe] abundances.
All GCs are old, with ages ≥13.5Gyr, and they have super-solar
metallicities. Looking at the color distribution, we find that the
inner ones tend to be redder and more metal-rich than the outer ones.
This is consistent with the two-phase formation scenario. Looking at
the full-spectral fitting results, at face value the outer GCs have a
larger [alpha/Fe] ratio, which is in line with what is found for the
stars that dominate the surface brightness profile at the same radii.
However, the values for outer and inner GCs are consistent within the
uncertainties. Interestingly, the stacked spectrum of the two most
central GCs appears to have the highest metallicity and [alpha/Fe],
although with larger uncertainties. They might be associated with the
core progenitor of NGC 3311.
The careful analysis of the MUSE-extracted 1D spectra for compact
sources in the center of NGC 3311 and its halo indicate that a
significant fraction (28%) do display emission lines. Once they are
removed, the selected bona fide GC candidates are old (≥13.5Gyr)
and have super-solar metallicities (slightly larger in the center) and
[alpha/Fe] (slightly larger for the outer GCs). Stellar population
analyses of the extracted spectra do not support the presence of an
intermediate (a few Gigayears) GC population in the central 40 arcsec
(10 kpc) radius of NGC 3311.
Description:
Spectra extracted from sources found in MUSE data of NGC3311 (see
sections 3.1 and 3.2).
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
list.dat 69 680 List of fits spectra
fits/* . 680 Individual fits spectra
--------------------------------------------------------------------------------
See also:
J/A+A/589/A139 : Stellar populations of NGC 3311 (Barbosa+, 2016)
J/A+A/609/A78 : MUSE combined data cubes for NGC 3311 (Barbosa+, 2018)
J/A+A/649/A93 : Stellar populations of NGC 3311 (Barbosa+, 2021)
Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Name Source name (fieldX_NNN) (source NNN in field X)
12- 20 F9.5 deg RAdeg Right Ascension of center (J2000)
22- 30 F9.5 deg DEdeg Declination of center (J2000)
32- 35 I4 --- Nx Number of pixels along X-axis
37- 41 F5.3 --- e Ellipticity of the source
43- 50 F8.4 mag mag Uncalibrated magnitude from extraction
52- 53 I2 Kibyte size Size of FITS file
55- 69 A15 --- FileName Name of FITS file, in subdirectory fits
--------------------------------------------------------------------------------
Acknowledgements:
Natalie Grasser, natalie.grasser(at)univie.ac.at
(End) Patricia Vannier [CDS] 23-Nov-2023