A multi-wavelength study of the evolution of early-type galaxies in groups: the ultraviolet view

Context. Isolated early-type galaxies are evolving in unusually poor environments for this morphological family, which is typical of cluster inhabitants. We investigate the mechanisms driving the evolution of these galaxies. Aims. Several studies indicate that interactions, accretions, and merging episodes leave their signature on the galaxy structure, from the nucleus down to the faint outskirts. We focus on revealing such signatures, if any, in a sample of isolated early-type galaxies, and we quantitatively revise their galaxy classification. Methods. We observed 20 (out of 104) isolated early-type galaxies, selected from the AMIGA catalog, with the 4KCCD camera at the Vatican Advanced Technology Telescope in the Sloan Digital Sky Survey g and r bands. These are the deepest observations of a sample of isolated early-type galaxies so far: on average, the light profiles reach μg ≈ 28.11 ± 0.70 mag arcsec−2 and μr ≈ 27.36 ± 0.68 mag arcsec−2. The analysis was performed using the AIDA package, providing point spread function-corrected 2D surface photometry up to the galaxy outskirts. The package provides a model of the 2D galaxy light distribution, which after model subtraction enhances the fine and peculiar structures in the residual image of the galaxies. Results. Our re-classification suggests that the sample is composed of bona fide early-type galaxies spanning from ellipticals to late-S0s galaxies. Most of the surface brightness profiles are best fitted with a bulge plus disc model, suggesting the presence of an underlying disc structure. The residuals obtained after the model subtraction show the nearly ubiquitous presence of fine structures, such as shells, stellar fans, rings, and tails. Shell systems are revealed in about 60% of these galaxies. Conclusions. Because interaction, accretion, and merging events are widely interpreted as the origin of the fans, ripples, shells and tails in galaxies, we suggest that most of these isolated early-type galaxies have experienced such events. Because they are isolated (after 2–3 Gyr), these galaxies are the cleanest environment in which to study phenomena connected with events like these.

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“…They were discussed as a signature of the disc instability during a merging episode (see e.g. Rampazzo et al 2018;Mazzei et al 2019).…”

Section: Spiral Arm-like Residualsmentioning

confidence: 99%

Morphology and surface photometry of a sample of isolated early-type galaxies from deep imaging

Rampazzo

Omizzolo

Uslenghi

et al. 2020

A&A

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High‐resolution morphology and surface photometry of KIG 685 and KIG 895 with ARGOS+LUCI using the Large Binocular Telescope

Rampazzo¹,

Uslenghi

Georgiev

et al. 2019

Astron Nachr

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We aim to refine the sample of isolated early‐type galaxies in the Analysis of the interstellar Medium of Isolated Galaxies (AMIGA) catalog via high‐resolution imaging. Here, we report the result from a pilot study investigating two candidates, KIG 685 and KIG 895, in K‐band with the laser guide star and wavefront sensing facility ARGOS using the Large Binocular Telescope (LBT). Observations, obtained during the commissioning time, achieved a point spread function (PSF) of ≈0.25″. We present the data reduction and the PSF analysis from the best closed‐loop exposures to investigate the galaxies' morphological structure, including their nuclear region. We used PROFILER for the decomposition of the azimuthal 1D light distribution and GALFIT for the 2D analysis, accounting for ARGOS's PSF. KIG 685 was found to be a S0 galaxy and has been modeled with two Sérsic components representing a pseudobulge (n1D = 2.87 ± 0.21, n2D = 2.29 ± 0.10) and a disk (n1D = 0.95 ± 0.16, n2D = 0.78 ± 0.10). Nearly symmetric ring‐/shell‐like structures emerge after subtracting the GALFIT model from the image. KIG 895 shows a clear irregular arm‐like structure, in which the northern outer arm is reminiscent of a tail. The galaxy body is a disk, best fitted by a single Sérsic profile (n1D = 1.22 ± 0.1; n2D = 1.32 ± 0.12), that is, KIG 895 is a bulge‐less, very late‐type spiral. ARGOS high‐resolution images clearly showed interaction signatures in KIG 895. We suggest that the ring‐/shell‐like residuals in KIG 685, a bona fide early‐type galaxy, point toward a past accretion event.

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Dorado and its member galaxies II: A UVIT picture of the NGC 1533 substructure

et al. 2021

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Dorado is a nearby (17.69 Mpc) strongly evolving galaxy group in the Southern Hemisphere. We are investigating the star formation in this group. This paper provides a FUV imaging of NGC 1533, IC 2038 and IC 2039, which form a substructure, south west of the Dorado group barycentre. FUV CaF2-1 UVIT-Astrosat images enrich our knowledge of the system provided by GALEX. In conjunction with deep optical wide-field, narrow-band Ha and 21-cm radio images we search for signatures of the interaction mechanisms looking in the FUV morphologies and derive the star formation rate. The shape of the FUV luminosity profile suggests the presence of a disk in all three galaxies. FUV emission is detected out to the optical size for IC 2038, and in compact structures corresponding to Ha and H II bright features in NGC 1533. A faint FUV emission, without an optical counterpart, reminiscent of the H I structure that surrounds the outskirts of NGC 1533 and extends up to IC 2038/2039, is revealed above the local background noise.

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A multi-wavelength study of the evolution of early-type galaxies in groups: the ultraviolet view

Cited by 6 publications

References 63 publications

Morphology and surface photometry of a sample of isolated early-type galaxies from deep imaging

Morphology and surface photometry of a sample of isolated early-type galaxies from deep imaging

High‐resolution morphology and surface photometry of KIG 685 and KIG 895 with ARGOS+LUCI using the Large Binocular Telescope

Dorado and its member galaxies II: A UVIT picture of the NGC 1533 substructure

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