| 1. |
- Adamo, Angela, et al.
(författare)
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Legacy ExtraGalactic UV Survey with The Hubble Space Telescope : Stellar Cluster Catalogs and First Insights Into Cluster Formation and Evolution in NGC 628
- 2017
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Ingår i: Astrophysical Journal. - : IOP PUBLISHING LTD. - 0004-637X .- 1538-4357. ; 841:2
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Tidskriftsartikel (refereegranskat)abstract
- We report the large effort that is producing comprehensive high-level young star cluster (YSC) catalogs for a significant fraction of galaxies observed with the Legacy ExtraGalactic UV Survey (LEGUS) Hubble treasury program. We present the methodology developed to extract cluster positions, verify their genuine nature, produce multiband photometry (from NUV to NIR), and derive their physical properties via spectral energy distribution fitting analyses. We use the nearby spiral galaxy NGC 628 as a test case for demonstrating the impact that LEGUS will have on our understanding of the formation and evolution of YSCs and compact stellar associations within their host galaxy. Our analysis of the cluster luminosity function from the UV to the NIR finds a steepening at the bright end and at all wavelengths suggesting a dearth of luminous clusters. The cluster mass function of NGC 628 is consistent with a power-law distribution of slopes similar to-2 and a truncation of a few times 10(5) M-circle dot. After their formation, YSCs and compact associations follow different evolutionary paths. YSCs survive for a longer time frame, confirming their being potentially bound systems. Associations disappear on timescales comparable to hierarchically organized star-forming regions, suggesting that they are expanding systems. We find massindependent cluster disruption in the inner region of NGC 628, while in the outer part of the galaxy there is little or no disruption. We observe faster disruption rates for low mass (<= 10(4) M-circle dot) clusters, suggesting that a massdependent component is necessary to fully describe the YSC disruption process in NGC 628.
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| 2. |
- Calzetti, D., et al.
(författare)
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LEGACY EXTRAGALACTIC UV SURVEY (LEGUS) WITH THE HUBBLE SPACE TELESCOPE. I. SURVEY DESCRIPTION
- 2015
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Ingår i: Astronomical Journal. - : American Astronomical Society. - 0004-6256 .- 1538-3881. ; 149:2
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Tidskriftsartikel (refereegranskat)abstract
- The Legacy ExtraGalactic UV Survey (LEGUS) is a Cycle 21 Treasury program on the Hubble Space Telescope aimed at the investigation of star formation and its relation with galactic environment in nearby galaxies, from the scales of individual stars to those of similar to kiloparsec-size clustered structures. Five-band imaging from the nearultraviolet to the I band with the Wide-Field Camera 3 (WFC3), plus parallel optical imaging with the Advanced Camera for Surveys (ACS), is being collected for selected pointings of 50 galaxies within the local 12 Mpc. The filters used for the observations with the WFC3 are F275W(lambda 2704 angstrom), F336W(lambda 3355 angstrom), F438W(lambda 4325 angstrom), F555W(lambda 5308 angstrom), and F814W(lambda 8024 angstrom); the parallel observations with the ACS use the filters F435W (lambda 4328 angstrom), F606W(lambda 5921 angstrom), and F814W(lambda 8057 angstrom). The multiband images are yielding accurate recent (less than or similar to 50 Myr) star formation histories from resolved massive stars and the extinction-corrected ages and masses of star clusters and associations. The extensive inventories of massive stars and clustered systems will be used to investigate the spatial and temporal evolution of star formation within galaxies. This will, in turn, inform theories of galaxy evolution and improve the understanding of the physical underpinning of the gas-star formation relation and the nature of star formation at high redshift. This paper describes the survey, its goals and observational strategy, and the initial scientific results. Because LEGUS will provide a reference survey and a foundation for future observations with the James Webb Space Telescope and with ALMA, a large number of data products are planned for delivery to the community.
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| 3. |
- Elmegreen, B.G., et al.
