Examinando por Autor "Roche, P. F."

Mostrando 1 - 5 de 5

Acceso Abierto
Cold molecular gas and PAH emission in the nuclear and circumnuclear regions of Seyfert galaxies
(EDP Sciences, 2020-07-07) Rosario, D.; Alonso-Herrero, Almudena; Pereira Santaella, Miguel; Rigopoulou, Dimitra; 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.; 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.
Acceso Abierto
Polycyclic aromatic hydrocarbon emission in galaxies as seen with JWST
(Royal Astronomical Society, 2024-08-01) Rigopoulou, Dimitra; Donnan, Fergus; García-Bernete, I.; Pereira Santaella, Miguel; Alonso-Herrero, Almudena; Davies, R.; Hunt, L. K.; Roche, P. F.; Shimizu, T.; Ministerio de Ciencia e Innovación (MICINN); Science and Technology Facilities Council (STFC)
We present a systematic study of mid-infrared spectra of galaxies including star-forming galaxies and active galactic nuclei observed with JWST MIRI-MRS and NIRSpec-IFU. We focus on the relative variations of the 3.3, 6.2, 7.7, 11.3, 12.7, and 17 m polycyclic aromatic hydrocarbon (PAH) features within spatially resolved regions of galaxies including NGC 3256, NGC 7469, VV 114, II Zw96, and NGC 5728. Using theoretical PAH models and extending our earlier work, we introduce a new PAH diagnostic involving the 17 m PAH feature. To determine the drivers of PAH band variations in galaxies, we compare observed PAH spectral bands to predictions from theoretical PAH models. We consider extinction, dehydrogenation, and PAH size and charge as possible drivers of PAH band variations. We find a surprising uniformity in PAH size distribution among the spatially resolved regions of the galaxies studied here, with no evidence for preferential destruction of the smallest grains, contrary to earlier findings. Neither extinction nor dehydrogenation play a crucial role in setting the observed PAH bands. Instead, we find that PAH charge plays a significant role in PAH inter-band variations. We find a tight relation between PAH charge and the intensity of the radiation field as traced by the [Ne iii][Ne ii] maps. In agreement with recent JWST results, we find a predominance of neutral PAH molecules in the nuclei of active galaxies and their outflows. Ionized PAHs are the dominant population in star-forming galaxies. We discuss the implications of our findings for the use of PAHs as ISM tracers in high redshift galaxies.
Acceso Abierto
The Galaxy Activity, Torus, and Outflow Survey (GATOS) V. Unveiling PAH survival and resilience in the circumnuclear regions of AGNs with JWST
(EDP Sciences, 2024-09-09) García-Bernete, Ismael; Rigopoulou, Dimitra; Donnan, Fergus; Alonso-Herrero, Almudena; Pereira Santaella, Miguel; Shimizu, T. Taro; Davies, Richard; Roche, P. F.; García-Burillo, Santiago; Labiano, Alvaro; Hermosa Muñoz, Laura; Zhang, Lulu; Audibert, A.; Bellocchi, Enrica; Bunker, A.; Combes, Francoise; Delaney, D.; Esparza-Arredondo, D.; Gandhi, P.; González-Martín, O.; Hönig, Sebastian; Imanishi, Masatoshi; Hicks, Erin K. S.; Fuller, L.; Leist, Mason Tanner; Levenson, N. A.; López-Rodríguez, E.; Packham, Christopher; Ramos Almeida, Cristina; Ricci, C.; Stalevski, Marko; Villar Martín, M.; Ward, M. J.; Science and Technology Facilities Council (STFC); Comunidad de Madrid; European Commission (EC); European Space Agency (ESA); Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT); Ministerio de Ciencia e Innovación (MICINN); National Aeronautics and Space Administration (NASA); Space Telescope Science Institute (STScI); Universidad Nacional Autónoma de México (UNAM)
This study analyses JWST MIRI/MRS observations of the infrared (IR) polycyclic aromatic hydrocarbon (PAH) bands in the nuclear (∼0.4″ at 11 μm; ∼75 pc) and circumnuclear regions (inner ∼kpc) of local active galactic nuclei (AGNs) from the Galactic Activity, Torus, and Outflow Survey (GATOS). We examine the PAH properties in the circumnuclear regions of AGNs and the projected direction of AGN-outflows and compare them to those in star-forming regions and the innermost regions of AGNs. This study employs 4.9–28.1 μm sub-arcsecond angular resolution data to investigate the properties of PAHs in three nearby sources (DL ∼ 30 − 40 Mpc). Our findings are aligned with previous JWST studies, demonstrating that the central regions of AGNs display a larger fraction of neutral PAH molecules (i.e. elevated 11.3/6.2 and 11.3/7.7 μm PAH ratios) in comparison to star-forming galaxies. We find that AGNs might affect not only the PAH population in the innermost region, but also in the extended regions up to ∼kpc scales. By comparing our observations to PAH diagnostic diagrams, we find that, in general, regions located in the projected direction of the AGN-outflow occupy similar positions on the PAH diagnostic diagrams as those of the innermost regions of AGNs. Star-forming regions that are not affected by the AGNs in these galaxies share the same part of the diagram as star-forming galaxies. We also examined the potential of the PAH-H2 diagram to disentangle AGN-versus-star-forming activity. Our results suggest that in Seyfert-like AGNs, the illumination and feedback from the AGN might affect the PAH population at nuclear and kpc scales, particularly with respect to the ionisation state of the PAH grains. However, PAH molecular sizes are rather similar. The carriers of the ionised PAH bands (6.2 and 7.7 μm) are less resilient than those of neutral PAH bands (11.3 μm), which might be particularly important for strongly AGN-host coupled systems. Therefore, caution must be applied when using PAH bands as star-formation rate indicators in these systems even at kpc scales, with the effects of the AGN being more important for ionised ones.
Acceso Abierto
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, Dimitra; Barale, M.; Clary, D. C.; Shan, X.; Alonso-Herrero, Almudena; García Bernete, I.; Hunt, L.; Berkeni, B.; Pereira Santaella, Miguel; 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, Almudena; Ward, M. J.; Acosta Pulido, J. A.; Pereira Santaella, Miguel; Hernán Caballero, A.; Asensio Ramos, A.; González Martín, O.; Levenson, N. A.; Mateos, S.; Carrera, F. J.; Ricci, C.; Roche, P. F.; Márquez Pérez, Isabel; 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.