ORCID Profile
0000-0002-0658-644X
Current Organisation
University of Coimbra
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Publisher: Oxford University Press (OUP)
Date: 22-05-2021
Abstract: Radio-emitting jets might be one of the main ingredients shaping the evolution of massive galaxies in the Universe since early cosmic times. However, identifying early radio active galactic nuclei (AGNs) and confirming this scenario have been hard to accomplish, with studies of s les of radio AGN hosts at z & 2 becoming routinely possible only recently. With the above in mind, we have carried out a survey with the Atacama Compact Array (ACA or Morita Array) at 1.3 mm (rms = 0.15 mJy) of 36 high-redshift radio AGN candidates found within 3.9 deg2 in the ELAIS-S1 field. The work presented here describes the survey and showcases a preliminary set of results. The selection of the s le was based on three criteria making use of infrared (IR) and radio fluxes only. The criterion providing the highest selection rate of high-redshift sources (86 per cent at z & 0.8) is one combining an IR colour cut and radio flux cut (S5.8μm/S3.6μm & 1.3 and $S_{\\rm 1.4\\, GHz}\\gt 1\\,$ mJy). Among the s le of 36 sources, 16 show a millimetre (mm) detection. In eight of these cases, the emission has a non-thermal origin. A zsp = 1.58 object, with a mm detection of non-thermal origin, shows a clear spatial offset between the jet-dominated mm continuum emission and that of the host’s molecular gas, as traced by serendipitously detected CO(5-4) emission. Among the objects with serendipitous line detections there is a source with a narrow jet-like region, as revealed by CS(6-5) emission stretching 20 kpc out of the host galaxy.
Publisher: Oxford University Press (OUP)
Date: 28-07-2022
Abstract: Following the discovery of SAGE0536AGN (z ∼ 0.14), with the strongest 10-μm silicate emission ever observed for an active galactic nucleus (AGN), we discovered SAGE0534AGN (z ∼ 1.01), a similar AGN but with less extreme silicate emission. Both were originally mistaken as evolved stars in the Magellanic Clouds. Lack of far-infrared emission, and therefore star formation, implies we are seeing the central engine of the AGN without contribution from the host galaxy. They could be a key link in galaxy evolution. We used a dimensionality reduction algorithm, t-distributed stochastic neighbour embedding with multiwavelength data from Gaia EDR3, VISTA survey of the Magellanic Clouds, AllWISE, and the Australian Square Kilometre Array Pathfinder to find these two unusual AGNs are grouped with 16 other objects separated from the rest, suggesting a rare class. Our spectroscopy at South African Astronomical Observatory/Southern African Large Telescope and literature data confirm at least 14 of these objects are extragalactic (0.13 & z & 1.23), all hosting AGN. Using spectral energy distribution fitter C igale we find that the majority of dust emission ($\\gt 70 {{\\ \\rm per\\ cent}}$) in these sources is due to the AGN. Host galaxies appear to be either in or transitioning into the green valley. There is a trend of a thinning torus, increasing X-ray luminosity, and decreasing Eddington ratio as the AGN transition through the green valley, implying that as the accretion supply depletes, the torus depletes and the column density reduces. Also, the near-infrared variability litude of these sources correlates with attenuation by the torus, implying the torus plays a role in the variability.
Publisher: Oxford University Press (OUP)
Date: 05-10-2020
Abstract: As the largest radio telescope in the world, the Square Kilometre Array (SKA) will lead the next generation of radio astronomy. The feats of engineering required to construct the telescope array will be matched only by the techniques developed to exploit the rich scientific value of the data. To drive forward the development of efficient and accurate analysis methods, we are designing a series of data challenges that will provide the scientific community with high-quality data sets for testing and evaluating new techniques. In this paper, we present a description and results from the first such Science Data Challenge 1 (SDC1). Based on SKA MID continuum simulated observations and covering three frequencies (560, 1400, and 9200 MHz) at three depths (8, 100, and 1000 h), SDC1 asked participants to apply source detection, characterization, and classification methods to simulated data. The challenge opened in 2018 November, with nine teams submitting results by the deadline of 2019 April. In this work, we analyse the results for eight of those teams, showcasing the variety of approaches that can be successfully used to find, characterize, and classify sources in a deep, crowded field. The results also demonstrate the importance of building domain knowledge and expertise on this kind of analysis to obtain the best performance. As high-resolution observations begin revealing the true complexity of the sky, one of the outstanding challenges emerging from this analysis is the ability to deal with highly resolved and complex sources as effectively as the unresolved source population.
Publisher: Elsevier BV
Date: 08-2018
Publisher: EDP Sciences
Date: 11-2016
Publisher: EDP Sciences
Date: 04-2013
Location: Portugal
No related grants have been discovered for Sonia Antón.