Examinando por Autor "Emonts, B. H. C."

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Acceso Abierto
Disc galaxy resolved in H I absorption against the radio lobe of 3C 433: Case study for future surveys.
(EDP Sciences, 2020-11-05) Morgantini, R.; Emonts, B. H. C.; Villar Martín, M.; Oosterloo, T.; Peletier, R.; European Commission (EC); Agencia Estatal de Investigación (AEI); National Aeronautics and Space Administration (NASA); 0000-0003-4989-3316; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
The neutral atomic gas content of galaxies is usually studied in the HI 21 cm emission line of hydrogen. However, as we go to higher redshifts, owing to the weak strength of the transition, we need very deep integrations to detect HI emission. The HI absorption does not suffer from this dependence on distance as long as there is a sufficiently bright radio source to provide the background continuum. However, resolved HI absorption studies of galaxies are rare. We report one such rare study of resolved HI absorption against the radio galaxy 3C 433 at z=0.101, detected with the Very Large Array. The absorption was known from single-dish observations, but owing to the higher spatial resolution of our data, we find that the absorber is located against the southern lobe of the radio galaxy. The resolved kinematics shows that the absorber has regular kinematics with an HI mass less than or similar to 3.4x10(8) M-circle dot for T-spin=100 K. We also present deep optical continuum observations and H alpha observations from the Gran Telescopio CANARIAS (GTC), which reveal that the absorber is likely to be a faint disc galaxy in the same environment as 3C 433, with a stellar mass of similar to 10(10) M-circle dot and a star-formation rate of 0.15 M-circle dot yr(-1) or less. Considering its HI mass, HI column density, stellar mass, and star-formation rate, this galaxy lies well below the main sequence of star forming galaxies. Its HI mass is lower than the galaxies studied in HI emission at z similar to 0.1. Our GTC imaging has revealed, furthermore, interesting alignments between H alpha and radio synchrotron emission in the HI companion and in the host galaxy of the active galactic nucleus as well as in the circumgalactic medium in between. This suggests that the shock ionization of gas by the propagating radio source may happen across a scale spanning many tens of kpc. Overall, our work supports the potential of studying the HI content in galaxies via absorption in the case of a fortuitous alignment with an extended radio continuum source. This approach may allow us to trace galaxies with low HI masses which would otherwise be missed by deep HI emission surveys. In conjunction with the deep all-sky optical surveys, the current and forthcoming blind HI surveys with the Square Kilometre Array (SKA) pathfinder facilities will be able to detect many such systems, though they may not be able to resolve the HI absorption spatially. Phase 1 of the SKA, with its sub-arcsecond resolution and high sensitivity, will be all the more able to resolve the absorption in such systems.
Acceso Abierto
Interactions between large-scale radio structures and gas in a sample of optically selected type 2 quasars
(EDP Sciences, 2021-06-10) Villar Martín, M.; Emonts, Bjorn H. C.; Cabrera Lavers, A.; Bellocchi, E.; Alonso Herrero, A.; Humphrey, A.; Dall´Agnol de Oliveira, B.; Storchi Bergmann, T.; Agencia Estatal de Investigación (AEI); Comunidad de Madrid; Fundacao para a Ciencia e a Tecnologia (FCT); Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Context. The role of radio mode feedback in non radio-loud quasars needs to be explored in depth to determine its true importance. Its effects can be identified based on the evidence of interactions between the radio structures and the ambient ionised gas. Aims. We investigate this interaction in a sample of 13 optically selected type 2 quasars (QSO2) at z < 0.2 with the Very Large Array (VLA) FIRST Survey radio detections, none of which are radio-loud. The ranges of [OIII]λ5007 and monochromatic radio luminosities are log(L[OIII]/erg s−1) ∼ 42.08–42.79 and log(P1.4 GHz/erg s−1 Hz−1) ∼ 30.08−31.76. All of them show complex optical morphologies, with signs of distortion across tens of kpc due to mergers and interactions. Methods. We searched for evidence of interactions between the radio structures and the ionised gas by characterising and comparing their morphologies. The former was traced by narrow band Hα images obtained with the GTC 10.4 m Spanish telescope and the Osiris instrument. The latter is traced by VLA radio maps obtained with A and B configurations to achieve both high resolution and brightness sensitivity. Results. The radio luminosity has an active galatic nucleus (AGN) component in 11 our of 13 QSO2, which is spatially extended in our radio data in 9 of them (jets, lobes, or other). The relative contribution of the extended radio emission to the total P1.4 GHz is in most cases in the range from 30% to 90%. The maximum sizes are in the range of dRmax of around a few to 500 kpc. The QSO2 undergoing interaction or merger events appear to be invariably associated with ionised gas spread over large spatial scales with maximum distances from the AGN in the range rmax ∼ 12−90 kpc. The morphology of the ionised gas at < 30 kpc is strongly influenced by AGN related processes. Evidence for radio-gas interactions exist in 10 out of 13 QSO2; that is, in all but one with confirmed AGN radio components. The interactions are identified across different spatial scales, from the nuclear narrow line region up to tens of kpc. Conclusions. Although this sample cannot be considered representative of the general population of QSO2, it supports the idea that large-scale low to modest power radio sources can exist in radio-quiet QSO2, which can provide a source of feedback on scales of the spheroidal component of galaxies and well into the circumgalactic medium, in systems where radiative mode feedback is expected to dominate.