Parsec-scale properties of brightest cluster galaxies

Liuzzo, E.; Giovannini, G.; Giroletti, M.; Taylor, G. B.

doi:10.1051/0004-6361/200913888

Cited by 32 publications

(49 citation statements)

References 116 publications

(173 reference statements)

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“…By comparison, in a complete sample of 34 BCGs in nearby Abell clusters (distance class <3, Liuzzo et al 2010) the 5 GHz VLBI detection rate is about 68%, with only one case of double source. We note that this source, 3C 75 in A 400, is a dumbbell galaxy where the two components are separated by a much larger distance (∼7.2 kpc in projection) than those detected in RBS 797.…”

Section: Nature Of the Vlbi Double Sourcementioning

confidence: 95%

A candidate supermassive binary black hole system in the brightest cluster galaxy of RBS 797

Gitti

Giroletti

Giovannini

et al. 2013

A&A

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Context. The radio source at the center of the cool-core galaxy cluster RBS 797 (z = 0.35) is known to exhibit a misalignment of its radio jets and lobes observed at different VLA scales, with the innermost ∼kpc-scale jets being almost orthogonal to the radio emission which extends for tens of kpc filling the X-ray cavities. Gitti et al. (2006, A&A, 448, 853) suggested that this peculiar radio morphology may indicate a recurrent activity of the central radio source, where the jet orientation is changing between the different outbursts due to the effects of supermassive binary black holes (SMBBHs). Aims. We aim to reveal the nuclear radio properties of the brightest cluster galaxy (BCG) in RBS 797 and to investigate the presence of a SMBBH system in its center. Methods. We performed new high-resolution observations at 5 GHz with the European VLBI Network (EVN) on May 3, 2013, reaching an angular resolution of ∼9 × 5 mas 2 and a sensitivity of 36 μJy beam −1 . We also re-analyzed VLA archival data at 4.8 GHz in A-and B-configurations. Results. We report the EVN detection of two compact components in the BCG of RBS 797, with a projected separation of ∼77 pc. We can envisage two possible scenarios: the two components are two different nuclei in a close binary system, or they are the core and a knot of its jet. Both interpretations are consistent with the presence of SMBBHs. Our re-analysis of VLA archival data seems to favor the first scenario, as we detect two pairs of radio jets misaligned by ∼90 degrees on the same ∼kpc scale emanating from the central radio core. If the two outbursts are almost contemporaneous, this is clear evidence of the presence of two active supermassive black holes whose radio nuclei are unresolved at VLA resolution. The nature of the double source detected by our EVN observations in the BCG of RBS 797 can be established only by future sensitive, multi-frequency VLBI observations. If confirmed, RBS 797 would be the first SMBBH system observed at medium-high redshift at VLBI resolution.

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Section: Nature Of the Vlbi Double Sourcementioning

confidence: 95%

A candidate supermassive binary black hole system in the brightest cluster galaxy of RBS 797

Gitti

Giroletti

Giovannini

et al. 2013

A&A

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“…The comparison between the total and core radio power and between radio and X-ray images suggests that at present the radio core is in a low-activity phase (Blanton et al 2004;Liuzzo et al 2010).…”

Section: B2 0149+35mentioning

confidence: 98%

“…The radio emission is completely embedded in the optical galaxy, and a gap of radio emission is present between the core and the SW lobe, while a faint jet connecting the core and the NE lobe is detected. Parsec-scale properties are discussed in detail in Liuzzo et al (2010): the source shows a one-sided structure with a total flux density of 10.1 mJy, and the core flux density is 7.27 mJy.…”

Section: B2 1257+28mentioning

confidence: 99%

Compact sources in the Bologna Complete Sample: high-resolution VLA observations and optical data

Liuzzo

Buttiglione

Giovannini

et al. 2013

A&A

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Context. Among radio galaxies, compact sources are a class of objects that are not yet well understood, and most of them cannot be included in classical populations of compact radio sources (flat-spectrum or compact steep-spectrum sources). Aims. Our main goal is to analyze the radio and optical properties of a sample of compact sources and compare them with Faranoff-Riley I and II extended radio galaxies. Methods. We selected in the Bologna Complete Sample a subsample of compact sources, naming it the C BCS sample. We collected new and literature subarcsecond resolution multi-frequency VLA images and optical data. We compared total and nuclear radio power with optical emission line measurements. Results. The [OIII] luminosity − 408 MHz total power relation found in high-and low-excitation galaxies as well as in young (CSS) sources holds also for the C BCSs. However, C BCSs present higher [OIII] luminosity than expected at a given total radio power, and they show the same correlation as core radio galaxies, but with a higher radio power. Conclusions. The C BCSs appear to be the high-power tail of core radio galaxies. For most of the C BCSs, the morphology seems to be strongly dependent on the presence of dense environments (e.g., cluster or HI-rich galaxies) and on a young age or restarted radio activity.

