The High-Z Universe

Understanding the physics and tracing the cosmic history of the galaxy mass assembly is one of the main open questions of galaxy formation and evolution. Despite the tremendous progress in observational cosmology, the accuracy in the estimate of cosmological parameters and the successful convergence on the LambdaCDM cosmological model, the mechanisms leading to the birth and the evolution of galaxies are still poorly known.

The empirical approach adopted is the investigation of galaxy formation and evolution to search for and to study the populations of distant galaxies.
Samples selected in the optical bands allow to cull star-forming galaxies where the redshifted ultraviolet (UV) radiation is dominated by hot, massive and short-lived stars. However, optical samples are affected by severe biases due to the strong influence of dust extinction and to the wide range of shapes of the spectral energy distributions (SEDs) depending on the level of star formation activity and on the age of the galaxy.
At longer wavelengths, the above problems are alleviated, as the rest-frame near-infrared radiation is dominated by low mass, long-lived stars. Also, the shapes of the SEDs in such a spectral range are very similar for all galaxy types, and the effects of dust extinction become less severe.

In addition, the rest-frame near-IR luminosity is known to correlate with the galaxy mass. The above advantages make galaxy samples selected in the near- (e.g. K-band at 2.2mum) or, even better, in the mid-IR (e.g. 4-8mum, now possible with the Spitzer Space Telescope) more suitable than optical samples to investigate galaxy evolution and, particularly, the history of galaxy stellar mass assembly.

At OAPd we are deeply involved in many ongoing survey projects as GOODS, GMASS, COSMOS and others, aimed at mapping the galaxy populations as a function of redshift and environment. These projects are establishing the observational facts that theoretical modelling will try to reproduce, ensuring full multiwavelength coverage from X-rays to radio making use of all main observational facilities worldwide, both on the ground and in space. Moreover, data from previous IR mission, i.e., the ISO mission which also involved people from OAPd, are now reduced and published.
These observations allowed us to deep our knowledge on the IR and far-IR luminosity functions (LF), which have long been used to constrain galaxy formation models and to quantify star formation and evolution both in luminosity and in density. Thanks to our ISOCAM, optical/near-IR observations and spectroscopy we presented the 60 micron LF and the bi-variate 15 micron LF, one of the few determinations based on ISO data, of a sample of galaxies on which numerous study of galaxy evolution still rely. Despite the fact that our redshift range exceeds 0.3, and our 60micron LF extends up to log(L60)=12, does not show any evidence of evolution.

The high-z Universe -PAST STUDIES

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

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