Examinando por Autor "Aalto, S."

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Acceso Abierto
A CO molecular gas wind 340 pc away from the Seyfert 2 nucleus in ESO 420-G13 probes an elusive radio jet
(EDP Sciences, 2020-01-21) Fernández Ontiveros, J. A.; Dasyra, K. M.; Hatziminaoglou, Evanthia; Malkan, M. A.; Pereira Santaella, M.; Papachristou, M.; Spinoglio, L.; Combes, F.; Aalto, S.; Nagar, N.; Imanishi, M.; Andreani, P.; Ricci, C.; Slater, R.; Agenzia Spaziale Italiana (ASI); Comunidad de Madrid; Hellenic Foundation for Research and Innovation (HFRI); Comisión Nacional de Investigación Científica y Tecnológica (CONICYT); http://dx.doi.org/10.13039/501100002848; Fernández Ontiveros, J. A. [0000-0001-9490-899X]; Hatziminaoglou, E. [0000-0003-0917-9636]; Spignoglio, L. [0000-0001-8840-1551]; Combes, F. [0000-0003-2658-7893]; Nagar, N. [0000-0001-6920-662X]; Imanishi, M. [0000-0001-6186-8792]; Andreani, P. [0000-0001-9493-0169]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
A prominent jet-driven outflow of CO(2-1) molecular gas is found along the kinematic minor axis of the Seyfert 2 galaxy ESO 420-G13, at a distance of 340-600 pc from the nucleus. The wind morphology resembles the characteristic funnel shape, formed by a highly collimated filamentary emission at the base, and likely traces the jet propagation through a tenuous medium, until a bifurcation point at 440 pc. Here the jet hits a dense molecular core and shatters, dispersing the molecular gas into several clumps and filaments within the expansion cone. We also trace the jet in ionised gas within the inner less than or similar to 340 pc using the [NeII](12.8 mu m) line emission, where the molecular gas follows a circular rotation pattern. The wind outflow carries a mass of similar to 8 x 10(6) M-circle dot at an average wind projected speed of similar to 160 km s(-1), which implies a mass outflow rate of similar to 14 M-circle dot yr(-1). Based on the structure of the outflow and the budget of energy and momentum, we discard radiation pressure from the active nucleus, star formation, and supernovae as possible launching mechanisms. ESO 420-G13 is the second case after NGC 1377 where a previously unknown jet is revealed through its interaction with the interstellar medium, suggesting that unknown jets in feeble radio nuclei might be more common than expected. Two possible jet-cloud configurations are discussed to explain an outflow at this distance from the AGN. The outflowing gas will likely not escape, thus a delay in the star formation rather than quenching is expected from this interaction, while the feedback effect would be confined within the central few hundred parsecs of the galaxy.
Acceso Abierto
ALMA observations of CS in NGC 1068: Chemistry and excitation
(Oxford Academics: Blackwell Publishing, 2020-07-02) Scourfield, M.; Viti, S.; García Burillo, S.; Saintonge, A.; Combes, F.; Fuente, A.; Henkel, C.; Alonso Herrero, A.; Harada, N.; Takano, S.; Nakajima, T.; Martín, S.; Krips, M.; Van der Werf, P. P.; Aalto, S.; Usero, A.; Kohno, K.; Agencia Estatal de Investigación (AEI); Alonso Herrero, A. [0000-0001-6794-2519]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
We present results from Atacama Large Millimeter/submillimeter Array (ALMA) observations of CS from the nearby galaxy NGC 1068 (∼14 Mpc). This Seyfert 2 barred galaxy possesses a circumnuclear disc (CND, r ∼ 200 pc) and a starburst ring (SB ring, r ∼ 1.3 kpc). These high-resolution maps (∼0.5 arcsec, ∼35 pc) allow us to analyse specific sub-regions in the galaxy and investigate differences in line intensity ratios and physical conditions, particularly those between the CND and SB ring. Local thermodynamic equilibrium (LTE) analysis of the gas is used to calculate CS densities in each sub-region, followed by the non-LTE analysis conducted using the radiative transfer code RADEX to fit observations and constrain gas temperature, CS column density and hydrogen density. Finally, the chemical code UCLCHEM is used to reconstruct the gas, allowing an insight into its origin and chemical history. The density of hydrogen in the CND is found to be ≥105 cm−2, although exact values vary, reaching 106 cm−2 at the active galactic nucleus. The conditions in the two arms of the SB ring appear similar to one another, though the density found (∼104 cm−2) is lower than in the CND. The temperature in the CND increases from east to west, and is also overall greater than found in the SB ring. These modelling methods indicate the requirement for multiphase gas components in order to fit the observed emission over the galaxy. A larger number of high-resolution transitions across the SLED may allow for further constraining of the conditions, particularly in the SB ring.
