Two channels for the formation of compact dwarf galaxies in clusters of galaxies

Abstract

We have identified two channels for the formation of compact dwarf galaxies in the Illustris simulation by reconstructing mass and distance histories of candidates located in the vicinity of the simulation's most massive cluster galaxies. One channel is tidal stripping of Milky Way mass galaxies that form outside of clusters and eventually sink into them, spiraling in toward central massive objects. Second channel of formation is an in-situ formation (in reference to the parent cluster) of dwarf mass galaxies, with negligible evolution and limited change in stellar mass. We find 19 compact dwarf galaxies at the centers of 14 clusters, consistent with observations. 30% of them have external origin while 70% are formed in-situ.

Galactic habitability re-examined: indications of bimodality

“…As far as nearby systems are concerned, the Large Magellanic Cloud, M32, Sagittarius dSph, Canis Major, M110/NGC 205, IC 225, and the Fornax dwarf represent targets of interest for future extragalactic biosignature and technosignature searches. Some of them have possibly very interesting history: compact ellipticals might emerge as a consequence of tidal stripping of giant spirals (e.g., Martinović and Micic, 2017) and this in particular might apply to M32 as has been recently suggested by D' Souza and Bell (2018). What are the implications of such evolutionary trajectory for habitability remain to be seen, since the hypothetical stripping in the case of M32 occurred 2 Gyr ago; if these events happen early enough, the low-irradiation regime is firmly established by the last snapshot at z = 0.…”

“…This implies the possibility that the low metallicity end of the Cloudlet population might in part originate from this recently-formed tidal dwarf galaxies. On the other hand, the two channels of dwarf galaxy formation discussed in Martinović and Micic (2017) imply that the Milky Way sized progenitors can be significantly striped to a dwarf sized objects when falling into the parent galactic cluster. This is consistent with the recent hypothesis of D' Souza and Bell (2018) for the origin of M32, which will be discussed in Section 4 below.…”

Compact elliptical galaxies hosting active galactic nuclei in isolated environment

“…They conform to the low-mass regime of the mass-size relation defined by massive early-type galaxies. Although the origin of cEs is still a subject of debate (Bekki et al 2001;Martinović & Micic 2017;Du et al 2019;Urrutia Zapata et al 2019), cEs are thought to be a mixture of objects formed via two main channels (i.e., nature or nurture) depending on their local environment (i.e., without or with a nearby massive host galaxy; Ferré-Mateu et al 2018, 2021aKim et al 2020).…”

Infrared variable stars in the compact elliptical galaxy M32

“…Such galaxies are thought to have formed via the tidal stripping of larger galaxies (e.g. Faber 1973;Bekki et al 2001;Ferré-Mateu et al 2018) or intrinsically as low-mass 'early-type' galaxies (Kormendy et al 2009;Martinović & Micic 2017). Indeed, M32 has been recently implicated to be the remnant core of a galaxy that underwent a significant merger with M31 (D'Souza & Bell 2018).…”