Publications by Patrick Roche


High resolution imaging of the magnetic field in the central parsec of the Galaxy

Planetary and Space Science Elsevier (2018)

P Roche, E Lopez Rodriguez, CM Telesco, R Schodel, C Packham

We discuss a high resolution (FWHM∼ 0:45 arcsec) image of the emissive polarization from warm dust in the minispiral in the Galactic Centre and discuss the implications for the magnetic field in the dusty filaments. The image was obtained at a wavelength of 12.5 μm with the CanariCam multimode mid-infrared imager on the Gran Telescopio Canarias. It confirms the results obtained from previous observations but also reveals new details of the polarization structures. In particular, we identify regions of coherent magnetic field emission at position angles of ∼ 45o to the predominantly north–south run of field lines in the Northern Arm which may be related to orbital motions inclined to the general flow of the Northern Arm. The luminous stars that have been identified as bow-shock sources in the Northern Arm do not disrupt or dilute the field but are linked by a coherent field structure, implying that the winds from these objects may push and compress the field but do not overwhelm it. The magnetic field in the low surface brightness regions in the East-West Bar to the south of SgrA* lies along the Bar, but the brighter regions generally have different polarization position angles, suggesting that they are distinct structures. In the region of the Northern Arm sampled here, there is only a weak correlation between the intensity of the emission and the degree of polarization. This is consistent with saturated grain alignment where the degree of polarization depends on geometric effects, including the angle of inclination of the field to the line of sight and superposition of filaments with different field directions, rather than the alignment efficiency.


Nuclear molecular outflow in the Seyfert galaxy NGC 3227

Astronomy and Astrophysics EDP Sciences 628 (2019) A65

A Alonso Herrero, S García-Burillo, M Pereira-Santaella, RI Davies, F Combes, M Vestergaard, SI Raimundo, A Bunker, T Díaz-Santos, P Gandhi, I García-Bernete, EKS Hicks, SF Hönig, LK Hunt, M Imanishi, T Izumi, NA Levenson, W Maciejewski1, C Packham, C Ramos Almeida, C Ricci, D Rigopoulou, P Roche, D Rosario, M Schartmann

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 μm 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 − vsys = 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 × 105 M⊙ and an equivalent average column density N(H2) = 2 − 3 × 1023 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.


Torus model properties of an ultra-hard X-ray selected sample of Seyfert galaxies

Monthly Notices of the Royal Astronomical Society Oxford University Press 486 (2019) 4917-4935

I Garcia-Benete, C Ramos Almeida, A Alonso-Herrero, M Ward, JA Acosta-Pulido, M Pereira-Santaella, A Hernan-Caballero, A Asensio Ramos, O Gonzalez-Martin, NA Levenson, S Mateos, FJ Carrera, C Ricci, P Roche, I Marquez, C Packham, J Masegosa, L Fuller

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.


High angular resolution ALMA images of dust and molecules in the SN 1987A ejecta

Astrophysical Journal American Astronomical Society 886 (2019) 51

P Cigan, M Matsuura, HL Gomez, R Indebetouw, P Roche

We present high angular resolution (~80 mas) ALMA continuum images of the SN 1987A system, together with CO J = 2 $\to $ 1, J = 6 $\to $ 5, and SiO J = 5 $\to $ 4 to J = 7 $\to $ 6 images, which clearly resolve the ejecta (dust continuum and molecules) and ring (synchrotron continuum) components. Dust in the ejecta is asymmetric and clumpy, and overall the dust fills the spatial void seen in Hα images, filling that region with material from heavier elements. The dust clumps generally fill the space where CO J = 6 $\to $ 5 is fainter, tentatively indicating that these dust clumps and CO are locationally and chemically linked. In these regions, carbonaceous dust grains might have formed after dissociation of CO. The dust grains would have cooled by radiation, and subsequent collisions of grains with gas would also cool the gas, suppressing the CO J = 6 $\to $ 5 intensity. The data show a dust peak spatially coincident with the molecular hole seen in previous ALMA CO J = 2 $\to $ 1 and SiO J = 5 $\to $ 4 images. That dust peak, combined with CO and SiO line spectra, suggests that the dust and gas could be at higher temperatures than the surrounding material, though higher density cannot be totally excluded. One of the possibilities is that a compact source provides additional heat at that location. Fits to the far-infrared–millimeter spectral energy distribution give ejecta dust temperatures of 18–23 K. We revise the ejecta dust mass to M dust = 0.2–0.4 ${M}_{\odot }$ for carbon or silicate grains, or a maximum of <0.7 ${M}_{\odot }$ for a mixture of grain species, using the predicted nucleosynthesis yields as an upper limit.


