ORCID Profile
0000-0002-8524-8413
Current Organisation
University of Oxford
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Publisher: Oxford University Press (OUP)
Date: 02-1988
Publisher: Oxford University Press (OUP)
Date: 02-2001
Publisher: Elsevier BV
Date: 04-1985
Publisher: Oxford University Press (OUP)
Date: 08-1994
Publisher: Oxford University Press (OUP)
Date: 06-1996
Publisher: EDP Sciences
Date: 07-2020
DOI: 10.1051/0004-6361/202037642
Abstract: We investigate the relation between the detection of the 11.3 μ m polycyclic aromatic hydrocarbon (PAH) feature in the nuclear (∼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 μ m PAH feature contain more cold molecular gas (median 1.6 × 10 7 M ⊙ ) and have higher column densities ( N (H 2 ) = 2 × 10 23 cm −2 ) over the regions s led 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 s le when exposed to 2.5 keV hard X-ray photons. We estimate shorter half-lives for naphthalene in nuclei without a 11.3 μ m PAH detection than in those with a detection. The Spitzer /IRS PAH ratios on circumnuclear scales (∼4″ ∼ 0.25−1.3 kpc) are in between model predictions for neutral and partly ionized PAHs. However, Seyfert galaxies in our s le 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 s le galaxies, the CO(2–1) emission in the inner ∼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.
Publisher: American Astronomical Society
Date: 07-1996
DOI: 10.1086/310125
Publisher: Oxford University Press (OUP)
Date: 06-1984
Publisher: Oxford University Press (OUP)
Date: 09-1991
Publisher: Oxford University Press (OUP)
Date: 07-1987
Publisher: Oxford University Press (OUP)
Date: 03-06-2017
Publisher: Oxford University Press (OUP)
Date: 20-04-2022
Abstract: We extend the prediction of vibrational spectra to large sized polycyclic aromatic hydrocarbon (PAH) molecules comprising up to ∼1500 carbon atoms by evaluating the efficiency of several computational chemistry methodologies. We employ classical mechanics methods (Amber and Gaff) with improved atomic point charges, semi-empirical (PM3, and density functional tight binding), and density functional theory (B3LYP) and conduct global optimizations and frequency calculations in order to investigate the impact of PAH size on the vibrational band positions. We primarily focus on the following mid-infrared emission bands 3.3, 6.2, 7.7, 8.6, 11.3, 12.7, and 17.0 μm. We developed a general Frequency Scaling Function ($\\mathcal {FSF}$) to shift the bands and to provide a systematic comparison versus the three methods for each PAH. We first validate this procedure on IR scaled spectra from the NASA Ames PAH Database, and extend it to new large PAHs. We show that when the $\\mathcal {FSF}$ is applied to the Amber and Gaff IR spectra, an agreement between the normal mode peak positions with those inferred from the B3LYP/4-31G model chemistry is achieved. As calculations become time intensive for large sized molecules Nc & 450, this proposed methodology has advantages. The $\\mathcal {FSF}$ has enabled extending the investigations to large PAHs where we clearly see the emergence of the 17.0 μm feature, and the weakening of the 3.3 μm one. We finally investigate the trends in the 3.3 μm/17.0 μm PAH band ratio as a function of PAH size and its response following the exposure to fields of varying radiation intensities.
