Outflows in the radio-intermediate quasar III Zw 2: a polarization study with the EVLA and uGMRT

Mohan²,

et al. 2022

ApJ

Observational searches for intermediate-mass black holes (IMBHs; 102–106 M ⊙) include relatively isolated dwarf galaxies. For those that host active galactic nuclei (AGNs), the IMBH nature may be discerned through the accretion–jet activity. We present radio observations of four AGN-hosting dwarf galaxies, which potentially harbor IMBHs. Very large array (VLA) observations indicate steep spectra (indices of −0.63 to −1.05) between 1.4 and 9 GHz. However, a comparison with the 9 GHz in-band spectral index shows a steepening for GH047 and GH158 (implying older/relic emission) and flattening for GH106 and GH163 (implying recent activity). Overlapping emission regions in the VLA 1.4 GHz and our very long baseline array (VLBA) 1.5 GHz observations, and possibly symmetric pc-scale extensions, are consistent with recent activity in the latter two. Using the compact VLBA radio luminosity, X-ray luminosity (probing the accretion activity), and the black hole masses, all AGNs are found to lie on the empirical fundamental plane relation. The four AGNs are radio-quiet with relatively higher Eddington ratios (0.04–0.32) and resemble X-ray binaries during spectral state transitions that entail an outflow ejection. Furthermore, the radio to X-ray luminosity ratio log R X of −3.9 to −5.6 in these four sources support the scenarios that include corona mass ejection from the accretion disk and wind activity. The growth to kpc-scales likely proceeds along a similar trajectory to young AGNs and peaked spectrum sources. These complex clues can thus aid in the detection and monitoring of IMBHs in the nearby universe.

Section: The Nature Of Radio Emissionsupporting

confidence: 82%

Radio Observations of Four Active Galactic Nuclei Hosting Intermediate-mass Black Hole Candidates: Studying the Outflow Activity and Evolution

Mohan²,

et al. 2022

ApJ

“…The polarization study indicates that the weak jet in this RIQ is suppressed by the surrounding strong wind-like component. Radio variability and polarization structures also indicate that the jet activity is intermittent, which may be explained by changing spectral states of the accretion disk in an ongoing merger event (Silpa et al 2021). Our VLBA observation of J2242+0334 reveals similar radio emission properties with III Zw 2, where the diffuse emission is the dominant component for the emission detected with the VLA.…”

Section: Comparison With Low-redshift Riqssupporting

confidence: 54%

“…Furthermore, a less powerful jet may interact with the surrounding medium, which could also result in extended radio emission. Such systems were identified in some local quasars with radio and X-ray observations (Wills et al 1999;Kunert-Bajraszewska et al 2010;Silpa et al 2021).…”

Section: Discussionmentioning

confidence: 98%

“…J2242+0334 is likely to be dominated by optically thin synchrotron emission (O'Dea & Saikia 2021;Silpa et al 2021;Patil et al 2022). Such optically thin synchrotron emission with resolved/extended morphology and steep spectra was typical for radio-quiet quasars observed at low redshifts (e.g.,Pei et al 2020).The radio emission, although diffuse, is unlikely to be powered primarily by nuclear star formation.…”

mentioning

confidence: 99%

See 1 more Smart Citation

VLBA Reveals the Absence of a Compact Radio Core in the Radio-intermediate Quasar J2242+0334 at z = 5.9

Liu

Wang

Momjian

et al. 2022

ApJL

High-resolution imaging is crucial for exploring the origin and mechanism of radio emission in quasars, especially at high redshifts. We present 1.5 GHz Very Long Baseline Array (VLBA) images of the radio continuum emission from the radio-intermediate quasar (RIQ) J2242+0334 at z = 5.9. This object was previously detected at both 1.5 GHz and 3 GHz with the Karl G. Jansky Very Large Array (VLA) as a point source. However, there is no clear detection in the VLBA images at both the full resolution of 10.7 mas × 4.5 mas (61.7 pc × 26.0 pc) and a tapered resolution of 26 mas × 21 mas (150 pc × 121 pc). This suggests that the radio emission from the quasar is diffuse on milliarcsecond scales with surface brightness fainter than the 3σ detection limit of 40.5 μJy beam−1 in the full-resolution image. The radio emission in the RIQ J2242+0334 is likely to be wind-like (i.e., diffuse) rather than in the form of collimated jets. This is different from the previous radio detections of the most luminous quasars at z ∼ 6 that are usually dominated by compact, high brightness temperature radio sources. Meanwhile, compared with RIQs at low redshifts, the case of J2242+0334 suggests that not all RIQs are beamed radio-quiet quasars. This optically faint RIQ provides an important and unique example to investigate the radio activity in the less powerful active galactic nuclei at the earliest cosmic epoch.

“…In RQQs with clear signs of AGN activity observed in optical and X-rays, large-scale extended jets or lobes are rarely observed and have only been observed on a few hundred parsecs in a few cases (Pedlar et al 1993;Carilli et al 1998;Silpa et al 2021). A challenging issue in low-resolution (e.g., arcsec scale) observations of RQQs is that the total radio flux density obtained is a mixture of multiple emission sources discussed above and cannot be directly linked to the optical and hard X-ray emission from the AGN.…”

Section: Introductionmentioning

confidence: 99%

VLBI Observations of a sample of Palomar-Green quasars I: parsec-scale morphology

Wang,

An,

Cheng

et al. 2022

Preprint

We observed 20 Palomar-Green (PG) quasars at low redshift (z < 0.5) with total flux density > 1 mJy, including 4 radio-loud quasars (RLQs) and 16 radio-quiet quasars (RQQs), using the Very Long Baseline Array (VLBA) at 5 GHz. Ten RQQs are clearly detected in the VLBA images, and a compact radio core is identified in eight of them, indicating the prevalence of active galactic nucleus (AGN)-related radio emission in this flux-density-limited RQQ sample. The RQQs and RLQs in our sample have a division at ∼30 mJy. The radio emission from RQQs appears to be the result of a combination of star formation and AGN-associated activities. All RQQs in our sample have a 5 GHz flux density ratio of Very Large Array (VLA) A-array to D-array f c = S VLA A /S VLA D above 0.2. The RQQs with f a (VLBA and VLA flux density ratio S VLBA /S VLA A ) > 0.2 versus f a < 0.2 show significant differences in morphology, compactness and total flux density. f a of RQQs is systematically lower than that of RLQs, probably due to the extended jets or relic jets of RQQs on 10s to 100s parsecs which are resolved out in VLBA images. Future larger samples, especially with the addition of milli-arcsec resolution radio images of RQQs with total flux densities below 1 mJy, can test the conclusions of this paper and contributes to the understanding of the radio emission mechanism of RQQs, and the dichotomy and physical connection between RQQs and RLQs.