The magnetic field in the central parsec of the Galaxy

Monthly Notices of the Royal Astronomical Society Oxford University Press 476 (2018) 235–245-

P Roche, E Lopes-Rodriguez, CM Telesco, R Schoedel, C Packham

We present a polarisation map of the warm dust emission from the minispiral in the central parsec of the Galactic centre. The observations were made at a wavelength of 12.5 μm with CanariCam mounted on the 10.4-m Gran Telescopio Canarias. The magnetic field traced by the polarised emission from aligned dust grains is consistent with previous observations, but the increased resolution of the present data reveals considerably more information on the detailed structure of the B field and its correspondence with the filamentary emission seen in both mid-infrared continuum emission and free-free emission at cm wavelengths. The magnetic field appears to be compressed and pushed by the outflows from luminous stars in the Northern Arm, but it is not disordered by them. We identify some magnetically coherent filaments that cross the Northern Arm at a Position Angle of ∼45o, and which may trace orbits inclined to the primary orientation of the Northern Arm and circumnuclear disk. In the East-West bar, the magnetic fields implied by the polarization in the lower intensity regions lie predominantly along the bar at a Position Angle of 130 − 140o. In contrast to the Northern Arm, the brighter regions of the bar tend to have lower degrees of polarization with a greater divergence in position angle compared to the local diffuse emission. It appears that the diffuse emission in the East-West bar traces the underlying field and that the bright compact sources are unrelated objects presumably projected onto the bar and with different field orientations.


ALMA spectral survey of Supernova 1987A — molecular inventory, chemistry, dynamics and explosive nucleosynthesis

Monthly Notices of the Royal Astronomical Society Oxford University Press 469 (2017) 3347-3362

M Matsuura, R Indebetouw, S Woosley, V Bujarrabal, FJ Abellán, R McCray, J Kamenetzky, C Fransson, MJ Barlow, HL Gomez, P Cigan, I De Looze, J Spyromilio, L Stavely-Smith, G Zanardo, P Roche, J Larsson, S Viti, JT Van Loon, JC Wheeler, M Baes, JM Marcaide, E Dwek, M Meixner, C-Y Ng

<p>We report the first molecular line survey of Supernova 1987A in the millimetre wavelength range. In the ALMA 210–300 and 340–360 GHz spectra, we detected cold (20–170 K) CO, 28SiO, HCO+ and SO, with weaker lines of 29SiO from ejecta. This is the first identification of HCO+ and SO in a young supernova remnant.We find a dip in the J=6–5 and 5–4 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 cause mixing of gas, with heavier elements much more disturbed, making more elongated structure.We obtained isotopologue ratios of 28SiO/29SiO&gt; 13, 28SiO/30SiO&gt;14, and 12CO/13CO&gt;21, with the most likely limits of 28SiO/29SiO&gt; 128, 28SiO/30SiO&gt; 189. Low 29Si and 30Si abundances in SN 1987A are consistent with nucleosynthesis models that show inefficient formation of neutron-rich isotopes in a low metallicity environment, such as the Large Magellanic Cloud. The deduced large mass of HCO+ (~ 5 X 10^-6 M⊙) and small SiS mass (&lt; 6 X 10^-5 M⊙) might be explained by some mixing of elements immediately after the explosion. The mixing might have caused some hydrogen from the envelope to sink into carbon and oxygen-rich zones after the explosion, enabling the formation of a substantial mass of HCO+. Oxygen atoms may have penetrated into silicon and sulphur zones, suppressing formation of SiS. Our ALMA observations open up a new window to investigate chemistry, dynamics and explosive-nucleosynthesis in supernovae.</p>


