Compact starbursts in ultraluminous infrared galaxies

Condon, J. J.; Huang, Zhenping; Yin, Qiang; Thuan, T. X.

doi:10.1086/170407

Cited by 508 publications

(817 citation statements)

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“…Therefore any such core does not contribute significantly to the overall energy budget of the nuclear region of the galaxy, and is not responsible for the overall flat spectrum of the nuclear region.. This degree of free-free absorption flattening indicates either a high star formation rate (Condon et al 1991) or that we are viewing the AGN through optically-thick narrow-line-region clouds (Roy et al 1994).…”

Section: Radio Spectral Indicesmentioning

confidence: 98%

“…The radio emission from ultra-luminous infrared galaxies is optically thick to free-free absorption, so that the typical synchrotron spectrum of these galaxies is flattened at low frequencies (Condon et al 1991).…”

Section: Radio Spectral Indicesmentioning

confidence: 99%

“…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

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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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Section: Radio Spectral Indicesmentioning

confidence: 98%

Section: Radio Spectral Indicesmentioning

confidence: 99%

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Star formation in southern Seyfert galaxies

Forbes¹,

Norris²

1998

Monthly Notices RAS

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“…From the VLBI spec-1 Typically, brightness temperatures (T b ) above 10 6 K indicate non-thermal emission from AGN (e.g. Kewley et al 2000;Middelberg et al 2011) while thermal emission from star formation has T b < 10 5 K (Sramek & Weedman 1986;Condon et al 1991;Kewley et al 2000). In Magliocchetti et al (2014) the authors showed that at z > 1.8 the radio emission in sources with 1.4 GHz radio luminosities above 4 × 10 24 W Hz −1 is caused by AGN activity, while the radio emission in sources with 1.4 GHz radio luminosities lower than 4 × 10 24 W Hz −1 is caused by star formation.…”

Section: Introductionmentioning

confidence: 99%

Radio spectra of bright compact sources at z>4.5

Coppejans

Velzen

Intema

et al. 2017

Mon. Not. R. Astron. Soc.

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High-redshift quasars are important to study galaxy and active galactic nuclei (AGN) evolution, test cosmological models, and study supermassive black hole growth. Optical searches for high-redshift sources have been very successful, but radio searches are not hampered by dust obscuration and should be more effective at finding sources at even higher redshifts. Identifying high-redshift sources based on radio data is, however, not trivial. Here we report on new multi-frequency Giant Metrewave Radio Telescope (GMRT) observations of eight z > 4.5 sources previously studied at high angular resolution with very long baseline interferometry (VLBI). Combining these observations with those from the literature, we construct broad-band radio spectra of all 30 z > 4.5 sources that have been observed with VLBI. In the sample we found flat, steep and peaked spectra in approximately equal proportions. Despite several selection effects, we conclude that the z > 4.5 VLBI (and likely also non-VLBI) sources have diverse spectra and that only about a quarter of the sources in the sample have flat spectra. Previously, the majority of high-redshift radio sources were identified based on their ultra-steep spectra (USS). Recently a new method has been proposed to identify these objects based on their megahertz-peaked spectra (MPS). Neither method would have identified more than 18 per cent of the high-redshift sources in this sample. More effective methods are necessary to reliably identify complete samples of high-redshift sources based on radio data.

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“…Supporting VLBI evidence for AGN emission often include quite high brightness temperatures (T B 10 5 K), radio luminosities exceeding that of nearby known nuclear supernova remnant (SNR) complexes (L 1.4 GHz > 10 22 W Hz −1 ), and non-thermal flat radio spectra (see Alexandroff et al 2012, and references therein). The radio emission may also come from nuclear star formation activity in the host galaxies (Kimball et al 2011;Padovani et al 2011;Bonzini et al 2013), while most of the star formation-related radio emission typically has T B ≤ 10 4 K (Condon et al 1991). Young radio supernovae (SNe) and SNRs may appear as compact sources in some cases (e.g.…”

Section: Introductionmentioning

confidence: 99%

Discovery of five low-luminosity active galactic nuclei at the centre of the Perseus cluster

Park

Yang

Oonk

et al. 2016

Mon. Not. R. Astron. Soc.

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According to optical stellar kinematics observations, an over-massive black hole candidate has been reported by van den Bosch et al. (2012) in the normal early-type galaxy NGC 1277. This galaxy is located in the central region of the Perseus cluster. Westerbork Synthesis Radio Telescope (WSRT) observations have shown that NGC 1277 and other early-type galaxies in the neighbourhood have radio counterparts. These nuclear radio sources have stable flux densities on time scale of years. In order to investigate the origin of the radio emission from these normal galaxies, we selected five sources (NGC 1270, NGC 1272, NGC 1277, NGC 1278 and VZw 339) residing in the central 10 arcminute region of the Perseus cluster and requested to re-correlate the data of an existing very long baseline interferometry (VLBI) experiment at these new positions. With the re-correlation data provided by the European VLBI Network (EVN), we imaged the five sources with a resolution of about eight milliarcseconds and detected all of them with a confidence level above 5σ at 1.4 GHz. They show compact structure and brightness temperatures above 10 7 K, which implies that the radio emission is non-thermal. We rule out ongoing nuclear star formation and conclude that these VLBIdetected radio sources are parsec-scale jet activity associated with the supermassive black holes in low luminosity active galactic nuclei (LLAGNs), although there are no clear signs of nuclear activity observed in the optical and infrared bands. Using the fundamental plane relation in black holes, we find no significant evidence for or against an extremely massive black hole hiding in NGC 1277.

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Compact starbursts in ultraluminous infrared galaxies

Cited by 508 publications

References 0 publications

Star formation in southern Seyfert galaxies

Star formation in southern Seyfert galaxies

Radio spectra of bright compact sources at z>4.5

Discovery of five low-luminosity active galactic nuclei at the centre of the Perseus cluster

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