Acceso Abierto
Physics of ULIRGs with MUSE and ALMA: The PUMA project II. Are local ULIRGs powered by AGN? The subkiloparsec view of the 220 GHz continuum
(EDP Sciences, 2021-07-12) Pereira Santaella, M.; Colina, L.; García Burillo, S.; Lamperti, I.; González Alfonso, E.; Perna, M.; Arribas, S.; Alonso Herrero, A.; Aalto, S.; Combes, F.; Labiano, Á.; Piqueras López, J.; Rigopoulou, D.; Van der Werf, P. P.; Comunidad de Madrid; Agencia Estatal de Investigación (AEI); Science and Technology Facilities Council (STFC); Pereira Santaella, M. [0000-0002-4005-9619]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
We analyze new high-resolution (400 pc) ∼220 GHz continuum and CO(2–1) Atacama Large Millimeter Array (ALMA) observations of a representative sample of 23 local (z < 0.165) ultra-luminous infrared systems (ULIRGs; 34 individual nuclei) as part of the “Physics of ULIRGs with MUSE and ALMA” (PUMA) project. The deconvolved half-light radii of the ∼220 GHz continuum sources, rcont, are between < 60 pc and 350 pc (median 80–100 pc). We associate these regions with the regions emitting the bulk of the infrared luminosity (LIR). The good agreement, within a factor of 2, between the observed ∼220 GHz fluxes and the extrapolation of the infrared gray-body as well as the small contributions from synchrotron and free–free emission support this assumption. The cold molecular gas emission sizes, rCO, are between 60 and 700 pc and are similar in advanced mergers and early interacting systems. On average, rCO are ∼2.5 times larger than rcont. Using these measurements, we derived the nuclear LIR and cold molecular gas surface densities (ΣLIR = 1011.5 − 1014.3 L⊙ kpc−2 and ΣH2 = 102.9 − 104.2 M⊙ pc−2, respectively). Assuming that the LIR is produced by star formation, the median ΣLIR corresponds to ΣSFR = 2500 M⊙ yr−1 kpc−2. This ΣSFR implies extremely short depletion times, ΣH2/ΣSFR < 1–15 Myr, and unphysical star formation efficiencies > 1 for 70% of the sample. Therefore, this favors the presence of an obscured active galactic nucleus (AGN) in these objects that could dominate the LIR. We also classify the ULIRG nuclei in two groups: (a) compact nuclei (rcont < 120 pc) with high mid-infrared excess emission (ΔL6−20 μm/LIR) found in optically classified AGN; and (b) nuclei following a relation with decreasing ΔL6−20 μm/LIR for decreasing rcont. The majority, 60%, of the nuclei in interacting systems lie in the low-rcont end (<120 pc) of this relation, while this is the case for only 30% of the mergers. This suggests that in the early stages of the interaction, the activity occurs in a very compact and dust-obscured region while, in more advanced merger stages, the activity is more extended, unless an optically detected AGN is present. Approximately two-thirds of the nuclei have nuclear radiation pressures above the Eddington limit. This is consistent with the ubiquitous detection of massive outflows in local ULIRGs and supports the importance of the radiation pressure in the outflow launching process.
Restringido
Star formation and nuclear activity in luminous infrared galaxies: an infrared through radio review
(Springer Link, 2021-01-13) Pérez Torres, M.; Mattila, S.; Alonso Herrero, A.; Aalto, S.; Efstathiou, A.; European Commission (EC); Agencia Estatal de Investigación (AEI); Ministerio de Economía y Competitividad (MINECO); Pérez Torres, 0000-0001-5654-0266; Centros de Excelencia Severo Ochoa, INSTITUTO DE ASTROFISICA DE ANDALUCIA (IAA), SEV-2017-0709; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Nearby galaxies offer unique laboratories allowing multi-wavelength spatially resolved studies of the interstellar medium, star formation and nuclear activity across a broad range of physical conditions. In particular, detailed studies of individual local luminous infrared galaxies (LIRGs) are crucial for gaining a better understanding of these processes and for developing and testing models that are used to explain statistical studies of large populations of such galaxies at high redshift for which it is currently impossible to reach a sufficient physical resolution. Here, we provide an overview of the impact of spatially resolved infrared, sub-millimetre and radio observations in the study of the interstellar medium, star formation and active galactic nuclei as well as their interplay in local LIRGs. We also present an overview of the modelling of their spectral energy distributions using state-of-the-art radiative transfer codes. These contribute necessary and powerful ‘workhorse’ tools for the study of LIRGs (and their more luminous counterparts) at higher redshifts which are unresolved in observations. We describe how spatially-resolved time-domain observations have recently opened a new window to study the nuclear activity in LIRGs. We describe in detail the observational characteristics of Arp 299 which is one of the best studied local LIRGs and exemplifies the power of the combination of time-domain and high-resolution observations at infrared to radio wavelengths together with radiative transfer modelling used to explain the spectral energy distributions of its different components. We summarise the previous achievements obtained using high-spatial resolution observations and provide an outlook into what we can expect to achieve with future facilities.