| 1. |
- Fernandez-Ontiveros, J. A., et al.
(författare)
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A CO molecular gas wind 340 pc away from the Seyfert 2 nucleus in ESO420-G13 probes an elusive radio jet*
- 2020
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 633
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
- Wiedner, M.C., et al.
(författare)
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Heterodyn receiver for the Origins Space Telescope concept 2
- 2018
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 10698
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Konferensbidrag (refereegranskat)abstract
- The Origins Space Telescope (OST) is a NASA study for a large satellite mission to be submitted to the 2020 Decadal Review. The proposed satellite has a fleet of instruments including the HEterodyne Receivers for OST (HERO). HERO is designed around the quest to follow the trail of water from the ISM to disks around protostars and planets. HERO will perform high-spectral resolution measurements with 2x9 pixel focal plane arrays at any frequency between 468GHz to 2,700GHz (617 to 111 μm). HERO builds on the successful Herschel/HIFI heritage, as well as recent technological innovations, allowing it to surpass any prior heterodyne instrument in terms of sensitivity and spectral coverage.
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| 3. |
- Aalto, Susanne, 1964
(författare)
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Molecular Clouds in Starburst Galaxies
- 1994
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Starbursts in the centres of galaxies are believed to be caused by funneling of gas towards the inner regions. Gravitational interactions between galaxies are known to cause vast rearrangements of their structure as well as induce bursts of star formation in their nuclear regions. However, radial gas-transport may also be the result of a bar- instability intrinsic to the system. This report deals with the effect of a starburst on the molecular medium of galaxies. The mm-wave, rotational transitions of interstellar molecules serve as probes of the physical conditions, kinematics and total mass of the molecular gas. Observations of the J=1-0, J=2-1 and J=3-2 transitions of 12Co, the J=1-0 and J=2-1 transitions of 13Co, the J=1-0 transitions of C180 and HCN and the J=2-1 transition of CS are used to determine the properties of the molecular gas in starbursting and normal galaxies. The mean escape probability approximation is used to solve the radiative transfer equations. The inferred properties of the molecular clouds in the centres of starburst galaxies differ from those of Galactic disk clouds. Such a deviation is likely to be induced by a central gas concentration and/or the nuclear starburst disrupting the clouds. Large 12CO/13CO J=1-0 intensity ratios (R>20) are measured towards luminous mergers implying unusual, high-pressure, molecular cloud ensembles. Model cloud ensembles for the merging system, NGC 3256, and the starburst spiral NGC 1808 suggest that the 12CO-emission is dominated by warm (Tk = 100 - 300 K), small (0.5-1 pc) and moderately dense (n = 2 - 7 x 103 cm-3) molecular clouds. Such temperatures and densities are typical of Galactic photon dominated regions (PDRs). Statistical studies of molecular line ratios towards galaxy centres indicate that the optical depth of the 12CO 1-0 emission is moderate, .tau.Ã? 1. Many starburst galaxies have large-scale excitation gradients indicating warm, dense gas in the centre, and normal cool molecular gas in their extended disks. NGC 3256, in particular, has a large R = 35 in the centre, while it is found to be only R = 10 - 15 at positions 43" off centre. The model cloud ensemble of NGC 1808 indicate that the 12CO-emitting gas may be diffuse rather than self-gravitating, this could be a common phenomenon in starburst galaxies.
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| 4. |
- Aalto, Susanne, 1964, et al.