Publisher: Oxford University Press (OUP)
Date: 09-1998
Publisher: Oxford University Press (OUP)
Date: 11-11-2009
Publisher: Springer-Verlag
Date: 2002
DOI: 10.1007/10856518_10
Publisher: Oxford University Press (OUP)
Date: 05-1986
Publisher: Zenodo
Date: 2020
Publisher: American Astronomical Society
Date: 05-1993
DOI: 10.1086/172672
Publisher: Oxford University Press (OUP)
Date: 09-1982
Publisher: Springer Science and Business Media LLC
Date: 02-1989
DOI: 10.1038/337533A0
Publisher: Elsevier BV
Date: 04-1987
Publisher: Oxford University Press (OUP)
Date: 03-1984
Publisher: Oxford University Press (OUP)
Date: 1986
Publisher: Elsevier BV
Date: 2004
Publisher: Oxford University Press (OUP)
Date: 11-1980
Publisher: EDP Sciences
Date: 30-09-2022
DOI: 10.1051/0004-6361/202244806
Abstract: Polycyclic aromatic hydrocarbons (PAHs) are carbon-based molecules that are ubiquitous in a variety of astrophysical objects and environments. In this work we use JWST/MIRI MRS spectroscopy of three Seyferts to compare their nuclear PAH emission with that of star-forming (SF) regions. This study represents the first of its kind to use sub-arcsecond angular resolution data of local luminous Seyferts ( L bol 10 44.46 erg s −1 ) with a wide wavelength coverage (4.9–28.1 μm). We present an analysis of their nuclear PAH properties by comparing the observed ratios with PAH diagnostic model grids derived from theoretical spectra. Our results show that a suite of PAH features is present in the innermost parts of luminous Seyfert galaxies (∼0.45″ at 12 μm in the inner ∼142–245 pc). We find that the nuclear regions of active galactic nuclei (AGN) lie at different positions of the PAH diagnostic diagrams, whereas the SF regions are concentrated around the average values of SF galaxies. In particular, we find that the nuclear PAH emission mainly originates in neutral PAHs. In contrast, PAH emission originating in the SF regions favours ionised PAH grains. The observed PAH ratios in the nuclear region of the AGN-dominated galaxy NGC 6552 indicate the presence of larger PAH molecules compared with those of the SF regions. Therefore, our results provide evidence that the AGN have a significant impact on the ionisation state (and probably the size) of the PAH grains on scales of ∼142–245 pc.
Publisher: Springer-Verlag
Date: 2002
DOI: 10.1007/10856518_25
Publisher: Oxford University Press (OUP)
Date: 06-2006
Publisher: Oxford University Press (OUP)
Date: 03-1984
Publisher: Oxford University Press (OUP)
Date: 02-2022
Publisher: Oxford University Press (OUP)
Date: 21-11-1999
Publisher: Oxford University Press (OUP)
Date: 07-1984
Publisher: Oxford University Press (OUP)
Date: 09-2013
Publisher: Elsevier BV
Date: 04-2020
Publisher: American Astronomical Society
Date: 10-02-1999
DOI: 10.1086/306766
Publisher: SPIE
Date: 12-07-2008
DOI: 10.1117/12.789843
Publisher: Oxford University Press (OUP)
Date: 15-05-1993
Publisher: EDP Sciences
Date: 08-2021
DOI: 10.1051/0004-6361/202141219
Abstract: We compare high angular resolution mid-infrared (mid-IR) and Atacama Large Millimeter/submillimeter Array (ALMA) far-infrared (far-IR) images of twelve nearby (median 21 Mpc) Seyfert galaxies selected from the Galaxy Activity, Torus, and Outflow Survey (GATOS). The mid-IR unresolved emission contributes more than 60% of the nuclear (diameters of 1.5″ ∼ 150 pc) emission in most galaxies. By contrast, the ALMA 870 μm continuum emission is mostlyresolved with a median diameter of 42 pc and typically along the equatorial direction of the torus (Paper I). The Eddington ratios and nuclear hydrogen column densities ( N H ) of half the s le are favorable to launching polar and/or equatorial dusty winds, according to numerical simulations. Six of these show mid-IR extended emission approximately in the polar direction as traced by the narrow line region and perpendicular to the ALMA emission. In a few galaxies, the nuclear N H might be too high to uplift large quantities of dusty material along the polar direction. Five galaxies have low N H and/or Eddington ratios and thus polar dusty winds are not likely. We generated new radiative transfer CAT3D-WIND disk+wind models and model images at 8, 12, and 700 μm. We tailored these models to the properties of the GATOS Seyferts in this work. At low wind-to-disk cloud ratios, the far-IR model images have disk- and ring-like morphologies. The characteristic “X”-shape associated with dusty winds is seen better in the far-IR at intermediate-high inclinations for the extended-wind configurations. In most of the explored models, the mid-IR emission mainly comes from the inner part of the disk and cone. Extended biconical and one-sided polar mid-IR emission is seen in extended-wind configurations and high wind-to-disk cloud ratios. When convolved to the typical angular resolution of our observations, the CAT3D-WIND model images reproduce qualitative aspects of the observed mid- and far-IR morphologies. However, low to intermediate values of the wind-to-disk ratio are required to account for the observed large fractions of unresolved mid-IR emission in our s le. This work and Paper I provide observational support for the torus+wind scenario. The wind component is more relevant at high Eddington ratios and/or active galactic nucleus luminosities, and polar dust emission is predicted at nuclear column densities of up to ∼10 24 cm −2 . The torus or disk component, on the other hand, prevails at low luminosities and/or Eddington ratios.
