E. Congiu
University of Padua
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Featured researches published by E. Congiu.
Astronomy and Astrophysics | 2016
M. Berton; A. Caccianiga; L. Foschini; Bradley M. Peterson; S. Mathur; G. Terreran; Stefano Ciroi; E. Congiu; V. Cracco; M. Frezzato; G. La Mura; Piero Rafanelli
Narrow-line Seyfert 1 galaxies (NLS1s) are an interesting subclass of active galactic nuclei (AGN), which tipically does not exhibit any strong radio emission. Seven percent of them, though, are radio-loud and often show a flat radio-spectrum (F-NLS1s). This, along to the detection of γ -ray emission coming from them, is usually interpreted as a sign of a relativistic beamed jet oriented along the line of sight. An important aspect of these AGN that must be understood is the nature of their parent population, in other words how do they appear when observed under different angles. In the recent literature it has been proposed that a specific class of radio-galaxies, compact-steep sources (CSS) classified as high excitation radio galaxies (HERG), can represent the parent population of F-NLS1s. To test this hypothesis in a quantitative way,in this paper we analyzed the only two statistically complete samples of CSS/HERGs and F-NLS1s available in the literature. We derived the black hole mass and Eddington ratio distributions, and we built for the first time the radio luminosity function of F-NLS1s. Finally, we applied a relativistic beaming model to the luminosity function of CSS/HERGs, and compared the result with the observed function of F-NLS1s. We found that compact steep-spectrum sources are valid parent candidates and that F-NLS1s, when observed with a different inclination, might actually appear as CSS/HERGs.
Astronomy and Astrophysics | 2017
E. Congiu; M. Berton; M. Giroletti; Robert Antonucci; A. Caccianiga; P. Kharb; M. L. Lister; L. Foschini; S. Ciroi; V. Cracco; M. Frezzato; E. Järvelä; G. La Mura; J. L. Richards; Piero Rafanelli
We present the first results of a radio survey of 79 narrow-line Seyfert 1 (NLS1) carried out with the Karl G. Jansky Very Large Array (JVLA) at 5 GHz in A configuration aimed at studying the radio properties of these sources. We report the detection of extended emission in one object: Mrk 783. This is intriguing, since the radio-loudness parameter R of this object is close to the threshold between radio-quiet and radio-loud active galactic nuclei (AGN). The galaxy is one of the few NLS1 showing such an extended emission at z < 0.1. The radio emission is divided in a compact core component and an extended component, observed on both sides of the nucleus and extending from 14 kpc south-east to 12 kpc north-west. There is no sign of a collimated jet, and the shape of the extended component is similar to those of some Seyfert galaxies. The properties of the emission are compatible with a relic produced by the intermittent activity cycle of the AGN.
Astronomy and Astrophysics | 2018
M. Berton; E. Congiu; E. Järvelä; Robert Antonucci; P. Kharb; M. L. Lister; Andrea Tarchi; A. Caccianiga; S. Chen; L. Foschini; A. Lähteenmäki; J. L. Richards; S. Ciroi; V. Cracco; M. Frezzato; G. La Mura; Piero Rafanelli
We report the first results of a survey on 74 narrow-line Seyfert 1 galaxies (NLS1s) carried out in 2015 with the Karl J. Jansky Very Large Array (JVLA) at 5 GHz in A-configuration. So far, this is the largest survey aimed to image the radio continuum of NLS1s. We produced radio maps in order to compare the general properties of three different samples of objects: radio-quiet NLS1s (RQNLS1s), steep-spectrum radio-loud NLS1s (S-NLS1s), and flat-spectrum radio-loud NLS1s (F-NLS1s). We find that the three classes correspond to different radio morphologies, with F-NLS1s being more compact, and RQNLS1s often showing diffuse emission on kpc scales. We also find that F-NLS1s might be low-luminosity and possibly young blazars, and that S-NLS1s are part of the parent population of F-NLS1s. Dedicated studies to RQNLS1s are needed in order to fully understand their role in the unification pictures.
Astronomy and Astrophysics | 2018
S. Chen; M. Berton; G. La Mura; E. Congiu; V. Cracco; L. Foschini; J.H. Fan; S. Ciroi; Piero Rafanelli; D. Bastieri
We present a new accurate catalog of narrow-line Seyfert 1 galaxies (NLS1s) in the southern hemisphere from the Six-degree Field Galaxy Survey (6dFGS) final data release, which is currently the most extensive spectroscopic survey available in the southern sky whose database has not yet been systematically explored. We classified 167 sources as NLS1s based on their optical spectral properties. We derived flux-calibrated spectra for the first time that the 6dFGS indeed does not provide. By analyzing these spectra, we obtained strong correlations between the monochromatic luminosity at 5100 A and the luminosity of Hbeta and [O III]5007 lines. The estimated central black hole mass and Eddington ratio have an average value of 9.55 x 10^6 M_Sun and 0.90 L_Edd respectively, which is a typical value for NLS1s. In the sample, 23 (13.8%) NLS1s were detected at radio frequencies, and 10 (6.0%) of them are radio-loud. Our results confirmed that radio-loud sources tend to have higher redshift, more massive black hole, and higher radio and optical luminosity than radio-quiet sources.
Frontiers in Astronomy and Space Sciences | 2017
M. Berton; Luigi Foschini; Alessandro Caccianiga; S. Ciroi; E. Congiu; V. Cracco; M. Frezzato; Giovanni La Mura; Piero Rafanelli
In recent years, the old paradigm according to which only high-mass black holes can launch powerful relativistic jets in active galactic nuclei (AGN) has begun to crumble. The discovery of
arXiv: Astrophysics of Galaxies | 2016
M. Berton; Luigi Foschini; Alessandro Caccianiga; Jennifer Lee Richards; Stefano Ciroi; E. Congiu; V. Cracco; Giovanni La Mura; Luca Marafatto; Piero Rafanelli
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Astronomy and Astrophysics | 2018
M. Berton; N. H. Liao; G. La Mura; E. Järvelä; E. Congiu; L. Foschini; M. Frezzato; V. Ramakrishnan; X. L. Fan; A. Lähteenmäki; T. Pursimo; V. Abate; J. M. Bai; P. Calcidese; S. Ciroi; L. Chen; V. Cracco; S. K. Li; M. Tornikoski; Piero Rafanelli
-rays coming from narrow-line Seyfert 1 galaxies (NLS1s), usually considered young and growing AGN harboring a central black hole with mass typically lower than 10
Frontiers in Astronomy and Space Sciences | 2017
E. Congiu; Marcella Contini; Stefano Ciroi; V. Cracco; Francesco Di Mille; M. Berton; M. Frezzato; Giovanni La Mura; Piero Rafanelli
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European Physical Journal D | 2017
Giovanni La Mura; G. Busetto; Stefano Ciroi; Piero Rafanelli; M. Berton; E. Congiu; V. Cracco; M. Frezzato
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Monthly Notices of the Royal Astronomical Society | 2017
E. Congiu; M. Contini; S. Ciroi; V. Cracco; M. Berton; F. Di Mille; M. Frezzato; G. La Mura; Piero Rafanelli
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