183 research outputs found

    Comparison of Prestellar Core Elongations and Large-scale Molecular Cloud Structures in the Lupus I Region

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    Turbulence and magnetic fields are expected to be important for regulating molecular cloud formation and evolution. However, their effects on sub-parsec to 100 parsec scales, leading to the formation of starless cores, are not well understood. We investigate the prestellar core structure morphologies obtained from analysis of the Herschel-SPIRE 350 μm maps of the Lupus I cloud. This distribution is first compared on a statistical basis to the large-scale shape of the main filament. We find the distribution of the elongation position angle of the cores to be consistent with a random distribution, which means no specific orientation of the morphology of the cores is observed with respect to the mean orientation of the large-scale filament in Lupus I, nor relative to a large-scale bent filament model. This distribution is also compared to the mean orientation of the large-scale magnetic fields probed at 350 μm with the Balloon-borne Large Aperture Telescope for Polarimetry during its 2010 campaign. Here again we do not find any correlation between the core morphology distribution and the average orientation of the magnetic fields on parsec scales. Our main conclusion is that the local filament dynamics—including secondary filaments that often run orthogonally to the primary filament—and possibly small-scale variations in the local magnetic field direction, could be the dominant factors for explaining the final orientation of each core

    A joint ALMA-Bolocam-Planck SZ study of the pressure distribution in RX J1347.5-1145

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    We report the joint analysis of single-dish and interferometric observations of the Sunyaev-Zeldovich (SZ) effect from the galaxy cluster RX J1347.5-1145. We have developed a parametric fitting procedure that uses native imaging and visibility data, and tested it using the rich data sets from ALMA, Bolocam, and Planck available for this object. RX J1347.5-1145 is a very hot and luminous cluster showing signatures of a merger. Previous X-ray-motivated SZ studies have highlighted the presence of an excess SZ signal south-east of the X-ray peak, which was generally interpreted as a strong, shock-induced pressure perturbation. Our model, when centred at the X-ray peak, confirms this. However, the presence of two almost equally bright giant elliptical galaxies separated by ∼100  kpc\sim100\;{\rm kpc} makes the choice of the cluster centre ambiguous, and allows for considerable freedom in modelling the structure of the galaxy cluster. For instance, we have shown that the SZ signal can be well-described by a single smooth ellipsoidal generalized Navarro-Frenk-White profile, where the best-fitting centroid is located between the two brightest cluster galaxies. This leads to a considerably weaker excess SZ signal from the south-eastern substructure. Further, the most prominent features seen in the X-ray can be explained as predominantly isobaric structures, alleviating the need for highly supersonic velocities, although overpressurized regions associated with the moving subhaloes are still present in our model.Comment: 20 pages (including appendices), 11 figures, and 4 tables; accepted for publication in MNRA

    The ALMA2030 Wideband Sensitivity Upgrade

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    The Wideband Sensitivity Upgrade (WSU) is the top priority initiative for the ALMA2030 Development Roadmap. The WSU will initially double, and eventually quadruple, ALMA's system bandwidth and will deliver improved sensitivity by upgrading the receivers, digital electronics and correlator. The WSU will afford significant improvements for every future ALMA observation, whether it is for continuum or spectral line science. The continuum imaging speed will increase by a factor of 3 for the 2x bandwidth upgrade, plus any gains from improved receiver temperatures. The spectral line imaging speed will improve by a factor of 2-3. The improvements provided by the WSU will be most dramatic for high spectral resolution observations, where the instantaneous bandwidth correlated at 0.1-0.2 km/s resolution will increase by 1-2 orders of magnitude in most receiver bands. The improved sensitivity and spectral tuning grasp will open new avenues of exploration and enable more efficient observations. The impact will span the vast array of topics that embodies ALMA's motto "In Search of our Cosmic Origins". The WSU will greatly expand the chemical inventory of protoplanetary disks, which will have profound implications for how and when planets form. Observations of the interstellar medium will measure a variety of molecular species to build large samples of clouds, cores and protostars. The WSU will also enable efficient surveys of galaxies at high redshift. The first elements of the WSU will be available later this decade, including a wideband Band 2 receiver, a wideband upgrade to Band 6, new digitizers and digital transmission system, and a new correlator. Other upgrades are under study, including the newly developed ACA spectrometer and upgrades to Bands 9 and 10. The gains enabled by the WSU will further enhance ALMA as the world leading facility for millimeter/submillimeter astronomy. [Abridged]Comment: 59 pages, 36 figures; ALMA Memo 621 at https://library.nrao.edu/alma.shtm

    Lupus I Observations from the 2010 Flight of the Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry

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    The Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry (BLASTPol) was created by adding polarimetric capability to the BLAST experiment that was flown in 2003, 2005, and 2006. BLASTPol inherited BLAST's 1.8 m primary and its Herschel/SPIRE heritage focal plane that allows simultaneous observation at 250, 350, and 500 μm. We flew BLASTPol in 2010 and again in 2012. Both were long duration Antarctic flights. Here we present polarimetry of the nearby filamentary dark cloud Lupus I obtained during the 2010 flight. Despite limitations imposed by the effects of a damaged optical component, we were able to clearly detect submillimeter polarization on degree scales. We compare the resulting BLASTPol magnetic field map with a similar map made via optical polarimetry. (The optical data were published in 1998 by J. Rizzo and collaborators.) The two maps partially overlap and are reasonably consistent with one another. We compare these magnetic field maps to the orientations of filaments in Lupus I, and we find that the dominant filament in the cloud is approximately perpendicular to the large-scale field, while secondary filaments appear to run parallel to the magnetic fields in their vicinities. This is similar to what is observed in Serpens South via near-IR polarimetry, and consistent with what is seen in MHD simulations by F. Nakamura and Z. Li

    The Physics of Galaxy Cluster Outskirts

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    As the largest virialized structures in the universe, galaxy clusters continue to grow and accrete matter from the cosmic web. Due to the low gas density in the outskirts of clusters, measurements are very challenging, requiring extremely sensitive telescopes across the entire electromagnetic spectrum. Observations using X-rays, the Sunyaev-Zeldovich effect, and weak lensing and galaxy distributions from the optical band, have over the last decade helped to unravel this exciting new frontier of cluster astrophysics, where the infall and virialization of matter takes place. Here, we review the current state of the art in our observational and theoretical understanding of cluster outskirts, and discuss future prospects for exploration using newly planned and proposed observatories.Comment: 56 pages. Review paper. Published in Space Science Review
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