The Combined NVSS-FIRST Galaxies (CoNFIG) sample - II. Comparison of space densities in the Fanaroff-Riley dichotomy

Gendre, M. A.; Best, P. N.; Wall, J. V.

doi:10.1111/j.1365-2966.2010.16413.x

Cited by 56 publications

(68 citation statements)

References 44 publications

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“…We initially selected the FRI-II sample from a subset of the Combined NVSS and FIRST Galaxies sample (Gendre & Wall 2008;Gendre et al 2010) (CoNFIG henceforth). This sample of radio sources was compiled specifically to address the need and lack of samples of FRI-II sources in the literature.…”

Section: Sample Selectionmentioning

confidence: 99%

“…Since all these are samples based on visual inspection, there is a possibility of confusion in the assigned class of a source due to different studies estimating different morphologies for the same source. To resolve this issue, we have excluded all cross-matched sources from the FRI and FRII samples which have been marked as confirmed WAT/NAT, W-shaped or Ring (and Ring-lobe) morphologies in either Gendre et al (2010) or Proctor (2011). We have removed the bent-tailed radio galaxies from the FRICAT by visual inspection.…”

Section: Sample Selectionmentioning

confidence: 99%

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Classifying Radio Galaxies with the Convolutional Neural Network

Aniyan

Thorat

2017

ApJS

161

176

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We present the application of deep machine learning technique to classify radio images of extended sources on a morphological basis using convolutional neural networks. In this study, we have taken the case of Fanaroff-Riley (FR) class of radio galaxies as well as radio galaxies with bent-tailed morphology. We have used archival data from the Very Large Array (VLA) -Faint Images of the Radio Sky at Twenty Centimeters (FIRST) survey and existing visually classified samples available in literature to train a neural network for morphological classification of these categories of radio sources. Our training sample size for each of these categories is ∼200 sources, which has been augmented by rotated versions of the same. Our study shows that convolutional neural networks can classify images of the FRI and FRII and bent-tailed radio galaxies with high accuracy (maximum precision at 95%) using well-defined samples and "fusion classifier", which combines the results of binary classifications, while allowing for a mechanism to find sources with unusual morphologies. The individual precision is highest for bent-tailed radio galaxies at 95% and is 91% and 75% for the FRI and FRII classes, respectively, whereas the recall is highest for FRI and FRIIs at 91% each, while bent-tailed class has a recall of 79%. These results show that our results are comparable to that of manual classification while being much faster. Finally, we discuss the computational and data-related challenges associated with morphological classification of radio galaxies with convolutional neural networks.

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Section: Sample Selectionmentioning

confidence: 99%

Section: Sample Selectionmentioning

confidence: 99%

Classifying Radio Galaxies with the Convolutional Neural Network

Aniyan

Thorat

2017

ApJS

161

176

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“…Toward lower radio power, contamination from the non-thermal radio continuum of vigorous starbursts becomes increasingly important. The high-redshift radio luminosity function of Willott et al (2001) and Gendre et al (2010) suggests that such galaxies are factors of 100 more common than the very powerful radio sources, with co-moving number densities on the order of a few 10 −7 Mpc −3 , sufficient to represent a short, generic phase in the evolution of massive galaxies, as we will argue below in Sect. 9.…”

Section: Introductionmentioning

confidence: 99%

“…The radio luminosity functions of Willott et al (2001) and Gendre et al (2010) suggest that galaxies with a radio power of 10 27−28 W Hz −1 have co-moving number densities of 10 −(7−6) Mpc −3 at z ∼ 2, whereas the general population of massive high-redshift galaxies have densities of a few 10 −5 Mpc −3 (e.g., Mancini et al 2009, for M stellar ≥ 10 10.5 M ). This suggests that phases of radio activity in this power range could be a generic phase in the evolution of massive galaxies at these redshifts, if the activity timescales are short enough, a few 10 7 yrs.…”

Section: A Generic Phase In the Evolution Of Massive High-redshift Gamentioning

confidence: 99%

Kinematic signatures of AGN feedback in moderately powerful radio galaxies atz~ 2 observed with SINFONI

