![]() Artistic image of the XMM satellite |
My research interests include the physics of
clusters and groups of galaxies and their use as tools for cosmology.
I'm mainly an X-ray observer using the current generation of X-ray
satellites: Chandra, XMM and
Suzaku, to gather every piece of information coming from X-ray
emission of their hot gas: gravitational mass distribution, mass of the hot
gas, entropy and metal abundance distributions. |
![]() Mass profile of the NGC 1550 group. Black dots represents the total mass, blue line is the dark matter, green is the X-ray emitting gas, red the stars of the central galaxy |
Mass profiles of clusters and groups of galaxiesIf the mass profiles of clusters of galaxies have been explored in detail,
until reccently there was little information about the gravitational mass
profiles of groups of galaxies. For this purpose we collected a sample of 16
relaxed groups with the best Chandra and XMM data: the mass profiles are well
described by an NFW model for the dark matter, stars from the central galaxy
plus the mass of the hot gas. Our results revealed a significant decrease
of the nFW concentration with virial mass, similar to that predicted by the
standard LambdaCDM cosmology. This provides a further confirmation of our
understanding of dark matter collapse, before only tested at the scale of
massive clusters, at the mass scale of groups. |
![]() X-ray cavities and filaments in the Chandra image of the NGC 5044 group |
AGN feedbackData from Chandra and XMM have revolutionized our models of cooling flows
at the center of galaxies and to a larger extent of galaxy formation. The gas
in these regions is not cooling as expected and the most promising heating
solution is feedback from the central AGN, by means of cavities and shocks
by the jets of the supermassive black holes. Again this phenomenon is not
explored at the scale of groups as intensively as at the scale of clusters.
I have been involved in particular in studying one of the brightes and close
groups, the Perseus of groups, NGC 5044 which shows dramatic X-ray cavities
and filaments. The Hα emitting gas is a crucial element to reveal the
complex dynamics of gas in this region and we have obtained a VIMOS IFU
observation to study in detail the emission in NGC 5044. |
![]() Spectral lines of metals in the spectrum of M87 |
Entropy and Metal AbundancesThe characterization of the entropy profiles in groups and clusters
can precisely reveal the deviations from the prediction of the self-similar
model based only on work of gravity and identify the level, epoch and sources
(AGNs and supernovae) of the injection of non-gravitational energy in the
X-ray emitting gas.
Chandra and XMM are extending the minimum luminosity and therefore temperature
and mass of clusters which can be studied at intermediate redshift, opening
the unexplored territory of the population of objects with temperature less
than 4 keV at redshift 0.2-0.6. I'm trying to collect and study objects
of this type serendipitously detected in particular by XMM because they are
among the best candidates to study the entropy increase. |