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
  • Una coppia di ricercatori dell’Università di Leeds ha analizzato con strumenti matematici i getti di plasma emessi a velocità relativistiche dai buchi neri supermassicci. Alcuni di essi si disintegrano in enormi sbuffi di materia a causa di una turbolenza che ha origine in un punto preciso

  • I ricercatori dello strumento Cosima, spettrometro di massa per ioni secondari a bordo della sonda Esa Rosetta, presentano su Monthly Notices of the Royal Astronomical Society un'analisi quantitativa degli elementi chimici della cometa 67P/Churyumov-Gerasimenko

  • La mappa del campo magnetico realizzata da un team di astronomi nei dintorni del buco nero nel sistema binario V404 Cygni presenta valori dell’intensità del campo magnetico fino a quattrocento volte inferiore a quelli attesi. Piergiorgio Casella (Inaf): «È un risultato senza precedenti, che apre la strada ad una comprensione maggiore di ciò che avviene attorno a questi oggetti misteriosi»

  • Due articoli firmati dall’astronomo svizzero André Maeder, entrambi pubblicati su ApJ, presentano un modello cosmologico che ambisce a spiegare ciò che osserviamo senza dover ricorrere a energia e materia oscure. È plausibile? Lo abbiamo chiesto a un cosmologo dell’Inaf, Carlo Burigana

  • Usando le antenne di Alma, un gruppo di ricercatori ha scoperto due galassie che si sarebbero formate quando l'universo aveva appena il 5 per cento dell'età attuale. Secondo i dati raccolti, i due oggetti lontanissimi erano avvolti da un’immensa struttura: un alone di materia oscura

  • Lo spettrografo di terza generazione installato al Very Large Telescope dell'Eso ha condotto con successo le sue prime osservazioni. Filippo Zerbi (Inaf): «Espresso è uno strumento fuori dal comune e fuori dal comune è stata la sfida decennale per concepirlo, realizzarlo e infine portarlo pienamente funzionale al telescopio»

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