Suchergebnisse

Statistical analysis of velocity fluctuations in the interstellar medium (ISM) of the Milky Way and NGC 4321 show that the motion of molecular gas over scales ranging from 0.1 to 1,000 pc is similar, and consistent with that generated by a combination of gravity and turbulence. ISM structure at one scale is therefore linked to structure at other scales. The density structure of the interstellar medium determines where stars form and release energy, momentum and heavy elements, driving galaxy evolution(1-4). Density variations are seeded and amplified by gas motion, but the exact nature of this motion is unknown across spatial scales and galactic environments(5). Although dense star-forming gas probably emerges from a combination of instabilities(6,7), convergent flows(8)and turbulence(9), establishing the precise origin is challenging because it requires gas motion to be quantified over many orders of magnitude in spatial scale. Here we measure(10-12)the motion of molecular gas in the Milky Way and in nearby galaxy NGC 4321, assembling observations that span a spatial dynamic range 10(-1)-10(3) pc. We detect ubiquitous velocity fluctuations across all spatial scales and galactic environments. Statistical analysis of these fluctuations indicates how star-forming gas is assembled. We discover oscillatory gas flows with wavelengths ranging from 0.3-400 pc. These flows are coupled to regularly spaced density enhancements that probably form via gravitational instabilities(13,14). We also identify stochastic and scale-free velocity and density fluctuations, consistent with the structure generated in turbulent flows(9). Our results demonstrate that the structure of the interstellar medium cannot be considered in isolation. Instead, its formation and evolution are controlled by nested, interdependent flows of matter covering many orders of magnitude in spatial scale. ; German Research Foundation (DFG) KR4801/1-1 KR4801/2-1 European Research Council (ERC) 714907 European Union's Horizon 2020 research and innovation program 639459 National Science Foundation (NSF) 1615105 1615109 1653300 NASA under ADAP NNX16AF48G NNX17AF39G Natural Sciences and Engineering Research Council of Canada RGPIN-2017-03987 National Science Foundation (NSF) 1816715 AST-9800334 AST-0098562 AST-0100793 AST-0228993 AST-0507657 German Research Foundation (DFG) SFB 881 Heidelberg Cluster of Excellence STRUCTURES of Germany's Excellence Strategy EXC-2181/1-390900948 ERC under the European Union's Horizon 2020 research and innovation programme 694343 European Union's Horizon 2020 research and innovation programme 726384 Programme National 'Physique et Chimie du Milieu Interstellaire' (PCMI) of CNRS/INSU INC/INP French Atomic Energy Commission Centre National D'etudes Spatiales Australian Government Australian Research Council UNSW, Sydney Monash Universities Commonwealth Scientific & Industrial Research Organisation (CSIRO)

