15 GHz compact structure in galactic nuclei

Carral, P.; Turner, Jean L.; Ho, Paul T. P.

doi:10.1086/169280

Cited by 85 publications

(151 citation statements)

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“…Whilst several radio sources were seen in the 15-GHz map of Carral et al (1990) (see also Figure 1) no compact emission was seen at the dynamical centre of the galaxy. At higher resolution, no emission from the galaxy was detected by Jones et al (1981) in a three-station VLBI experiment at 18 cm in 1978.…”

Section: A Polar Ring Galaxymentioning

confidence: 99%

“…The two e-MERLIN continuum datasets from mid-2013 both show a strong compact source at the same po- Figure 1. MERLIN archive data at 4.8 GHz from an observation on Jan 9 th 1998 (left), and VLA A-array 15-GHz data from 1986 (right; Carral et al 1990). The only radio source visible in the MERLIN data is a supernova remnant, located towards the north-east end of the main disk of the galaxy.…”

Section: Archival Observationsmentioning

confidence: 99%

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A new period of activity in the core of NGC 660

Argo

Bemmel

Connolly

et al. 2015

Mon. Not. R. Astron. Soc.

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The core of the nearby galaxy NGC 660 has recently undergone a spectacular radio outburst; using a combination of archival radio and Chandra X-ray data, together with new observations, the nature of this event is investigated. Radio observations made using e-MERLIN in mid-2013 show a new compact and extremely bright continuum source at the centre of the galaxy. High angular resolution observations carried out with the European VLBI Network show an obvious jet-like feature to the north east and evidence of a weak extension to the west, possibly a counter-jet. We also examine high angular resolution Hi spectra of these new sources, and the radio spectral energy distribution using the new wide-band capabilities of e-MERLIN. We compare the properties of the new object with possible explanations, concluding that we are seeing a period of new AGN activity in the core of this polar ring galaxy.

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Section: A Polar Ring Galaxymentioning

confidence: 99%

Section: Archival Observationsmentioning

confidence: 99%

A new period of activity in the core of NGC 660

Argo

Bemmel

Connolly

et al. 2015

Mon. Not. R. Astron. Soc.

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“…As in NGC 660, formaldehyde is seen in absorption against the extended central radio continuum source suggesting the presence of large masses of high-density molecular gas (Mangum et al 2008, and references therein). Indeed, the center of NGC 3628 resembles that of NGC 660 also by its complement of compact radio continuum sources (none coinciding with the nucleus) representing active regions in the circumnuclear star-burst contributing about 10% to the total radio continuum emission (Carral et al 1990), and by its H92α radio recombination line emission from high-density HII regions (n HII ≈ 10 4 cm −3 -Anantharamaiah et al 1993;Zhao et al 1997). The central core of NGC 3628 is also bright in X-rays, and the galaxy has an extended halo of soft X-ray emission surrounding a central outflow, apparently a galactic (star-burstdriven) super-wind bubble (Dahlem et al 1996(Dahlem et al , 1998Strickland et al 2004a,b;Grimes et al 2005;Flohic et al 2006).…”

Section: Ngc 3628mentioning

confidence: 99%

“…Indeed, high-density ionized gas is implied by the H92α radio recombination line emission detected by Phookun et al (1998). High-frequency (15 GHz) radio continuum maps reveal several compact continuum sources most likely large complexes of high-density star-forming regions and a compact nuclear source is lacking at radio wavelengths (Carral et al 1990) nor is there any obvious X-ray counterpart to the nucleus (Dudik et al 2005). A detailed study of the galaxy, including HI and J = 1−0, J = 2−1 12 CO mapping (Nobeyama, 17 , IRAM, 12 ) was carried out by Van Driel et al (1995).…”

Section: Ngc 660mentioning

confidence: 99%

CI and CO in nearby galaxy centers

Israel¹

2009

A&A

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Aims. We study the physical properties and mass of molecular gas in the central regions of galaxies with active nuclei. Methods. Maps and measurements of the J = 1-0, J = 2-1, J = 3-2, J = 4-3 12 CO, the J = 1-0, J = 2-1 and J = 3-2 13 CO lines in the central arcminute squared of NGC 278, NGC 660, NGC 3628, NGC 4631, and NGC 4666, as well as 492 GHz [CI] maps in three of these are used to model the molecular gas. Results. All five objects contain bright CO emission in the central regions. Clear central concentrations were found in NGC 660, NGC 3628, and NGC 4666, but not in the weakest CO emitters NGC 278 and NGC 4631. In all cases, the observed lines could be modeled only with at least two distinct gas components. The physical condition of the molecular gas is found to differ from galaxy to galaxy. Relatively tenuous (density 100-1000 cm −3 ) and high kinetic temperature (100-150 K) gas occur in all galaxies, except perhaps NGC 3628, mixed with cooler (10-30 K) and denser (0.3−1.0 × 10 4 cm −3 ) gas. The CO-to-H 2 conversion factor X is typically an order of magnitude less than the "standard" value in the Solar Neighborhood in all galaxy centers. The molecular gas is constrained within radii between 0.6 and 1.5 kpc from the nuclei. Within these radii, H 2 masses are typically 0.6−1.5 × 10 8 M , which corresponds to no more than a few per cent of the dynamical mass in the same region.

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“…Ulvestad & Wilson 1984;Kronberg et al 1985;Antonucci & Ulvestad 1988;Carral, Turner & Ho 1990;Condon et al 1991;Forbes et al 1994;Collison et al 1994;Sandqvist et al 1995).…”

Section: Introductionunclassified

Star formation in southern Seyfert galaxies

Forbes¹,

Norris²

1998

Monthly Notices RAS

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We have produced radio maps, using the ATCA, of the central regions of six southern Seyfert 2 galaxies (NGC 1365, 4945, 6221, 6810, 7582, and Circinus) with circumnuclear star formation, to estimate the relative contribution of star formation activity compared to activity from the active galactic nucleus (AGN). The radio morphologies range from extended diffuse structures to compact nuclear emission, with no evidence, even in the relatively compact sources, for synchrotron self-absorption. In each case the radio to far-infrared (FIR) ratio has a value consistent with star formation, and in all but one case the radio to [FeII] ratio is also consistent with star formation. We derive supernova rates and conclude that, despite the presence of a Seyfert nucleus in these galaxies, the radio, FIR, and [FeII] line emission are dominated by processes associated with the circumnuclear star formation (i.e. supernova remnants and H II regions) rather than with the AGN.

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15 GHz compact structure in galactic nuclei

Cited by 85 publications

References 0 publications

A new period of activity in the core of NGC 660

A new period of activity in the core of NGC 660

CI and CO in nearby galaxy centers

Star formation in southern Seyfert galaxies

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