Publisher: Oxford University Press (OUP)
Date: 21-04-2006
Publisher: Oxford University Press (OUP)
Date: 15-09-1992
Publisher: Oxford University Press (OUP)
Date: 02-2001
Publisher: Springer Netherlands
Date: 1986
Publisher: Oxford University Press (OUP)
Date: 07-1986
Publisher: American Astronomical Society
Date: 12-2007
DOI: 10.1086/522826
Publisher: Oxford University Press (OUP)
Date: 03-1988
Publisher: Oxford University Press (OUP)
Date: 02-1989
Publisher: EDP Sciences
Date: 2023
DOI: 10.1051/0004-6361/202244937
Abstract: Context. Compact obscured nuclei (CONs) represent an extreme phase of galaxy evolution where rapid supermassive black hole growth and/or compact star-forming activity is completely obscured by gas and dust. Aims. We investigate the properties of CONs in the mid-infrared and explore techniques aimed at identifying these objects, such as through the equivalent width (EW) ratios of their polycyclic aromatic hydrocarbon (PAH) features. Methods. We modelled Spitzer spectra by decomposing the continua into nuclear and star-forming components, from which we then measured the nuclear optical depth, τ N , of the 9.8 μm silicate absorption feature. We also used Spitzer spectral maps to investigate how PAH EW ratios vary with aperture size for objects that host CONs. Results. We find that the nuclear optical depth, τ N , strongly correlates with the HCN-vib emission line in the millimetre for CONs, with a Pearson correlation coefficient of 0.91. We find the PAH EW ratio technique to be effective at selecting CONs and robust against highly inclined galaxies, where strong dust lanes may mimic a CON-like spectrum by producing a high τ N . Our analysis of the Spitzer spectral maps shows that the efficacy of the PAH EW ratios in isolating CONs is reduced when there is a strong star-forming component from the host galaxy. In addition, we find that the use of the inferred nuclear optical depth is a reliable method for identifying CONs in 36 −7 +8 % of ultra-luminous infrared galaxies and 17 −3 +3 % of luminous infrared galaxies, consistent with previous work. Conclusions. We confirm mid-infrared spectra to be a powerful diagnostic of CONs. The increased sensitivity of JWST will allow the identification of CONs at cosmic noon, revealing this extreme but hidden phase of galaxy evolution.
Publisher: Oxford University Press (OUP)
Date: 08-1985
Publisher: Oxford University Press (OUP)
Date: 06-2000
Publisher: Oxford University Press (OUP)
Date: 1986
Publisher: Oxford University Press (OUP)
Date: 08-1981
Publisher: Oxford University Press (OUP)
Date: 09-1981
Publisher: American Astronomical Society
Date: 22-06-2017
Publisher: Oxford University Press (OUP)
Date: 07-1988
Publisher: Oxford University Press (OUP)
Date: 04-1989
Publisher: Oxford University Press (OUP)
Date: 09-1982
Publisher: Oxford University Press (OUP)
Date: 04-2015
DOI: 10.1093/MNRAS/STV495
Publisher: American Astronomical Society
Date: 10-02-2010
Publisher: Cambridge University Press (CUP)
Date: 1990
DOI: 10.1017/S1323358000023420
Abstract: A survey of the optical spectra of IRAS galaxies, made with the AAT, has shown that the majority have strong emission lines. Ratios of the emission lines have been plotted on the Veilleux-Osterbrock diagram ([O III]/H β against [N II]/H α ) this shows that the IRAS galaxies comprise several classes. In our s le the majority appear to be starburst galaxies, but Seyfert, Liner and narrow-line galaxies are also represented. Co-added spectra of the galaxy classes are presented. On the basis of optical spectroscopy, it appears that the starburst phenomenon is capable of generating luminosities exceeding 10 12 L ⊙ .