(författare)
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The hidden heart of the luminous infrared galaxy IC 860: I. A molecular inflow feeding opaque, extreme nuclear activity
- 2019
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 627
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Tidskriftsartikel (refereegranskat)abstract
- High-resolution (0.'03-0.'09 (9-26 pc)) ALMA (100-350 GHz (λ3 to 0.8 mm)) and (0.'04 (11 pc)) VLA 45 GHz measurements have been used to image continuum and spectral line emission from the inner (100 pc) region of the nearby infrared luminous galaxy IC 860. We detect compact (r ∼ 10 pc), luminous, 3 to 0.8 mm continuum emission in the core of IC 860, with brightness temperatures TB > 160 K. The 45 GHz continuum is equally compact but significantly fainter in flux. We suggest that the 3 to 0.8 mm continuum emerges from hot dust with radius r ∼ 8 pc and temperature Td ∼ 280 K, and that it is opaque at millimetre wavelengths, implying a very large H2 column density N(H2)≥ 1026 cm-2. Vibrationally excited lines of HCN v2 = 1f J = 4 - 3 and 3-2 (HCN-VIB) are seen in emission and spatially resolved on scales of 40-50 pc. The line-to-continuum ratio drops towards the inner r = 4 pc, resulting in a ring-like morphology. This may be due to high opacities and matching HCN-VIB excitation- and continuum temperatures. The HCN-VIB emission reveals a north-south nuclear velocity gradient with projected rotation velocities of v = 100 km s-1 at r = 10 pc. The brightest emission is oriented perpendicular to the velocity gradient, with a peak HCN-VIB 3-2 TB of 115 K (above the continuum). Vibrational ground-state lines of HCN 3-2 and 4-3, HC15N 4-3, HCO+ 3-2 and 4-3, and CS 7-6 show complex line absorption and emission features towards the dusty nucleus. Redshifted, reversed P-Cygni profiles are seen for HCN and HCO+ consistent with gas inflow with vin ≤ 50 km s-1. Foreground absorption structures outline the flow, and can be traced from the north-east into the nucleus. In contrast, CS 7-6 has blueshifted line profiles with line wings extending out to -180 km s-1. We suggest that a dense and slow outflow is hidden behind a foreground layer of obscuring, inflowing gas. The centre of IC 860 is in a phase of rapid evolution where an inflow is building up a massive nuclear column density of gas and dust that feeds star formation and/or AGN activity. The slow, dense outflow may be signaling the onset of feedback. The inner, r = 10 pc, IR luminosity may be powered by an AGN or a compact starburst, which then would likely require a top-heavy initial mass function.
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| 5. |
- Aladro, Rebeca, 1979, et al.
(författare)
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Molecular gas in the northern nucleus of Mrk 273: Physical and chemical properties of the disc and its outflow
- 2018
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 617
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Tidskriftsartikel (refereegranskat)abstract
- Aiming to characterise the properties of the molecular gas in the ultra-luminous infrared galaxy Mrk 273 and its outflow, we used the NOEMA interferometer to image the dense-gas molecular tracers HCN, HCO+, HNC, HOC+ and HC3N at similar to 86 GHz and similar to 256 GHz with angular resolutions of 4.'' 9 x 4.'' 5 (similar to 3.7 x 3.4 kpc) and 0.'' 61 x 0.'' 55 (similar to 460 x 420 pc). We also modelled the flux of several H2O lines observed with Herschel using a radiative transfer code that includes excitation by collisions and far-infrared photons. The disc of the Mrk 273 north nucleus has two components with decoupled kinematics. The gas in the outer parts (R similar to 1.5 kpc) rotates with a south-east to north-west direction, while in the inner disc (R similar to 300 pc) follows a north-east to south-west rotation. The central 300 pc, which hosts a compact starburst region, is filled with dense and warm gas, and contains a dynamical mass of (4-5) x 10(9) M-circle dot, a luminosity of L'HCN = (3-4) x 10(8) K km s(-1) pc(2), and a dust temperature of 55 K. At the very centre, a compact core with R similar to 50 pc has a luminosity of LIR = 4 x 10(11) L-circle dot (30% of the total infrared luminosity), and a dust temperature of 95 K. The core is expanding at low velocities similar to 50-100 km s(-1), probably affected by the outflowing gas. We detect the blue-shifted component of the outflow, while the red-shifted counterpart remains undetected in our data. Its cold and dense phase reaches fast velocities up to similar to 1000 km s(-1), while the warm outflowing gas has more moderate maximum velocities of similar to 600 km s(-1). The outflow is compact, being detected as far as 460 pc from the centre in the northern direction, and has a mass of dense gas <= 8 x 10(8) M-circle dot. The difference between the position angles of the inner disc (similar to 70 degrees) and the outflow (similar to 10 degrees) indicates that the outflow is likely powered by the AGN, and not by the starburst. Regarding the chemistry in Mrk 273, we measure an extremely low HCO+/HOC+ ratio of 10 +/- 5 in the inner disc of Mrk 273.
