The VLBA Imaging and Polarimetry Survey at 5 GHz

Helmboldt, J. F.; Taylor, G. B.; Tremblay, S. E.; Fassnacht, C. D.; Walker, R. C.; Myers, S. T.; Sjouwerman, Loránt O.; Pearson, T. J.; Readhead, A. C. S.; Weintraub, L.; Gehrels, N.; Romani, Roger W.; Healey, S. E.; Michelson, P. F.; Blandford, R. D.; Cotter, Garret

doi:10.1086/511005

Cited by 192 publications

(258 citation statements)

References 23 publications

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“…2 angular resolution) measured a flux density of ∼ 0.3 Jy (Patnaik et al 1992). A VLBA observation at 5 GHz with milliarcsecond resolution in 2006 resulted in a flux density of ∼ 33 mJy (Helmboldt et al 2007). One explanation for this could be the presence of significant extended emission, which is integrated in the low angular resolution of Green Bank 91 m and VLA telescopes, while is resolved in the milliarcsecond images of VLBA.…”

Section: Monochromatic Luminositiesmentioning

confidence: 99%

Properties of flat-spectrum radio-loud narrow-line Seyfert 1 galaxies

Foschini

Berton

Caccianiga

et al. 2015

A&A

188

344

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We have conducted a multiwavelength survey of 42 radio loud narrow-1ine Seyfert 1 galaxies (RLNLS1s), selected by searching among all the known sources of this type and omitting those with steep radio spectra. We analyse data from radio frequencies to X-rays, and supplement these with information available from online catalogues and the literature in order to cover the full electromagnetic spectrum. This is the largest known multiwavelength survey for this type of source. We detected 90% of the sources in X-rays and found 17% at γ rays. Extreme variability at high energies was also found, down to timescales as short as hours. In some sources, dramatic spectral and flux changes suggest interplay between a relativistic jet and the accretion disk. The estimated masses of the central black holes are in the range ∼ 10 6−8 M ⊙ , lower than those of blazars, while the accretion luminosities span a range from ∼ 0.01 to ∼ 0.49 times the Eddington limit, with an outlier at 0.003, similar to those of quasars. The distribution of the calculated jet power spans a range from ∼ 10 42.6 to ∼ 10 45.6 erg s −1 , generally lower than quasars and BL Lac objects, but partially overlapping with the latter. Once normalised by the mass of the central black holes, the jet power of the three types of active galactic nuclei are consistent with each other, indicating that the jets are similar and the observational differences are due to scaling factors. Despite the observational differences, the central engine of RLNLS1s is apparently quite similar to that of blazars. The historical difficulties in finding radio-loud narrow-line Seyfert 1 galaxies might be due to their low power and to intermittent jet activity.

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Section: Monochromatic Luminositiesmentioning

confidence: 99%

Properties of flat-spectrum radio-loud narrow-line Seyfert 1 galaxies

Foschini

Berton

Caccianiga

et al. 2015

A&A

188

344

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“…These sources are mainly drawn from the Radio Fundamental Catalogue (RFC) comprising all sources observed with VLBI for astrometry and geodesy programmes. They also include data from major VLBI surveys such as the VLBA Calibrator Survey (e.g., Beasley et al 2002;Petrov et al 2005;Kovalev et al 2007), the VLBI Imaging and Polarimetry Survey (Helmboldt et al 2007;Petrov & Taylor 2011), and the VLBA 2-cm Survey Kellermann et al (1998Kellermann et al ( , 2004, among others. For their sample of sources, they fit two circular Gaussian components to the self-calibrated visibilities for each source, then select the most compact component as the core component for which they determine the FWHM angular sizes.…”

Section: Published Vlbi Core Sizesmentioning

confidence: 99%

The MASIV Survey – IV. Relationship between intra-day scintillation and intrinsic variability of radio AGNs

