NGC 6845: metallicity gradients and star formation in a complex compact group

Abstract

We have obtained Gemini/GMOS spectra of 28 regions located across the interacting group NGC 6845, spanning from the inner regions of the four major galaxies (NGC 6845A, B, C, D) to the tidal tails of NGC 6845A. All regions in the tails are star-forming objects with ages younger than 10 Myr. We derived the gas-phase metallicity gradients across NGC 6845A and its two tails and we find that these are shallower than those for isolated galaxies. NGC 6845A has a gas-phase oxygen central metallicity of \mbox{12+log(O/H)$\sim$8.5} and a flat gas-phase metallicity gradient ($\beta$=0.002$\pm$0.004 dex kpc${}^{-1}$) out to $\sim$4 $\times$ R${}_{25}$ (to the end of the longest tidal tail). Considering the mass-metallicity relation, the central region of NGC 6845A displays a lower oxygen abundance than the expected for its mass. Taking into account this fact and considering the flat oxygen distribution measured along the eastern tidal tail, we suggest that an interaction event has produced a dilution in the central metallicity of this galaxy and the observed flattening in its metal distribution. We found that the star formation process along the eastern tidal structure has not been efficient enough to increase the oxygen abundances in this place, suggesting that this structure was formed from enriched material.

Accepted for publication in MNRAS, 18 pages, 11 figures, 6 tables

References in corpus (11)

• HyperLEDA. III. The catalogue of extragalactic distances
• The MOSDEF Survey: Mass, Metallicity, and Star-formation Rate at z~2.3
• SLUG -- Stochastically Lighting Up Galaxies. III: A Suite of Tools for Simulated Photometry, Spectroscopy, and Bayesian Inference with Stochastic Stellar Populations
• The oxygen abundance in the inner HII regions of M101. Implications for the calibration of strong-line metallicity indicators
• SLUG - Stochastically Lighting Up Galaxies. II: Quantifying the Effects of Stochasticity on Star Formation Rate Indicators
• Star-formation in the HI bridge between M81 and M82
• Stochastic `Beads on a String' in the Accretion Tail of Arp 285
• Interaction effects on galaxy pairs with Gemini/GMOS- II: Oxygen abundance gradients
• An HI Threshold for Star Cluster Formation in Tidal Debris
• Multi-object Spectroscopy of Young Star Clusters in NGC 4676
• HI aperture synthesis and optical observations of the pair of galaxies NGC 6907 and 6908

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• A MUSE view of the multiple interacting system HCG 31
• Star formation in low density HI gas around the Elliptical Galaxy NGC2865
• Resolved properties of a luminous "hinge clump" in the compact group of galaxies NGC\,6845