Publisher: Oxford University Press (OUP)
Date: 04-1993
Publisher: Oxford University Press (OUP)
Date: 02-1999
Publisher: Oxford University Press (OUP)
Date: 21-04-2009
Publisher: Oxford University Press (OUP)
Date: 04-1984
Publisher: Oxford University Press (OUP)
Date: 09-1987
Publisher: American Astronomical Society
Date: 11-2006
DOI: 10.1086/507462
Publisher: Oxford University Press (OUP)
Date: 15-11-1993
Publisher: EDP Sciences
Date: 08-2023
DOI: 10.1051/0004-6361/202345858
Abstract: Context. Active galactic nuclei (AGN) are surrounded by dust within the central parsecs. The dusty circumnuclear structures, referred to as the torus, are mainly heated by radiation from the AGN and emitted at infrared wavelengths, producing the emergent dust continuum and silicate features. Fits to the infrared spectra from the nuclear regions of AGN can place constraints on the dust properties, distribution, and geometry by comparison with models. However, none of the currently available models fully describe the observations of AGN currently available. Aims. Among the aspects least explored, here we focus on the role of dust grain size. We offer the community a new spectral energy distribution (SED) library which is based on the two-phase torus model developed before with the inclusion of the grain size as a model parameter, parameterized by the maximum grain size P size or equivalently the mass-weighted average grain size ⟨ P ⟩. Methods. We created 691 200 SEDs using the SKIRT code, where the maximum grain size can vary within the range P size = 0.01 − 10.0 μm (⟨ P ⟩ = 0.007 − 3.41 μm). We fit this new library and several existing libraries to a s le of 68 nearby and luminous AGN with Spitzer /IRS spectra dominated by AGN-heated dust. Results. We find that the GoMar23 model can adequately reproduce up to ∼85–88% of the spectra. The dust grain size parameter significantly improves the final fit in up to 90% of these spectra. Statistical tests indicate that the grain size is the third most important parameter in the fitting procedure (after the size and half opening angle of the torus). The requirement of a foreground extinction by our model is lower compared to purely clumpy models. We find that ∼41% of our s le requires that the maximum dust grain size is as large as P size ∼ 10 μm (⟨ P ⟩∼3.41 μm). Nonetheless, we also remark that disk+wind and clumpy torus models are still required to reproduce the spectra of a nonnegligible fraction of objects, suggesting the need for several dust geometries to explain the infrared continuum of AGN. Conclusions. This work provides tentative evidence for dust grain growth in the proximity of the AGN.
Publisher: SPIE
Date: 07-03-2003
DOI: 10.1117/12.460987
Publisher: Oxford University Press (OUP)
Date: 09-1981
Publisher: Oxford University Press (OUP)
Date: 11-1993
Publisher: EDP Sciences
Date: 08-2019
DOI: 10.1051/0004-6361/201935431
Abstract: ALMA observations have revealed nuclear dusty molecular disks or tori with characteristic sizes 15−40 pc in the few Seyferts and low -luminosity AGN that have been studied so far. These structures are generally decoupled both morphologically and kinematically from the host galaxy disk. We present ALMA observations of the CO(2–1) and CO(3–2) molecular gas transitions and associated (sub-) millimeter continua of the nearby Seyfert 1.5 galaxy NGC 3227 with angular resolutions 0.085 − 0.21″ (7–15 pc). On large scales, the cold molecular gas shows circular motions as well as streaming motions on scales of a few hundred parsecs that are associated with a large-scale bar. We fit the nuclear ALMA 1.3 mm emission with an unresolved component and an extended component. The 850 μ m emission shows at least two extended components, one along the major axis of the nuclear disk, and the other along the axis of the ionization cone. The molecular gas in the central region (1″ ∼ 73 pc) shows several CO clumps with complex kinematics that appears to be dominated by noncircular motions. While we cannot conclusively demonstrate the presence of a warped nuclear disk, we also detected noncircular motions along the kinematic minor axis. They reach line-of-sight velocities of v − v sys = 150 − 200 km s −1 . Assuming that the radial motions are in the plane of the galaxy, we interpret them as a nuclear molecular outflow due to molecular gas in the host galaxy that is entrained by the AGN wind. We derive molecular outflow rates of 5 M ⊙ yr −1 and 0.6 M ⊙ yr −1 at projected distances of up to 30 pc to the northeast and southwest of the AGN, respectively. At the AGN location we estimate a mass in molecular gas of 5 × 10 5 M ⊙ and an equivalent average column density N (H 2 ) = 2 − 3 × 10 23 cm −2 in the inner 15 pc. The nuclear CO(2–1) and CO(3–2) molecular gas and submillimeter continuum emission of NGC 3227 do not resemble the classical compact torus. Rather, these emissions extend for several tens of parsecs and appear connected with the circumnuclear ring in the host galaxy disk, as found in other local AGN.
