MNRAS 000,1–16 (2020) Preprint 14 July 2020 Compiled using MNRAS LATEX style file v3.0 Early-type galaxies in the Antlia Cluster: global properties Juan P. Calderón1;2;3?, Lilia P. Bassino1;2;3, Sergio A. Cellone1;3;4, Matías Gómez5 and Juan P. Caso1;2;3 1Consejo Nacional de Investigaciones Científicas y Técnicas, Godoy Cruz 2290, C1425FQB, Ciudad Autónoma de Buenos Aires, Argentina 2Instituto de Astrofísica de La Plata (CCT La Plata – CONICET - UNLP), Paseo del Bosque S/N, B1900FWA La Plata, Argentina 3Facultad de Ciencias Astronómicas y Geofísicas de la Universidad Nacional de La Plata, Paseo del Bosque S/N, B1900FWA La Plata, Argentina 4Complejo Astronómico El Leoncito (CONICET - UNLP - UNC - UNSJ), San Juan, Argentina 5Departamento de Ciencias Físicas, Facultad de Ciencias Exactas, Universidad Andres Bello, Santiago, Chile ... ABSTRACT We present an extension of our previous research on the early-type galaxy population of the Antlia cluster (d ∼ 35 Mpc), achieving a total coverage of ∼ 2.6 deg2 and performing surface photometry for ∼ 300 galaxies, 130 of which are new uncatalogued ones. Such new galaxies mainly fall in the low surface brightness (LSB) regime, but there are also some lenticulars (S0) which support the existence of unique functions that connect bright and dwarf galaxies in the scaling relations. We analyse the projected spatial distribution of galaxies up to a distance of ∼ 800 kpc from NGC 3268, the adopted centre, as well as the radial velocity distribution and the correlation between galaxy colour and effective radius with the projected spatial distribution. We also obtain the luminosity function of the early-type galaxies and the distribution of stellar masses using the T1-band magnitudes and adopted mass-luminosity ratios. Additionally, we correlate the central galaxy distribution with an X-ray emission map from the literature. Based on the analysis of the radial velocities and galaxy colour distributions, we find that galaxies redder than the colour-magnitude relation (CMR) have a velocity distribution strongly concentrated towards the values of the dominant galaxies and are homogeneously distributed throughout the cluster. Those bluer than the CMR, in turn, have a much more extended radial velocity distribution and are concentrated towards the centre of the cluster. We also identify 12 candidates to ultra diffuse galaxies (UDG), that seem to be split into two families, and speculate about their origins in the context of the cluster structure. Key words: galaxies: clusters: general – galaxies: clusters: individual: Antlia – galaxies: fundamental parameters – galaxies: dwarf – galaxies: elliptical and lenticular, cD 1 INTRODUCTION ness regime have been usually classified as dwarf ellipticals (dEs), at fainter magnitudes (MV & −16 mag) ETGs are represented by Over the last years, low luminosity galaxies have received increas- dwarf spheroidals (dSphs, Grebel et al. 2003), which show effective ing attention from the community, due to newly discovered galaxies radii (r ) smaller than ∼ 1 kpc, and are supposed to have experi- in nearby clusters, with unexpected surface brightness and size e enced intense gas and metal removal due to galactic winds (Kirby arXiv:2007.05598v1 [astro-ph.GA] 10 Jul 2020 properties. The complexity attained by modern ΛCDM models in et al. 2011). Still lower in the luminosity scale, the ultrafaint dwarf reference to baryonic effects (Tissera et al. 2010; Vera-Ciro et al. galaxies (UFDGs, Willman et al. 2005) are characterised for be- 2011; Gargiulo et al. 2019) and the new observational evidence ing the most dark matter dominated, the most metal-poor, and least brought by larger detector arrays —MOSAIC II1, Dark Energy chemically evolved stellar systems ever investigated (Simon 2019). Camera (Flaugher et al. 2015, DECam) and OmegaCAM Camera The stellar systems with the lowest surface brightness, observed (Kuijken et al. 2002, OmegaCAM)— have led the research on the in nearby clusters as Virgo, Fornax, and Coma, are the so called distribution and properties of these newly detected galaxies. These ultra diffuse galaxies (UDGs, van Dokkum et al. 2015; Lim et al. galaxies with extreme properties represent new challenges for the 2018). They have large radii (r & 1 kpc), moderate stellar masses, theoretical models of galaxy formation and evolution. e and their low surface brightnesses (µ ∼ 27 mag arcsec−2) make While early-type galaxies (ETGs) in the lowest surface bright- 0;V them only accessible to very deep observations (Eigenthaler et al. 2018). Amorisco & Loeb(2016) show that the origin of UDGs in clusters could be well explained by the classical model of disk ? E-mail: [email protected] 1 https://www.noao.edu/ctio/mosaic/ formation in haloes with higher initial angular momentum. © 2020 The Authors 2 J. P. Calderón et al. Modern imaging surveys —e.g.: Next Generation Virgo Clus- Antlia is the nearest isothermal non-cool core cluster (kT ∼ 2 keV, ter Survey (NGVS, Ferrarese et al. 2012), Fornax Deep Survey Wong