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| 6. |
- Baldi, R. D., et al.
(författare)
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LeMMINGs - II. The e-MERLIN legacy survey of nearby galaxies. The deepest radio view of the Palomar sample on parsec scale
- 2021
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 500:4, s. 4749-4767
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Tidskriftsartikel (refereegranskat)abstract
- We present the second data release of high-resolution (≤0.2 arcsec) 1.5-GHz radio images of 177 nearby galaxies from the Palomar sample, observed with the e-MERLIN array, as part of the Legacy e-MERLIN Multi-band Imaging of Nearby Galaxies Sample (LeMMINGs) survey. Together with the 103 targets of the first LeMMINGs data release, this represents a complete sample of 280 local active (LINER and Seyfert) and inactive galaxies (H ii galaxies and absorption line galaxies, ALG). This large program is the deepest radio survey of the local Universe, ≳1017.6 W Hz-1, regardless of the host and nuclear type: we detect radio emission ≳0.25 mJy beam-1 for 125/280 galaxies (44.6 per cent) with sizes of typically ≲100 pc. Of those 125, 106 targets show a core which coincides within 1.2 arcsec with the optical nucleus. Although we observed mostly cores, around one third of the detected galaxies features jetted morphologies. The detected radio core luminosities of the sample range between ∼1034 and 1040 erg s-1. LINERs and Seyferts are the most luminous sources, whereas H ii galaxies are the least. LINERs show FR I-like core-brightened radio structures while Seyferts reveal the highest fraction of symmetric morphologies. The majority of H ii galaxies have single radio core or complex extended structures, which probably conceal a nuclear starburst and/or a weak active nucleus (seven of them show clear jets). ALGs, which are typically found in evolved ellipticals, although the least numerous, exhibit on average the most luminous radio structures, similar to LINERs.
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| 7. |
- Barrientos, Alejandro, et al.
(författare)
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Towards the prediction of molecular parameters from astronomical emission lines using Neural Networks
- 2021
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Ingår i: Experimental Astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 52:1-2, s. 157-182
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Tidskriftsartikel (refereegranskat)abstract
- Molecular astronomy is a field that is blooming in the era of large observatories such as the Atacama Large Millimeter/Submillimeter Array (ALMA). With modern, sensitive, and high spectral resolution radio telescopes like ALMA and the Square Kilometer Array, the size of the data cubes is rapidly escalating, generating a need for powerful automatic analysis tools. This work introduces MolPred, a pilot study to perform predictions of molecular parameters such as excitation temperature (Tex) and column density (log(N)) from input spectra by the use of neural networks. We used as test cases the spectra of CO, HCO+, SiO and CH3CN between 80 and 400 GHz. Training spectra were generated with MADCUBA, a state-of-the-art spectral analysis tool. Our algorithm was designed to allow the generation of predictions for multiple molecules in parallel. Using neural networks, we can predict the column density and excitation temperature of these molecules with a mean absolute error of 8.5% for CO, 4.1% for HCO+, 1.5% for SiO and 1.6% for CH3CN. The prediction accuracy depends on the noise level, line saturation, and number of transitions. We performed predictions upon real ALMA data. The values predicted by our neural network for this real data differ by 13% from the MADCUBA values on average. Current limitations of our tool include not considering linewidth, source size, multiple velocity components, and line blending.
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| 8. |
- Bergner, Jenny, et al.