Publisher: Springer Netherlands
Date: 1987
Publisher: Elsevier BV
Date: 2001
Publisher: Oxford University Press (OUP)
Date: 11-05-1998
Publisher: Oxford University Press (OUP)
Date: 15-03-2016
DOI: 10.1093/MNRAS/STW626
Publisher: Oxford University Press (OUP)
Date: 05-04-2017
DOI: 10.1093/MNRAS/STX830
Publisher: Oxford University Press (OUP)
Date: 30-09-2016
Publisher: Oxford University Press (OUP)
Date: 16-01-2018
DOI: 10.1093/MNRAS/STY129
Publisher: Springer Netherlands
Date: 1984
Publisher: AIP
Date: 1982
DOI: 10.1063/1.33496
Publisher: AIP
Date: 2005
DOI: 10.1063/1.2146254
Publisher: Oxford University Press (OUP)
Date: 11-2012
Publisher: American Astronomical Society
Date: 12-1991
DOI: 10.1086/170737
Publisher: Oxford University Press (OUP)
Date: 10-1980
Publisher: SPIE
Date: 13-09-2007
DOI: 10.1117/12.734420
Publisher: Springer Science and Business Media LLC
Date: 12-1994
DOI: 10.1007/BF00627105
Publisher: Elsevier BV
Date: 05-1985
Publisher: Oxford University Press (OUP)
Date: 03-1994
Publisher: Oxford University Press (OUP)
Date: 04-1985
Publisher: AIP
Date: 1997
DOI: 10.1063/1.52737
Publisher: Oxford University Press (OUP)
Date: 03-1985
Publisher: Oxford University Press (OUP)
Date: 15-02-1991
Publisher: Oxford University Press (OUP)
Date: 09-1998
Publisher: Oxford University Press (OUP)
Date: 21-04-1997
Publisher: American Astronomical Society
Date: 06-12-2004
DOI: 10.1086/427691
Publisher: Oxford University Press (OUP)
Date: 11-1988
Publisher: Wiley
Date: 09-2003
Publisher: Oxford University Press (OUP)
Date: 11-1989
Publisher: Oxford University Press (OUP)
Date: 11-1995
Publisher: American Astronomical Society
Date: 11-07-2011
Publisher: Oxford University Press (OUP)
Date: 10-1983
Publisher: Oxford University Press (OUP)
Date: 12-1989
Publisher: American Astronomical Society
Date: 1984
DOI: 10.1086/113496
Publisher: Oxford University Press (OUP)
Date: 15-05-1993
Publisher: American Astronomical Society
Date: 31-12-2014
Publisher: Oxford University Press (OUP)
Date: 05-10-2007
Publisher: SPIE
Date: 03-07-1998
DOI: 10.1117/12.316512
Publisher: Oxford University Press (OUP)
Date: 21-10-2002
Publisher: Oxford University Press (OUP)
Date: 04-1983
Publisher: Oxford University Press (OUP)
Date: 11-1983
Publisher: Cambridge University Press (CUP)
Date: 02-2017
DOI: 10.1017/S1743921317004719
Abstract: Supernova (SN) 1987A has provided a unique opportunity to study how SN ejecta evolve in 30 years time scale. We report our ALMA spectral observations of SN 1987A, taken in 2014, 2015 and 2016, with detections of CO, 28 SiO, HCO + and SO, with weaker lines of 29 SiO. We find a dip in the SiO line profiles, suggesting that the ejecta morphology is likely elongated. The difference of the CO and SiO line profiles is consistent with hydrodynamic simulations, which show that Rayleigh-Taylor instabilities causes mixing of gas, with heavier elements much more disturbed, making more elongated structure. Using 28 SiO and its isotopologues, Si isotope ratios were estimated for the first time in SN 1987A. The estimated ratios appear to be consistent with theoretical predictions of inefficient formation of neutron rich atoms at lower metallicity, such as observed in the Large Magellanic Cloud (about half a solar metallicity). The deduced large HCO + mass and small SiS mass, which are inconsistent to the predictions of chemical model, might be explained by some mixing of elements immediately after the explosion. The mixing might have made some hydrogen from the envelope to sink into carbon and oxygen-rich zone during early days after the explosion, enabling the formation of a substantial mass of HCO + . Oxygen atoms may penetrate into silicon and sulphur zone, suppressing formation of SiS. Our ALMA observations open up a new window to investigate chemistry, dynamics and explosive-nucleosynthesis in supernovae.
