OH-selected AGB and post-AGB stellar objects II.Blue versus red evolution off the AGB

Using objects found in a systematic survey of the galactic Plane in the 1612-MHz OH line, we discuss in detail two ``sequences'' of post-AGB evolution, a red and a blue. We argue that the red and the blue groups separate by initial mass at 4Msun, based on evolutionary-sequence turn-off colours, spectral energy distributions, outflow velocities and scaleheight. The higher-mass (blue) objects may have earlier AGB termination. The lower-mass (red) objects undergo very sudden reddening for IRAS colour R21\sim1.2; these sources must all undergo a very similar process at AGB termination. The transition colour corresponds to average initial masses of 1.7Msun. A combined IRAS-MSX colour proves a very sensitive tool to distinguish lower-mass, early post-AGB objects from sources still on the AGB and also to distinguish more evolved post-AGB objects from star-forming regions. The high-mass blue objects are the likely precursors of bipolar planetary nebulae, whereas the low-mass red objects will evolve into elliptical planetary nebulae.Comment: 12 pages, LaTex, 7 figures (1 colour), AJ (accepted

Galaxies with Spiral Structure up to z = 0.87 --Limits on M/L and the Stellar Velocity Dispersion

We consider seven distant galaxies with clearly evident spiral structure from HST images. Three of these were chosen from Vogt et al. (1996) (VFP) and have measured rotational velocities. Five were chosen from the Medium Deep Survey and are studied in Sarajedini et al. 1996 (SGGR), and one galaxy is found in both papers. We place upper limits on their mass-to-light ratios (M/L) by computing M/L_B for a maximal disk. We find that these galaxies have maximal disk mass-to-light ratios M/L_B = 1.5 - 3.5 M_sol/L_Bsol at the low end, but within the range seen in nearby galaxies. The mass-to-light ratios are low enough to suggest that the galaxies contain a young, rapidly formed stellar population. By using a Toomre stability criterion for formation of spiral structure, we place constraints on the ratio of M/L to the stellar velocity dispersion. If these galaxies have maximal disks they would have to be nearly unstable so as to have small enough velocity dispersions that their disks are not unrealistically thick. This suggests that there is a substantial amount of dark matter present in the luminous regions of the galaxy.Comment: AAS Latex + PS Figure, accepted for publication in A

Economisch perspectief van de PAS. Baten en kosten van de Programmatische Aanpak Stikstof in Natura 2000-gebieden

De Programmatische Aanpak Stikstof (PAS), onderdeel van Natura 2000, is economisch voordelig voor ons land. Van 2013 tot 2020 zijn de economische baten zo'n 100-200 mln. euro/jaar hoger dan de kosten. De baten van de PAS voor de sectoren landbouw, industrie en verkeer en vervoer bedragen in die periode naar schatting 200 tot 300 mln. euro/jaar, terwijl de economische kosten op een kleine 100 mln. euro/jaar worden geschat. De PAS leidt tot duidelijkheid voor ondernemers. Die duidelijkheid levert economisch voordeel op. De veehouderij bij de stikstofgevoelige Natura 2000-gebieden kan zich blijven ontwikkelen, wat met name gunstig is voor de rundveehouderij. De PAS is daarnaast voor ondernemers gunstig, omdat ze minder on-derzoekskosten voor het verkrijgen van een Natuurbeschermingswetvergunning hoeven te maken. Andere baten van de PAS, die ontstaan bij de aanleg van wegen en in de industrie, blijken moeilijk te kwantificeren vanwege het ontbreken van voldoende gegevens

HappyHier: hoe gelukkig is men waar? : Gegevensverzameling en bepaling van de invloed van het type grondgebruik, deel I

