Multiwavelength studies of unidentified sources

The observations of the sky in hard X-rays collected with the INTEGRAL and Swift satellites have shown that about 30% of the detected sources consists of objects of still unknown nature.

In order to identify each of these cosmic sources, all the information available throughout the electromagnetic spectrum, from radio waves to gamma rays, is gathered: this is done by searching through catalogs or digital archives available online, or through targeted observations of these objects.

The combined use of the data available at multiple wavelengths allows one to understand the physical mechanisms that determine the emission from these sources, as well as their chemical composition, distance, and, ultimately, their nature.

REM optic observations

REM (Rapid Eye Mount) is a fully robotic 60-cm fast-slewing (10d/s) telescope placed at La Silla (Chile).

The telescope hosts two instruments: the REM InfraRed camera (REMIR) and the REM Optical Slitless Spectrograph (ROSS), which are able to acquire images on time scales of less than 10 s. A dichroic splits the incoming light beam in order to feed simultaneously both instruments.

REM is mainly dedicated to the search and follow up of the optical/infrared counterparts of transient sources detected by high energy satellites.

Identifying such counterparts, measuring their brightness in different bands and monitoring their evolution, can help us understanding the nature of the object that gave rise to the transient phenomenon. In addition, if the couterpart is bright enough, we can take a spectrum of it by using larger telescope and from the possible presence of absorption and/or emission lines of known chemical elements we can also measure the distance of the object.

Star formation activity in distant galaxies

The most modern telescopes and innovative theories of the recent years provide the first indirect evidence of growth of primordial gas, as shown in this artistic vision. Such a smooth fueling would sustain the star formation activity in galaxies without invoking violent major mergers of galaxies.

The most distant galaxies are under investigation!

They are evolving in a non-violent way.

This result has been obtained by cosmologists using the most powerful telescopes of the European Southern Observatory located in the southern hemisphere.

According to the most modern theories, the galaxies were formed by primordial structures, in which the stars have been originated.

When the Universe was a few billion years, the star formation has experienced a peak of activity thanks to the availability of a large amount gas, the fuel needed to feed them.

However, since then our Universe changed. Today, the galaxies do not form anymore thousands of stellar masses per year, but only a few of them.

What are the mechanisms that regulate this important galactic property?

The cosmologists have discovered that our Universe is dominated by non-violent, smooth mechanisms. In recent years we are getting the first evidence of growth of primordial gas that would feed the star formation, without the need to collect this gas through violent interactions between galaxies.

Star formation process

Star formation is a fundamental astrophysical process; it controls phenomena ranging from the evolution of galaxies and nucleosynthesis to the origins of planetary systems and abodes for life. Currently, we know that the great majority of stars are born in clusters and these in turn are created by the gravitational collapse of giant molecular clouds but there are still a number of open questions regarding the specifics of this  process. To name just a few:

(1) What triggers star formation?

(2) How do the properties of star-forming regions vary among different types of galaxies and environments of different gas densities and compositions?

(3) How do these different environments affect the history of star formation?

(4) Is the stellar initial mass function universal or determined by local conditions?

To properly answer these questions , we have carried out an integrated program on star formation in the nearby universe which fully exploits the formidable capabilities of the Hubble Space Telescope, the VLT, CHANDRA and HERSCHEL. In this study, we have concentrated on the well-resolved massive cluster R136 in 30 Doradus in the LMC (the nearest super star cluster) and NGC 3603 one of the most massive and compact clusters in the Milky Way. Our program consists of broad-band multi-wavelength imaging over the entire range from the X-rays and UV to the near- and far-IR, aimed at studying the ages and metallicities of stellar populations, revealing young stars that are still hidden by dust at optical wavelengths, and showing the integrated properties of star clusters.

Narrow-band imaging of the same environments allow us to measure star formation rates, gas pressure, chemical abundances, extinction, and shock morphologies.  This data allows us to illuminate and understand how stars are born and evolve from the Big Bang to the present.