Publisher: Oxford University Press (OUP)
Date: 02-09-2015
Publisher: Oxford University Press (OUP)
Date: 11-01-2009
Publisher: Springer Berlin Heidelberg
Date: 1990
Publisher: Oxford University Press (OUP)
Date: 06-2000
Publisher: Oxford University Press (OUP)
Date: 03-1984
Publisher: Oxford University Press (OUP)
Date: 08-1996
Publisher: Oxford University Press (OUP)
Date: 04-1985
Publisher: American Astronomical Society
Date: 05-1981
DOI: 10.1086/158857
Publisher: Oxford University Press (OUP)
Date: 10-2000
Publisher: Springer Netherlands
Date: 1986
Publisher: American Astronomical Society
Date: 04-1996
DOI: 10.1086/177111
Publisher: Oxford University Press (OUP)
Date: 09-1987
Publisher: Oxford University Press (OUP)
Date: 10-1988
Publisher: Oxford University Press (OUP)
Date: 21-03-1997
Publisher: Oxford University Press (OUP)
Date: 15-09-1991
Publisher: IOP Publishing
Date: 30-07-2012
Publisher: Springer Netherlands
Date: 2013
Publisher: American Astronomical Society
Date: 10-1991
DOI: 10.1086/170600
Publisher: Oxford University Press (OUP)
Date: 02-2004
Publisher: Springer Netherlands
Date: 1986
Publisher: Oxford University Press (OUP)
Date: 06-1996
Publisher: Oxford University Press (OUP)
Date: 10-2001
Publisher: Oxford University Press (OUP)
Date: 05-1983
Publisher: Oxford University Press (OUP)
Date: 11-2006
Publisher: EDP Sciences
Date: 07-2022
DOI: 10.1051/0004-6361/202142749
Abstract: Compact obscured nuclei (CONs) are mainly found in local luminous and ultraluminous infrared galaxies (U/LIRGs). In the local Universe, these sources are generally selected through the detection of the HCN–vib (3-2) emission line at submillimetre wavelengths. In this work, we present a diagnostic method to select deeply buried nuclei based on mid-infrared (mid-IR) polycyclic aromatic hydrocarbons (PAHs) and mid-IR continuum ratios. Using Spitzer InfraRed Spectrograph (IRS) spectra of a representative s le of local ULIRGs ( z 0.27), we examine their PAH and underlying continuum emission ratios. For deeply embedded sources, we find that the 9.7 μm silicate absorption band has a particularly pronounced effect on the 11.3 μm PAH feature. The low flux level in the nuclear silicate absorption band enhances the 11.3 μm PAH feature contrast (high PAH equivalent width) compared to that of the other PAH features. The technique has been extended to include the use of the underlying 11.3/12.7 and 11.3/6.2 μm continuum ratios. However, the latter are affected by the extinction coming from both the host galaxy and the nuclear region, whereas the foreground (host-galaxy) extinction is cancelled out when using the PAH equivalent width ratios. We apply our method to local U/LIRGs from the HERUS and GOALS s les and classify 14 ULIRGs and 10 LIRGs as CON candidates, which corresponds to 30% of the ULIRGs and 7% of the LIRGs from these s les. We find that the observed continuum ratios of CON-dominated sources can be explained by assuming torus models with a tapered disc geometry and a smooth dust distribution. This suggests that the nuclear dusty structure of deeply obscured galaxy nuclei has an extremely high dust coverage. Finally, we demonstrate that the use of mid-IR colour–colour diagrams is an effective way to select CON-dominated sources at different redshifts. In particular, the combination of filters of the James Webb Space Telescope/Mid-Infrared Instrument will enable the selection of CONs out to z ∼ 1.5. This will allow the selection of CONs to be extended to high redshifts where U/LIRGs are more numerous.
