The milliarcsecond-scale radio structure of AB Doradus A

Context. The fast rotator, pre-main sequence star AB Dor A is a strong and persistent radio emitter. The extraordinary coronal flaring activity is thought to be the origin of compact radio emission and other associated phenomena, such as large slingshot prominences. Aims. We aim to investigate the radio emission mechanism and the milliarcsecond radio structure around AB Dor A. Methods. We performed phase-referenced VLBI observations at 22.3 GHz, 8.4 GHz, and 1.4 GHz over more than one decade using the Australian VLBI array. Results. Our 8.4 GHz images show a double core-halo morphology, similar at all epochs, with emission extending at heights between 5 and 18 stellar radii. Furthermore, the sequence of the 8.4 GHz maps shows a clear variation of the source structure within the observing time. However, images at 1.4 GHz and 22.3 GHz are compatible with a compact source. The phase-reference position at 8.4 GHz and 1.4 GHz are coincident with those expected from the well-known milliarcsecond-precise astrometry of this star, meanwhile the 22.3 GHz position is 4σ off the prediction in the north-west direction. The origin of this offset is still unclear. Conclusions. We have considered several models to explain the morphology and evolution of the inner radio structure detected in AB Dor A. These models include emission from the stellar polar caps, a flaring, magnetically-driven loop structure, and the presence of helmet streamers. We also investigated a possible close companion to AB Dor A. Our results confirm the extraordinary coronal magnetic activity of this star, capable of producing compact radio structures at very large heights that have so far only been seen in binary interacting systems.J.B.C., R.A., J.C.G., and J.M.M. were partially supported by the Spanish MINECO projects AYA2012-38491-C02-01, AYA2015-63939- C2-2-P, PGC2018-098915-B-C22 and by the Generalitat Valenciana projects PROMETEO/2009/104 and PROMETEOII/2014/05

NIKA2: a mm camera for cluster cosmology

Galaxy clusters constitute a major cosmological probe. However, Planck 2015 results have shown a weak tension between CMB-derived and cluster-derived cosmological parameters. This tension might be due to poor knowledge of the cluster mass and observable relationship. As for now, arcmin resolution Sunyaev-Zeldovich (SZ) observations (e.g. SPT, ACT and Planck) only allowed detailed studies of the intra cluster medium for low redshift clusters (z < 0:2). For high redshift clusters ( z > 0:5) high resolution and high sensitivity SZ observations are needed. With both a wide field of view (6.5 arcmin) and a high angular resolution (17.7 and 11.2 arcsec at 150 and 260 GHz), the NIKA2 camera installed at the IRAM 30-m telescope (Pico Veleta, Spain) is particularly well adapted for these observations. The NIKA2 SZ observation program will map a large sample of clusters (50) at redshifts between 0.5 and 0.9. As a pilot study for NIKA2, several clusters of galaxies have been observed with the pathfinder, NIKA, at the IRAM 30-m telescope to cover the various configurations and observation conditions expected for NIKA2

The AB Doradus system revisited: The dynamical mass of AB Dor A/C

Context. The study of pre-main-sequence (PMS) stars with model-independent measurements of their masses is essential to check the validity of theoretical models of stellar evolution. The well-known PMS binary AB Dor A/C is an important benchmark for this task, since it displays intense and compact radio emission, which makes possible the application of high-precision astrometric techniques to this system. Aims. We aim to revisit the dynamical masses of the components of AB Dor A/C to refine earlier comparisons between the measurements of stellar parameters and the predictions of stellar models. Methods. We observed in phase-reference mode the binary AB Dor A/C, 0.2′′ separation, with the Australian Long Baseline Array at 8.4 GHz. The astrometric information resulting from our observations was analyzed along with previously reported VLBI, optical (Hipparcos), and infrared measurements. Results. The main star AB Dor A is clearly detected in all the VLBI observations, which allowed us to analyze the orbital motion of the system and to obtain model-independent dynamical masses of 0.90 ± 0.08 M⊙ and 0.090 ± 0.008 M⊙, for AB Dor A and AB Dor C, respectively. Comparisons with PMS stellar evolution models favor and age of 40−50 Myr for AB Dor A and of 25−120 Myr for AB Dor C. Conclusions. We show that the orbital motion of the AB Dor A/C system is remarkably well determined, leading to precise estimates of the dynamical masses. Comparison of our results with the prediction of evolutionary models support the observational evidence that theoretical models tend to slightly underestimate the mass of the low-mass stars

