The Extended Environment of M17: A Star Formation History

M17 is one of the youngest and most massive nearby star-formation regions in the Galaxy. It features a bright H II region erupting as a blister from the side of a giant molecular cloud (GMC). Combining photometry from the Spitzer GLIMPSE survey with complementary infrared (IR) surveys, we identify candidate young stellar objects (YSOs) throughout a 1.5 deg x 1 deg field that includes the M17 complex. The long sightline through the Galaxy behind M17 creates significant contamination in our YSO sample from unassociated sources with similar IR colors. Removing contaminants, we produce a highly-reliable catalog of 96 candidate YSOs with a high probability of association with the M17 complex. We fit model spectral energy distributions to these sources and constrain their physical properties. Extrapolating the mass function of 62 intermediate-mass YSOs (M >3 Msun), we estimate that >1000 stars are in the process of forming in the extended outer regions of M17. From IR survey images from IRAS and GLIMPSE, we find that M17 lies on the rim of a large shell structure ~0.5 deg in diameter (~20 pc at 2.1 kpc). We present new maps of CO and 13CO (J=2-1) emission, which show that the shell is a coherent, kinematic structure associated with M17 at v = 19 km/s. The shell is an extended bubble outlining the photodissociation region of a faint, diffuse H II region several Myr old. We provide evidence that massive star formation has been triggered by the expansion of the bubble. The formation of the massive cluster ionizing the M17 H II region itself may have been similarly triggered. We conclude that the star formation history in the extended environment of M17 has been punctuated by successive waves of massive star formation propagating through a GMC complex.Comment: 31 pages, 15 figures, accepted for publication in ApJ. For a version with higher-quality figures, see http://www.astro.wisc.edu/glimpse/Povich2009_M17.pd

Spitzer Space Telescope observations of the Carina Nebula: The steady march of feedback-driven star formation

We report the first results of imaging the Carina Nebula with Spitzer/IRAC, providing a catalog of point sources and YSOs based on SED fits. We discuss several aspects of the extended emission, including dust pillars that result when a clumpy molecular cloud is shredded by massive star feedback. There are few "extended green objects" (EGOs) normally taken as signposts of outflow activity, and none of the HH jets detected optically are seen as EGOs. A population of "extended red objects" tends to be found around OB stars, some with clear bow-shocks. These are dusty shocks where stellar winds collide with flows off nearby clouds. Finally, the relative distributions of O stars and subclusters of YSOs as compared to dust pillars shows that while some YSOs are located within pillars, many more stars and YSOs reside just outside pillar heads. We suggest that pillars are transient phenomena, part of a continuous outwardly propagating wave of star formation driven by massive star feedback. As pillars are destroyed, they leave newly formed stars in their wake, which are then subsumed into the young OB association. Altogether, the current generation of YSOs shows no strong deviation from a normal IMF. The number of YSOs suggests a roughly constant star-formation rate over the past 3Myr, implying that star formation in pillars constitutes an important mechanism to construct unbound OB associations. Accelerated pillars may give birth to O-type stars that, after several Myr, could appear to have formed in isolation.Comment: 25 pages, 15 figures, MNRAS accepte

Kepler eclipsing binary stars. VII. the catalogue of eclipsing binaries found in the entire Kepler data set

The primary Kepler Mission provided nearly continuous monitoring of ~200,000 objects with unprecedented photometric precision. We present the final catalog of eclipsing binary systems within the 105 deg2 Kepler field of view. This release incorporates the full extent of the data from the primary mission (Q0-Q17 Data Release). As a result, new systems have been added, additional false positives have been removed, ephemerides and principal parameters have been recomputed, classifications have been revised to rely on analytical models, and eclipse timing variations have been computed for each system. We identify several classes of systems including those that exhibit tertiary eclipse events, systems that show clear evidence of additional bodies, heartbeat systems, systems with changing eclipse depths, and systems exhibiting only one eclipse event over the duration of the mission. We have updated the period and galactic latitude distribution diagrams and included a catalog completeness evaluation. The total number of identified eclipsing and ellipsoidal binary systems in the Kepler field of view has increased to 2878, 1.3% of all observed Kepler targets

Moonlighting Proteins Hal3 and Vhs3 Form a Heteromeric PPCDC with Ykl088w in Yeast CoA Biosynthesis

