| 1. |
- Aalto, Susanne, 1964, et al.
(författare)
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Luminous, pc-scale CO 6-5 emission in the obscured nucleus of NGC 1377
- 2017
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 608, s. A22-
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Tidskriftsartikel (refereegranskat)abstract
- High-resolution submillimeter line and continuum observations are important in probing the morphology, column density, and dynamics of the molecular gas and dust around obscured active galactic nuclei (AGNs). With high-resolution (0'.06 x 0'.05 (6 x 5 pc)) ALMA 690 GHz observations we have found bright (T-B > 80 K) and compact (full width half maximum size (FWHM) size of 10 x 7 pc) CO 6-5 line emission in the nuclear region of the extremely radio-quiet galaxy NGC 1377. The CO 6-5 intensity is partially aligned with the previously discovered jet/outflow of NGC 1377 and is tracing dense (n > 10(4 )cm(-3)) hot molecular gas at the base of the outflow. The velocity structure is complex and shifts across the jet/outflow are discussed in terms of separate overlapping kinematical components or rotation. High-velocity gas (Delta v +/- 145 km s(-1)) is detected inside r
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| 2. |
- 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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| 3. |
- Falstad, Niklas, 1987, et al.
(författare)
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Hidden molecular outflow in the LIRG Zw 049.057
- 2018
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 609
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Tidskriftsartikel (refereegranskat)abstract
- Context. Feedback in the form of mass outflows driven by star formation or active galactic nuclei is a key component of galaxy evolution. The luminous infrared galaxy Zw 049.057 harbours a compact obscured nucleus with a possible far-infrared signature of outflowing molecular gas. Due to the high optical depths at far-infrared wavelengths, however, the interpretation of the outflow signature is uncertain. At millimeter and radio wavelengths, the radiation is better able to penetrate the large columns of gas and dust responsible for the obscuration. Aims. We aim to investigate the molecular gas distribution and kinematics in the nucleus of Zw 049.057 in order to confirm and locate the molecular outflow, with the ultimate goal to understand how the nuclear activity affects the host galaxy. Methods. We used high angular resolution observations from the Submillimeter Array (SMA), the Atacama Large Millimeter/submillimeter Array (ALMA), and the Karl G. Jansky Very Large Array (VLA) to image the CO J = 2-1 and J = 6-5 emission, the 690 GHz continuum, the radio centimeter continuum, and absorptions by rotationally excited OH. Results. The CO line profiles exhibit wings extending ~ 300 km s -1 beyond the systemic velocity. At centimeter wavelengths, we find a compact (~ 40 pc) continuum component in the nucleus, with weaker emission extending several 100 pc approximately along the major and minor axes of the galaxy. In the OH absorption lines toward the compact continuum, wings extending to a similar velocity as for the CO are only seen on the blue side of the profile. The weak centimeter continuum emission along the minor axis is aligned with a highly collimated, jet-like dust feature previously seen in near-infrared images of the galaxy. Comparison of the apparent optical depths in the OH lines indicate that the excitation conditions in Zw 049.057 differ from those within other OH megamaser galaxies. Conclusions. We interpret the wings in the spectral lines as signatures of a nuclear molecular outflow. A relation between this outflow and the minor axis radio feature is possible, although further studies are required to investigate this possible association and understand the connection between the outflow and the nuclear activity. Finally, we suggest that the differing OH excitation conditions are further evidence that Zw 049.057 is in a transition phase between megamaser and kilomaser activity.
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| 4. |
- Martin, S., et al.
(författare)
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ALCHEMI, an ALMA Comprehensive High-resolution Extragalactic Molecular Inventory: Survey presentation and first results from the ACA array
- 2021
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 656
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Tidskriftsartikel (refereegranskat)abstract
- Context. The interstellar medium is the locus of physical processes affecting the evolution of galaxies which drive or are the result of star formation activity, supermassive black hole growth, and feedback. The resulting physical conditions determine the observable chemical abundances that can be explored through molecular emission observations at millimeter and submillimeter wavelengths. Aims. Our goal is to unveiling the molecular richness of the central region of the prototypical nearby starburst galaxy NGC 253 at an unprecedented combination of sensitivity, spatial resolution, and frequency coverage. Methods. We used the Atacama Large Millimeter/submillimeter Array (ALMA), covering a nearly contiguous 289 GHz frequency range between 84.2 and 373.2 GHz, to image the continuum and spectral line emission at 1.6″(∼28 pc) resolution down to a sensitivity of 30 - 50 mK. This article describes the ALMA Comprehensive High-resolution Extragalactic Molecular Inventory (ALCHEMI) large program. We focus on the analysis of the spectra extracted from the 15″ (∼255 pc) resolution ALMA Compact Array data. Results. We modeled the molecular emission assuming local thermodynamic equilibrium with 78 species being detected. Additionally, multiple hydrogen and helium recombination lines are identified. Spectral lines contribute 5 to 36% of the total emission in frequency bins of 50 GHz. We report the first extragalactic detections of C2H5OH, HOCN, HC3HO, and several rare isotopologues. Isotopic ratios of carbon, oxygen, sulfur, nitrogen, and silicon were measured with multiple species. Concluison. Infrared pumped vibrationaly excited HCN, HNC, and HC3N emission, originating in massive star formation locations, is clearly detected at low resolution, while we do not detect it for HCO+. We suggest high temperature conditions in these regions driving a seemingly "carbon-rich"chemistry which may also explain the observed high abundance of organic species close to those in Galactic hot cores. The Lvib/LIR ratio was used as a proxy to estimate a 3% contribution from the proto super star cluster to the global infrared emission. Measured isotopic ratios with high dipole moment species agree with those within the central kiloparsec of the Galaxy, while those derived from 13C/18O are a factor of five larger, confirming the existence of multiple interstellar medium components within NGC 253 with different degrees of nucleosynthesis enrichment. The ALCHEMI data set provides a unique template for studies of star-forming galaxies in the early Universe.
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