Diagnosis and management of aspergillosis in the Netherlands: a national survey

A survey of diagnosis and treatment of invasive aspergillosis was conducted in eight University Medical Centers (UMCs) and eight non-academic teaching hospitals in the Netherlands. Against a background of emerging azole resistance in Aspergillus fumigatus routine resistance screening of clinical isolates was performed primarily in the UMCs. Azole resistance rates at the hospital level varied between 5% and 10%, although rates up to 30% were reported in high-risk wards. Voriconazole remained first choice for invasive aspergillosis in 13 out of 16 hospitals. In documented azole resistance 14 out of 16 centres treated patients with liposomal amphotericin B.Medical Microbiolog

NIKA2 Performance and Cosmology Program with Galaxy Clusters

International audienceNIKA2 is a dual-band millimetric camera of thousands of Kinetic InductanceDetectors (KID) installed at the IRAM 30-meter telescope in the Spanish SierraNevada. The instrument commissioning was completed in September 2017, and NIKA2is now open to the scientific community and will operate for the next decade.NIKA2 has well-adapted instrumental design and performance to produce high-resolution maps of the thermal Sunyaev-Zel'dovich (SZ) effect towardintermediate and high redshift galaxy clusters. Moreover, it benefits from aguaranteed time large program dedicated to mapping a representative sample ofgalaxy clusters via SZ and that includes X-ray follow-ups. The main expectedoutputs of the SZ large program are the constraints on the redshift evolution ofthe pressure profile and the mass-observable relation. The first SZ mapping of agalaxy cluster with NIKA2 was produced, as part of the SZ large program. Wefound a sizable impact of the intracluster medium dynamics on the integrated SZobservables. This shows NIKA2 capabilities for the precise characterisation ofthe mass-observable relation that is required for accurate cosmology with galaxyclusters

Exploiting NIKA2/ XMM-Newton imaging synergy for intermediate-mass high- z galaxy clusters within the NIKA2 SZ large program: Observations of ACT-CL J0215.4+0030 at z ∼0.9

High-resolution mapping of the intracluster medium (ICM) up to high redshift and down to low masses is crucial to derive accurate mass estimates of the galaxy cluster and to understand the systematic eects aecting cosmological studies based on galaxy clusters. We present a spatially resolved Sunyaev-Zel'dovich (SZ)/X-ray analysis of ACT-CL J0215.4+0030, a high-redshift (z = 0:865) galaxy cluster of intermediate mass (M500 ' 3:5 1014 M) observed as part of the ongoing NIKA2 SZ large program, which is a follow-up of a representative sample of objects at 0:5 z 0:9. In addition to the faintness and small angular size induced by its mass and redshift, the cluster is contaminated by point sources that significantly aect the SZ signal. This is therefore an interesting case study for the most challenging sources of the NIKA2 cluster sample. We present the NIKA2 observations of this cluster and the resulting data.We identified the point sources that aect the NIKA2 maps of the cluster as submillimeter galaxies with counterparts in catalogs of sources constructed by the SPIRE instrument on board the Herschel observatory. We reconstructed the ICM pressure profile by performing a joint analysis of the SZ signal and of the point-source component in the NIKA2 150 GHz map. This cluster is a very weak source that lies below the selection limit of the Planck catalog. Nonetheless, we obtained high-quality estimates of the ICM thermodynamical properties with NIKA2. We compared the pressure profile extracted from the NIKA2 map to the pressure profile obtained from X-ray data alone by deprojecting the public XMM-Newton observations of the cluster.We combined the NIKA2 pressure profile with the X-ray deprojected density to extract detailed information on the ICM. The radial distribution of its thermodynamic properties (the pressure, temperature and entropy) indicate that the cluster has a highly disturbed core. We also computed the hydrostatic mass of the cluster, which is compatible with estimations from SZ and X-ray scaling relations. We conclude that the NIKA2 SZ large program can deliver quality information on the thermodynamics of the ICM even for one of its faintest clusters after a careful treatment of the contamination by point sources.With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737

NIKA2: a millimeter camera for cluster cosmology

International audienceGalaxy clusters constitute a major cosmological probe. However, Planck 2015 results have showna weak tension between CMB-derived and cluster-derived cosmological parameters. This tensionmight be due to poor knowledge of the cluster mass and observable relationship. As for now,arcmin resolution Sunyaev-Zeldovich (SZ) observations (e.g. SPT, ACT and Planck) only alloweddetailed studies of the intra cluster medium for low redshift clusters (z 0:5) high resolution and high sensitivity SZ observations are needed. With botha wide field of view (6.5 arcmin) and a high angular resolution (17.7 and 11.2 arcsec at 150and 260 GHz), the NIKA2 camera installed at the IRAM 30-m telescope (Pico Veleta, Spain) isparticularly well adapted for these observations. The NIKA2 SZ observation program will map alarge sample of clusters (50) at redshifts between 0.5 and 0.9. As a pilot study for NIKA2, severalclusters of galaxies have been observed with the pathfinder, NIKA, at the IRAM 30-m telescopeto cover the various configurations and observation conditions expected for NIKA2