Digging deeper into NGC\,6868 I: stellar population

Abstract

We use Gemini integral field unit observations to map the stellar population properties in the inner region ($\sim 680\times 470$ pc${}^2$) of the galaxy NGC 6868. In order to understand the physical and chemical properties of the stellar content of this galaxy, we performed stellar population synthesis using the starlight code with the MILES simple stellar population models. We measured the absorption line indices Fe4383, Mg${}_2$, Mg${}_b$, Fe5270, Fe5335 for the whole FoV, and used them to derive Fe3 and [MgFe]'. These indices were used to derive [$\alpha$/Fe]. This galaxy is dominated by old metal-rich populations (12.6 Gyr; 1.0 and 1.6 Z${}_{\odot }$) with a negative metallicity gradient. We also found a recent ($\sim 63$ Myr) metal-rich (1.6 Z${}_{\odot }$) residual star formation in the centre of the galaxy. A dust lane with a peak extinction in the V band of 0.65 mag is seen. No signs of ordered stellar motion are found and the stellar kinematics is dispersion dominated. All indices show a spatial profile varying significantly along the FoV. Mg${}_2$ shows a shallow gradient, compatible with the occurrence of mergers in the past. Mg${}_b$ and Fe3 profiles suggest different enrichment processes for these elements. We observe three distinct regions: for $R<100$pc and $R>220$pc, Mg${}_2$, Mg${}_b$ anti correlate with respect to Fe3 and [MgFe]', and for $100\text{pc}<R<220\text{pc}$, they correlate, hinting at different enrichment histories. The [$\alpha$/Fe] profile is really complex and has a central value of $\sim 0.2$ dex. We interpret this as the result of a past merger with another galaxy with a different [$\alpha$/Fe] history, thus explaining the [$\alpha$/Fe] maps.

14 pages, 14 figures, accepted for publication in MNRAS

References in corpus (25)

• The EAGLE project: Simulating the evolution and assembly of galaxies and their environments
• The propagation of uncertainties in stellar population synthesis modeling I: The relevance of uncertain aspects of stellar evolution and the IMF to the derived physical properties of galaxies
• Improving the full spectrum fitting method: accurate convolution with Gauss-Hermite functions
• 3D-HST+CANDELS: The Evolution of the Galaxy Size-Mass Distribution since $z=3$
• UV-extended E-MILES stellar population models: young components in massive early-type galaxies
• CRATES: An All-Sky Survey of Flat-Spectrum Radio Sources
• Star formation in AEGIS field galaxies since z=1.1 . Staged galaxy formation, and a model of mass-dependent gas exhaustion
• Evolutionary stellar population synthesis with MILES - II. Scaled-solar and α-enhanced models
• Observational Constraints on the Feeding of Supermassive Black Holes
• Probing the near infrared stellar population of Seyfert galaxies
• PCA Tomography: how to extract information from datacubes
• Sub one percent mass fractions of young stars in red massive galaxies
• Truncated Star Formation in Compact Groups of Galaxies: A Stellar Population Study
• Optical/NIR stellar absorption and emission-line indices from luminous infrared galaxies
• The Dwarf Galaxy Population in Nearby Groups. The data
• A treatment procedure for GMOS/IFU data cubes: application to NGC 2835
• Gemini NIFS survey of feeding and feedback processes in nearby Active Galaxies: VI -- Stellar Populations
• IFU spectroscopy of 10 early type galactic nuclei: II - Nuclear emission line properties
• Star formation in AGNs at the hundred parsec scale using MIR high resolution images
• Young stellar population gradients in central cluster galaxies from NUV and optical spectroscopy
• Star formation, metallicity gradient and ionized gas: clues to the formation of the elliptical galaxies NGC6868 and NGC5903
• Lessons from the massive relic NGC 1277: remaining in-situ star formation in the cores of massive galaxies
• Chemical abundance of LINER galaxies -- Metallicity calibrations based on SDSS-IV MaNGA
• Detection of young ($\le$20 Myr) stellar populations in apparently quenched low-mass galaxies using red spectral line indices
• The DIVING${}^{3D}$ Survey -- Deep IFS View of Nuclei of Galaxies -- I. Definition and Sample Presentation