Astronomy & Astrophysics manuscript no. Meusinger_12jun20 c ESO 2020 June 16, 2020 The galaxy population within the virial radius of the Perseus cluster? H. Meusinger1; 2, C. Rudolf1, B. Stecklum1, M. Hoeft1, R. Mauersberger3, and D. Apai4 1 Thüringer Landessternwarte, Sternwarte 5, 07778 Tautenburg, Germany, e-mail: [email protected] 2 Universität Leipzig, Fakultät für Physik und Geowissenschaften, Linnestraße 5, 04103 Leipzig, Germany 3 Max Planck Institute for Radio Astronomy, Auf dem Hügel 69, 53121 Bonn (Endenich), Germany 4 Steward Observatory and the Lunar and Planetary Laboratory, The University of Arizona, Tucson, AZ 85721, USA Received XXXXXX; accepted XXXXXX ABSTRACT Context. The Perseus cluster is one of the most massive nearby galaxy clusters and is fascinating in various respects. Though the galaxies in the central cluster region have been intensively investigated, an analysis of the galaxy population in a larger field is still outstanding. Aims. This paper investigates the galaxies that are brighter than B ≈ 20 within a field corresponding to the Abell radius of the Perseus cluster. Our first aim is to compile a new catalogue in a wide field around the centre of the Perseus cluster. The second aim of this study is to employ this catalogue for a systematic study of the cluster galaxy population with an emphasis on morphology and activity. Methods. We selected the galaxies in a 10 square degrees field of the Perseus cluster on Schmidt CCD images in B and Hα in com- bination with SDSS images. Morphological information was obtained both from the ‘eyeball’ inspection and the surface brightness profile analysis. We obtained low-resolution spectra for 82 galaxies and exploited the spectra archive of SDSS and redshift data from the literature. Results. We present a catalogue of 1294 galaxies with morphological information for 90% of the galaxies and spectroscopic red- shifts for 24% of them. We selected a heterogeneous sample of 313 spectroscopically confirmed cluster members and two different magnitude-limited samples with incomplete redshift data. These galaxy samples were used to derive such properties as the projected radial velocity dispersion profile, projected radial density profile, galaxy luminosity function, supermassive black hole mass function, total stellar mass, virial mass, and virial radius, to search for indications of substructure, to select active galaxies, and to study the relation between morphology, activity, density, and position. In addition, we present brief individual descriptions of 18 cluster galaxies with conspicuous morphological peculiarities. Key words. galaxies: clusters: individual: Perseus – galaxies: luminosity function, mass function – galaxies: evolution – galaxies: interactions – galaxies: active 1. Introduction ton et al. 2003; Baldry et al. 2004; Eales et al. 2018). Many stud- ies have found that galaxy properties depend on local density, Galaxy clusters are the largest gravitationally bound structures with red-sequence galaxies preferably found in dense regions of in the Universe and they are powerful tracers of the structures galaxy clusters and blue-cloud galaxies in less dense environ- of matter on the largest scales. The mass of galaxy clusters is ments (e.g. Dressler 1980; Postman & Geller 1984; Balogh et al. thought to be dominated by an unseen and presumably collision- 2004; Rawle et al. 2013; Crone Odekon et al. 2018; Liu et al. less component of dark matter (∼ 85%) and a diffuse, hot intra- 2019; Mishra et al. 2019), though other studies concluded that cluster gas (intracluster medium, or ICM). The baryonic matter environment only has a little effect once the morphology and lu- in the cluster galaxies contributes only a few per cent to the clus- minosity of a galaxy is fixed (e.g. Park et al. 2008; Davies et al. ter mass. However, rich clusters host enough galaxies to provide 2019; Man et al. 2019). It has also been suggested that large- a fascinating laboratory for studying not only cluster properties, scale structure has an important affect on galaxy evolution be- but also key processes of galaxy evolution under diverse external yond the known trends with local density (e.g. Rojas et al. 2004; influences. arXiv:2006.07631v1 [astro-ph.GA] 13 Jun 2020 Hoyle et al. 2005; Fadda et al. 2008; Biviano et al. 2011; Koyama Understanding the role of environmental effects on galaxy et al. 2011; Chen et al. 2017; Vulcani et al. 2019). properties is crucial to understand galaxy evolution. In the local Universe, the galaxies populate two distinct areas in diagrams In a cluster environment, galaxies are subject to interactions showing colour versus luminosity or star formation rate (SFR) with other galaxies, with the cluster gravitational potential well, versus stellar mass: a red sequence of passive, mostly early-type and with the ICM (for a review see Boselli & Gavazzi 2006). galaxies and a blue cloud of star-forming