HST images of B2 radio galaxies: A link between circum-nuclear dust and radio properties?

Ruiter, H. R. de; Parma, P.; Capetti, A.; Fanti, R.; Morganti, Raffaella

doi:10.1051/0004-6361:20021462

Cited by 35 publications

(57 citation statements)

References 21 publications

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“…Our classification of dust structures is consistent with results from de Ruiter et al (2002). The 11 sources with H i absorption all have dust, and are split between extended dust (5) and disks (6).…”

Section: Dust Morphologysupporting

confidence: 87%

“…In contrast, the optical nuclei of FR I radio galaxies appear unobscured (e.g. de Koff et al 1996;Chiaberge et al 1999;Capetti et al 2002), though the host galaxies often have kiloparsec-scale dust rings and lanes (de Koff et al 2000;Verdoes-Kleijn et al 2002;de Ruiter et al 2002). Chiaberge et al (1999) found that the brightness of the optical core correlates with the brightness of the radio core.…”

Section: Introductionmentioning

confidence: 99%

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A relation between circumnuclear H I, dust, and optical cores in low-power radio galaxies

Bemmel

Morganti

Oosterloo

et al. 2012

A&A

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From new observations and literature data we investigate the presence of H i, dust, and optical cores in the central kiloparsec of low-power radio galaxies. The goal of this pilot study is to identify physical relations between these components, which can help us to study kinematics and feeding mechanisms in future samples of active galaxies. Our results are consistent with neutral gas being associated with dust on sub-kiloparsec scales. Objects that have H i absorption always have significant amounts of dust in their host galaxy. If there is no visible dust in the host galaxy, there is also no H i absorption. The presence of an unresolved optical core correlates with the H i column density, with the core being absent in high-column density sources. This work opens a path for studying the kinematics of cold material in the central regions of active galaxies by combining information of H i absorption and molecular lines. Consistent with previous work, we find no evidence for a compact, parsec-scale obscuring torus in low-power radio galaxies.

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Section: Dust Morphologysupporting

confidence: 87%

Section: Introductionmentioning

confidence: 99%

A relation between circumnuclear H I, dust, and optical cores in low-power radio galaxies

Bemmel

Morganti

Oosterloo

et al. 2012

A&A

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“…1). Using HST data, de Ruiter et al (2002) derive a typical gas column density of 2.7 × 10 20 cm −2 for the gas clouds seen in NGC 315, a value very similar to that found in our radio observations for the H i in emission. We obtain the same column density for the narrow absorption if we assume T spin = 100 K. This could further support the idea that the gas is at larger radius since such value for T spin is characteristic for the ISM not affected by the active nucleus.…”

Section: The Narrow Hi Absorptionsupporting

confidence: 84%

Is cold gas fuelling the radio galaxy NGC 315?

Morganti

Peck

Oosterloo

et al. 2009

A&A

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We present WSRT, VLA and VLBI observations of the H i absorption in the radio galaxy NGC 315. The main result is that two H i absorbing systems are detected against the central region. In addition to the known highly redshifted, very narrow component, we detect relatively broad (FWZI ∼ 150 km s −1 ) absorption. This broad component is redshifted by ∼80 km s −1 compared to the systemic velocity, while the narrow absorption is redshifted ∼490 km s −1 . Both H i absorption components are spatially resolved at the pcscale of the VLBI observations. The broad component shows strong gradients in density (or excitation) and velocity along the jet. We conclude that this gas is physically close to the AGN, although the nature of the gas resulting in the broad absorption is not completely clear. The possibility that it is entrained by the radio jet (and partly responsible of the deceleration of the jet) appears unlikely. Gas located in a thick circumnuclear toroidal structure, with orientation similar to the dusty, circumnuclear disk observed with HST, cannot be completely ruled out although it appears difficult to reconcile with the observed morphology and kinematics of the H i. A perhaps more likely scenario is that the gas producing the broad absorption could be (directly or indirectly) connected with the fueling of the AGN, i.e. gas that is falling into the nucleus. If this is the case, the accretion rate derived is similar (considering all uncertainties) to that found for other X-ray luminous elliptical galaxies, although lower than that derived from the radio core luminosity for NGC 315. The data also show that, in contrast to the broad component, the density distribution of the narrow component is featureless. Moreover, in the WSRT observations we do detect a small amount of H i in emission a few kpc SW of the AGN, coincident with faint optical absorption features and at velocities very similar to the narrow absorption. This suggests that the gas causing the narrow absorption is not close to the AGN and is more likely caused by clouds falling into NGC 315. The environment of NGC 315 turns out to be indeed quite gas rich since we detect five gas-rich companion galaxies in the immediate vicinity of NGC 315.

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“…Extended reservoirs of diffuse atomic gas are not unusual in early-type galaxies (Oosterloo et al 2007). Dust lanes in radio galaxies are often perpendicular to the jet (de Koff et al 2000), and have masses that depend on jet power (de Ruiter et al 2002), suggesting that the ISM "knows about the jet".…”

Section: Jet-disk Symbiosismentioning

confidence: 99%

Dense gas without star formation: the kpc-sized turbulent molecular disk in 3C 326 N

Nesvadba

Boulanger

Lehnert

et al. 2011

A&A

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We report the discovery of a 3 kpc disk of few 10 9 M of dense, warm H 2 in the nearby radio galaxy 3C 326 N, which shows no signs of ongoing or recent star formation and falls a factor of 60 below the Schmidt-Kennicutt law. Our VLT/SINFONI imaging spectroscopy shows broad (FWHM ∼ 500 km s −1 ) ro-vibrational H 2 lines across the entire disk, with irregular profiles and line ratios consistent with shocks. The ratio of turbulent to gravitational energy suggests that the gas is highly turbulent and not gravitationally bound. In the absence of the driving by the jet, the short turbulent dissipation times indicate that the gas should collapse rapidly and form stars, at odds with the recent star-formation history. Motivated by hydrodynamic models of rapid H 2 formation boosted by turbulent compression, we propose that the molecules formed from diffuse atomic gas in the turbulent jet cocoon. Since the gas is not self-gravitating, it cannot form molecular clouds or stars while the jet is active, and is likely to disperse and become atomic again after the nuclear activity ceases. We speculate that very low star-formation rates are to be expected under such conditions, provided that the large-scale turbulence controls the gas dynamics in molecular clouds. Our results illustrate that jets may create large molecular reservoirs as expected in "positive feedback" scenarios of AGN-triggered star formation, but that this alone is insufficient to trigger star formation.

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HST images of B2 radio galaxies: A link between circum-nuclear dust and radio properties?

Cited by 35 publications

References 21 publications

A relation between circumnuclear H I, dust, and optical cores in low-power radio galaxies

A relation between circumnuclear H I, dust, and optical cores in low-power radio galaxies

Is cold gas fuelling the radio galaxy NGC 315?

Dense gas without star formation: the kpc-sized turbulent molecular disk in 3C 326 N

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