A Caltech Library Service

Search for AGN counterparts of unidentified Fermi-LAT sources with optical polarimetry: Demonstration of the technique

Mandarakas, N. and Blinov, D. and Liodakis, I. and Kouroumpatzakis, K. and Zezas, A. and Panopoulou, G. V. and Myserlis, I. and Angelakis, E. and Hovatta, T. and Kiehlmann, S. and Kokolakis, K. and Paleologou, E. and Pouliasi, A. and Skalidis, R. and Pavlidou, V. (2019) Search for AGN counterparts of unidentified Fermi-LAT sources with optical polarimetry: Demonstration of the technique. Astronomy and Astrophysics, 623 . Art. No. A61. ISSN 0004-6361.

[img] PDF - Published Version
See Usage Policy.

[img] PDF - Accepted Version
See Usage Policy.


Use this Persistent URL to link to this item:


Context. The third Fermi-LAT catalog (3FGL) presented the data of the first four years of observations from the Fermi Gamma-ray Space Telescope mission. There are 3034 sources, 1010 of which still remain unidentified. Identifying and classifying γ-ray emitters is of high significance with regard to studying high-energy astrophysics. Aims. We demonstrate that optical polarimetry can be an advantageous and practical tool in the hunt for counterparts of the unidentified γ-ray sources (UGSs). Methods. Using data from the RoboPol project, we validated that a significant fraction of active galactic nuclei (AGN) associated with 3FGL sources can be identified due to their high optical polarization exceeding that of the field stars. We performed an optical polarimetric survey within 3σ uncertainties of four unidentified 3FGL sources. Results. We discovered a previously unknown extragalactic object within the positional uncertainty of 3FGL J0221.2+2518. We obtained its spectrum and measured a redshift of z = 0.0609 ± 0.0004. Using these measurements and archival data we demonstrate that this source is a candidate counterpart for 3FGL J0221.2+2518 and most probably is a composite object: a star-forming galaxy accompanied by AGN. Conclusions. We conclude that polarimetry can be a powerful asset in the search for AGN candidate counterparts for unidentified Fermi sources. Future extensive polarimetric surveys at high Galactic latitudes (e.g., PASIPHAE) will allow the association of a significant fraction of currently unidentified γ-ray sources.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Liodakis, I.0000-0001-9200-4006
Zezas, A.0000-0001-8952-676X
Panopoulou, G. V.0000-0001-7482-5759
Angelakis, E.0000-0001-7327-5441
Hovatta, T.0000-0002-2024-8199
Kiehlmann, S.0000-0001-6314-9177
Additional Information:© ESO 2019. Received 18 October 2018 / Accepted 15 January 2019 We thank Richard Britto and Marcello Giroletti for useful comments that improved this work. We thank the Swift Observatory Team, in particular Brad Cenko, for their rapid approval and scheduling of ToO observations. The RoboPol project is a collaboration between Caltech in the USA, MPIfR in Germany, Toruń Centre for Astronomy in Poland, the University of Crete/FORTH in Greece, and IUCAA in India. D.B. acknowledges support from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program under grant agreement No 771282. G.V.P. acknowledges support by the European Commission Seventh Framework Programme (FP7) through the Marie Curie Career Integration Grant PCIG-GA-2011-293531 “SFOnset”. K.K., A.Z., and R.S. acknowledge funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement n. 617001. This research has made use of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration This research has made use of the SVO Filter Profile Service ( supported by the Spanish MINECO through grant AyA2014-55216, The SVO Filter Profile Service (Rodrigo, C., Solano, E., Bayo, A. and The Filter Profile Service Access Protocol (Rodrigo, C., Solano, E.
Funding AgencyGrant Number
European Research Council (ERC)771282
Marie Curie FellowshipPCIG-GA-2011-293531 'SFOnset'
European Research Council (ERC)617001
Ministerio de Economía, Industria y Competitividad (MINECO)AyA2014-55216
Subject Keywords:techniques: polarimetric / galaxies: active / gamma rays: galaxies
Record Number:CaltechAUTHORS:20190314-105458511
Persistent URL:
Official Citation:Search for AGN counterparts of unidentified Fermi-LAT sources with optical polarimetry - Demonstration of the technique N. Mandarakas, D. Blinov, I. Liodakis, K. Kouroumpatzakis, A. Zezas, G. V. Panopoulou, I. Myserlis, E. Angelakis, T. Hovatta, S. Kiehlmann, K. Kokolakis, E. Paleologou, A. Pouliasi, R. Skalidis and V. Pavlidou A&A, 623 (2019) A61 DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:93803
Deposited By: George Porter
Deposited On:14 Mar 2019 19:33
Last Modified:03 Oct 2019 20:57

Repository Staff Only: item control page