galaxies, which are These processes may influence fundamental properties like SFR, mostly of late morphological types (Strateva et al. 2001; Blan- stellar mass assembly, colour, luminosity, and morphology, and they may cause galaxies to migrate from the blue cloud to the ? The full galaxy catalogue is only available in electronic form at red sequence, and probably back. Tidal interactions and mergers the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via of galaxies, a key mechanism of structure evolution in hierarchi- http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/ cal models, can act as triggers for star formation (SF; Toomre Article number, page 1 of 40 A&A proofs: manuscript no. Meusinger_12jun20 & Toomre 1972; Larson & Tinsley 1978; Barton et al. 2000; ample of energetic feedback from the central active galactic nu- Hopkins et al. 2008; Holincheck et al. 2016) and can perturb the cleus (AGN) was observed: Cavities in the ICM are filled with structure of the involved galaxies on time-scales of the order of radio emission from the AGN, which is pumping out relativistic a gigayear (Gyr; e.g. Mihos & Hernquist 1996; Di Matteo et al. electrons into the surrounding X-ray gas (Branduardi-Raymont 2007; Duc & Renaud 2013). Slow encounters and major mergers et al. 1981; Boehringer et al. 1993; Fabian et al. 2011a). Deep are unlikely to occur in the dense cluster core regions where the Chandra images revealed fine structures in the ICM, such as bub- velocity dispersion is high (∼ 1000 km s−1), but may play a role bles, ripples and weak shock fronts within about 100 kpc from in the cluster outskirts where galaxy groups are falling into the the core that are thought to be related to the activity of the AGN cluster potential. As a galaxy passes through the ICM, ram pres- in NGC 1275 and to the re-heating of the cooling gas (Mathews sure can strip out its interstellar medium (Gunn & Gott 1972) and et al. 2006; Fabian et al. 2011a). gas-rich galaxies can lose more and more of their cold gas reser- Although appearing relatively relaxed, e.g. compared to voir for SF. Ram pressure stripping seems evident both from dy- other nearby clusters, there is some indication that the Perseus namical simulations (e.g. Abadi et al. 1999; Roediger et al. 2006) cluster is not yet virialised: the deviation from spherical symme- and from observations of cluster galaxies (e.g. Oosterloo & van try indicated by the chain of bright galaxies, the non-uniform dis- Gorkom 2005; Lee et al. 2017) that show tails of neutral hydro- tribution of morphological types (Andreon 1994), the displace- gen and also of molecular gas clouds. Interactions may also stall ment of the X-ray centroid from the centre of the optical galaxy the supply of external gas. Such ‘strangulation’ or ‘starvation’ positions (Ulmer et al. 1992), and the large-scale substructures has been identified as one of the main mechanisms for quenching in the X-ray emission (Churazov et al. 2003). The global east- star formation in cluster galaxies (e.g. Larson et al. 1980; Peng west asymmetry, along with other structures in the distributions et al. 2015), although the exact physical mechanism is still un- of the temperature and surface brightness of the hot gas can be known. The combined effect of tidal interactions of an infalling modelled as due to an ongoing merger close to the direction of galaxy with the cluster potential and of subsequent high-speed the chain of bright galaxies (Churazov et al. 2003; Simionescu encounters with other cluster members (‘galaxy harassment’) is et al. 2012). A spiral-like feature extending from the core out- also thought to be suitable for quenching the SF activity and wards is interpreted as a sloshing cold front (Ichinohe et al. 2019, causing morphological transformations from late-type to early and references therein). Gas sloshing observed on larger scale types (e.g. Moore et al. 1996; Bialas et al. 2015). Other rele- might be related to a disturbance of the cluster potential caused vant processes include minor mergers (e.g. Kaviraj 2014; Martin by a recent or ongoing merger (Markevitch & Vikhlinin 2007). et al. 2018) and gas outflow caused by the feedback of an ac- Cluster mergers produce large-scale shock waves in the intra- tive galactic nucleus (AGN; e.g. Fabian 2012; Heckman & Best cluster medium (ICM) where frequently Mach numbers two to 2014; Harrison et al. 2018). Although the relative importance of four are measured. These shock fronts may affect the interstellar the various processes remains a matter of debate, it is very likely medium and thus the SF properties of cluster galaxies (Mulroy that at least some of them play a role in the evolution of cluster et al. 2017). galaxies. The environmental dependence of galaxy properties is It has long been known that the Perseus cluster harbours a ra- discernible from the comparison of the galaxy populations in the dio mini-halo (e.g.