Fornax, Virgo, Coma Et Al.: Stellar Systems in High Density Environments

Astronomical News

Report on the Workshop Fornax, Virgo, Coma et al.: Stellar Systems in High Density Environments

held at ESO Headquarters, Garching, Germany, 27 June – 1 July 2011

Magda Arnaboldi1

1 ESO

The workshop focused on recent observational progress in the understanding of stellar systems in the nearby clusters Fornax, Virgo, Coma et al. and provided a forum for comparing the results from theory and observations on galaxy evolution in high density environments at redshift zero.

Over the decade, the nearby galaxy clusters — Fornax, Virgo, Coma, Hydra and Centaurus, to name a few — have been the favourite targets of imaging and spec- troscopic surveys like the Hubble Space Telescope Advanced Camera for Surveys Figure 1. Photo of the participants at the workshop, which took place at the end of the work- (HST ACS), nearby cluster surveys (Virgo, taken in the grounds of ESO Headquarters in shop indicate that the Virgo cluster and Garching during a coffee break on a sunny morning Fornax and Coma surveys), the Next in June. the other nearby clusters continue to fulfil Generation Virgo cluster Survey (NGVS) the expectations formulated in 1984. at the Canada France Hawaii Telescope (CFHT), the SAURON and ATLAS-3D sur- placed within the 3D structure of these veys of nearby galaxies and the 2dF For- clusters and information can be collected Workshop programme nax cluster survey. on the effect of high density environments on the morphology and evolution Given the ambitious scientific pro- The strong scientific motivation for these of individual galaxies. The measure- gramme, the sessions ran over five days extensive observational studies is driven ments of the physical parameters of gal- of the week, including several exciting by the presence of the oldest stellar axies, on all mass scales and surface poster sessions, where the authors pre- populations and the products of the final brightness levels, can then be compared sented short two-minute talks on their collapse of massive stellar systems with predictions from theoretical models work, 24 invited talks and 22 oral contri- 3 from star clusters with masses of 10 MA for the evolution of galaxies and larger- butions. The poster announcing the to the brightest cluster galaxies with scale structures. In this sense, the study workshop is shown in Figure 2. The com- 13 masses of 10 MA. On account of their of nearby clusters complements those plete programme of the workshop, in proximity, which ensures excellent in focused on clusters at high redshift: it cluding the presentations (in PDF format) trinsic spatial resolution in comparison provides independent constraints which is available1, and is linked to the Astro- with more distant galaxy clusters and allow models for galaxies and structure physics Data System (ADS). allows the observations of individual stel- evolution to be tested further. lar sources that are not accessible fur- The workshop started during the after- ther away, nearby clusters are excellent There is an important tradition of work- noon of Monday, 27 June, with a ses- laboratories in which to study the physi- shops dedicated to nearby clusters at sion dedicated to invited reviews on top- cal properties of old stellar populations ESO, and more than 120 participants ics important as background for the by resolving individual star clusters reach- (see Figure 1) gathered at ESO Head- properties of stellar systems in high den- ing down to single stars. quarters to join in the discussions. As it sity environments that were to be happened, the ESO workshop Fornax, addressed during the following sessions. In addition to the study of the stellar Virgo, Coma et al. took place 27 years The five reviews presented the general component, by using several tracers for after the ESO workshop on the Virgo observational properties of clusters, the measuring the distances of the different cluster in 1984 (Richter & Binggeli, 1985). morphology of clusters at high redshifts galaxies in these clusters, it is possible Twenty-seven years ago, the Virgo clus- from high resolution numerical simula- to construct the volume distribution and ter was labelled the “Rosetta stone” tions, galaxies and their black holes, set constraints on how and when the for many problems in extragalactic astron- active galactic nuclei (AGN) feedback and different components, dark matter and omy in the foreword section of the work- the size evolution of massive galaxies. baryons, come together to form the shop proceedings. Clearly, the enthusiasm The next day was dedicated to an over- structures that we now see. The various of the participants during the intensive view of the surveys of nearby clusters at galaxy morphological types can also be sessions and the vibrant discussion different wavelengths, from X-ray, optical

