GASP. VIII. Capturing the Birth of a Tidal Dwarf Galaxy in a Merging System at z ∼ 0.05

Abstract

Within the GAs Stripping Phenomena in galaxies with MUSE (GASP) sample, we identified an ongoing 1:1 merger between two galaxies and the consequent formation of a tidal dwarf galaxy (TDG). The system is observed at z = 0.05043 and is part of a poor group. Exploiting the exquisite quality of the MUSE/VLT data, we present the spatially resolved kinematics and physical properties of gas and stars of this object and describe its evolutionary history. An old (luminosity weighted age ∼ 2 × 10 9 yr), gas poor, early-type-like galaxy is merging with a younger (luminosity weighted age ∼ 2.5 × 10 8 yr), gas rich, late-type galaxy . The system has a quite strong metallicity gradient, indicative of an early-stage phase. Comparing the spatial extension of the star formation at different epochs, we date the beginning of the merger between 2 × 10 7 yr < t < 5.7 × 10 8 yr ago. The gas kinematic pattern reflects that of the late-type object and is distorted in correspondence to the location of the impact . The stellar kinematic instead is more chaotic, as expected for mergers. The gas redistribution in the system induces high levels of star formation between the two components, where we indeed detect the birth of the TDG. This stellar structure has a mass of ∼ 6 × 10 9 M , a radius of ∼ 2 kpc and, even though it has already accreted large quantities of gas and stars, it is still located within the disk of the progenitor, is characterized by a high velocity dispersion, indicating that it is still forming, is dusty and has high levels of star formation (SFR∼ 0.3M yr −1 ). This TDG is originated in an early-stage merger, while these structures usually form in more evolved systems.

A Detailed Study of the Most Relaxed SPT-selected Galaxy Clusters: Properties of the Cool Core and Central Galaxy

“…Combining the amount of star formation with the stellar mass of the donor galaxy yields a specific star formation rate of 0.4 Gyr −1 . For comparison, this is only slightly higher than typical stripped dwarf galaxies in the GASP survey (sSF R ∼ 0.2 − 0.3 Gyr −1 ; Vulcani et al 2017;George et al 2018), and much less than we see in starburst galaxies such as M82 and NGC1569 (sSFR ∼ 1. implied sSFR in the nearest potential donor galaxy is ∼10 Gyr −1 , which is an order of magnitude higher than the most vigorous starbursts that we observe (e.g., Jarrett et al 2017). As discussed in McDonald et al (2012), this is strong evidence against the fueling of star formation by the stripping of infalling gas in this system, as it would require several (∼10) gas-rich galaxies all simultaneously donating their gas.…”

GASP XVIII: star formation quenching due to AGN feedback in the central region of a jellyfish galaxy

“…GASP (GAs Stripping Phenomena in galaxies with MUSE) aims at investigating the gas removal process in a sample of 114 disk galaxies at redshifts 0.04-0.07, using the spatially resolved integral field unit spectrograph MUSE (Poggianti et al 2017b). This program focuses on galaxies in various stages of ram pressure stripping in clusters (Jaffé et al 2018;Vulcani et al 2018c), from pre-stripping (undisturbed galaxies of a control sample), to initial stripping, peak stripping (Bellhouse et al 2017;Gullieuszik et al 2017;Poggianti et al 2017b;Moretti et al 2018), and post-stripping (Fritz et al 2017), and passive, and on a number of physical processes in groups and filaments ranging from stripping to gas accretion, mergers, and cosmic web (Vulcani et al 2017(Vulcani et al , 2018a. JO201 1 with a spectroscopic redshift z ∼ 0.056 is located at a luminosity distance of ∼ 250 Mpc in the Abell 85 galaxy cluster 2 .…”

GASP – XII. The variety of physical processes occurring in a single galaxy group in formation

“…A complete description of the survey strategy, data reduction, and analysis procedures is presented in Poggianti et al (2017)(Paper I). First results on single objects in clusters are discussed in Bellhouse et al 2017, (Paper II);Fritz et al 2017, (Paper III); Gullieuszik et al 2017, (Paper IV); Moretti et al 2018, (Paper V); and in lower-density environments in Vulcani et al 2017, (Paper VIII); Vulcani et al 2018, (Paper VII).…”