The Combined NVSS-FIRST Galaxies (CoNFIG) sample - I. Sample definition, classification and evolution

Gendre, M. A.; Wall, J. V.

doi:10.1111/j.1365-2966.2008.13792.x

Cited by 28 publications

(18 citation statements)

References 126 publications

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“…The vast majority of radio sources brighter than ∼1mJy at ∼GHz frequencies are powerful AGN that lie at far greater distance than the Fornax cluster (e.g. Magliocchetti et al 2000;Gendre & Wall 2008;de Zotti et al 2010). Nevertheless, it is desirable to confirm this for the sources used in our particular RM grid experiment, for reasons described in Section 1.…”

Section: Cluster-relative Los Source Positions From Redshift Catalogumentioning

confidence: 95%

Early Science from POSSUM: Shocks, turbulence, and a massive new reservoir of ionised gas in the Fornax cluster

Anderson

Heald

Eilek

et al. 2021

Publ. Astron. Soc. Aust.

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We present the first Faraday rotation measure (RM) grid study of an individual low-mass cluster—the Fornax cluster—which is presently undergoing a series of mergers. Exploiting commissioning data for the POlarisation Sky Survey of the Universe’s Magnetism (POSSUM) covering a ${\sim}34$ square degree sky area using the Australian Square Kilometre Array Pathfinder (ASKAP), we achieve an RM grid density of ${\sim}25$ RMs per square degree from a 280-MHz band centred at 887 MHz, which is similar to expectations for forthcoming GHz-frequency ${\sim}3\pi$ -steradian sky surveys. These data allow us to probe the extended magnetoionic structure of the cluster and its surroundings in unprecedented detail. We find that the scatter in the Faraday RM of confirmed background sources is increased by $16.8\pm2.4$ rad m−2 within 1 $^\circ$ (360 kpc) projected distance to the cluster centre, which is 2–4 times larger than the spatial extent of the presently detectable X-ray-emitting intracluster medium (ICM). The mass of the Faraday-active plasma is larger than that of the X-ray-emitting ICM and exists in a density regime that broadly matches expectations for moderately dense components of the Warm-Hot Intergalactic Medium. We argue that forthcoming RM grids from both targeted and survey observations may be a singular probe of cosmic plasma in this regime. The morphology of the global Faraday depth enhancement is not uniform and isotropic but rather exhibits the classic morphology of an astrophysical bow shock on the southwest side of the main Fornax cluster, and an extended, swept-back wake on the northeastern side. Our favoured explanation for these phenomena is an ongoing merger between the main cluster and a subcluster to the southwest. The shock’s Mach angle and stand-off distance lead to a self-consistent transonic merger speed with Mach 1.06. The region hosting the Faraday depth enhancement also appears to show a decrement in both total and polarised radio emission compared to the broader field. We evaluate cosmic variance and free-free absorption by a pervasive cold dense gas surrounding NGC 1399 as possible causes but find both explanations unsatisfactory, warranting further observations. Generally, our study illustrates the scientific returns that can be expected from all-sky grids of discrete sources generated by forthcoming all-sky radio surveys.

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Section: Cluster-relative Los Source Positions From Redshift Catalogumentioning

confidence: 95%

Early Science from POSSUM: Shocks, turbulence, and a massive new reservoir of ionised gas in the Fornax cluster

Anderson

Heald

Eilek

et al. 2021

Publ. Astron. Soc. Aust.

