Examinando por Autor "Roche, P. F."

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Acceso Abierto
Cold molecular gas and PAH emission in the nuclear and circumnuclear regions of Seyfert galaxies
(EDP Sciences, 2020-07-07) Alonso Herrero, A.; Pereira Santaella, M.; Rigopoulou, D.; García Bernete, I.; García Burillo, S.; Domínguez Fernández, A. J.; Combes, F.; Davies, R. I.; Díaz Santos, T.; Esparza Borges, E.; González Martín, O.; Hernán Caballero, A.; Hicks, E. K. S.; Hönig, S. F.; Levenson, N. A.; Ramos Almeida, C.; Roche, P. F.; Rosario, D.; Agencia Estatal de Investigación (AEI); Comunidad de Madrid; Science and Technology Facilities Council (STFC); Universidad Nacional Autónoma de México (UNAM); European Research Council (ERC); National Aeronautics and Space Administration (NASA); 0000-0001-8353-649X; 0000-0003-0699-6083; 0000-0002-0001-3587; 0000-0002-8524-8413; 0000-0003-4949-7217; 0000-0002-6353-1111
We investigate the relation between the detection of the 11.3 mu m polycyclic aromatic hydrocarbon (PAH) feature in the nuclear (similar to 24-230 pc) regions of 22 nearby Seyfert galaxies and the properties of the cold molecular gas. For the former we use ground-based (0.3-0.6 '' resolution) mid-infrared (mid-IR) spectroscopy. The cold molecular gas is traced by ALMA and NOEMA high (0.2-1.1 '') angular resolution observations of the CO(2-1) transition. Galaxies with a nuclear detection of the 11.3 mu m PAH feature contain more cold molecular gas (median 1.6x10(7) M-circle dot) and have higher column densities (N(H-2) = 2x10(23) cm(-2)) over the regions sampled by the mid-IR slits than those without a detection. This suggests that molecular gas plays a role in shielding the PAH molecules in the harsh environments of Seyfert nuclei. Choosing the PAH molecule naphthalene as an illustration, we compute its half-life in the nuclear regions of our sample when exposed to 2.5 keV hard X-ray photons. We estimate shorter half-lives for naphthalene in nuclei without a 11.3 mu m PAH detection than in those with a detection. The Spitzer/IRS PAH ratios on circumnuclear scales (similar to 4 ''similar to 0.25-1.3 kpc) are in between model predictions for neutral and partly ionized PAHs. However, Seyfert galaxies in our sample with the highest nuclear H-2 column densities are not generally closer to the neutral PAH tracks. This is because in the majority of our sample galaxies, the CO(2-1) emission in the inner similar to 4 '' is not centrally peaked and in some galaxies traces circumnuclear sites of strong star formation activity. Spatially resolved observations with the MIRI medium-resolution spectrograph on the James Webb Space Telescope will be able to distinguish the effects of an active galactic nucleus (AGN) and star formation on the PAH emission in nearby AGN.
Restringido
The properties of polycyclic aromatic hydrocarbons in galaxies: constraints on PAH sizes, charge and radiation fields
(Oxford Academics: Oxford University Press, 2021-04-12) Rigopoulou, D.; Barale, M.; Clary, D. C.; Shan, X.; Alonso Herrero, A.; García Bernete, I.; Hunt, L.; Berkeni, B.; Pereira Santaella, M.; Roche, P. F.; Science and Technology Facilities Council (STFC); Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Based on theoretical spectra computed using Density Functional Theory we study the properties of polycyclic aromatic hydrocarbons (PAH). In particular using bin-average spectra of PAH molecules with varying number of carbons we investigate how the intensity of the mid-infrared emission bands, 3.3, 6.2, 7.7, and 11.3 μm, respond to changes in the number of carbons, charge of the molecule, and the hardness of the radiation field that impinges the molecule. We confirm that the 6.2/7.7 band ratio is a good predictor for the size of the PAH molecule (based on the number of carbons present). We also investigate the efficacy of the 11.3/3.3 ratio to trace the size of PAH molecules and note the dependence of this ratio on the hardness of the radiation field. While the ratio can potentially also be used to trace PAH molecular size, a better understanding of the impact of the underlying radiation field on the 3.3 μm feature and the effect of the extinction on the ratio should be evaluated. The newly developed diagnostics are compared to band ratios measured in a variety of galaxies observed with the Infrared Spectrograph on board the Spitzer Space Telescope. We demonstrate that the band ratios can be used to probe the conditions of the interstellar medium in galaxies and differentiate between environments encountered in normal star forming galaxies and active galactic nuclei. Our work highlights the immense potential that PAH observations with the James Webb Space Telescope will have on our understanding of the PAH emission itself and of the physical conditions in galaxies near and far.
Acceso Abierto
Torus model properties of an ultra-hard X-ray selected sample of Seyfert galaxies
(Oxford Academics: Oxford University Press, 2019-04-10) García Bernete, I.; Ramos Almeida, C.; Alonso Herrero, A.; Ward, M. J.; Acosta Pulido, J. A.; Pereira Santaella, M.; Hernán Caballero, A.; Asensio Ramos, A.; González Martín, O.; Levenson, N. A.; Mateos, S.; Carrera, F. J.; Ricci, C.; Roche, P. F.; Márquez, I.; Packham, C.; Masegosa, J.; Fuller, L.; Agencia Estatal de Investigación (AEI); Science and Technology Facilities Council (STFC); Ministerio de Economía y Competitividad (MINECO); Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
We characterize for the first time the torus properties of an ultra-hard X-ray (14–195 keV) volume-limited (DL < 40 Mpc) sample of 24 Seyfert (Sy) galaxies (BCS40 sample). The sample was selected from the Swift/BAT nine-month catalogue. We use high angular resolution nuclear infrared (IR) photometry and N-band spectroscopy, the CLUMPY torus models and a Bayesian tool to characterize the properties of the nuclear dust. In the case of the Sy1s, we estimate the accretion disc contribution to the subarcsecond resolution nuclear IR SEDs (∼0.4 arcsec) which is, on average, 46 ± 28, 23 ± 13, and 11 ± 5 per cent in the J, H, and K bands, respectively. This indicates that the accretion disc templates that assume a steep fall for longer wavelengths than 1 μm might underestimate its contribution to the near-IR emission. Using both optical (broad versus narrow lines) and X-ray (unabsorbed versus absorbed) classifications, we compare the global posterior distribution of the torus model parameters. We confirm that Sy2s have larger values of the torus covering factor (CT ∼ 0.95) than Sy1s (CT ∼ 0.65) in our volume-limited Seyfert sample. These findings are independent of whether we use an optical or X-ray classification. We find that the torus covering factor remains essentially constant within the errors in our luminosity range and there is no clear dependence with the Eddington ratio. Finally, we find tentative evidence that even an ultra-hard X-ray selection is missing a significant fraction of highly absorbed type 2 sources with very high covering factor tori.