(författare)
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Astrochemistry With the Orbiting Astronomical Satellite for Investigating Stellar Systems
- 2022
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Ingår i: Frontiers in Astronomy and Space Sciences. - : Frontiers Media SA. - 2296-987X. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Chemistry along the star- and planet-formation sequence regulates how prebiotic building blocks—carriers of the elements CHNOPS—are incorporated into nascent planetesimals and planets. Spectral line observations across the electromagnetic spectrum are needed to fully characterize interstellar CHNOPS chemistry, yet to date there are only limited astrochemical constraints at THz frequencies. Here, we highlight advances to the study of CHNOPS astrochemistry that will be possible with the Orbiting Astronomical Satellite for Investigating Stellar Systems (OASIS). OASIS is a NASA mission concept for a space-based observatory that will utilize an inflatable 14-m reflector along with a heterodyne receiver system to observe at THz frequencies with unprecedented sensitivity and angular resolution. As part of a survey of H2O and HD toward ∼100 protostellar and protoplanetary disk systems, OASIS will also obtain statistical constraints on the emission of complex organics from protostellar hot corinos and envelopes as well as light hydrides including NH3 and H2S toward protoplanetary disks. Line surveys of high-mass hot cores, protostellar outflow shocks, and prestellar cores will also leverage the unique capabilities of OASIS to probe high-excitation organics and small hydrides, as is needed to fully understand the chemistry of these objects.
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| 9. |
- Brunetti, Nathan, et al.
(författare)
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Highly turbulent gas on GMC scales in NGC 3256, the nearest luminous infrared galaxy
- 2021
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 500:4, s. 4730-4748
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Tidskriftsartikel (refereegranskat)abstract
- We present the highest resolution CO (2-1) observations obtained to date (0.25 arcsec) of NGC 3256 and use them to determine the detailed properties of the molecular interstellar medium in the central 6 kpc of this merger. Distributions of physical quantities are reported from pixel-by-pixel measurements at 55 and 120 pc scales and compared to disc galaxies observed by PHANGS-ALMA (Physics at High Angular resolution in Nearby GalaxieS with Atacama Large Millimeter/Submillimeter Array). Mass surface densities range from 8 to 5500 M-circle dot pc(-2) and velocity dispersions from 10 to 200 km s(-1). Peak brightness temperatures as large as 37 K are measured, indicating the gas in NGC 3256 may be hotter than all regions in nearby disc galaxies measured by PHANGS-ALMA. Brightness temperatures even surpass those in the overlap region of NGC 4038/9 at the same scales. The majority of the gas appears unbound with median virial parameters of 7-19, although external pressure may bind some of the gas. High internal turbulent pressures of 10(5)-10(10) K cm(-3) are found. Given the lack of significant trends in surface density, brightness temperature, and velocity dispersion with physical scale we argue the molecular gas is made up of a smooth medium down to 55 pc scales, unlike the more structured medium found in the PHANGS-ALMA disc galaxies.
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| 10. |
- Jutte, E., et al.
(författare)
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The molecular gas content of the advanced S plus E merger NGC4441 Evidence for an extended decoupled nuclear disc?
- 2010
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 509:1, s. A19-
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Tidskriftsartikel (refereegranskat)abstract
- Context. Despite their importance to galaxy evolution, mergers between a spiral and an elliptical (S+E mergers) have been poorly studied so far. NGC 4441 is a nearby candidate of an advanced remnant of such a merger, showing typical tidal structures such as an optical tail and two shells as well as two Hi tails. Aims. Studying the molecular gas content provides clues about the impact of a recent merger event on the star formation. Simulations of S+E mergers yield conflicting predictions about both the strength and the extent of an induced starburst. Thus, observations of the amount and the distribution of the molecular gas, the raw material of star formation, are needed to understand the influence of the merger on the star formation history. Methods. (CO)-C-12 and (CO)-C-13 (1-0) and (2-1) observations were obtained using the Onsala Space Observatory 20 m and IRAM 30 m telescope as well as the Plateau de Bure interferometer. These data allow us to carry out a basic analysis of the molecular gas properties, such as estimates of the molecular gas mass, temperature, and density and the star formation efficiency. Results. The CO observations detect an extended molecular gas reservoir out to similar to 4 kpc, with a total molecular gas mass of similar to 5 x 10(8) M-circle dot. Furthermore, high resolution imaging shows a central molecular gas feature, which is probably a rotating disc hosting most of the molecular gas (similar to 4 x 10(8) M-circle dot). This nuclear disc has a different sense of rotation to the large-scale Hi structure, indicating a kinematically decoupled core. We modeled the state of the interstellar medium with the radiative transfer code RADEX, using the ratios of the (CO)-C-12 to (CO)-C-13 line strenghts. The results are consistent with a diffuse (n
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