Publisher: Oxford University Press (OUP)
Date: 15-03-1995
Publisher: Oxford University Press (OUP)
Date: 05-1982
Publisher: American Astronomical Society
Date: 02-1996
DOI: 10.1086/176819
Publisher: Springer Netherlands
Date: 2005
Publisher: Cambridge University Press (CUP)
Date: 1993
DOI: 10.1017/S1323358000025777
Abstract: The star-formation process is an outstanding and largely unsolved problem in astrophysics. The role of magnetic fields is unclear but is widely considered to be important at all stages of protostellar evolution, from cloud collapse to ZAMS. For ex le, in some hydromagnetic models, the field may assist in removing angular momentum, thereby driving accretion and perhaps bipolar outflows. Spectropolarimetry between 8 and 13μm provides information on the direction of the transverse component of a magnetic field through the alignment of dust grains. We present results of 8–13μm spectropolarimetric observations of a number of bipolar molecular outflow sources, and compare the field directions observed with the axes of the outflows and putative disk-like structures observed to be associated with some of the objects. There is a strong correlation, though so far with limited statistics, between the magnetic field and disk orientations. We compare our results with magnetic field configurations predicted by current models for hydromagnetically driven winds from the disks around Young Stellar Objects (YSOs). Our results appear to argue against the Pudritz and Norman model and instead seem to support the Uchida and Shibata model.
Publisher: American Astronomical Society
Date: 03-05-2007
DOI: 10.1086/518602
Publisher: American Astronomical Society
Date: 19-11-2019
Publisher: Oxford University Press (OUP)
Date: 12-1984
Publisher: Springer Science and Business Media LLC
Date: 1990
DOI: 10.1038/343045A0
Publisher: Oxford University Press (OUP)
Date: 11-02-2007
Publisher: Oxford University Press (OUP)
Date: 06-2005
Publisher: Oxford University Press (OUP)
Date: 15-03-1995
Publisher: Oxford University Press (OUP)
Date: 06-1988
Publisher: Oxford University Press (OUP)
Date: 09-1998
Publisher: Oxford University Press (OUP)
Date: 11-12-2008
Publisher: Oxford University Press (OUP)
Date: 21-02-2000
Publisher: American Astronomical Society
Date: 11-1979
DOI: 10.1086/157455
Publisher: EDP Sciences
Date: 07-2023
DOI: 10.1051/0004-6361/202346074
Abstract: We present new ALMA observations of the CO(3−2) transition and associated 854 μm continuum at 0.06 − 0.3″ resolution, together with new VLT/SINFONI observations of NGC 7172. This is a luminous (bolometric luminosity of ≃10 44 erg s −1 ) Seyfert galaxy that belongs to the Galaxy Activity, Torus, and Outflow Survey (GATOS). The ALMA CO(3−2) observations reveal the presence of a highly inclined cold molecular gas ring with an approximate radius of 3 − 4″ ≃ 540 − 720 pc, which is likely associated with an inner Lindblad resonance of a putative stellar bar. There are noncircular motions in the VLT/SINFONI [Si VI ] λ 1.96 μm and H 2 at 2.12 μm, and ALMA CO(3−2) velocity fields. After subtracting the stellar velocity field, we detected [Si VI ] blueshifted velocities of a few hundred km s −1 to the south of the active galactic nucleus (AGN) position. They trace outflowing ionized gas outside the plane of the galaxy and out to projected distances of ≃200 pc. The CO(3−2) position-velocity diagram along the kinematic minor axis displays noncircular motions with observed velocities of up to ∼150 km s −1 . Assuming that these are taking place in the disk of the galaxy, the observed velocity signs imply that the molecular gas ring is not only rotating but also outflowing. We derived an integrated cold molecular gas mass outflow rate of ∼40 M ⊙ yr −1 for the ring. Using the ALMA 854 μm extended emission map, we resolved a 32 pc radius torus with a gas mass of 8 × 10 5 M ⊙ . These torus properties are similar to other Seyfert galaxies in the GATOS s le. We measured a decreased cold molecular gas concentration in the nuclear-torus region relative to the circumnuclear region when compared to other less luminous Seyfert galaxies. We conclude that the effects of AGN feedback in NGC 7172, which are likely caused by the AGN wind and/or the moderate luminosity radio jet, are seen as a large-scale outflowing molecular gas ring and accompanying redistribution of molecular gas in the nuclear regions.
