Boston University  Blazar Group
Large VLBA Project BEAM-ME (successor to VLBA-BU-BLAZAR): Total & Polarized Intensity Images of Gamma-Ray Bright Blazars at 43 & 86 GHz
  1222+216 light curves  1222+216 on
kpc scales     

Above left: Movie of the jet of gamma-ray bright quasar 1222+216 (or 4C21.35), at a redshift of 0.435 (distance of 3.8 billion light-years), so that 0.5 mas (milli-arcseconds) corresponds to 9.2 light-years. The images used to make the movie are from the Very Long Baseline Array. Colors indicate brightness. Although we think that the jet flows continously from near the black hole (which is invisible and located near the bottom of the frame), "blobs" of brightness appear and move down the jet (at speeds that appear to be faster than light - just an illusion) as the jet becomes bright in gamma rays (as observed by NASA's Fermi Gamma-ray Space Telescope) and at other frequencies.

Above middle: Brightness vs. time. Top panel: Gamma-ray (blue: Fermi; green vertical lines: times of detection of > 0.3 TeV gamma-rays by MAGIC and VERITAS); middle panel: visible light
; bottom panel: light curves at microwave frequencies (red: 43 GHz from the VLBI core - the bright feature at the southern end of the jet seen in the movie; white: 230 GHz from the entire jet measured by the SubMillimeter Array). Red vertical arrows mark times when a new blob first appears in the jet.
Above right: The same quasar but on scales of tens of thousands of light-years, showing how the jet twists.We think that the jet is really coming almost right at us, so the bends appear more dramatic than they are in 3D. False color: X-ray image from NASA's Chandra X-ray Observatory; contours: 1.4 GHz radio image from the Jansky Very Large Array. The Very Long Baseline Array and t
he Jansky Very Large Array are instruments of the National Radio Astronomy Observatory. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated by Associated Universities, Inc.

Monthly Images of Gamma-Ray Blazars with the VLBA at 43 & 86 GHz + Gamma-ray & Optical Light Curves

VLBA Programs: Blazars Entering the Astrophysical Multi-Messenger Era (BEAM-ME, August 2020 to present) and  VLBA-BU-BLAZAR (2007 to July 2020)

List of publications from these programs

Publications describing program and presenting overall results: Jorstad & Marscher (2016, Galaxies, vol. 4, article no. 47), Jorstad et al. (2017, Astrophysical Journal, vol. 846, article no. 98), and Weaver et al. (2022, Astrophysical Journal Supplement Series, vol. 260, article no. 12).

Data products available: (1) Individual images in total intensity and polarized intensity, CLEAN model files, and calibrated visibility (uv) data files. The images were all made with the Very Long Baseline Array at a frequency of 43 GHz or 86 GHz. (See the bottom of this page for proper acknowledgment of the VLBA.)
(2) Flux and polarization data from the Boston University blazar monitoring program, which includes our group's analysis of public data from the Large Area Telescope on the Fermi Gamma-ray Space Telescope, our observations with Boston University's Perkins Telescope, and our previous program of photometric observations with the robotic Liverpool Telescope, in collaboration with Professor Ian McHardy of the University of Southampton.

A plot of multi-waveband flux and linear polarization vs. time since 2008 is also displayed for each object. Click on the source of interest to connect to the images, data files, and plots. If you need any of the optical data files for your research, send email to Dr. Svetlana Jorstad.

Spectral energy distributions: Full version of paper by K.E. Williamson et al. (2014, Astrophysical Journal, vol. 789, article no. 135), including figures and data tables for all blazars studied. The paper, entitled "Comprehensive Monitoring of Gamma-ray Bright Blazars. I. Statistical Study of Optical, X-ray, and Gamma-ray Spectral Slopes," examines changes in the near-IR/optical/UV, X-ray, and gamma-ray spectral energy distributions at different flux states of 33 of the objects listed below (all of the quasars and BL Lac objects; not included are the radio galaxies 3C 84, 3C 111, and 3C 120).

Note: If you use any of these images or data in a publication, please acknowledge via the statements:
This study makes use of VLBA data from the VLBA-BU Blazar Monitoring Program (BEAM-ME and VLBA-BU-BLAZAR;, 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.

Please note: The VLBA had pointing problems, especially at millimeter wavelengths, from May to September 2019. Because of this, the flux calibration for each epoch during this period needs to be verified with 37 GHz data from colleagues at the Metsaehovi Radio Observatory in Finland. This has slowed the imaging process. The flux scales may still be inaccurate even after correction, since pointing errors introduce different flux errors for different objects, so an accurate global correction is not possible. If you need images that are not yet available on this website, feel free to contact Alan Marscher to request them.

