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SMILE: Search for MIlli-LEnses

Casadio, C. and Blinov, D. and Readhead, A. C. S. and Browne, I. W. A. and Wilkinson, P. N. and Hovatta, T. and Mandarakas, N. and Pavlidou, V. and Tassis, K. and Vedantham, H. K. and Zensus, J. A. and Diamantopoulos, V. and Dolapsaki, K. E. and Gkimisi, K. and Kalaitzidakis, G. and Mastorakis, M. and Nikolaou, K. and Ntormousi, E. and Pelgrims, V. and Psarras, K. (2021) SMILE: Search for MIlli-LEnses. Monthly Notices of the Royal Astronomical Society: Letters, 507 (1). L6-L10. ISSN 1745-3925. doi:10.1093/mnrasl/slab082.

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Dark matter (DM) haloes with masses below ∼10⁸ M_⊙, which would help to discriminate between DM models, may be detected through their gravitational effect on distant sources. The same applies to primordial black holes, considered as an alternative scenario to DM particle models. However, there is still no evidence for the existence of such objects. With the aim of finding compact objects in the mass range of ∼10⁶–10⁹ M_⊙, we search for strong gravitational lenses on milliarcsec scales (<150 mas). For our search, we used the Astrogeo very long baseline interferometry (VLBI) FITS image data base – the largest publicly available data base, containing multifrequency VLBI data of 13 828 individual sources. We used the citizen science approach to visually inspect all sources in all available frequencies in search for images with multiple compact components on mas scales. At the final stage, sources were excluded based on the surface brightness preservation criterion. We obtained a sample of 40 sources that passed all steps and therefore are judged to be mas lens candidates. These sources are currently followed up with ongoing European VLBI network observations at 5 and 22 GHz. Based on spectral index measurements, we suggest that two of our candidates have a higher probability to be associated with gravitational lenses.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper ItemAstrogeo VLBI FITS image database
Casadio, C.0000-0003-1117-2863
Blinov, D.0000-0003-0611-5784
Readhead, A. C. S.0000-0001-9152-961X
Browne, I. W. A.0000-0002-0743-8430
Hovatta, T.0000-0002-2024-8199
Pavlidou, V.0000-0002-0870-1368
Tassis, K.0000-0002-8831-2038
Vedantham, H. K.0000-0002-0872-181X
Zensus, J. A.0000-0001-7470-3321
Gkimisi, K.0000-0002-3267-8612
Ntormousi, E.0000-0002-4324-0034
Pelgrims, V.0000-0002-5053-3847
Additional Information:© 2021 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2021 July 13. Received 2021 July 8; in original form 2021 April 23. Published: 20 July 2021. CC, DB, NM, V. Pelgrims, and KT acknowledge support from the European Research Council (ERC) under the European Union Horizon 2020 research and innovation program under the grant agreement number 771282. V. Pavlidou acknowledges support from the Foundation of Research and Technology - Hellas Synergy Grants Program through project MagMASim, jointly implemented by the Institute of Astrophysics and the Institute of Applied and Computational Mathematics and by the Hellenic Foundation for Research and Innovation (HFRI) under the ‘First Call for H.F.R.I. Research Projects to support Faculty members and Researchers and the procurement of high-cost research equipment grant’ (Project 1552 CIRCE). TH was supported by the Academy of Finland projects 317383, 320085, and 322535. We thank Fotini Bouzelou and John Kypriotakis, who also helped in the search for lens candidates. We would like to thank the MPIfR internal referee Silke Britzen for the careful reading of the manuscript. We would like also to thank Leonid Petrov for maintaining the Astrogeo VLBI FITS image data base and A. Bertarini, L. Vega Garcia, N. Corey, Y. Cui, L. Gurvits, X. He, Y. Y. Kovalev, S-S. Lee, R. Lico, E. Liuzzo, A. Marscher, S. Jorstad, C. Marvin, D. Homan, M. Lister, A. Pushkarev, E. Ros, T. Savolainen, K. Sokolovski, A. Tao, G. Taylor, A. de Witt, M. Xu, and B. Zhang for making VLBI images they produced publicly available. We found that a practice to upload VLBI images to a publicly available data base brings great benefits to the scientific community. This research has made use of ALADIN SKY ATLAS developed at CDS, Strasbourg Observatory, France (Bonnarel et al. 2000). Data Availability: The FITS images and UV-FITS files underlying this article are publicly available at the Astrogeo VLBI FITS image data base ( The usage policy of the Astrogeo VLBI FITS image data base as well as the presence of unpublished material within the data base does not permit the publication of either images or source-related data obtained along with this study.
Group:Astronomy Department
Funding AgencyGrant Number
European Research Council (ERC)771282
Foundation of Research and Technology-Hellas Synergy Grants ProgramUNSPECIFIED
Institute of AstrophysicsUNSPECIFIED
Institute of Applied and Computational MathematicsUNSPECIFIED
Hellenic Foundation for Research and Innovation (HFRI)1552 CIRCE
Academy of Finland317383
Academy of Finland320085
Academy of Finland322535
Subject Keywords:dark matter – gravitational lensing: strong – quasars: general – techniques: interferometric
Issue or Number:1
Record Number:CaltechAUTHORS:20211222-561495000
Persistent URL:
Official Citation:C Casadio, D Blinov, A C S Readhead, I W A Browne, P N Wilkinson, T Hovatta, N Mandarakas, V Pavlidou, K Tassis, H K Vedantham, J A Zensus, V Diamantopoulos, K E Dolapsaki, K Gkimisi, G Kalaitzidakis, M Mastorakis, K Nikolaou, E Ntormousi, V Pelgrims, K Psarras, SMILE: Search for MIlli-LEnses, Monthly Notices of the Royal Astronomical Society: Letters, Volume 507, Issue 1, October 2021, Pages L6–L10,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:112635
Deposited By: Tony Diaz
Deposited On:22 Dec 2021 19:12
Last Modified:22 Dec 2021 19:12

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