Abstract
The possible existence of two dark-matter-free galaxies (NGC 1052-DF2 and NGC 1052-DF4) in the field of the early-type galaxy NGC 1052 presents a challenge to theories of dwarf galaxy formation according to the current cosmological paradigm. We carried out a search for signatures of past interactions connected to the putative hosts of NGC 1052-DF2 and NGC 1052-DF4 using a very deep L-band image obtained with the 0.7 m Jeanne Rich telescope that reach a surface brightness limit of 28.5 mag arcsec−2 in the r band. We found several low-surface brightness features, possibly consistent with an ongoing merger history in this group. We find a tidal interaction between NGC 1052 and NGC 1047, confirming a physical association. Furthermore, we find a stellar loop around NGC 1052 in the direction of NGC 1042 and a stellar stream pointing in the direction of NGC 1052-DF2, but they are not directly connected. We find no evidence for a recent tidal interaction for NGC 1052-DF2 and NGC 1052-DF4. No LSB features have been uncovered around the spiral galaxy NGC 1042, which leaves the association (physical or projected) between NGC 1052 and NGC 1042 ambiguous, although they have similar radial velocities. Their association will only be established when accurate distances to both objects have been measured.
Highlights
The discovery of two apparently dark-matter-free dwarf galaxies in the field of the early-type galaxy NGC 1052 has sparked strong interest with numerous follow-up studies
This means that the possible absence of dark matter in these galaxies is a direct contradiction of the current cosmological paradigm
Several scenarios have been suggested, for example, that they were tidally stripped from their dark matter by a close passage to NGC 1052 (Ogiya 2018), or that they are the direct results of a tidal interaction, that is, tidal dwarf galaxies (TDG; Duc 2012; Duc et al 2014)
Summary
The discovery of two apparently dark-matter-free dwarf galaxies in the field of the early-type galaxy NGC 1052 has sparked strong interest with numerous follow-up studies (e.g., van Dokkum et al 2018a,b; Trujillo et al 2019; Martin et al 2018; Kroupa et al 2018; Famaey et al 2018; Emsellem et al 2019; Fensch et al 2019; Müller et al 2019; Nusser 2019; Laporte et al 2019). These two galaxies, NGC 1052-DF21 (van Dokkum et al 2018a) and NGC 1052-DF4 (van Dokkum et al 2019), are very extended (reff > 1500 pc) and very dim (mueff,V > 25 mag arcsec−2) at a putative distance of NGC 1052, but their distances are still a matter of active debate (van Dokkum et al 2018b; Trujillo et al 2019) Objects of this size and luminosity were first discovered in the Virgo cluster by Sandage & Binggeli (1984), and recent surveys of galaxies with low surface brightness (LSB) identified them in different galactic environments (e.g., Mihos et al 2015; Merritt et al 2016; van der Burg et al 2016; Ordenes-Briceño et al 2016; Wittmann et al 2017; Venhola et al 2017; Román & Trujillo 2017a,b; Karachentsev et al 2015; Eigenthaler et al 2018; Müller et al 2018a; Greco et al 2018; Mancera Piña et al 2019).
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