36 The Messenger 146 – December 2011 Figure 2. The poster of the ESO work- – What is the distribution of dwarf sphe- shop, Fornax, Virgo, Coma et al.: Stellar roidals and UDCs in nearby clusters? systems in high density environments. It illustrates the large-scale structures in – What produces low luminosity galaxies the local Universe and examples of galax- (Mv > -16) that are common to both ies in a range of luminosities and sizes. groups and clusters? Are there enough This poster will appear as background in low-luminosity irregulars to explain the the Warner Brothers series The Big Bang Theory. many observed low-luminosity dwarf ellipticals? – What is the relation between UCDs and bulges in compact dwarf galaxies? – What are the most important scientific goals for future integral field unit spec- troscopic surveys?

These questions represent a forward look in this area of research, which builds on 27 years of extragalactic studies in the nearby clusters since the ESO workshop on the Virgo cluster. Identifying these key questions sets an ideal bridge to the future as it highlights those exciting research areas that can be tackled by the European Extremely Large Telescope (E-ELT), as the high angular resolution and collecting power of an extremely large telescope are essential ingredients for the study of stellar populations at dis- and near-infrared, to millimetre and radio fall into the potential well and through the tances larger than 10 Mpc. wavelengths. On Wednesday the work- hot diffuse X-ray halo in the nearby shop started with a session dedicated to clusters. Finally the workshop ended with Again, the nearby clusters Fornax, Virgo, the faint end of the galaxy luminosity a lively discussion chaired by Ortwin Coma et al. will be the first obvious function with presentations on the physi- Gerhard and Roger Davies. targets for this new exciting era in extra- cal properties of globular clusters, ultra- galactic astronomy with many new compact dwarfs (UCDs), and dwarf gal- The discussion was structured around amazing discoveries to be expected. axies. It then moved on from photometry several questions which came about dur- to kinematics and from the faint to the ing the working sessions. These questions bright end of the galaxy luminosity func- covered nearly all the topics presented at Acknowledgements tion. Several topics were covered in this the workshop and are listed below: The LOC members Lodovico Coccato, Luca Cortese, session: the inner and outer halo dynam- Michael Hilker, Marina Rejkuba and Christina Stoffer ics of early-type galaxies; the role played – Is the current observational under- are acknowledged for their hard work and support. by merger events in shaping both light standing of how the most massive gal- The support by ESO students, and by Fei Zhao in and kinematics in these objects; and the axies form reconciled with the hierar- particular, during question time is gratefully acknowledged. The intense and stimulating scientific pro- mass determination in massive galaxies chical formation paradigm? Are the gramme of the workshop was defined by the SOC using X-rays. observed distributions of angular whose members were: Magda Arnaboldi, Noubuo momentum, colour gradients, alpha- Arimoto, Michele Cappellari, Eric Emsellem, Bill On the following day, the topics of the element-to-iron ratio ( /Fe) and galaxy Harris, Ken Freeman, John Kormendy, Harald α Kuntschner, Ortwin Gerhard, Claudia Maraston, morning session covered the bright end sizes compatible with these predictions? Lucio Mayer, Simona Mei, Bianca Poggianti, of the luminosity function of galaxies – Where does the high metallicity in the Sadanori Okamura, Tom Richtler. in the nearby clusters and their physical hot coronae in clusters come from? properties. In the afternoon session, – Are S0 galaxies stripped or starved spi- References the subject shifted to the studies of the rals? intra-cluster light (ICL), with presentations – Does harassment cause significant star Richter, O.-G. & Binggeli, B. (eds) 1985, ESO of results coming from both observa- formation in gas driven to the centre of Workshop on the Virgo Cluster of Galaxies tions and numerical simulations. On the galaxies? last day of the workshop, the morning – How important is the star formation Links session was dedicated to the discussion outside galaxies as seen in Hα filaments of the gas properties of galaxies with and stripped gas? 1 Conference presentations available at: emphasis on the ram pressure stripping – How do we learn from the ICL about http://www.eso.org/sci/meetings/2011/fornax_ virgo2011/programme_final.html of gas experienced by galaxies as they galaxy evolution?

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