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“…Others have built upon the FR scheme and used more sophisticated criteria to classify the RGs, such as the presence of jets or "hot spots" toward the edge of the lobes (e.g., OL89; Leahy 1993;Gendre & Wall 2008). In the analyses presented below, we will seek the best way to distinguish various populations of RGs; in doing so we will find ourselves defining several subsets of class a (a 0.9 , a <0.8 , a maj , and a 0.9,em ; see Table 2).…”

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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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“…We construct the LRG sample by combining the CoNFIG catalog (Gendre & Wall 2008;Gendre et al 2010), the FR0CAT catalog (Baldi et al 2018), the FRICAT catalog (Capetti et al 2017b), the FRIICAT catalog (Capetti et al 2017a), and the catalogs of Cheung (2007) and Proctor (2011) (Table 1 and Table 2). To be specific, we first include all 392 compacts, 284 FRIs, 587 FRIIs, and 430 BTs labeled in the CoN -FIG, FR0CAT, FRICAT, and FRIICAT catalogs in the LRG sample.…”

Section: Classification Tree and Sample Selectionmentioning

confidence: 99%

“…The primary motivation of this paper is to develop an automatic open-source tool that can classify a large sample of radio galaxies based on morphological representation learning (LeCun et al 2015) with high computational efficiency, small resource consumption, and powerful predictive capabilities, so as to enable relevant studies on portable computers. In order to do this we have designed a convolutional autoencoder (CAE) based on a deep CNN, unsupervisedly pre-trained the CAE with 14,245 unlabeled images of radio AGNs in the Best-Heckman sample (Best & Heckman 2012, BH12 hereafter), and supervisedly fine-tuned the CAE with images of 1442 radio AGNs that have already been labeled in the literature (Gendre & Wall 2008;Gendre et al 2010;Capetti et al 2017b,a;Baldi et al 2018;Cheung 2007;Proctor 2011). Given that currently no large labeled radio galaxy (LRG) sample is available for neural network training, this approach (i.e., unsupervisedly pre-training the network with a large unlabeled sample and supervisedly fine-tuning it with a relatively small labeled sample) can best extract information hidden in the images and make the classification robust to morphological variability (e.g., Erhan et al 2010;Hinton et al 2012;Christodoulidis et al 2016; see also LeCun et al 2015 for a review).…”

Section: Introductionmentioning

confidence: 99%

A Machine Learning Based Morphological Classification of 14,245 Radio AGNs Selected from the Best–Heckman Sample

Ma¹,

Zhu³

et al. 2019

ApJS

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We present a morphological classification of 14,245 radio active galactic nuclei (AGNs) into six types, i.e., typical Fanaroff-Riley Class I / II (FRI/II), FRI/II-like bent-tailed, X-shaped radio galaxy, and ringlike radio galaxy, by designing a convolutional neural network (CNN) based autoencoder, namely MCRGNet, and applying it to a labeled radio galaxy (LRG) sample containing 1442 AGNs and an unlabeled radio galaxy (unLRG) sample containing 14,245 unlabeled AGNs selected from the Best-Heckman sample. We train MCRGNet and implement the classification task by a three-step strategy, i.e., pre-training, fine-tuning, and classification, which combines both unsupervised and supervised learnings. A four-layer dichotomous tree is designed to classify the radio AGNs, which leads to a significantly better performance than the direct six-type classification. On the LRG sample, our MCRGNet achieves a total precision of ∼ 93% and an averaged sensitivity of ∼ 87%, which are better than those obtained in previous works. On the unLRG sample, whose labels have been human-inspected, the neural network achieves a total precision of ∼ 80%. Also, using the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) to calculate the r-band absolute magnitude (M opt ) and using the flux densities to calculate the radio luminosity (L radio ), we find that the distributions of the unLRG sources on the L radio -M opt plane do not show an apparent redshift evolution and could confirm with a sufficiently large sample that there could not exist an abrupt separation between FRIs and FRIIs as reported in some previous works.

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The Combined NVSS-FIRST Galaxies (CoNFIG) sample - I. Sample definition, classification and evolution

Cited by 28 publications

References 126 publications

Early Science from POSSUM: Shocks, turbulence, and a massive new reservoir of ionised gas in the Fornax cluster

Early Science from POSSUM: Shocks, turbulence, and a massive new reservoir of ionised gas in the Fornax cluster

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

A Machine Learning Based Morphological Classification of 14,245 Radio AGNs Selected from the Best–Heckman Sample

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