J/A+A/649/A93 Stellar populations of NGC 3311 (Barbosa+, 2021)
A preserved high-z compact progenitor in the heart of NGC 3311 revealed with
MUSE 2D stellar population analysis.
Barbosa C.E., Spiniello, C., Arnaboldi M., Coccato L., Hilker M.,
Richtler T.
<Astron. Astrophys. 649, A93 (2021)>
=2021A&A...649A..93B 2021A&A...649A..93B (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Galaxies, optical ; Abundances
Keywords: galaxies: clusters: individual: Hydra I -
galaxies: individual: NGC 3311 -
galaxies: elliptical and lenticular, cD -
galaxies: kinematics and dynamics - galaxies: structure -
galaxies: stellar content
Abstract:
Massive early-type galaxies are believed to be the end result of an
extended mass accretion history. The stars formed in situ,
very early during the initial phase of the assembly, might have
originated from an extremely intense and rapid burst of star
formation. These stars may still be found within the cores of such
galaxies at z=0, depending on their accretion and merger histories.
We wish to investigate the presence of a surviving high-z compact
progenitor component in the brightest galaxy of the Hydra∼I cluster,
NGC∼3311, by mapping its 2D kinematics and stellar population out to 2
effective radii. Our goal is to understand the formation of its
several structural components and trace their mass assembly back in
time.
We combine MUSE observations, a customized and extended version of the
state-of-the-art EMILES single stellar population models, and a newly
developed parametric fully Bayesian framework to model the observed
spectra using full-spectrum fitting.
We present 2D maps, as well as radial profiles, of the stellar
velocity dispersion, age, total metallicity, α-element, sodium
abundance ([Na/Fe]), and the initial mass function slope. All
properties have significant gradients, confirming the existence of
multiple structural components, also including a "blue spot"
characterized by younger and metal-richer stars. We find that the
component dominating the light budget of NGC 3311 within R<2.0kpc,
is the surviving z=0 analogue of a high-z compact core, according to
the definition of Pulsoni et al. (2021). This concentrated structure
has a relatively small velocity dispersion (sigma∼180km/s), is
very old (ages∼11Gyr), metal-rich ([Z/H]∼0.2 and [Na/Fe]∼0.4), and
has a bottom-heavy IMF (with slope Gammab∼2.4). In the outer region,
instead, the line-of-sight velocity distribution becomes increasingly
broader, and the stars have younger age. They are also metal and
sodium poorer but α-element richer. The low-mass end of the IMF
slope becomes Chabrier-like with increasing galactocentric distances.
The existence of multiple structural components in NGC 3311 from
photometry, kinematics, and stellar populations confirms the
predictions from the two-phase formation scenario for NGC 3311,
according to which a first very short, high-z star formation episode
formed a compact stellar structure in its core, which then grew in
size by the extended mass assembly of relatively massive satellites.
Interestingly, the outer stellar population has an overabundant
[alpha/Fe], most likely because NGC 3311, located at the center of the
galaxy cluster, accreted stars from rapidly quenched satellites.
Description:
Stellar population properties for NGC 3311 from MUSE observations,
obtained with Bayesian full-spectrum fitting. Representative values
for the parameters are determined with the median of the marginalized
posterior distributions, and upper(lower) uncertainties are determined
from deviations of the 84(16)-th percentile of the posterior
distributions relative to the median.
Objects:
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RA (2000) DE Designation(s)
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10 36 36.0 -27 31 04 Hydra I = ACO 1060
10 36 42.82 -27 31 42.0 NGC 3311 = LEDA 31478
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 386 76 Results of our work
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See also:
J/A+A/589/A139 : Stellar populations of NGC 3311 (Barbosa+, 2016)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- ID Number of the Voronoi bin (fieldA_NNNN)
13- 22 F10.7 kpc X Projected X coordinate relative to
the center of NGC 3311( 1)
24- 33 F10.7 kpc Y Projected Y coordinate relative to
the center of NGC 3311 (1)
35- 44 F10.7 kpc R Projected radial distance relative to
the center of NGC 3311 (1)
46- 53 F8.3 deg PA [] Position angle relative the center
55- 63 F9.5 10/nm SNR Signal-to-Noise ratio
65- 71 F7.5 --- Gammab Bimodal IMF slope
73- 80 F8.6 --- e_Gammab Lower error of IMF slope
82- 89 F8.6 --- E_Gammab Upper error of IMF slope
91- 98 F8.5 [Sun] [Z/H] Total metallicity
100-107 F8.6 [Sun] e_[Z/H] Lower error of metallicity
109-116 F8.6 [Sun] E_[Z/H] Upper error of metallicity
118-125 F8.5 Gyr Age Age of stellar population
127-134 F8.6 Gyr e_Age Lower error of age
136-143 F8.6 Gyr E_Age Upper error of age
145-151 F7.5 [Sun] [alpha/Fe] Alpha-elements abundance
153-160 F8.6 [Sun] e_[alpha/Fe] Lower error of alpha abundance
162-169 F8.6 [Sun] E_[alpha/Fe] Upper error of alpha abundance
171-177 F7.5 [Sun] [Na/Fe] Sodium abundance
179-186 F8.6 [Sun] e_[Na/Fe] Lower error of Na abundance
188-195 F8.6 [Sun] E_[Na/Fe] Upper error of Na abundance
197-203 F7.5 mag Av Total extinction
205-212 F8.6 mag e_Av Lower error of extinction
214-221 F8.6 mag E_Av Upper error of extinction
223-229 F7.5 --- Rv Total-to-selective extinction
231-238 F8.6 --- e_Rv Lower error of selective extinction
240-247 F8.6 --- E_Rv Upper error of selective extinction
249-258 F10.5 km/s V Stellar systemic velocity
260-268 F9.6 km/s e_V Lower error of velocity
270-278 F9.6 km/s E_V Upper error of velocity
280-288 F9.5 km/s sigma Stellar velocity dispersion
290-298 F9.6 km/s e_sigma Lower error of velocity dispersion
300-308 F9.6 km/s E_sigma Upper error of velocity dispersion
310-316 F7.5 Sun M/L Mass-to-light ratio in the r-band
318-325 F8.6 Sun e_M/L Lower error in the mass-to-light
327-334 F8.6 Sun E_M/L Upper error in the mass-to-light
336-342 F7.5 --- alpha IMF mismatch parameter
344-351 F8.6 --- e_alpha Lower error of IMF mismatch parameter
353-360 F8.6 --- E_alpha Upper error of IMF mismatch parameter
362-368 F7.5 [Sun/kpc+2] logSigma Surface stellar mass
370-377 F8.6 [Sun/kpc+2] e_logSigma Lower error of surface stellar mass
379-386 F8.6 [Sun/kpc+2] E_logSigma Upper error of surface stellar mass
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Note (1): Radial distances to the center of NGC 3311 are calculated assuming
a distance of 50.7Mpc to the core of the Hydra I cluster.
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Acknowledgements:
Carlos E. Barbosa, kadu.barbosa(at)gmail.com
(End) Patricia Vannier [CDS] 09-Mar-2021