SMILE: Discriminating milli-lens systems in a pilot project
| Autor: | Pötzl, F. M., Casadio, C., Kalaitzidakis, G., Álvarez-Ortega, D., Kumar, A., Missaglia, V., Blinov, D., Janssen, M., Loudas, N., Pavlidou, V., Readhead, A. C. S., Tassis, K., Wilkinson, P. N., Zensus, J. A. |
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| Rok vydání: | 2024 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| Popis: | Dark Matter (DM) remains poorly probed on critical, sub-galactic scales, where predictions from different models diverge in terms of abundance and density profiles of halos. Gravitational lens systems on milli-arcsecond scales (milli-lenses) are expected for a population of dense DM halos, or free-floating supermassive black holes (SMBHs), that might be comprised of primordial black holes (PBHs), in the mass range of $10^6$ to $10^9 M_\odot$. In this paper, we aim to look for milli-lens systems via a systematic search in a large sample of radio-loud AGN observed with very-long-baseline interferometry (VLBI). We present the observational strategy to discriminate milli-lenses from contaminant objects mimicking a milli-lens morphology. In a pilot project, we have investigated VLBI images from 13,828 sources from the Astrogeo VLBI image database and reduced the number of candidates to 40 in a first step. We present here the images and analysis of sensitive follow-up observations with the EVN at 5 and 22 GHz, and streamline our analysis to reject milli-lens candidates. Using constraints such as the surface brightness ratio, conservation of spectral shape, stability of flux ratios over time, and changes in morphology, we can confidently discriminate between milli-lenses and their mimickers. Using the above constraints, we rule out 32 out of our initial 40 candidates as milli-lenses, demonstrating the power of our approach. Also, we find many new candidates for compact symmetric objects, that are thought to be short-lived, jetted radio sources. This serves as a pathfinder for the final sample used for the SMILE (Search for MIlli-LEnses) project, which will allow us to constrain DM models by comparing the results to theoretical predictions. This SMILE sample will consist of $\sim$5,000 sources based on the VLA CLASS survey, including many observations obtained for this project specifically. Comment: 35 pages, 36 figures, submitted for publication in Astronomy & Astrophysics |
| Databáze: | arXiv |
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