ALMA observations of Molecules in Supernova 1987A

Proceedings of the International Astronomical Union Cambridge University Press 12 (2017) 294-299

M Matsuura, R Indebetouw, S Woosley, V Bujarrabal, FJ Abellán, R McCray, J Kamenetzky, C Fransson, MJ Barlow, HL Gomez, P Cigan, I De Looze, J Spyromilio, L Staveley-Smith, G Zanardo, P Roche, J Larsson, S Viti, JT van Loon, JC Wheeler, M Baes, R Chevalier, P Lundqvist, JM Marcaide, E Dwek

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, 28SiO, HCO+ and SO, with weaker lines of 29SiO. 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 28SiO 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.


A mid-infrared statistical investigation of clumpy torus model predictions

Monthly Notices of the Royal Astronomical Society Oxford University Press 470 (2017) 2578-2598

J García-González, A Alonso-Herrero, S Hönig, A Hernán-Caballero, C Ramos Almeida, N Levenson, PF Roche, O González-Martín, C Packham, M Kishimoto

We present new calculations of the CAT3D clumpy torus models, which now include a more physical dust sublimation model as well as AGN anisotropic emission. These new models allow graphite grains to persist at temperatures higher than the silicate dust sublimation temperature. This produces stronger near-infrared emission and bluer mid-infrared (MIR) spectral slopes. We make a statistical comparison of the CAT3D model MIR predictions with a compilation of sub-arcsecond resolution ground-based MIR spectroscopy of 52 nearby Seyfert galaxies (median distance of 36 Mpc) and 10 quasars. We focus on the AGN MIR spectral index αMIR and the strength of the 9.7 μm silicate feature SSil. As with other clumpy torus models, the new CAT3D models do not reproduce the Seyfert galaxies with deep silicate absorption (SSil &lt; −1). Excluding those, we conclude that the new CAT3D models are in better agreement with the observed αMIR and SSil of Seyfert galaxies and quasars. We find that Seyfert 2 are reproduced with models with low photon escape probabilities, while the quasars and the Seyfert 1-1.5 require generally models with higher photon escape probabilities. Quasars and Seyfert 1-1.5 tend to show steeper radial cloud distributions and fewer clouds along an equatorial line-of-sight than Seyfert 2. Introducing AGN anisotropic emission besides the more physical dust sublimation models alleviates the problem of requiring inverted radial cloud distributions (i.e., more clouds towards the outer parts of the torus) to explain the MIR spectral indices of type 2 Seyferts.


Infrared polarimetry of Mrk 231: scattering off hot dust grains in the central core

Monthly Notices of the Royal Astronomical Society Oxford University Press (2016)

E Lopez-Rodriguez, C Packham, TJ Jones, R Siebenmorgen, P Roche, NA Levenson, A Alonso-Herrero, E Perlman, K Ichikawa, C Ramos Almeida, O González-Martín, R Nikutta, M Martinez-Paredez, D Shenoy, MS Gordon, CM Telesco

