Separation of the Galactic Synchrotron Foreground and the CMB Polarization Measurements

The polarization of the CMBR represents a powerful test for modern cosmology. It allows to break the degeneracy of fundamental cosmological parameters, and also to observe the contribution of gravitational waves background to the CMBR anisotropy. To observe the CMBR polarization several experiments are either in progress or planned and SPOrt is one of the most promising planned by ESA. At the same time the observation of the CMBR polarization is a difficult task and one of the reasons is the presence of polarized foreground emission. For instance, galactic polarized synchrotron emission (according to some estimates) can completely mimic the polarization of the CMBR. Nevertheless, one can use mathematical properties of the spherical harmonics of the distribution of radiation over the sky to separate different contributions. In this paper the mathematical properties of the polarized synchrotron foreground and the physical mechanism that produces it are discussed. The separation of synchrotron polarization from the polarization generated by density cosmological perturbations is discussed as well.Comment: 10 LaTeX pages, acceptted to AIP Conference Proceedin

Black Hole Relics in String Gravity: Last Stages of Hawking Evaporation

One of the most intriguing problem of modern physics is the question of the endpoint of black hole evaporation. Based on Einstein-dilaton-Gauss-Bonnet four dimensional string gravity model we show that black holes do not disappear and that the end of the evaporation process leaves some relic. The possibility of experimental detection of the remnant black holes is investigated. If they really exist, such objects could be a considerable part of the non baryonic dark matter in our Universe.Comment: 15 pages, accepted to Class. Quant. Gra

Further spectroscopic observations of the CSL-1 object

CSL-1 is a peculiar object (R.A._{2000}= 12h 23m 30.5"; Dec_{2000}= -12deg 38' 57.0") which, for its photometric and spectroscopic properties, is possibly the first case of gravitational lensing by a cosmic string. In this paper we present additional evidences, based on medium-high resolution VLT + FORS1 observations, that the spectra of the two components of CSL-1 are identical within a confidence level higher than 99.9% and the velocity difference of the two components is consistent with zero. This result adds further confidence to the interpretation of the system as a true lens.Comment: In press on ApJ Letters. 10 pages, 3 figures - Accepted version with additional statistical evidenc

Lens candidates in the Capodimonte Deep Field in the vicinity of the CSL1 object

CSL1 is a peculiar object discovered in the OACDF. Photometric and spectroscopic investigation strongly suggest that it may be the first case of gravitational lensing by cosmic string. In this paper we derive and discuss a statistical excess of a gravitational lens candidates present in OACDF region surrounding CSL1. This excess cannot be explained on the basis of conventional gravitational lens statistic alone, but is compatible with the proposed cosmic string scenario.Comment: 8 pages, 2 figures, submitted to Pis'ma v Astron. Zhurnal (russian

CSL-1: a chance projection effect or serendipitous discovery of a gravitational lens induced by a cosmic string?

CSL-1 (Capodimonte--Sternberg--Lens Candidate, No.1) is an extragalactic double source detected in the OAC-DF (Osservatorio Astronomico di Capodimonte - Deep Field). It can be interpreted either as the chance alignment of two identical galaxies at z=0.46 or as the first case of gravitational lensing by a cosmic string. Extensive modeling shows in fact that cosmic strings are the only type of lens which (at least at low angular resolution) can produce undistorted double images of a background source. We propose an experimentum crucis to disentangle between these two possible explanations. If the lensing by a cosmic string should be confirmed, it would provide the first measurements of energy scale of symmetry breaking and of the energy scale of Grand Unified Theory (GUT).Comment: Accepted for publication in the Mon. Not. Royal Astron. Societ

Gauging the dark matter fraction in a L∗L_* S0 galaxy at z=0.47 through gravitational lensing from deep HST/ACS imaging

We analyze a new gravitational lens, OAC-GL J1223-1239, serendipitously found in a deep I-band image of the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS). The lens is a L_*, edge-on S0 galaxy at z=0.4656. The gravitational arc has a radius of 0.42 arcsec. We have determined the total mass and the dark matter (DM) fraction within the Einstein radius as a function of the lensed source redshift, which is presently unknown. For z ~ 1.3, which is in the middle of the redshift range plausible for the source according to some external constraints, we find the central velocity dispersion to be ~180 km/s. With this value, close to that obtained by means of the Faber-Jackson relation at the lens redshift, we compute a 30% DM fraction within the Einstein radius (given the uncertainty in the source redshift, the allowed range for the DM fraction is 25-35 % in our lensing model). When compared with the galaxies in the local Universe, the lensing galaxy, OAC-GL J1223-1239 seems to fall in the transition regime between massive DM dominated galaxies and lower-mass, DM deficient systems.Comment: 18 pages, 5 figures; accepted for publication in Ap