| 1. |
- Aalto, Susanne, 1964
(författare)
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Galaxies and Galaxy Nuclei: From Hot Cores to Cold Outflows
- 2015
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Ingår i: 4th ALMA Science Conference on Revolution in Astronomy with ALMA: The Third Year, Tokyo, Japan, 8-11 December. - 9781583818831 ; 499, s. 85-93
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Konferensbidrag (refereegranskat)abstract
- Studying the molecular phase of the interstellar medium in galaxies is fundamental for the understanding of the onset and evolution of star formation and the growth of supermassive black holes. We can use molecules as observational tools exploiting them as tracers of chemical, physical and dynamical conditions. In this short review, key molecules (e.g. HCN, HCO+, HNC, HC3N, CN) in identifying the nature of buried activity and its evolution are discussed including some standard astrochemical scenarios. Furthermore, we can use IR excited molecular emission to probe the very inner regions of luminous infrared galaxies (LIRGs) allowing us to get past the optically thick dust barrier of the compact obscured nuclei. We show that the vibrationally excited lines are important probes of nuclei where lines of CO, HCN and HCO+ in their vibrational ground state (v=0) may be self-absorbed. Finally, molecular outflows are briefly discussed-including the new ALMA discovery of a highly collimated (jet-like) reversed molecular outflow in the lenticular, extremely radio-quiet galaxy NGC1377.
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| 2. |
- Costagliola, Francesco, 1981, et al.
(författare)
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An ALMA Spectral Scan of the Obscured Luminous Infrared Galaxy NGC 4418
- 2015
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Ingår i: 4th ALMA Science Conference on Revolution in Astronomy with ALMA: The Third Year, Tokyo, Japan, 8-11 December. - 9781583818831 ; 499, s. 95-98
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Konferensbidrag (refereegranskat)abstract
- Until recently, the study of the molecular interstellar medium of galaxies has been mostly focused on a few, relatively abundant, molecular species. Recent attempts at modeling the molecular emission of active galaxies have shown that standard high-density tracers do not provide univocal results and are not able to discriminate between different relevant environments (e.g., star-formation vs AGN). Spectral lines surveys allow us to explore the richness of the molecular spectrum of galaxies, provide tighter constrains to astrochemical models, and find new more sensitive tracers of specific gas properties. What started as a time-consuming pioneering work has become now routinely accessible with the advent of ALMA. Here we report the results of the first ALMA spectral scan of an obscured luminous infrared galaxy (LIRG), NGC 4418. The galaxy has a very compact IR core and narrow emission lines that make it the perfect target for the study of vibrationally excited molecules. More than 300 emission lines from 45 molecular species were identified and modeled via an LTE and NLTE analysis. The molecular excitation and abundances derived offer a unique insight into the chemistry of obscured LIRGs.
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| 3. |
- Knudsen, Kirsten Kraiberg, 1976, et al.
(författare)
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Stacking of Interferometric Data: New Tools for Stacking of ALMA Data
- 2015
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Ingår i: 4th ALMA Science Conference on Revolution in Astronomy with ALMA: The Third Year, Tokyo, Japan, 8-11 December. - 9781583818831 ; 499, s. 81-82
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Radio and mm observations play an important role in determining the star formation properties of high-redshift galaxies. With the unprecedented sensitivity, ALMA now enable studies of faint, distant star-forming galaxies. However, most galaxies with low star formation rates at high redshift are too faint to be detected individually at these wavelengths. A way to study such galaxies is to use stacking. By averaging the emission of a large number of galaxies detected in optical or near-infrared surveys, we can achieve statistical detection. We investigate methods for stacking data from interferometric surveys. Interferometry poses unique challenges in stacking due to the nature of this data. We have compared stacking of uv-data with stacking of imaged data, the latter being the commonly used approach. Using simulated data, we find that uv-stacking may provide up to 50% less noise and that image based stacking systematically loses around 10% of the flux. More importantly, we find that the uv-stacking yield more robust results, especially in the case of (marginally) resolved sources and mosaicked data.
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| 4. |
- Matsushita, S., et al.
(författare)
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HCN(1-0) Maser Emission by IR Pumping from Unresolved AGN Disk/Torus Toward the Seyfert 2 Nucleus of M51?