We present high-angular (0.17−0.35 arcsec) resolution imaging polarimetric observations of Mrk 231 in the 3.1 µm filter using MMT-Pol on the 6.5-m MMT, and in the 8.7 µm, 10.3 µm, and 11.6 µm filters using CanariCam on the 10.4-m Gran Telescopio CANARIAS. In combination with already published observations, we compile the 1−12 µm total and polarized nuclear spectral energy distribution (SED). The total flux SED in the central 400 pc is explained as the combination of 1) a hot (731 ± 4 K) dusty structure, directly irradiated by the central engine, which is at 1.6 ± 0.1 pc away and attributed to be in the pc-scale polar region, 2) an optically-thick, smooth and disk-like dusty structure (‘torus’) with an inclination of 48 ± 23◦ surrounding the central engine, and 3) an extinguished (AV = 36 ± 5 mag) starburst component. The polarized SED decreases from 0.77 ± 0.14 per cent at 1.2 µm to 0.31 ± 0.15 per cent at 11.6 µm and follows a power-law function, λ ∼0.57. The polarization angle remains constant (∼108◦ ) in the 1−12 µm wavelength range. The dominant polarization mechanism is explained as scattering off hot dust grains in the pc-scale polar regions.


Very deep inside the SN 1987A core ejecta: Molecular structures seen in 3D

Astrophysical Journal Letters American Astronomical Society 842 (2017) aa784c

FJ Abellan, R Indebetouw, JM Marcaide, P Roche, Et al.

Most massive stars end their lives in core-collapse supernova explosions and enrich the interstellar medium with explosively nucleosynthesized elements. Following core collapse, the explosion is subject to instabilities as the shock propagates outward through the progenitor star. Observations of the composition and structure of the innermost regions of a core-collapse supernova provide a direct probe of the instabilities and nucleosynthetic products. SN 1987A in the Large Magellanic Cloud is one of very few supernovae for which the inner ejecta can be spatially resolved but are not yet strongly affected by interaction with the surroundings. Our observations of SN 1987A with the Atacama Large Millimeter/submillimeter Array are of the highest resolution to date and reveal the detailed morphology of cold molecular gas in the innermost regions of the remnant. The 3D distributions of carbon and silicon monoxide (CO and SiO) emission differ, but both have a central deficit, or torus-like distribution, possibly a result of radioactive heating during the first weeks ("nickel heating"). The size scales of the clumpy distribution are compared quantitatively to models, demonstrating how progenitor and explosion physics can be constrained.


The complex evolutionary paths of local infrared bright galaxies: a high-angular resolution mid-infrared view

Monthly Notices of the Royal Astronomical Society Oxford University Press 463 (2016) 2405-2424

P Roche, A Alonso-Herrero, R Poulton, A Hernán-Caballero, I Aretxaga, M Martínez-Paredes, C Ramos Almeida, M Pereira-Santaella, T Díaz-Santos, NA Levenson, C Packham, L Colina, P Esquej, O González-Martín, K Ichikawa, M Imanishi, JM Rodríguez Espinosa, C Telesco

We investigate the evolutionary connection between local infrared (IR)-bright galaxies (logLIR ≥11.4 Lʘ) and quasars. We use high-angular resolution (∼0.3–0.4 arcsec∼few hundred parsecs) 8–13µm ground-based spectroscopy to disentangle the active galactic nuclei (AGN) id-IR properties from those of star formation. The comparison between the nuclear 11.3µm polycyclic aromatic hydrocarbon feature emission and that measured with Spitzer/Spitzer Infrared Spectrograph indicates that the star formation is extended over a few kpc in the IRbright galaxies. The AGN contribution to the total IR luminosity of IR-bright galaxies is lower than in quasars. Although the dust distribution is predicted to change as IR-bright galaxies evolve to IR-bright quasars and then to optical quasars, we show that the AGN mid-IR emission of all the quasars in our sample is not significantly different. In contrast, the nuclear emission of IR-bright galaxies with low AGN contributions appears more heavily embedded in dust although there is no clear trend with the interaction stage or projected nuclear separation. This suggests that the changes in the distribution of the nuclear obscuring material may be taking place rapidly and at different interaction stages washing out the evidence of an evolutionary path. When compared to normal AGN, the nuclear star formation activity of quasars appears to be dimming, whereas it is enhanced in some IR-bright nuclei, suggesting that the latter are in an earlier star formation-dominated phase.