Publisher: Oxford University Press (OUP)
Date: 07-2005
Publisher: American Astronomical Society
Date: 10-1983
DOI: 10.1086/161396
Publisher: Oxford University Press (OUP)
Date: 02-1989
Publisher: Oxford University Press (OUP)
Date: 02-1991
Publisher: Oxford University Press (OUP)
Date: 07-03-2016
DOI: 10.1093/MNRAS/STW541
Publisher: Oxford University Press (OUP)
Date: 05-1986
Publisher: Oxford University Press (OUP)
Date: 05-10-2007
Publisher: Oxford University Press (OUP)
Date: 2005
Publisher: Springer Science and Business Media LLC
Date: 08-1984
DOI: 10.1038/310660A0
Publisher: Oxford University Press (OUP)
Date: 07-1986
Publisher: Oxford University Press (OUP)
Date: 11-2001
Publisher: Oxford University Press (OUP)
Date: 20-12-2022
Abstract: Compact Obscured Nuclei (CONs) potentially hide extreme supermassive black hole (SMBH) growth behind large column densities of gas/dust. We present a spectroscopic analysis of the heavily obscured nucleus and the surrounding environment of the eastern region of the nearby (z = 0.02007) interacting galaxy VV 114 with the JWST Mid-InfraRed Instrument (MIRI). We model the spectrum from 4.9 to 28 μm to extract polycyclic aromatic hydrocarbon (PAH) emission and the underlying obscured continuum. We find that the NE nucleus (A) is highly obscured where the low PAH equivalent width (EW) ratio, EW(12.7)/EW(11.3), reveals a dust enshrouded continuum source. This is confirmed by decomposing the continuum into nuclear and star-forming where the nuclear component is found to be typical of CONs. The 11.3/6.2 PAH flux ratio is consistent with originating in star-forming regions rather than typical AGN. The second nucleus (B) is much less obscured, with PAH flux ratios also typical of star-forming regions. We do not detect any high ionization lines such as [Ne v] or [Ne vi] which suggests that if an AGN is present it must be highly obscured. Additionally, we detect a shock front south of the secondary nucleus (B) in the [Fe ii] (5.34 μm) line and in warm molecular hydrogen. The 6.2 PAH emission does not spatially coincide with the low-J transitions of H2 but rather appears strong at the shock front which may suggest destruction of the ionized PAHs in the post-shock gas behind the shock front.
Publisher: Oxford University Press (OUP)
Date: 10-1983
Publisher: Oxford University Press (OUP)
Date: 08-1985
Publisher: Oxford University Press (OUP)
Date: 06-1984
Publisher: EDP Sciences
Date: 11-2022
DOI: 10.1051/0004-6361/202244230
Abstract: We present a statistical analysis of the properties of the obscuring material around active galactic nuclei (AGN). This study represents the first of its kind for an ultra-hard X-ray (14–195 keV Swift /BAT), volume-limited ( D L 40 Mpc) s le of 24 Seyfert (Sy) galaxies (BCS 40 s le) using high angular resolution infrared data and various torus models: smooth, clumpy, and two-phase torus models and clumpy disc+wind models. We find that torus models (i.e. without including the polar dusty wind component) and disc+wind models provide the best fits for a comparable number of galaxies, 8 out of 24 (33.3%) and 9 out of 24 (37.5%), respectively. We find that the best-fit models depend on the hydrogen column density ( N H X−ray ), which is related to the X-ray (unobscured or obscured) and optical (Sy1/Sy2) classification. In particular, smooth, clumpy, and two-phase torus models are best at reproducing the infrared (IR) emission of AGN with relatively high hydrogen column density (median value of log ( N H X−ray cm −2 ) = 23.5 ± 0.8 i.e. Sy2). However, clumpy disc+wind models provide the best fits to the nuclear IR spectral energy distributions (SEDs) of Sy1/1.8/1.9 (median value of log ( N H X−ray cm −2 ) = 21.0 ± 1.0) – specifically, in the near-infrared (NIR) range. The success of the disc+wind models in fitting the NIR emission of Sy1 galaxies is due to the combination of adding large graphite grains to the dust composition and self-obscuration effects caused by the wind at intermediate inclinations. In general, we find that the Seyfert galaxies having unfavourable (favourable) conditions, namely, nuclear hydrogen column density and Eddington ratio, for launching IR dusty polar outflows are best-fitted with smooth, clumpy, and two-phase torus (disc+wind) models, confirming the predictions from simulations. Therefore, our results indicate that the nature of the inner dusty structure in AGN depends on the intrinsic AGN properties.
Publisher: Oxford University Press (OUP)
Date: 23-03-2015
DOI: 10.1093/MNRAS/STV338
Publisher: Oxford University Press (OUP)
Date: 15-08-1991
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Patrick Roche.