- 2015
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Ingår i: 4th ALMA Science Conference on Revolution in Astronomy with ALMA: The Third Year, Tokyo, Japan, 8-11 December. - 9781583818831 ; 499, s. 153-154
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Konferensbidrag (refereegranskat)abstract
- We present similar to 1 '' (similar to 34 pc) resolution observations of HCN(1-0) together with CO J=1-0, 2-1, and 3-2 toward the Seyfert 2 nucleus of M51 using IRAM PdBI and SMA. HCN shows a strong emission at the nucleus only at the systemic velocity, where no obvious CO emission. HCN(1-0)/CO(1-0) > 2 at this region. Based on our radiative transfer calculations, we suggest that this strong HCN emission is affected by the IR pumping and possibly weak HCN masing. This suggests the presence of an edge-on rotating circumnuclear dense molecular gas disk or torus, which remains unresolved at our resolution.
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| 5. |
- Muller, Sebastien, 1976
(författare)
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ALMA and PKS 1830-211: the Molecular Absorption and the Background Blazar
- 2015
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Ingår i: 4th ALMA Science Conference on Revolution in Astronomy with ALMA: The Third Year, Tokyo, Japan, 8-11 December. - 9781583818831 ; 499, s. 51-54
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Konferensbidrag (refereegranskat)abstract
- The line of sight to the lensed blazar PKS1830-211 intercepts the disk of a foreground spiral galaxy at z=0.89, yielding absorption detected in 40+ molecular species. These molecules can be used as cosmological probes at a look-back time of more than half the present age of the Universe. We can determine their excitation and measure the temperature of the cosmic microwave background, compare their kinematics and set constraints on the variations of the fundamental constants, measure the isotopic ratios from different isotopologues and investigate the elemental enrichment from stellar processes, and, of course, investigate the chemistry in the disk of the absorber. Besides, we obtained ALMA data observed serendipitously at the time of a strong gamma-ray flare of the background blazar, allowing us to investigate its submm activity and the submm to gamma-ray connection. Last we present the first ALMA polarimetry results, with the highest Faraday rotation ever measured, revealing a strong magnetic field at the base of the jet in PKS 1830-211. In short, one target, but many and diverse science results !
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| 6. |
- O Gorman, Eamon, 1984, et al.
(författare)
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ALMA Observations of Anisotropic Dust Mass Loss around VY CMa
- 2015
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Ingår i: 4th ALMA Science Conference on Revolution in Astronomy with ALMA: The Third Year, Tokyo, Japan, 8-11 December. - 9781583818831 ; 499, s. 335-336
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Konferensbidrag (refereegranskat)abstract
- We present high resolution ALMA Science Verification data of the continuum emission around the highly evolved oxygen-rich red supergiant VY CMa. These data enable us to study the dust in its inner circumstellar environment at a spatial resolution of 129 mas at 321 GHz and 59 mas at 658 GHz, thus allowing us to trace dust on spatial scales down to 11 R-star (71 AU). Two prominent dust components are detected and resolved. We find that at least 17% of the dust mass around VY CMa is located in clumps ejected within a more quiescent roughly spherical stellar wind, with a quiescent dust mass loss rate of 5 x 10(-6) M-circle dot yr(-1). The anisotropic morphology of the dust indicates a continuous, directed mass loss over a few decades, suggesting that this mass loss cannot be driven by large convection cells alone.
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| 7. |
- Olofsson, Hans, 1952, et al.
(författare)
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An ALMA View of the Complex Circumstellar Environment of the Post-AGB Object HD 101584
- 2015
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Ingår i: 4th ALMA Science Conference on Revolution in Astronomy with ALMA: The Third Year, Tokyo, Japan, 8-11 December. - 9781583818831 - 9781583818824 ; 499, s. 319-322
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Konferensbidrag (refereegranskat)abstract
- We use (CO)-C-12, (CO)-C-13, and (CO)-O-18 J = 2-1 lines and 1.3 mm continuum ALMA observations to study the circumstellar evolution of the binary HD 101584, a post-AGB star and a low-mass companion, which is-most likely a post-common envelope-evolution system. It is inferred that the circumstellar medium has a bipolar hour-glass structure, seen almost pole-on, formed by an energetic, approximate to 150 km s(-1), jet. Significant amount of material resides in an unresolved central region. It is proposed that the circumstellar morphology is related to an event which took place approximate to 500 yr ago, possibly a capture event where the companion spiraled in towards the AGB star. However, the kinetic energy of the accelerated gas exceeds the released orbital energy. Hence, the observed phenomenon does not match current common-envelope scenarios, and another process must augment, or even dominate, the ejection process.
