J/A+A/700/A64 Radial gradients of K-band features in M87 (La Barbera+, 2025)
Puzzling radial gradients of K-band absorption features in the giant elliptical
galaxy M87.
La Barbera F., Vazdekis A., Pasquali A., Heidt J., Eftekhari E.,
Beasley M.A., Gargiulo A., Bisogni S., Spiniello C., Cassara L.P., Sarzi M.
<Astron. Astrophys. 700, A64 (2025)>
=2025A&A...700A..64L 2025A&A...700A..64L (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, spectra ; Spectra, infrared
Keywords: galaxies: elliptical and lenticular, cD - galaxies: formation -
galaxies: fundamental parameters - galaxies: stellar content
Abstract:
We present new K-band spectroscopy for the giant elliptical galaxy M87
in the Virgo cluster, taken with the Large Binocular Telescope Utility
Camera in the Infrared (LUCI) spectrograph at the Large Binocular
Telescope (LBT). The new data are used to study line strengths of
K-band absorption features from different chemical species, namely Fe,
Mg, Ca, Na, and CO, as a function of galactocentric distance, out to
∼40° from the center (about half of the galaxy effective radius).
The radial trends of spectral indices are compared to those for the
bulge of M31, observed with the same instrument. For M87, most K-band
indices exhibit flat radial profiles, with the exception of NaI2.21,
which decreases outward, with a negative radial gradient. Significant
offsets are found between indices for M87 and those for the bulge of
M31, the latter having weaker line strengths for almost all features,
but Fe and Ca, for which we find similar trends in both systems. We
find that the behavior of CO features -- most prominent in giant
stars -- is difficult to explain, consistent with previous results
for the central regions of massive galaxies. In particular, the CO
indices are stronger in M87 than M31, and do not exhibit significant
radial gradients in M87, despite its IMF being bottom heavier than M31
especially in its central region. Predictions of state-of-the-art
stellar population models, based on results from the optical spectral
range, are able to match only the Na and Ca indices of M87, while a
significant mismatch is found for all other indices. This shows that
state-of-the-art stellar population models should be improved
significantly in order to provide reliable constraints on the stellar
population content of galaxies in the near-infrared spectral range.
Description:
We make the seven binned spectra publicly available, as shown in
Figure 1 of our paper. The spectra are provided in the restframe, in
the air system. Since no absolute flux calibration has been performed,
each spectrum is normalized to its median value over the entire
spectral range. The spectra are named as M87_?.dat, where ? is a
running number, increasing from 1 to 7 with galactocentric distance.
We adopt an effective radius of Re=81.2" for M87, as in Cappellari et
al. (2011MNRAS.413..813C 2011MNRAS.413..813C, Cat. J/MNRAS/413/813).
Objects:
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RA (2000) DE Designation(s)
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12 30 49.42 +12 23 28.0 M87 = MCG+02-32-105
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
m87_1.dat 51 2113 Spectrum at a distance of 0.065Re
m87_2.dat 51 2113 Spectrum at a distance of 0.083Re
m87_3.dat 51 2113 Spectrum at a distance of 0.106Re
m87_4.dat 51 2113 Spectrum at a distance of 0.139Re
m87_5.dat 51 2113 Spectrum at a distance of 0.185Re
m87_6.dat 51 2113 Spectrum at a distance of 0.273Re
m87_7.dat 51 2113 Spectrum at a distance of 0.537Re
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Byte-by-byte Description of file: m87_?.dat
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Bytes Format Units Label Explanations
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1- 13 F13.7 0.1nm lambda Wavelength (restframe, in the air system)
15- 32 E18.8 --- Flux Normalized to the median flux vector value
34- 51 E18.8 --- e_Flux Normalized error of the flux vector
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History:
From Francesco La Barbera, francesco.labarbera(at)inaf.it
Acknowledgements:
F.L.B., A.P. and E.E. acknowledge support from the INAF minigrant
1.05.23.04.01. AV and MAB acknowledges support from grants
PID2021-123313NA-I00 and PID2022-140869NB-I00 from the Spanish
Ministry of Science and Innovation. The data are based on LUCI-LBT
spectroscopy acquired under LBTB and LBTI time.
References:
Cappellari et al., 2011MNRAS.413..813C 2011MNRAS.413..813C, Cat. J/MNRAS/413/813
La Barbera et al., 2021MNRAS.505..415L 2021MNRAS.505..415L
La Barbera et al., 2024A&A...687A.156L 2024A&A...687A.156L
Sarzi et al., 2018MNRAS.478.4084S 2018MNRAS.478.4084S
(End) Patricia Vannier [CDS] 09-Jul-2025