This study set out to measure what influence the type of environment has on how happy people say they feel at a certain moment in time, with the aim of formulating rules for quantifying the effect of spatial changes on wellbeing. A smartphone app was developed for use by a broad sample population in the Netherlands, with push notifications prompting people to report how they felt at a certain moment. From 1 May to 28 July of 2016, 4318 unique participants made use of this HappyHier app, filling in at least one questionnaire on location. The results show that people are happier outdoors than indoors. And when they are outdoors, they are happier in predominantly natural surroundings than in more built-up areas. Moreover, from the ratings given to the surroundings, it can be concluded that they have a more positive effect when the participants found them more restful or stimulating. People’s impressions of the beauty of their surroundings had less influenc

2020 ESC Guidelines on acute coronary syndrome without ST-segment elevation Recommendations and critical appraisal from the Dutch ACS and Interventional Cardiology working groups

Recently, the European Society of Cardiology (ESC) has updated its guidelines for the management of patients with acute coronary syndrome (ACS) without ST-segment elevation. The current consensus document of the Dutch ACS working group and the Working Group of Interventional Cardiology of the Netherlands Society of Cardiology aims to put the 2020 ESC Guidelines into the Dutch perspective and to provide practical recommendations for Dutch cardiologists, focusing on antiplatelet therapy, risk assessment and criteria for invasive strategy.</p

Astrometric Microlensing with the GAIA satellite

GAIA is the ``super-Hipparcos'' survey satellite selected as a Cornerstone 6 mission by the European Space Agency. GAIA can measure microlensing by the small excursions of the light centroid that occur during events. The all-sky source-averaged astrometric microlensing optical depth is about 10^{-5}. Some 25000 sources will have a significant variation of the centroid shift, together with a closest approach, during the lifetime of the mission. A covariance analysis is used to study the propagation of errors and the estimation of parameters from realistic sampling of the GAIA datastream of transits in the along-scan direction during microlensing events. Monte Carlo simulations are used to study the 2500 events for which the mass can be recovered with an error of less than 50 per cent. These high quality events are dominated by disk lenses within a few tens of parsecs and source stars within a few hundred parsecs. We show that the local mass function can be recovered from the high quality sample to good accuracy. GAIA is the first instrument with the capabilities of measuring the mass locally in very faint objects like black holes and very cool white and brown dwarfs. For only 5 per cent of all astrometric events will GAIA record even one photometric datapoint. There is a need for a dedicated telescope that densely samples the Galactic Centre and spiral arms, as this can improve the accuracy of parameter estimation by a factor of about 10.Comment: 18 pages, 18 figures, MNRAS, in pres

Outer-Disk Populations in NGC 7793: Evidence for Stellar Radial Migration

We analyzed the radial surface brightness profile of the spiral galaxy NGC 7793 using HST/ACS images from the GHOSTS survey and a new HST/WFC3 image across the disk break. We used the photometry of resolved stars to select distinct populations covering a wide range of stellar ages. We found breaks in the radial profiles of all stellar populations at 280" (~5.1 kpc). Beyond this disk break, the profiles become steeper for younger populations. This same trend is seen in numerical simulations where the outer disk is formed almost entirely by radial migration. We also found that the older stars of NGC 7793 extend significantly farther than the underlying HI disk. They are thus unlikely to have formed entirely at their current radii, unless the gas disk was substantially larger in the past. These observations thus provide evidence for substantial stellar radial migration in late-type disks.Comment: 8 pages, 6 figure. Accepted for publication in Ap

2020 ESC Guidelines on acute coronary syndrome without ST-segment elevation: recommendations and critical appraisal from the Dutch ACS and Interventional Cardiology working groups

Recently, the European Society of Cardiology (ESC) has updated its guidelines for the management of patients with acute coronary syndrome (ACS) without ST-segment elevation. The current consensus document of the Dutch ACS working group and the Working Group of Interventional Cardiology of the Netherlands Society of Cardiology aims to put the 2020 ESC Guidelines into the Dutch perspective and to provide practical recommendations for Dutch cardiologists, focusing on antiplatelet therapy, risk assessment and criteria for invasive strategy.Cardiolog