Koay

Macquart

Jauncey

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We investigate the relationship between 5 GHz interstellar scintillation (ISS) and 15 GHz intrinsic variability of compact, radio-selected AGNs drawn from the Microarcsecond Scintillation-Induced Variability (MASIV) Survey and the Owens Valley Radio Observatory (OVRO) blazar monitoring program. We discover that the strongest scintillators at 5 GHz (modulation index, m 5 ≥ 0.02) all exhibit strong 15 GHz intrinsic variability (m 15 ≥ 0.1). This relationship can be attributed mainly to the mutual dependence of intrinsic variability and ISS amplitudes on radio core compactness at ∼ 100 µas scales, and to a lesser extent, on their mutual dependences on source flux density, arcsec-scale core dominance and redshift. However, not all sources displaying strong intrinsic variations show high amplitude scintillation, since ISS is also strongly dependent on Galactic line-of-sight scattering properties. This observed relationship between intrinsic variability and ISS highlights the importance of optimizing the observing frequency, cadence, timespan and sky coverage of future radio variability surveys, such that these two effects can be better distinguished to study the underlying physics. For the full MASIV sample, we find that Fermi-detected gamma-ray loud sources exhibit significantly higher 5 GHz ISS amplitudes than gamma-ray quiet sources. This relationship is weaker than the known correlation between gamma-ray loudness and the 15 GHz variability amplitudes, most likely due to jet opacity effects.

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“…This galaxy hosts a low-power, ∼10 22 W Hz −1 , radio AGN (Hummel 1980;Wrobel & Heeschen 1984;Wrobel 1991) with a flat spectrum radio core (Hummel 1980;Hummel et al 1984;Kharb et al 2012). Very long baseline interferometry (VLBI) observations have revealed a jet-like structure on the northern side of the nucleus of NGC 3998 (Filho et al 2002;Helmboldt 2007). The radio core is known to be variable (see also Sect.…”

Section: Overview Of Ngc 3998mentioning

confidence: 99%

“…(1) Wrobel & Heeschen (1984); (2) Gregory et al (1996); (3) Condon et al (1998); (4) Kharb et al (2012); (5) Helmboldt (2007).…”

Section: Atomic Gas In Ngc 3998mentioning

confidence: 99%

A rare example of low surface-brightness radio lobes in a gas-rich early-type galaxy: the story of NGC 3998

Frank

Morganti

Oosterloo

et al. 2016

A&A

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We study the nearby lenticular galaxy NGC 3998. This galaxy is known to host a low-power radio AGN with a kpc-size one-sided jet and a large, nearly polar H i disc. It is therefore a good system to study to understand the relation between the availability of cold-gas and the triggering of AGNs in galaxies. Our new WSRT data reveal two faint, S-shaped radio lobes extending out to ∼10 kpc from the galaxy centre. Remarkably, we find that the inner H i disc warps back towards the stellar mid-plane in a way that mirrors the warping of the radio lobes. We suggest that the polar H i disc was accreted through a minor merger, and that the torques causing it to warp in the inner regions are also responsible for feeding the AGN. The "S" shape of the radio lobes would then be due to the radio jets adapting to the changing angular momentum of the accreted gas. The extended radio jets are likely poorly collimated, which would explain their quick fading and, therefore, their rarity in galaxies similar to NGC 3998. The fuelling of the central super-massive black hole is likely occurring via "discrete events", suggested by the observed variability of the radio core and the extremely high core dominance, which we attribute to the formation and ejection of a new jet resulting from a recent fuelling event.

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The VLBA Imaging and Polarimetry Survey at 5 GHz

Cited by 192 publications

References 23 publications

Properties of flat-spectrum radio-loud narrow-line Seyfert 1 galaxies

Properties of flat-spectrum radio-loud narrow-line Seyfert 1 galaxies

The MASIV Survey – IV. Relationship between intra-day scintillation and intrinsic variability of radio AGNs

A rare example of low surface-brightness radio lobes in a gas-rich early-type galaxy: the story of NGC 3998

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