Search Publications
Gravitational detection of a low-mass dark satellite galaxy at cosmological distance
Vegetti, S.; McKean, J. P.; Auger, M. W. +3 more
The mass function of dwarf satellite galaxies that are observed around Local Group galaxies differs substantially from simulations based on cold dark matter: the simulations predict many more dwarf galaxies than are seen. The Local Group, however, may be anomalous in this regard. A massive dark satellite in an early-type lens galaxy at a redshift …
A magnified young galaxy from about 500 million years after the Big Bang
Donahue, Megan; Broadhurst, Tom; Kelson, Daniel D. +33 more
Re-ionization of the intergalactic medium occurred in the early Universe at redshift z ~ 6-11, following the formation of the first generation of stars. Those young galaxies (where the bulk of stars formed) at a cosmic age of less than about 500 million years (z <~ 10) remain largely unexplored because they are at or beyond the sensitivity limi…
The intense starburst HDF 850.1 in a galaxy overdensity at z ≈ 5.2 in the Hubble Deep Field
Carilli, Chris; Dickinson, Mark; Ellis, Richard +24 more
The Hubble Deep Field provides one of the deepest multiwavelength views of the distant Universe and has led to the detection of thousands of galaxies seen throughout cosmic time. An early map of the Hubble Deep Field at a wavelength of 850 micrometres, which is sensitive to dust emission powered by star formation, revealed the brightest source in …
An absence of ex-companion stars in the type Ia supernova remnant SNR 0509-67.5
Schaefer, Bradley E.; Pagnotta, Ashley
A type Ia supernova is thought to begin with the explosion of a white dwarf star. The explosion could be triggered by the merger of two white dwarfs (a `double-degenerate' origin), or by mass transfer from a companion star (the `single-degenerate' path). The identity of the progenitor is still controversial; for example, a recent argument against …
Two stellar-mass black holes in the globular cluster M22
Strader, Jay; Maccarone, Thomas J.; Seth, Anil C. +2 more
Hundreds of stellar-mass black holes probably form in a typical globular star cluster, with all but one predicted to be ejected through dynamical interactions. Some observational support for this idea is provided by the lack of X-ray-emitting binary stars comprising one black hole and one other star (`black-hole/X-ray binaries') in Milky Way globu…
Dynamical age differences among coeval star clusters as revealed by blue stragglers
Dalessandro, E.; Sanna, N.; Beccari, G. +11 more
Globular star clusters that formed at the same cosmic time may have evolved rather differently from the dynamical point of view (because that evolution depends on the internal environment) through a variety of processes that tend progressively to segregate stars more massive than the average towards the cluster centre. Therefore clusters with the …
An over-massive black hole in the compact lenticular galaxy NGC 1277
van der Wel, Arjen; Gebhardt, Karl; van de Ven, Glenn +3 more
Most massive galaxies have supermassive black holes at their centres, and the masses of the black holes are believed to correlate with properties of the host-galaxy bulge component. Several explanations have been proposed for the existence of these locally established empirical relationships, including the non-causal, statistical process of galaxy…
The age of the Milky Way inner halo
Kalirai, Jason S.
The Milky Way galaxy has several components, such as the bulge, disk and halo. Unravelling the assembly history of these stellar populations is often restricted because of difficulties in measuring accurate ages for low-mass, hydrogen-burning stars. Unlike these progenitors, white dwarf stars, the `cinders' of stellar evolution, are remarkably sim…
High velocity dispersion in a rare grand-design spiral galaxy at redshift z = 2.18
Erb, Dawn K.; Shapley, Alice E.; Steidel, Charles C. +3 more
Although grand-design spiral galaxies are relatively common in the local Universe, only one has been spectroscopically confirmed to lie at redshift z > 2 (HDFX 28; z = 2.011); and it may prove to be a major merger that simply resembles a spiral in projection. The rarity of spirals has been explained as a result of disks being dynamically `hot' …
Observation of interstellar lithium in the low-metallicity Small Magellanic Cloud
Mathews, Grant J.; Lehner, Nicolas; Howk, J. Christopher +1 more
The primordial abundances of light elements produced in the standard theory of Big Bang nucleosynthesis (BBN) depend only on the cosmic ratio of baryons to photons, a quantity inferred from observations of the microwave background. The predicted primordial 7Li abundance is four times that measured in the atmospheres of Galactic halo sta…