et al. 2016), without a central brightness excess (Nakazawa (FDS, Venhola et al. 2017), or Next Generation Fornax Survey et al. 2000). NGC 3268 is the centre of the X-ray emission, which is (NGFS, Eigenthaler et al. 2018)— allow to perform very deep multi- elongated toward a subgroup centred on NGC 3258 (Pedersen et al. band photometry, covering at the same time a projected area on the 1997; Nakazawa et al. 2000; Smith Castelli et al. 2008a). In addi- sky similar to that attained by old photographic plates. This enables tion, the galaxy projected distribution presents a similar orientation, the study of the projected spatial distribution of the different pop- mainly in the direction defined by the two dominant Es. The Antlia ulations that coexist in the clusters, even outside the virial radius. cluster seems to be dynamically younger than Virgo and Fornax, but Despite that, at such low surface brightness levels, cluster member- unexpectedly relaxed when it is compared to other groups (Wong ship through spectroscopic redshift determinations is very difficult et al. 2016), which is also suggested by optical surveys (FS90; Hess to achieve. Anyway, such surveys have provided us with important et al. 2015). The globular cluster systems of the two brightest Es data to study the effects of tidal interactions in galaxy evolution. The have been studied by Caso et al.(2017, and references therein). most relevant environmental effect for the evolution of early-type In the present paper, we perform a new surface photometry of dwarfs is harassment (Moore et al. 1996), which is related with the Antlia ETGs that complements previous papers Calderón et al. repeated tidal encounters between the infalling galaxy and other (2015, hereafter Paper I), and Calderón et al.(2018, hereafter Paper cluster members or the cluster gravitational potential. This could II). Our study covers the largest area considered by any survey of produce a galaxy mass loss that depends on the orbit of the infalling this cluster until now, which motivates us to analyse the projected galaxy within the cluster, and it is expected to be more efficient spatial density of galaxies up to ∼ 700 kpc from the cluster centre, for low-mass galaxies (Smith et al. 2010). On the other hand, the assuming an Antlia distance of ∼ 35:2 Mpc (Dirsch et al. 2003). We motion of the infalling galaxy across the intracluster medium could also recalculate the relations between structural parameters of the produce the loss of the galaxy atomic gas and, consequently, the ETGs, now including more Es at the bright end than previous works. interruption of star formation (Gunn & Gott 1972). Hydrodynami- Moreover, we study the correlation between colour, effective radius, cal simulations (Roediger & Brüggen 2008, and references therein) and radial velocity with the projected spatial distribution. Finally, indicate that this effect is not only due to gravitational interactions, we build the luminosity function of the cluster and estimate stellar but also to mixing turbulence and viscous effects. Additionally, an masses. alternative effect, called strangulation, has been proposed, in which This paper is organized as follows: in Sec.2 we describe the the infall of cool gas into the galaxy is stopped (Balogh et al. 2000). data reduction, fit of the surface brightness profiles, membership This can happen when a subhalo of dark matter is created from a classification, and the catalogue presented in this paper. In Sec.3 previously existing larger halo. The infall of gas associated to the we report the results on the new colour-magnitude relation (CMR), subhalo can be cut, which results in a gradual decrease in the stel- structural parameters, spatial projected distribution, and galaxy lar formation, causing the galaxy colour to become redder (Wang colour correlations. The discussion of the results is given in Sec.4 et al. 2009). The result of the strangulation effect is a galaxy with and finally, the main conclusions are summarized in Sec.5. higher metallicity and stellar mass than its progenitor (Peng et al. 2015). The efficiency of those physical processes is directly related with the parameters that define the structure and dynamics of each 2 OBSERVATIONS AND DATA REDUCTION galaxy, such as total mass, relative orbits and velocities; and also their spatial distribution inside the cluster potential. The so-called We perform a photometric study on four new fields that comple- morphology-density relation (Dressler et al. 1997; van der Wel et al. ments those carried out in previous surveys on the Antlia cluster of 2010), which locates the ETGs mainly in the central areas of the galaxies. These fields were observed with the MOSAIC II camera clusters, and the late-type galaxies (LTGs) in the surrounding areas, mounted on the 4-m Blanco telescope at the Cerro Tololo Inter- would be a result partially due to the role played by environmental American Observatory (CTIO, Chile), during the nights of Febru- processes in the evolution of galaxies.