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“…Bondi accretion has been suggested by several studies (Croton et al 2006;Allen et al 2006;Hardcastle et al 2007;Balmaverde et al 2008). Taking the core luminosity measured by Liuzzo et al (2010) and following the reasoning of Balmaverde et al (2008), connecting the radio core luminosity to the radio jet power and relating that to the Bondi accretion power (P B = 0.1Ṁc 2 ), we estimate that the accretion rate of 4C 35.06 is on the order of 0.2 M yr −1 . If part of the detected H I is associated with infalling gas (something possible given the width of the profile that also spans to redshifted velocities) it could provide the required fueling material.…”

Section: Presence Of Cold Gasmentioning

confidence: 66%

“…Liuzzo et al (2010) did a study of UGC 2489 using the Very Long Baseline Array (VLBA) and they detected an extended source on a milli arcsec scale with a core flux density of ∼2.6 mJy, stating that the VLBA detection coincides with one of the cores of the cD galaxy UGC 2489 (Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

The peculiar radio galaxy 4C 35.06: a case for recurrent AGN activity?

Shulevski

Morganti

Barthel

et al. 2015

A&A

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Using observations obtained with the LOw Fequency ARray (LOFAR), the Westerbork Synthesis Radio Telescope (WSRT) and archival Very Large Array (VLA) data, we have traced the radio emission to large scales in the complex source 4C 35.06 located in the core of the galaxy cluster Abell 407. At higher spatial resolution (∼4 ), the source was known to have two inner radio lobes spanning 31 kpc and a diffuse, low-brightness extension running parallel to them, offset by about 11 kpc (in projection). At 62 MHz, we detect the radio emission of this structure extending out to 210 kpc. At 1.4 GHz and intermediate spatial resolution (∼30 ), the structure appears to have a helical morphology. We have derived the characteristics of the radio spectral index across the source. We show that the source morphology is most likely the result of at least two episodes of AGN activity separated by a dormant period of around 35 Myr. The outermost regions of radio emission have a steep spectral index (α < −1), indicative of old plasma. We connect the spectral index properties of the resolved source structure with the integrated flux density spectral index of 4C 35.06 and suggest an explanation for its unusual integrated flux density spectral shape (a moderately steep power law with no discernible spectral break), possibly providing a proxy for future studies of more distant radio sources through inferring their detailed spectral index properties and activity history from their integrated spectral indices. The AGN is hosted by one of the galaxies located in the cluster core of Abell 407. We propose that it is intermittently active as it moves in the dense environment in the cluster core. In this scenario, the AGN turned on sometime in the past, and has produced the helical pattern of emission, possibly a sign of jet precession/merger during that episode of activity. Using LOFAR, we can trace the relic plasma from that episode of activity out to greater distances from the core than ever before. Using the the WSRT, we detect H I in absorption against the center of the radio source. The absorption profile is relatively broad (FWHM of 288 km s −1 ), similar to what is found in other clusters. The derived column density is N HI ∼ 4 × 10 20 cm −2 for a T spin = 100 K. This detection supports the connection -already suggested for other restarted radio sources -between the presence of cold gas and restarting activity. The cold gas appears to be dominated by a blue-shifted component although the broad H I profile could also include gas with different kinematics. Understanding the duty cycle of the radio emission as well as the triggering mechanism for starting (or restarting) the radio-loud activity can provide important constraints to quantify the impact of AGN feedback on galaxy evolution. The study of these mechanisms at low frequencies using morphological and spectral information promises to bring new important insights in this field.

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Parsec-scale properties of brightest cluster galaxies

Cited by 32 publications

References 116 publications

A candidate supermassive binary black hole system in the brightest cluster galaxy of RBS 797

A candidate supermassive binary black hole system in the brightest cluster galaxy of RBS 797

Compact sources in the Bologna Complete Sample: high-resolution VLA observations and optical data

The peculiar radio galaxy 4C 35.06: a case for recurrent AGN activity?

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