S. Torres-Flores

Star-forming regions and the metallicity gradients in the tidal tails: the case of NGC 92

We present new Gemini/GMOS spectroscopic and archival imaging data of the interacting galaxy NGC 92, which is part of a compact group and displays an extended tidal tail. We have studied the physical properties of 20 star-forming complexes in this system. We found that the star-forming regions located in the tidal tail of NGC 92 have ages younger than similar to 8 Myr, which suggests that these objects were formed in situ. The spectroscopic data reveal that these regions have slightly sub-solar metallicities, suggesting that they were formed from pre-enriched material. Using the oxygen abundances derived for each system, we found that the extended tidal tail of NGC 92 has a flat metallicity distribution. Although this scenario is consistent with N-body simulations of interacting systems, where there is gas mixing triggered by the interaction, archival H alpha Fabry-Perot data cubes of NGC 92 have not shown a velocity gradient along the tail of this galaxy, which under certain assumptions could be interpreted as a lack of gas flow in the tail. Our results suggest that a fraction of the enriched gas that was originally located in the centre of the galaxy was expelled into the tidal tail when the interacting process that formed the tail happened. However, we cannot exclude the scenario in which the star formation in the tail has increased its original oxygen abundance.

The Tully–Fisher relations for Hickson compact group galaxies★

We used K-band photometry, maximum rotational velocities derived from Fabry-Perot data and H i observed and predicted masses to study, for the first time, the K band, stellar and baryonic Tully-Fisher relations for galaxies in Hickson compact groups. We compared these relations with the ones defined for galaxies in less dense environments from the Gassendi HAlpha survey of Spirals and from a sample of gas-rich galaxies. We find that most of the Hickson compact group galaxies lie on the K-band Tully-Fisher relation defined by field galaxies with a few low-mass outliers, namely HCG 49b and HCG 96c, which appear to have had strong recent burst of star formation. The stellar Tully-Fisher relation for compact group galaxies presents a similar dispersion to that of the K-band relation, and it has no significant outliers when a proper computation of the stellar mass is done for the strongly star-forming galaxies. The scatter in these relations can be reduced if the gaseous component is taken into account, i.e. if a baryonic Tully-Fisher relation is considered. In order to explain the positions of the galaxies off the K-band Tully-Fisher relation, we favour a scenario in which their luminosities are brightened due to strong star formation or AGN activity. We argue that strong bursts of star formation can affect the B- and K-band luminosities of HCG 49b and HCG 96c and in the case of the latter also AGN activity may affect the K-band magnitude considerably, without affecting their total masses.

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

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)

The Hα kinematics of interacting galaxies in 12 compact groups

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A census of Hα emitters in the intergalactic medium of the NGC 2865 system

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Probing the nature of the pre-merging system Hickson Compact Group 31 through integral field unit data

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WITNESSING GAS MIXING IN THE METAL DISTRIBUTION OF THE HICKSON COMPACT GROUP HCG 31

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Kinematics and physical properties of the nearby galaxy NGC 4656 and its TDG candidate

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Star formation in low density HI gas around the elliptical galaxy NGC 2865

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3D Studies of Galaxies in Compact Groups

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