Catching evolution of galaxies in nearby groups

Catching evolution of galaxies in nearby groups

Groups of galaxies contain about 60% of the galaxies in the Local Universe. Furthermore, the fraction of star-forming galaxies in groups is midway between the field and clusters environments, i.e. potentially groups hide the key of the puzzle of the galaxy evolution. Some physical mechanisms would transform actively star forming, gas rich, spiral galaxies in the filed into cluster-like galaxies, i.e. gas poor, mostly passively evolving early-type (Es+S0s) galaxies. Groups, as a whole, are driven from an ``active" (e.g. star forming) phase, typical of field, to a more ``passive" phase, typical of clusters, during the formation/virialization of groups, through a quenching of the star formation and a morphological transformation.

 

What mechanisms drives and what are the phases of this transformation?

Since the velocity of individual galaxies within groups, generated by the gravitational attraction are much smaller than within clusters, galaxy-galaxy merging and interactions are more favoured in groups than in clusters. Mergers can transform spiral galaxies into ellipticals and may also quench future star formation by ejecting the interstellar medium via starburst, AGN or shock-driven winds. Simulations of groups evolution suggest that the quenching of star formation does not happen suddenly! Galaxies has already transformed into ellipticals before the star formation stops. This happen when the groups is nearly assembled and as a consequence of the quenching of gas accretion and stripping (to a lesser degree). The same fate happens to disk galaxies that, as they join the group, are turned into red-and-dead disks. Together with galaxy-galaxy interaction and merging, ``ram-pressure'' stripping seems to have a role in removing the hot gas from the halo around galaxies. This mechanism, called strangulation, could in a long period of time (> 1Gyr) to reduce also the cold gas replenishment up to a complete cutoff of the star.r

Understanding the co-evolution of groups and their members then requires a considerable observational effort, starting from the group definition, e.g. considering the presence of possible substructures, and a correct galaxy morphological (and kinematical) classification. Multi-wavelength surface photometric and 2D kinematical studies are necessary to investigate the effect of galaxy-galaxy and galaxy-ICM interaction i.e.  the galaxy transforming mechanisms.

Looking for variation in the star formation properties of galaxies we are pushed to use observations sensible even to small variation of such properties like the far UV. Nearby groups are the more suitable targets for a detailed study of the galaxies but we are forced to use wide field instruments since group members may cover sky areas of the order of few square degrees. In this context we are using Galaxy Evolution Explorer (GALEX) imaging combined with Digital Sky Survey (SDSS) images for a set of groups showing a different type of galaxy population. We are considering from loose group dominated by spirals up to to more compact configurations rich of elliptical and S0 galaxies. The Far UV photometry can map accurately the star formation properties of the galaxies in the groups. We show here images coming from recent studies of groups similar to the Local Group where is located our galaxy the Milky Way (Marino et al. 2010) and of USGC U268 and USGC U376 groups in the Leo cloud (Marino et al. 2013).

People: Roberto Rampazzo, Daniela Bettoni, Lucio Buson and Paola Mazzei

Collaborations: Antonietta Marino and Giuseppe Galletta (Univ. di Padova); Bianchi Luciana and David Thilker (JHU, Baltimore, USA)


Recent publications: Marino et al. (2013, MNRAS, 428, 476); Marino et al. (2011, ApJ, 736, 154); Rampazzo et al. (2011, Ap&SS, 335, 243)

News – MEDIA INAF

Il notiziario online dell'Istituto Nazionale di Astrofisica
  • Un impatto fra il Pianeta rosso e un piccolo planetoide, grande quanto Cerere o Vesta, potrebbe essere all'origine di Phobos e Deimos. L’ipotesi è avvalorata da un nuovo studio del Southwest Research Institute pubblicato oggi su Science Advances

  • Uno studio della Boulder Colorado University indaga la natura di due formazioni a forma di ali nella galassia Ngc 6240. Si tratta di materiale espulso dalla galassia dal vento stellare e da due buchi neri supermassicci che presto si fonderanno. Il materiale mancante fa prevedere un minore tasso di formazione di nuove stelle.

  • Con un rapporto di contrasto di uno su cento milioni e uno spettrografo a campo integrale da 10mila pixel, la camera hi-tech sviluppata a UC Santa Barbara e al Caltech promette di produrre numerose immagini dirette di pianeti extrasolari. E funziona anche da sensore di fronte d’onda

  • Pronti per la pubblicazione i dati sullo spettro di 340mila stelle nella Via Lattea. Studiati con una precisione senza precedenti, permetteranno – assieme ai dati del telescopio spaziale europeo Gaia – la creazione del più completo atlante stellare mai creato

  • Nella remota galassia attiva Xid2028 un flusso notevole di materia si disperde nello spazio e impoverisce le riserve di gas nella galassia stessa, che nell’arco di dieci milioni di anni potrebbe non avere più la materia prima per forgiare nuove stelle. La scoperta vede protagonisti i ricercatori dell'Inaf

  • Nico Cappelluti, astrofisico romagnolo all’università di Miami, assieme ad altri ricercatori di università statunitensi potrebbe avere scoperto un segnale del decadimento di materia oscura. Lo studio, di cui avevamo già parlato, è ora in via di pubblicazione su The Astrophysical Journal

Go to top

We use cookies to improve our website and your experience when using it. Cookies used for the essential operation of the site have already been set. To find out more about the cookies we use and how to delete them, see our privacy policy.

I accept cookies from this site.

EU Cookie Directive Module Information