A1 Vertaisarvioitu alkuperäisartikkeli tieteellisessä lehdessä
VLTI-GRAVITY observations of blazars; 
Tekijät: Hovatta, Talvikki; Lindfors, Elina; Korhonen, Heidi; Kharb, Preeti; Wittkowski, Markus; Labdon, Aaron; Pursimo, Tapio; Wiik, Kaj
Kustantaja: EDP Sciences
Julkaisuvuosi: 2026
Lehti: Astronomy and Astrophysics
Artikkelin numero: A15
Vuosikerta: 710
ISSN: 0004-6361
eISSN: 1432-0746
DOI: https://doi.org/10.1051/0004-6361/202558568
Julkaisun avoimuus kirjaamishetkellä: Avoimesti saatavilla
Julkaisukanavan avoimuus : Kokonaan avoin julkaisukanava
Verkko-osoite: https://doi.org/10.1051/0004-6361/202558568
Rinnakkaistallenteen osoite: https://research.utu.fi/converis/portal/detail/Publication/527094230
Rinnakkaistallenteen lisenssi: CC BY
Rinnakkaistallennetun julkaisun versio: Kustantajan versio
Aims. Parsec-scale jets of blazars have so far been spatially resolved only in millimeter and submillimeter wavelengths, where very long baseline interferometry can be used to obtain milliarcsecond-scale images of the jets. We have attempted to spatially resolve the near-infrared emission in jet-dominated blazars for the first time.
Methods. We used the VLTI-GRAVITY instrument to obtain milliarcsecond-scale near-infrared interferometric observations of a flaring blazar Ton 599. Additionally, we observed four non-flaring blazars using the GRAVITY-wide mode, where a nearby bright star is used as a fringe tracker.
Results. We modeled the squared visibilities of Ton 599 and found that they are incompatible with a single unresolved point source unless there is a significant amount of additional unknown coherence loss in the instrument. With the present data, we cannot distinguish between a model with an unresolved point source and extended emission or coherence loss and a model with a single Gaussian component. This suggests that we are seeing the unresolved or only partially resolved jet-base in near-infrared wavelengths. The wide-field mode of GRAVITY was challenging for the additional relatively faint targets, resulting in either non-detections or poor-quality data that could not be modeled.
Conclusions. Our observations demonstrate that it is possible to detect the compact jet emission in blazars with near-infrared interferometry, suggesting that with the improved GRAVITY+ instrument it will be possible to spatially resolve and image the near-infrared emission of blazar jets.
Ladattava julkaisu This is an electronic reprint of the original article. |  |
Julkaisussa olevat rahoitustiedot:
We thank the referee for the useful comments that helped to improve the clarity of the paper. TH acknowledges support from the Research Council of Finland projects 317383, 320085, 345899, and 362571 and from the European Union ERC-2024-COG – PARTICLES – 101169986. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council Executive Agency. Neither the European Union nor the granting authority can be held responsible for them. EL was supported by the Research Council of Finland projects 317636, 320045, and 346071. HK acknowledges the financial support from European Southern Observatory’s Science Support Discretionary Fund (SSDF) and the Visitor and Mobility program of the Finnish Centre for Astronomy with ESO (FINCA). PK acknowledges the support of the Department of Atomic Energy, Government of India, under the project 12-R&D-TFR-5.02-0700 and the Visitor and Mobility program of the Finnish Centre for Astronomy with ESO (FINCA). Based on observations collected at the European Southern Observatory under ESO programmes 108.221C.001, 111.24L9.001, 112.25FL.001, and 113.26E7.001. We thank the director of the REM telescope Emilio Molinari for approving our DDT request (proposal 44908) and Dino Fugazza for the swift scheduling of our observations. Tuorla blazar monitoring program makes use of data from the Joan Oró Telescope (TJO) of the Montsec Observatory (OdM), which is owned by the Catalan Government and operated by the Institute for Space Studies of Catalonia (IEEC). This study makes use of VLBA data from the VLBA-BU Blazar Monitoring Program (BEAM-ME and VLBA-BU-BLAZAR; http://www.bu.edu/blazars/BEAM-ME.html), funded by NASA through the Fermi Guest Investigator Program. The VLBA is an instrument of the National Radio Astronomy Observatory. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated by Associated Universities, Inc. This research has made use of data from the MOJAVE database that is maintained by the MOJAVE team (Lister et al. 2018). This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation.
