[View Abstracts by Session]

Session: Cosmology and Relativistic Astrophysics

Name: Dr. Felix Pötzl (IA-FORTH)
Coauthors: No coauthors were included.
Type: Oral
Title: Results from the SMILE pilot study to distinguish milli-lens systems
Abstract:

The existence of very low mass (<~ 10^9 M_sun) dark matter (DM) halos is a critical prediction of the Lambda CDM paradigm, and yet still has to be proven observationally. Low mass DM halos, nearly void of stars, may possibly be detected only through the gravitational effect they exert on ordinary matter. The SMILE (Search for MIlli LEnses) project aims at probing the number density of low mass (~ 10^6 - 10^9 M_sun) DM halos searching for gravitational lens systems at milliarcsecond scales (milli-lenses), where the lens is expected to have a mass in the range of interest. This is achieved by studying radio images of active galactic nuclei made with Very-Long-Baseline Interferometry (VLBI). In a recent pilot project, we have searched for milli-lens candidates in a sample consisting of 13,828 compact radio sources from the Astrogeo VLBI FITS image database. Forty candidates with compact double structures have been found using a citizen-science approach, for which I will present the ongoing analysis of follow-up observations with the European VLBI Network at 5 and 22 GHz in phase-referencing mode. These observations with increased sensitivity and frequency coverage allow us to better constrain the nature of the lens candidates. We find some interesting sources that are still viable lens candidates, given constrains such as surface brightness ratio, stability of flux density ratio of components over time, and their spectrum. Other sources are potential compact symmetric objects or even binary black hole candidates, and thus also deserve closer attention.