Premi a l'excel·lència investigadora. 2010Unlike most other organisms, the essential five-step Coenzyme A biosynthetic pathway has not been fully resolved in yeast. Specifically, the gene(s) encoding the phosphopantothenoylcysteine decarboxylase (PPCDC) activity still remains unidentified. Sequence homology analyses suggest three candidates, namely Ykl088w, Hal3 and Vhs3, as putative PPCDC enzymes in Saccharomyces cerevisiae. Interestingly, Hal3 and Vhs3 have been characterized as negative regulatory subunits of the Ppz1 protein phosphatase. Here we show that YKL088w does not encode a third Ppz1 regulatory subunit, and that the essential roles of Ykl088w and the Hal3/Vhs3 pair are complementary, cannot be interchanged and can be attributed to PPCDC-related functions. We demonstrate that while known eukaryotic PPCDCs are homotrimers, the active yeast enzyme is a heterotrimer which consists of Ykl088w and Hal3/Vhs3 monomers that separately provides two essential catalytic residues. Our results unveil Hal3/Vhs3 as moonlighting proteins, involved in both CoA biosynthesis and protein phosphatase regulation

VORTICITY, SHOCKS, AND MAGNETIC FIELDS IN SUBSONIC, ICM- LIKE TURBULENCE

We analyze data from high resolution simulations of the generation of compressible, MHD turbulence with properties chosen to resemble conditions in galaxy clusters. In particular, the flow is driven to have turbulence Mach number M-t similar to 1/2 in an isothermal medium with an initially very weak, uniform seed magnetic field (beta = P-g/P-B= 10(6)). Since cluster turbulence is likely to result from a mix of sheared (solenoidal) and compressive forcing processes, we examine the distinct turbulence properties for both cases. In one set of simulations velocity forcing is entirely solenoidal (del . delta u= 0), while in the other it is entirely compressive (del x delta u = 0). Both cases develop a mixture of solenoidal and compressive turbulent motions, since each generates the other. The development of compressive turbulent motions leads to shocks, even when the turbulence is solenoidally forced and subsonic. Shocks, in turn, produce and amplify vorticity, which is especially important in compressively forced turbulence. To clarify those processes we include a pair of appendices that look in detail at vorticity evolution in association with shocks. From our simulation analyses we find that magnetic fields amplified to near saturation levels in predominantly solenoidal turbulence can actually enhance vorticity on small scales by concentrating and stabilizing shear. The properties, evolution rates, and relative contributions of the kinetic and magnetic turbulent elements depend strongly on the character of the forcing. Specifically, shocks are stronger, but vorticity evolution and magnetic field amplification are slower and weaker when the turbulence is compressively forced. We identify a simple relation to estimate characteristic shock strengths in terms of the turbulence Mach number and the character of the forcing. Our results will be helpful in understanding flow motions in galaxy clustersopen10

Giant Molecular Clouds in the Early-type Galaxy NGC 4526

D. Utomo, et al., “Giant Molecular Clouds in the Early-Type Galaxy NGC 4526”, The Astrophysical Journal, Vol. 803(1), April 2015. © 2015. The American Astronomical Society. All rights reserved.We present a high spatial resolution (≈20 pc) of 12CO(2 −1) observations of the lenticular galaxy NGC 4526. We identify 103 resolved giant molecular clouds (GMCs) and measure their properties: size R, velocity dispersion σv, and luminosity L. This is the first GMC catalog of an early-type galaxy. We find that the GMC population in NGC 4526 is gravitationally bound, with a virial parameter α ∼ 1. The mass distribution, dN/dM ∝ M−2.39 ± 0.03, is steeper than that for GMCs in the inner Milky Way, but comparable to that found in some late-type galaxies. We find no size–line width correlation for the NGC 4526 clouds, in contradiction to the expectation from Larson’s relation. In general, the GMCs in NGC 4526 are more luminous, denser, and have a higher velocity dispersion than equal-size GMCs in the Milky Way and other galaxies in the Local Group. These may be due to higher interstellar radiation field than in the Milky Way disk and weaker external pressure than in the Galactic center. In addition, a kinematic measurement of cloud rotation shows that the rotation is driven by the galactic shear. For the vast majority of the clouds, the rotational energy is less than the turbulent and gravitational energy, while the four innermost clouds are unbound and will likely be torn apart by the strong shear at the galactic center. We combine our data with the archival data of other galaxies to show that the surface density Σ of GMCs is not approximately constant, as previously believed, but varies by ∼3 orders of magnitude. We also show that the size and velocity dispersion of the GMC population across galaxies are related to the surface density, as expected from the gravitational and pressure equilibrium, i.e., σv R−1/2 ∝ Σ1/2.Peer reviewe