A mid-infrared spectroscopic atlas of local active galactic nuclei on sub-arcsecond resolution using GTC/CanariCam

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 455 (2016) 563-583

A Alonso-Herrero, P Esquej, PF Roche, C Ramos Almeida, O Gonzalez-Martin, C Packham, NA Levenson, RE Mason, A Hernan-Caballero, M Pereira-Santaella, C Alvarez, I Aretxaga, E Lopez-Rodriguez, L Colina, T Diaz-Santos, M Imanishi, JM Rodriguez Espinosa, E Perlman


The nuclear and integrated far-infrared emission of nearby Seyfert galaxies

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 458 (2016) 4512-4529

J Garcia-Gonzalez, A Alonso-Herrero, A Hernan-Caballero, M Pereira-Santaella, C Ramos-Almeida, JA Acosta-Pulido, T Diaz-Santos, P Esquej, O Gonzalez-Martin, K Ichikawa, E Lopez-Rodriguez, M Povic, PF Roche, M Sanchez-Portal


Mid-infrared imaging- and spectro-polarimetric subarcsecond observations of NGC 1068

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 458 (2016) 3851-3866

E Lopez-Rodriguez, C Packham, PF Roche, A Alonso-Herrero, T Diaz-Santos, R Nikutta, O Gonzalez-Martin, CA Alvarez, P Esquej, JM Rodriguez Espinosa, E Perlman, C Ramos Almeida, CM Telesco


MID-IR SPECTRA OF TYPE Ia SN 2014J IN M82 SPANNING THE FIRST 4 MONTHS

ASTROPHYSICAL JOURNAL 798 (2015) ARTN 93

CM Telesco, P Hoeflich, D Li, C Alvarez, CM Wright, PJ Barnes, S Fernandez, JH Hough, NA Levenson, N Marinas, C Packham, E Pantin, R Rebolo, P Roche, H Zhang


The nuclear and extended infrared emission of the Seyfert galaxy NGC 2992 and the interacting system Arp 245

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 449 (2015) 1309-1326

I Garcia-Bernete, C Ramos Almeida, JA Acosta-Pulido, A Alonso-Herrero, M Sanchez-Portal, M Castillo, M Pereira-Santaella, P Esquej, O Gonzalez-Martin, T Diaz-Santos, P Roche, S Fisher, M Povic, AM Perez Garcia, I Valtchanov, C Packham, NA Levenson


The silicate absorption profile in the interstellar medium towards the heavily obscured nucleus of NGC 4418

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 449 (2015) 2598-2603

PF Roche, A Alonso-Herrero, O Gonzalez-Martin


Magnetic field structures in star-forming regions: mid-infrared imaging polarimetry of K3-50

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 453 (2015) 2622-2636

P Barnes, D Li, C Telesco, N Tanakul, N Marinas, C Wright, C Packham, E Pantin, P Roche, J Hough


A mid-infrared view of the inner parsecs of the Seyfert galaxy Mrk 1066 using CanariCam/GTC

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 445 (2014) 1130-1143

C Ramos Almeida, A Alonso-Herrero, P Esquej, O Gonzalez-Martin, RA Riffel, I Garcia-Bernete, JM Rodriguez Espinosa, C Packham, NA Levenson, P Roche, T Diaz-Santos, I Aretxaga, C Alvarez


Nuclear 11.3 mu m PAH emission in local active galactic nuclei

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 443 (2014) 2766-2782

A Alonso-Herrero, C Ramos Almeida, P Esquej, PF Roche, A Hernan-Caballero, SF Honig, O Gonzalez-Martin, I Aretxaga, RE Mason, C Packham, NA Levenson, JM Rodriguez Espinosa, R Siebenmorgen, M Pereira-Santaella, T Diaz-Santos, L Colina, C Alvarez, CM Telesco

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