Search Publications
A stripped-companion origin for Be stars: clues from the putative black holes HR 6819 and LB-1
El-Badry, Kareem; Quataert, Eliot
HR 6819 is a bright (V = 5.36), blue star recently proposed to be a triple containing a detached black hole (BH). We show that the system is a binary and does not contain a BH. Using spectral decomposition, we disentangle the observed composite spectra into two components: a rapidly rotating Be star and a slowly rotating B star with low surface gr…
Discovery of magnetic fields along stacked cosmic filaments as revealed by radio and X-ray emission
Vazza, F.; West, J. L.; Galvin, T. J. +5 more
Diffuse filaments connect galaxy clusters to form the cosmic web. Detecting these filaments could yield information on the magnetic field strength, cosmic ray population, and temperature of intercluster gas; yet, the faint and large-scale nature of these bridges makes direct detections very challenging. Using multiple independent all-sky radio and…
The X-SHOOTER Lyman α survey at z = 2 (XLS-z2) I: what makes a galaxy a Lyman α emitter?
Hayes, Matthew; Schaerer, Daniel; Sobral, David +9 more
We present the first results from the X-SHOOTER Lyman α survey at z = 2 (XLS-z2). XLS-z2 is a deep spectroscopic survey of 35 Lyman α emitters (LAEs) utilizing ≈90 h of exposure time with Very Large Telescope/X-SHOOTER and covers rest-frame Ly α to H α emission with R ≈ 4000. We present the sample selection, the observations, and the data reductio…
New insight into the magnetism of degenerate stars from the analysis of a volume-limited sample of white dwarfs
Bagnulo, S.; Landstreet, J. D.
Many stars evolve into magnetic white dwarfs (MWDs), and observations may help to understand when the magnetic field appears at the stellar surface, if and how it evolves during the cooling phase, and, above all, what are the mechanisms that generate it. After obtaining new spectropolarimetric observations and combining them with previous literatu…
Tree-ring structure of Galactic bar resonance
Schönrich, Ralph; Chiba, Rimpei
Galaxy models have long predicted that galactic bars slow down by losing angular momentum to their postulated dark haloes. When the bar slows down, resonance sweeps radially outwards through the galactic disc while growing in volume, thereby sequentially capturing new stars at its surface/separatrix. Since trapped stars conserve their action of li…
Radii of young star clusters in nearby galaxies
Gnedin, Oleg Y.; Brown, Gillen
We measure the projected half-light radii of young star clusters in 31 galaxies from the Legacy Extragalactic UV Survey (LEGUS). We implement a custom pipeline specifically designed to be robust against contamination, which allows us to measure radii for 6097 clusters. This is the largest sample of young star cluster radii currently available. We …
A self-lensing binary massive black hole interpretation of quasi-periodic eruptions
Ingram, Adam; Aigrain, Suzanne; Motta, Sara E. +1 more
Binary supermassive black hole (SMBH) systems result from galaxy mergers, and will eventually coalesce due to gravitational wave (GW) emission if the binary separation can be reduced to ≲0.1 pc by other mechanisms. Here, we explore a gravitational self-lensing binary SMBH model for the sharp (duration ~1 h), quasi-regular X-ray flares - dubbed qua…
MUSE analysis of gas around galaxies (MAGG) - III. The gas and galaxy environment of z = 3-4.5 quasars
Fynbo, J. P. U.; Fossati, M.; Lusso, E. +9 more
We present a study of the environment of 27 z = 3-4.5 bright quasars from the MUSE Analysis of Gas around Galaxies (MAGG) survey. With medium-depth Multi Unit Spectroscopic Explorer (MUSE) observations (4 h on target per field), we characterize the effects of quasars on their surroundings by studying simultaneously the properties of extended gas n…
Dust temperature in ALMA [C II]-detected high-z galaxies
Zanella, A.; Ferrara, A.; Vallini, L. +4 more
At redshift z > 5, the far-infrared (FIR) continuum spectra of main-sequence galaxies are sparsely sampled, often with a single data point. The dust temperature Td,SED, thus has to be assumed in the FIR continuum fitting. This introduces large uncertainties regarding the derived dust mass (Md), FIR luminosity, and obscured…
The GALAH survey: a census of lithium-rich giant stars
Lewis, Geraint F.; Ting, Yuan-Sen; Buder, Sven +20 more
We investigate the properties of 1262 red giant stars with high photospheric abundances of lithium observed by the GALAH and K2-HERMES surveys, and discuss them in the context of proposed mechanisms for lithium enrichment and redepletion in giant stars. We confirm that Li-rich giants are rare, making up only 1.2 per cent of our giant star sample. …