The Ultra-Fast Outflow of the Quasar PG 1211+143 as Viewed by Time-Averaged Chandra Grating Spectroscopy

This is an author-created, un-copyedited version of an article published in The Astrophysical Journal. The Version of Record is available online at https://doi.org/10.3847/1538-4357/aaa427We present a detailed X-ray spectral study of the quasar PG 1211+143 based on Chandra High Energy Transmission Grating Spectrometer (HETGS) observations collected in a multi-wavelength campaign with UV data using the Hubble Space Telescope Cosmic Origins Spectrograph (HST-COS) and radio bands using the Jansky Very Large Array (VLA). We constructed a multi-wavelength ionizing spectral energy distribution using these observations and archival infrared data to create xstar photoionization models specific to the PG 1211+143 flux behavior during the epoch of our observations. Our analysis of the Chandra-HETGS spectra yields complex absorption lines from H-like and He-like ions of Ne, Mg, and Si, which confirm the presence of an ultra-fast outflow (UFO) with a velocity of approximately -17,300 km s -1 (outflow redshift z out ∼ -0.0561) in the rest frame of PG 1211+143. This absorber is well described by an ionization parameter and column density. This corresponds to a stable region of the absorber's thermal stability curve, and furthermore its implied neutral hydrogen column is broadly consistent with a broad Lyα absorption line at a mean outflow velocity of approximately -16,980 km s -1 detected by our HST-COS observations. Our findings represent the first simultaneous detection of a UFO in both X-ray and UV observations. Our VLA observations provide evidence for an active jet in PG 1211+143, which may be connected to the X-ray and UV outflows; this possibility can be evaluated using very-long-baseline interferometric observations.Peer reviewedFinal Accepted Versio

A review on substances and processes relevant for optical remote sensing of extremely turbid marine areas, with a focus on the Wadden Sea

The interpretation of optical remote sensing data of estuaries and tidal flat areas is hampered by optical complexity and often extreme turbidity. Extremely high concentrations of suspended matter, chlorophyll and dissolved organic matter, local differences, seasonal and tidal variations and resuspension are important factors influencing the optical properties in such areas. This review gives an overview of the processes in estuaries and tidal flat areas and the implications of these for remote sensing in such areas, using the Wadden Sea as a case study area. Results show that remote sensing research in extremely turbid estuaries and tidal areas is possible. However, this requires sensors with a large ground resolution, algorithms tuned for high concentrations of various substances and the local specific optical properties of these substances, a simultaneous detection of water colour and land-water boundaries, a very short time lag between acquisition of remote sensing and in situ data used for validation and sufficient geophysical and ecological knowledge of the area. © 2010 The Author(s)

Individual-level socioeconomic status is associated with worse asthma morbidity in patients with asthma

<p>Abstract</p> <p>Background</p> <p>Low socioeconomic status (SES) has been linked to higher morbidity in patients with chronic diseases, but may be particularly relevant to asthma, as asthmatics of lower SES may have higher exposures to indoor (e.g., cockroaches, tobacco smoke) and outdoor (e.g., urban pollution) allergens, thus increasing risk for exacerbations.</p> <p>Methods</p> <p>This study assessed associations between adult SES (measured according to educational level) and asthma morbidity, including asthma control; asthma-related emergency health service use; asthma self-efficacy, and asthma-related quality of life, in a Canadian cohort of 781 adult asthmatics. All patients underwent a sociodemographic and medical history interview and pulmonary function testing on the day of their asthma clinic visit, and completed a battery of questionnaires (Asthma Control Questionnaire, Asthma Quality of Life Questionnaire, and Asthma Self-Efficacy Scale). General Linear Models assessed associations between SES and each morbidity measure.</p> <p>Results</p> <p>Lower SES was associated with worse asthma control (F = 11.63, p < .001), greater emergency health service use (F = 5.09, p = .024), and worse asthma self-efficacy (F = 12.04, p < .01), independent of covariates. Logistic regression analyses revealed that patients with <12 years of education were 55% more likely to report an asthma-related emergency health service visit in the last year (OR = 1.55, 95%CI = 1.05-2.27). Lower SES was not related to worse asthma-related quality of life.</p> <p>Conclusions</p> <p>Results suggest that lower SES (measured according to education level), is associated with several indices of worse asthma morbidity, particularly worse asthma control, in adult asthmatics independent of disease severity. Results are consistent with previous studies linking lower SES to worse asthma in children, and add asthma to the list of chronic diseases affected by individual-level SES.</p