0219+428 (3C66A) *

43+86 GHz
0316+413 (3C84)

0336-019 (CTA26)
0415+379 (3C111)

0420-014 (OA129)

0430+052 (3C120)
43+86 GHz

0552+398 +

43+86 GHz
0735+178 0827+243 (OJ248)
0829+046 **


0851+202 (OJ287)
43+86 GHz

1055+018 (4C+01.28)
43+86 GHz
1101+384 (Mrk421)

1127-145 *

1156+295 (4C+29.45)
43+86 GHz
1219+285 (WCom,ON+231)
1222+216 (4C+21.35)

1226+023 (3C273)
43+86 GHz
1253-055 (3C279)
43+86 GHz

1334-127  +

1406-076  **

43+86 GHz
1611+343 (DA406)  *

1622-297  ***

1633+382 (4C+38.41)
43+86 GHz
1641+399 (3C345)

1652+398 (Mrk501)

1730-130 (NRAO 530)
43+86 GHz
1741-038  +

1749+096 (OT081)
43+86 GHz
1959+650  ++

2134+004  +
2145+067  +
2200+420 (BLLac)
43+86 GHz
2223-052 (3C446)

2227-088  +

2230+114 (CTA102)
43+86 GHz
2251+158 (3C454.3)
43+86 GHz

* Last date observed: 4 June 2020 ;    ** Last date observed: 5 July 2020;      *** Last date observed: 3 July 2017
 + First date observed: 7 August 2020;      ++ First date observed: 4 September 2017
43+86 GHz: Observed at both 43 & 86 GHz every 2nd month starting on 6 September 2020
Boston U.: Prof. Alan Marscher, Dr. Svetlana Jorstad, graduate students Zachary Weaver and Melissa Hallum, & undergraduate students Hannah Willy and Paula Fudolig

Instituto de Astrofisica de Andalucia (Granada, Spain): Drs. José Luis Gómez & Iván Agudo, and graduate student Antonio Fuentes

Astro Space Center of the Lebedev Physical Institute (Moscow, Russia): Prof. Yuri Y. Kovalev, graduate students Nikita Kosogorov & Alexander Plavin
Institut de Radioastronomie Millimetrique (Granada, Spain): Dr. Ioannis Myserlis

Sobolev Astronomical Institute, St. Petersburg State University (Russia): Dr. Valeri M. Larionov (deceased), Dr. Sergei Savchenko, Dr. Darya Morozova, and researcher Ivan Troitskiy

Max-Planck-Institut fuer Radioastronomie (Bonn, Germany): Dr. Nicholas MacDonald

Universidad de Concepción (Chile): Dr. Venkatessh Ramakrishnan

Description of program [see also the paper by Jorstad & Marscher (2016)]: We observe about once per month with the Very Long Baseline Array (VLBA) to obtain images of 34 blazar and 3 radio galaxy jets at 43 GHz. The images and polarization are used by us in concert with light curves (brightness vs. time) obtained with NASA's Fermi Gamma-ray Space Telescope (gamma-rays) and RXTE (to the end of 2012) and Swift (X-rays); see our X-ray research page. We can sometimes match the direction of polarization of a feature in the VLBA image with the direction of polarization seen during an outburst in visible light to identify where on the image the visible light is generated. If, as is often the case, events in the visible light curve are seen also in the X-ray and gamma-ray light curves, we can associate the X-ray and gamma-ray emission site with the same feature on the VLBA image. In this way, we can map the emission across the electromagnetic spectrum onto the VLBA images, which have a resolution of about 100 microarcseconds, or about 1000 times finer than can be achieved with the Hubble Space Telescope.

In most blazars, events near (but not inside!) the supermassive black hole inject extra energy into the jet. As this energetic disturbance propagates downstream away from the black hole, it energizes electrons, probably through the formation of a shock wave. This causes the disturbance to become bright at microwave, infrared, and visible wavelengths through the emission of synchrotron radiation. The electrons can also knock (scatter) up to X-ray and gamma-ray energies the synchrotron photons and other photons produced, for example, in nearby hot clouds. The order in which the blazar becomes brighter at different wavelengths probes the physical conditions in the jet on scales even finer than we can resolve in the VLBA images. But we need the images to tell us where in the jet the brightened region is located: in the part of the jet that we see on the images or even closer to the black hole. Our comprehensive program of imaging with the VLBA and densely sampled light curves with Fermi, AGILE (an Italian gamma-ray satellite) , RXTE, Swift, and various ground-based observatories at visible, infrared, and microwave wavelengths, are providing the information necessary to figure out where the electrons get energized and perhaps also how gas falling onto a black hole creates such high-speed, high-energy jets.

For more information on blazars, see our research page.

The Very Long Baseline Array (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.

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Go to the personal web pages of: Alan Marscher ---- Svetlana Jorstad