Observing nearby galaxies with submillimeter telescopes on the ground has two major challenges. First, the brightness is significantly reduced at long submillimeter wavelengths compared to the brightness at the peak of the dust emission. Second, it is necessary to use a high-pass spatial filter to remove atmospheric noise on large angular scales, which has the unwelcome side effect of also removing the galaxy's large-scale structure. We have developed a technique for producing high-resolution submillimeter images of galaxies of large angular size by using the telescope on the ground to determine the small-scale structure (the large Fourier components) and a space telescope (Herschel or Planck) to determine the large-scale structure (the small Fourier components). Using this technique, we are carrying out the HARP and SCUBA-2 High Resolution Terahertz Andromeda Galaxy Survey (HASHTAG), an international Large Program on the James Clerk Maxwell Telescope, with one aim being to produce the first high-fidelity high-resolution submillimeter images of Andromeda. In this paper, we describe the survey, the method we have developed for combining the space-based and ground-based data, and we present the first HASHTAG images of Andromeda at 450 and 850 mu m. We also have created a method to predict the CO(J = 3-2) line flux across M31, which contaminates the 850 mu m band. We find that while normally the contamination is below our sensitivity limit, it can be significant (up to 28%) in a few of the brightest regions of the 10 kpc ring. We therefore also provide images with the predicted line emission removed. ; National Key R&D Program of China 2017YFA0402700 UK Research & Innovation (UKRI) Science & Technology Facilities Council (STFC) Canada Foundation for Innovation CGIAR European Regional Development Fund (ERDF) via the Welsh Government UK Research & Innovation (UKRI) Science & Technology Facilities Council (STFC) ST/K000926/1 European Research Council (ERC) European Commission ERC-2014-CoG-647939 National Research Foundation 2018R1D1A1B07048314 National Natural Science Foundation of China (NSFC) 12073002 11721303 11991052 STFC consolidated grant "Astrophysics at Oxford" ST/H002456/1 ST/K00106X/1 UK Research & Innovation (UKRI) Science & Technology Facilities Council (STFC) ST/S00033X/1 National Natural Science Foundation of China (NSFC) 11873086 U1631237 11873028 Yunnan Province of China 2017HC018 Chinese Academy of Sciences National Basic Research Program of China 2017YFA0402704 2016YFA0400702 National Natural Science Foundation of China (NSFC) 11861131007 12033004 Chinese Academy of Sciences Key Research Program of Frontier Sciences QYZDJ-SSW-SLH008 National Commission for Scientific and Technological Research of Chile (CONICYT) through a CAS-CONICYT Joint Postdoctoral Fellowship Academia Sinica - Taiwan AS-IA-106-M03 Ministry of Science and Technology, Taiwan MOST107-2119-M-001-031-MY3 European Research Council (ERC) European Commission SNDUST ERC-2015-AdG-694520 National Key Research and Development Program of China 2017YFA0402703 National Science Centre, Poland through the POLONEZ 2015/19/P/ST9/04010 SONATA BIS grant 2018/30/E/ST9/00208 Natural Sciences and Engineering Research Council of Canada (NSERC) CGIAR Canada Research Chairs European Research Council (ERC) 694343 ; Versión publicada - versión final del editor

The PHANGS program is building the first data set to enable the multiphase, multiscale study of star formation across the nearby spiral galaxy population. This effort is enabled by large survey programs with the Atacama Large Millimeter/submillimeter Array (ALMA), MUSE on the Very Large Telescope, and the Hubble Space Telescope (HST), with which we have obtained CO(2–1) imaging, optical spectroscopic mapping, and high-resolution UV– optical imaging, respectively. Here, we present PHANGS-HST, which has obtained NUV–U–B–V–I imaging of the disks of 38 spiral galaxies at distances of 4–23 Mpc, and parallel V- and I-band imaging of their halos, to provide a census of tens of thousands of compact star clusters and multiscale stellar associations. The combination of HST, ALMA, and VLT/MUSE observations will yield an unprecedented joint catalog of the observed and physical properties of ∼100,000 star clusters, associations, H II regions, and molecular clouds. With these basic units of star formation, PHANGS will systematically chart the evolutionary cycling between gas and stars across a diversity of galactic environments found in nearby galaxies. We discuss the design of the PHANGS-HST survey and provide an overview of the HST data processing pipeline and first results. We highlight new methods for selecting star cluster candidates, morphological classification of candidates with convolutional neural networks, and identification of stellar associations over a range of physical scales with a watershed algorithm. We describe the cross-observatory imaging, catalogs, and software products to be released. The PHANGS high-level science products will seed a broad range of investigations, in particular, the study of embedded stellar populations and dust with the James Webb Space Telescope, for which a PHANGS Cycle 1 Treasury program to obtain eight-band 2–21 μm imaging has been approved. ; National Aeronautics & Space Administration (NASA) NAS 5-26555 Aparece en contenido como:NASA 15654 German Research Foundation (DFG) KR4801/1-1 KR4801/2-1 European Research Council (ERC) 714907 Aparece en contenido como:European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program via the ERC Starting Grant MUSTANG 726384/Empire 694343 Aparece en contenido como:European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program German Research Foundation (DFG) SFB 881 138713538 Aparece en contenido como:DFG via the collaborative research center Heidelberg Cluster of Excellence STRUCTURES EXC-2181/1-390900948 ERC via the ERC Synergy Grant ECOGAL 855130 German Research Foundation (DFG) SFB 881 138713538 KR4598/2-1 Natural Sciences and Engineering Research Council of Canada (NSERC) RGPIN-2017-03987 ; Versión publicada - versión final del editor