Collet

Nesvadba

Breuck

et al. 2016

A&A

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Most successful galaxy formation scenarios now postulate that the intense star formation in massive, high-redshift galaxies during their major growth period was truncated when powerful AGNs launched galaxy-wide outflows of gas that removed large parts of the interstellar medium. SINFONI imaging spectroscopy of the most powerful radio galaxies at z ∼ 2 show clear signatures of such winds, but are too rare to be good representatives of a generic phase in the evolution of all massive galaxies at high redshift. Here we present SINFONI imaging spectroscopy of the rest-frame optical emission-line gas in 12 radio galaxies at redshifts ∼2. Our sample spans a range in radio power that is intermediate between the most powerful radio galaxies with known wind signatures at these redshifts and vigorous starburst galaxies, and are about two orders of magnitude more common than the most powerful radio galaxies. Thus, if AGN feedback is a generic phase of massive galaxy evolution for reasonable values of the AGN duty cycle, these are just the sources where AGN feedback should be most important. Our sources show a diverse set of gas kinematics ranging from regular velocity gradients with amplitudes of Δv = 200−400 km s −1 consistent with rotating disks to very irregular kinematics with multiple velocity jumps of a few 100 km s −1 . Line widths are generally high, typically around FWHM = 800 km s −1 , more similar to the more powerful high-z radio galaxies than mass-selected samples of massive high-z galaxies without bright AGNs, and consistent with the velocity range expected from recent hydrodynamic models. A broad Hα line in one target implies a black hole mass of a few 10 9 M . Velocity offsets of putative satellite galaxies near a few targets suggest dynamical masses of a few 10 11 M for our sources, akin to the most powerful high-z radio galaxies. Ionized gas masses are 1−2 orders of magnitude lower than in the most powerful radio galaxies, and the extinction in the gas is relatively low, up to A V ∼ 2 mag. The ratio of line widths, σ, to bulk velocity, v, is so large that even the gas in galaxies with regular velocity fields is unlikely to be gravitationally bound. It is unclear, however, whether the large line widths are due to turbulence or unresolved, local outflows as are sometimes observed at low redshifts. We compare our sources with sets of radio galaxies at low and high redshift, finding that they may have more in common with gas-rich nearby radio galaxies with similar jet power than with the most powerful high-z radio galaxies. Comparison of the kinetic energy with the energy supply from the AGNs through jet and radiation pressure suggests that the radio source still plays a dominant role for feedback, consistent with low-redshift radio-loud quasars.

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“…Type IIs are usually found in less dense environments, and strong emission lines can often be seen in their optical spectra (e.g., Zirbel 1997;Kauffmann et al 2008); type Is, on the other hand, are usually hosted by giant elliptical galaxies, and on average have weaker or no optical nuclear emission lines, which puts them on a different radio power-emission line luminosity correlation than that of FR IIs (Hine & Longair 1979;Zirbel & Baum 1995, see below). The cosmological evolution of the two types may also differ significantly (e.g., Willott et al 2001; but see Gendre et al 2010). Collectively, these differences are usually referred to as the FR I/II dichotomy, which has been the focus of numerous studies (e.g., Heckman et al 1994;Baum et al 1995;Hardcastle et al 2007;Kauffmann et al 2008;Baldi & Capetti 2010, and references therein).…”

Section: Introductionmentioning

confidence: 99%

ON THE POPULATIONS OF RADIO GALAXIES WITH EXTENDED MORPHOLOGY ATz< 0.3

Lin

Shen

Strauss

et al. 2010

ApJ

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Extended extragalactic radio sources have traditionally been classified into Fanaroff & Riley (FR) I and II types, based on the ratio r s of the separation S between the brightest regions on either sides of the host galaxy and the total size T of the radio source (r s ≡ S/T ). In this paper, we examine the distribution of various physical properties as a function of r s of 1040 luminous (L L * ) extended radio galaxies (RGs) at z < 0.3 selected with well-defined criteria from the SDSS, NVSS, and FIRST surveys. About 2/3 of the RGs are lobe dominated (LD) and 1/3 have prominent jets. If we follow the original definition of the FR types, i.e., a division based solely on r s , FR I and FR II RGs overlap in their host galaxy properties. However, the rare LD sources with r s 0.8 and [O iii] λ5007 line luminosity > 10 6 L are markedly different on average from the rest of the RGs, in the sense that they are hosted in lower mass galaxies, live in relatively sparse environments, and likely have higher accretion rates onto the central supermassive black hole (SMBH). Thus, these high emission line luminosity, high-r s LD RGs, and the rest of RGs form a well-defined dichotomy. Motivated by the stark differences in the nuclear emission line properties of the RG subsamples, we suggest that the accretion rate onto the SMBH may play the primary role in creating the different morphologies. At relatively high accretion rates, the accretion system may produce powerful jets that create the "classical double" morphology (roughly corresponding to the LD sources with r s 0.8 and emission lines); at lower accretion rates, the jets from a radiatively inefficient accretion flow generate radio lobes without apparent "hot spots" at the edge (corresponding to the majority of LD sources). At slightly lower accretion rates and in galaxies with dense galactic structure, sources with prominent jets result. It is possible that while the high accretion rate systems could affect sub-Mpc scale environments, the jets from lower accretion rate systems may efficiently suppress activity within the host galaxies.

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The Combined NVSS-FIRST Galaxies (CoNFIG) sample - II. Comparison of space densities in the Fanaroff-Riley dichotomy

Cited by 56 publications

References 44 publications

Classifying Radio Galaxies with the Convolutional Neural Network

Classifying Radio Galaxies with the Convolutional Neural Network

Kinematic signatures of AGN feedback in moderately powerful radio galaxies atz~ 2 observed with SINFONI

ON THE POPULATIONS OF RADIO GALAXIES WITH EXTENDED MORPHOLOGY ATz< 0.3

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