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| 8. |
- Ramstedt, Sofia, et al.
(författare)
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The Outflows of Binary AGB Stars
- 2015
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Ingår i: 4th ALMA Science Conference on Revolution in Astronomy with ALMA: The Third Year, Tokyo, Japan, 8-11 December. - 9781583818831 - 9781583818824 ; 499, s. 331-334
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Konferensbidrag (refereegranskat)abstract
- The required conditions for stars to evolve into planetary nebulae (PNs) continues to puzzle. Since PNs are found in a wide variety of shapes, processes that could sculpt circumstellar envelopes (CSEs) are being investigated. A binary companion will have a strong gravitational effect, but known binary AGB stars are rare. Using ALMA in Cycle 1 and 2, we have observed a small sample of well-studied, binary AGB stars, covering a decisive range in separation, in order to determine the influence of a companion on the circumstellar morphology of the AGB primary. The first steps toward interpreting and analyzing the data have been taken, and the results will be compared to 3D Smoothed Particle Hydrodynamics (SPH) models of the gravitational interaction.
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| 9. |
- Richards, A. M. S., et al.
(författare)
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ALMA Reveals VY CMa's Sub-mm H2O Maser and Dust Distribution
- 2015
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Ingår i: 4th ALMA Science Conference on Revolution in Astronomy with ALMA: The Third Year, Tokyo, Japan, 8-11 December. - 9781583818831 ; 499, s. 337-338
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Konferensbidrag (refereegranskat)abstract
- Cool, evolved stars have copious, enriched winds but observation constrains do not yet fully constrain models for need the dynamics of mass loss from the pulsating stellar surface to 10 stellar radii, where radiation pressure on dust is fully effective. We retrieved ALMA Science Verification data providing images of sub-mm line and continuum emission from VY CMa. This enables us to locate water masers with milli-arcsec precision and resolve the dusty continuum. The 658-, 321- and 325-GHz masers lie in irregular, thick shells at increasing distances from the centre of expansion. For the first time this is confirmed as the stellar position. Their distribution is broadly consistent with excitation models but the conditions and kinematics are complicated by wind collisions, clumping and asymmetries.
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| 10. |
- Sahai, R., et al.
(författare)
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The Coldest Object in the Universe: Probing the Mass Distribution of the Ultra-Cold Outflow and Dusty Disk in the Boomerang Nebula
- 2015
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Ingår i: 4th ALMA Science Conference on Revolution in Astronomy with ALMA: The Third Year, Tokyo, Japan, 8-11 December. - 9781583818831 ; 499, s. 327-330
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Konferensbidrag (refereegranskat)abstract
- Our Cycle 0 ALMA observations confirmed that the Boomerang Nebula is the coldest known object in the Universe, with a massive high-speed outflow that has cooled significantly below the temperature of the cosmic background (CMB). The Boomerang's prodigious mass-loss rate (0.001M(circle dot) yr(-1)) and low-luminosity (300L(circle dot)) make it a key object for understanding the remarkable transition of the circumstellar envelopes of AGB stars into bipolar planetary nebulae. We have obtained new ACA CO 1-0 data that recover much of the flux lost in the Cycle 0 data, and reveal heretofore unseen distant regions of the ultra-cold outflow reheated to temperatures above the CMB. Our CO J=3-2 data reveal the precise, highly collimated shape of an inner bipolar structure and its dense central waist, with unprecedented angular resolution (0.4 ''). The waist shows a core-halo structure in the thermal dust emission at 0.88 mm, and its derived flux at this wavelength, compared with the 3.3, 2.6, and 1.3 mm fluxes support the presence of about 5 x 10(-4) M(circle dot)of very large (similar to mm-sized), cold (similar to 30K) grains. We also find the unexpected presence of weak SO emission, possibly resulting from the release of S from grains due to high-speed shocks.
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