25 research outputs found

    Physical Properties of Giant Molecular Clouds in the Large Magellanic Cloud

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    The Magellanic Mopra Assessment (MAGMA) is a high angular resolution CO mapping survey of giant molecular clouds (GMCs) in the Large and Small Magellanic Clouds using the Mopra Telescope. Here we report on the basic physical properties of 125 GMCs in the LMC that have been surveyed to date. The observed clouds exhibit scaling relations that are similar to those determined for Galactic GMCs, although LMC clouds have narrower linewidths and lower CO luminosities than Galactic clouds of a similar size. The average mass surface density of the LMC clouds is 50 Msol/pc2, approximately half that of GMCs in the inner Milky Way. We compare the properties of GMCs with and without signs of massive star formation, finding that non-star-forming GMCs have lower peak CO brightness than star-forming GMCs. We compare the properties of GMCs with estimates for local interstellar conditions: specifically, we investigate the HI column density, radiation field, stellar mass surface density and the external pressure. Very few cloud properties demonstrate a clear dependence on the environment; the exceptions are significant positive correlations between i) the HI column density and the GMC velocity dispersion, ii) the stellar mass surface density and the average peak CO brightness, and iii) the stellar mass surface density and the CO surface brightness. The molecular mass surface density of GMCs without signs of massive star formation shows no dependence on the local radiation field, which is inconsistent with the photoionization-regulated star formation theory proposed by McKee (1989). We find some evidence that the mass surface density of the MAGMA clouds increases with the interstellar pressure, as proposed by Elmegreen (1989), but the detailed predictions of this model are not fulfilled once estimates for the local radiation field, metallicity and GMC envelope mass are taken into account.Comment: 28 pages, 10 figures, accepted by MNRA

    Far-infrared observations of a massive cluster forming in the Monoceros R2 filament hub

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    We present far-infrared observations of Monoceros R2 (a giant molecular cloud at approximately 830 pc distance, containing several sites of active star formation), as observed at 70 ÎŒm, 160 ÎŒm, 250 ÎŒm, 350 ÎŒm, and 500 ÎŒm by the Photodetector Array Camera and Spectrometer (PACS) and Spectral and Photometric Imaging Receiver (SPIRE) instruments on the Herschel Space Observatory as part of the Herschel imaging survey of OB young stellar objects (HOBYS) Key programme. The Herschel data are complemented by SCUBA-2 data in the submillimetre range, and WISE and Spitzer data in the mid-infrared. In addition, C18O data from the IRAM 30-m Telescope are presented, and used for kinematic information. Sources were extracted from the maps with getsources, and from the fluxes measured, spectral energy distributions were constructed, allowing measurements of source mass and dust temperature. Of 177 Herschel sources robustly detected in the region (a detection with high signal-to-noise and low axis ratio at multiple wavelengths), including protostars and starless cores, 29 are found in a filamentary hub at the centre of the region (a little over 1% of the observed area). These objects are on average smaller, more massive, and more luminous than those in the surrounding regions (which together suggest that they are at a later stage of evolution), a result that cannot be explained entirely by selection effects. These results suggest a picture in which the hub may have begun star formation at a point significantly earlier than the outer regions, possibly forming as a result of feedback from earlier star formation. Furthermore, the hub may be sustaining its star formation by accreting material from the surrounding filaments

    A <i>Herschel</i> and BIMA study of the sequential star formation near the W 48A H II region

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    We present the results of Herschel HOBYS (Herschel imaging survey of OB Young Stellar objects) photometric mapping combined with Berkeley Illinois Maryland Association (BIMA) observations and additional archival data, and perform an in-depth study of the evolutionary phases of the star-forming clumps in W 48A and their surroundings. Age estimates for the compact sources were derived from bolometric luminosities and envelope masses, which were obtained from the dust continuum emission, and agree within an order of magnitude with age estimates from molecular line and radio data. The clumps in W 48A are linearly aligned by age (east-old to west-young): we find a ultra-compact (UC) H II region, a young stellar object (YSO) with class II methanol maser emission, a YSO with a massive outflow and finally the NH2D prestellar cores from Pillai et al. This remarkable positioning reflects the (star) formation history of the region. We find that it is unlikely that the star formation in the W 48A molecular cloud was triggered by the UC H II region and discuss the Aquila supershell expansion as a major influence on the evolution of W 48A. We conclude that the combination of Herschel continuum data with interferometric molecular line and radio continuum data is important to derive trustworthy age estimates and interpret the origin of large-scale structures through kinematic information

    Leveraging In-Home Supportive Services Programs to Engage People in Advance Care Planning: Input from Staff, Providers, and Client Stakeholders

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    Background: In-Home Supportive Services (IHSS) cares for millions of Medicaid-eligible older adults who are often homebound and socially isolated. Advance care planning (ACP) can be challenging for this population, and IHSS programs may play an important role. Objective: To explore the feasibility of an IHSS ACP program for frail older adults. Design: Semistructured focus groups. Setting/Subjects: Fifty IHSS stakeholders (20 administrators, 9 case managers, 13 in-home caregivers, and 8 clients) participated in 10 focus groups in San Francisco. Measurements: Qualitative thematic content analysis by two independent coders. Results: Four main themes emerged: (1) Unmet needs: patients' wishes unknown during a medical crisis, lack of education/training for clients and staff; (2) Barriers: conflict of interest and potential medical overreach of IHSS caregivers, lack of billing avenues, time limitations, and cultural, literacy, and language barriers; (3) Facilitators: leveraging established workflows, available technology, and training programs; and (4) Implementation: use a tailored, optional approach based on clients' readiness, focus on case managers not caregivers to prevent conflict of interest; use established intake, follow-up, and training procedures; consider cultural and literacy-appropriate messaging; and standardize easy-to-use procedures, simple scripts, and educational guides, within established workflow to support case managers. Conclusions: An IHSS ACP program is important and feasible for Medicaid-eligible, frail older adults. Implementation suggestions for success by IHSS stakeholders include focusing on case managers rather than in-home caregivers to prevent conflict of interest; tailoring programs to clients' readiness, literacy, and language; creating educational programs for IHSS staff, clients, and community; and standardizing easy-to-use guides and procedures into IHSS workflows
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