Search Publications

Mapping the Outer Edge of the Young Stellar Cluster in the Galactic Center

Lu, J. R.; Do, T.; Ghez, A. +3 more

We present new near-infrared spectroscopic observations of the outer edges of the young stellar cluster around the supermassive black hole at the Galactic center. The observations show a break in the surface density profile of young stars at ∼13″ (0.52 pc). These observations spectroscopically confirm previous suggestions of a break based on photo…

Constraints on primordial magnetic fields from the optical depth of the cosmic microwave background

Komatsu, Eiichiro; Kunze, Kerstin E.

Damping of magnetic fields via ambipolar diffusion and decay of magnetohydrodynamical (MHD) turbulence in the post decoupling era heats the intergalactic medium (IGM). Delayed recombination of hydrogen atoms in the IGM yields an optical depth to scattering of the cosmic microwave background (CMB). The optical depth generated at z ≫ 10 does not aff…

The Role of Bars in AGN Fueling in Disk Galaxies Over the Last Seven Billion Years

Santini, Paola; Knapen, Johan H.; Salvato, Mara +3 more

We present empirical constraints on the influence of stellar bars on the fueling of active galactic nuclei (AGNs) out to z = 0.84 using a sample of X-ray-selected AGNs hosted in luminous non-interacting face-on and moderately inclined disk galaxies from the Chandra COSMOS survey. Using high-resolution Hubble Space Telescope imaging to identify bar…

Preserved glass-rich impactites on Mars

Mustard, J. F.; Cannon, K. M.

Forward Modeling of Standing Slow Modes in Flaring Coronal Loops

Banerjee, D.; Antolin, P.; Van Doorsselaere, T. +1 more

Standing slow-mode waves in hot flaring loops are exclusively observed in spectrometers and are used to diagnose the magnetic field strength and temperature of the loop structure. Owing to the lack of spatial information, the longitudinal mode cannot be effectively identified. In this study, we simulate standing slow-mode waves in flaring loops an…

UV solar irradiance in observations and the NRLSSI and SATIRE-S models

Solanki, S. K.; Yeo, K. L.; Krivova, N. A. +3 more

Total solar irradiance and UV spectral solar irradiance has been monitored since 1978 through a succession of space missions. This is accompanied by the development of models aimed at replicating solar irradiance by relating the variability to solar magnetic activity. The Naval Research Laboratory Solar Spectral Irradiance (NRLSSI) and Spectral An…

Biases in the determination of dynamical parameters of star clusters: today and in the Gaia era

Balbinot, E.; Hénault-Brunet, V.; Gieles, M. +4 more

The structural and dynamical properties of star clusters are generally derived by means of the comparison between steady-state analytic models and the available observables. With the aim of studying the biases of this approach, we fitted different analytic models to simulated observations obtained from a suite of direct N-body simulations of star …

Predicted properties of multiple images of the strongly lensed supernova SN Refsdal.

Oguri, M.

We construct a mass model of the cluster MACS J1149.6+2223 to study the expected properties of multiple images of SN Refsdal, the first example of a gravitationally lensed supernova with resolved multiple images recently reported by Kelly et al. We find that the best-fitting model predicts six supernova images in total, i.e. two extra images in ad…

A spectroscopic investigation of the O-type star population in four Cygnus OB associations. II. Determination of the fundamental parameters

Rauw, G.; De Becker, M.; Mahy, L. +2 more

Aims: Having established the binary status of nineteen O-type stars located in four Cygnus OB associations, we now determine their fundamental parameters to constrain their properties and their evolutionary status. We also investigate their surface nitrogen abundances, which we compare with other results from the literature obtained for galac…

The Multi-layer Variable Absorbers in NGC 1365 Revealed by XMM-Newton and NuSTAR

Harrison, F.; Stern, D.; Zhang, W. W. +15 more

Between 2012 July and 2013 February, NuSTAR and XMM-Newton performed four long-look joint observations of the type 1.8 Seyfert, NGC 1365. We have analyzed the variable absorption seen in these observations in order to characterize the geometry of the absorbing material. Two of the observations caught NGC 1365 in an unusually low absorption state, …