(författare)
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Hubble Space Telescope Observations of the Interacting Galaxies NGC 2207 and IC 2163
- 2000
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Ingår i: Astronomical Journal. - : American Astronomical Society. - 1538-3881 .- 0004-6256. ; 120:2, s. 630-644
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Tidskriftsartikel (refereegranskat)abstract
- Hubble Space Telescope (HST) images of the galaxies NGC 2207 and IC 2163 show star formation and dust structures in a system that has experienced a recent grazing encounter. Tidal forces from NGC 2207 compressed and elongated the disk of IC 2163, forming an oval ridge of star formation along a caustic where the perturbed gas rebounded after its inward excursion. Gas flowing away from this ridge has a peculiar structure characterized by thin parallel dust filaments transverse to the direction of motion. The filaments become thicker and longer as the gas approaches the tidal arm. Star formation that occurs in the filaments consistently lags behind, as if the exponential disk pressure gradient pushes outward on the gas but not on the young stars. Numerical models suggest that the filaments come from flocculent spiral arms that were present before the interaction. The arms stretch out into parallel filaments as the tidal tail forms. A dust lane at the outer edge of the tidal tail is a shock front where the flow abruptly changes direction. Gas at small-to-intermediate radii along this edge flows back toward the galaxy, while elsewhere in the tidal arm, the gas flows outward.A spiral arm of NGC 2207 that is backlit by IC 2163 is seen with HST to contain several parallel, knotty filaments spanning the full width of the arm. These filaments are probably shock fronts in a density wave. The parallel structure suggests that the shocks occur in several places throughout the arm, or that the interarm gas is composed of spiral-like wisps that merge together in the arms. Blue clusters of star formation inside the clumps of these dust lanes show density-wave triggering in unprecedented detail. The star formation process seems to be one of local gravitational collapse, rather than cloud collisions. Spiral arms inside the oval of IC 2163 have a familiar geometry reminiscent of a bar, although there is no obvious stellar bar. The shape and orientation of these arms suggest they could be the result of inner Lindblad resonance–related orbits in the cos 2θ tidal potential that formed the oval. Their presence suggests that tidal forces alone may initiate a temporary nuclear gas flow and eventual starburst without first forming a stellar bar. Several emission structures resembling jets or conical flows that are 100–1000 pc long appear in these galaxies. In the western arm of NGC 2207, there is a dense dark cloud with a conical shape 400 pc long and a bright compact cluster at the tip, and there is a conical emission nebula of the same length that points away from the cluster in the other direction. This region also coincides with a nonthermal radio continuum source that is ~1000 times the luminosity of Cas A at λ = 20 cm. Surrounding clusters in arclike patterns may have been triggered by enormous explosions.
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| 4. |
- Schick-Makaroff, K., et al.
(författare)
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An Evidence-Based Theory About PRO Use in Kidney Care: A Realist Synthesis
- 2022
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Ingår i: Patient-Patient Centered Outcomes Research. - : Springer Science and Business Media LLC. - 1178-1653 .- 1178-1661. ; 15, s. 21-38
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Tidskriftsartikel (refereegranskat)abstract
- Background There is international interest on the use of patient-reported outcomes (PROs) in nephrology. Objectives Our objectives were to develop a kidney-specific program theory about use of PROs in nephrology that may enhance person-centered care, both at individual and aggregated levels of care, and to test and refine this theory through a systematic review of the empirical literature. Together, these objectives articulate what works or does not work, for whom, and why. Methods Realist synthesis methodology guided the electronic database and gray literature searches (in January 2017 and October 2018), screening, and extraction conducted independently by three reviewers. Sources included all nephrology patients and/or practitioners. Through a process of extraction and synthesis, each included source was examined to assess how contexts may trigger mechanisms to influence specific outcomes. Results After screening 19,961 references, 84 theoretical and 34 empirical sources were used. PROs are proposed to be useful for providing nephrology care through three types of use. The first type is use of individual-level PRO data at point of care, receiving the majority of theoretical and empirical explorations. Clinician use to support person-centered care, and patient use to support patient engagement, are purported to improve satisfaction, health, and quality of life. Contextual factors specific to the kidney care setting that may influence the use of PRO data include the complexity of kidney disease symptom burden, symptoms that may be stigmatized, comorbidities, and time or administrative constraints in dialysis settings. Electronic collection of PROs may facilitate PRO use given these contexts. The second type is use of aggregated PRO data at point of care, including public reporting of PROs to inform decisions at point of care and improve quality of care, and use of PROs for treatment decisions. The third type is use of aggregated PRO data by organizations, including publicly available PRO data to compare centers. In single-payer systems, regular collection of PROs by dialysis centers can be achieved through economic incentives. Both the second and third types of PRO use include pressures that may trigger quality improvement processes. Conclusion The current state of the evidence is primarily theoretical. There is pressing need for empirical research to improve the evidence-base of PRO use at individual and aggregated levels of nephrology care.
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