29 research outputs found
Joint constraints on the Galactic dark matter halo and Galactic Centre from hypervelocity stars
Article / Letter to editorSterrewach
Joint constraints on the Galactic dark matter halo and GC from hypervelocity stars
The mass assembly history of the Milky Way can inform both theory of galaxy formation and the underlying cosmological model. Thus, observational constraints on the properties of both its baryonic and dark matter contents are sought. Here, we show that hypervelocity stars (HVSs) can in principle provide such constraints. We model the observed velocity distribution of HVSs, produced by tidal break-up of stellar binaries caused by Sgr A*. Considering a Galactic Centre (GC) binary population consistent with that inferred in more observationally accessible regions, a fit to current HVS data with significance level >5 per cent can only be obtained if the escape velocity from the GC to 50 kpc is VG ≲ 850 km s^(−1), regardless of the enclosed mass distribution. When a Navarro, Frenk and White matter density profile for the dark matter halo is assumed, haloes with VG ≲ 850 km s^(−1) are in agreement with predictions in the Λ cold dark matter model and a subset of models around M200 ∼ 0.5–1.5 × 10^(12) M_⊙ and rs ≲ 35 kpc can also reproduce Galactic circular velocity data. HVS data alone cannot currently exclude potentials with VG > 850 km s^(−1). Finally, specific constraints on the halo mass from HVS data are highly dependent on the assumed baryonic mass potentials. This first attempt to simultaneously constrain GC and dark halo properties is primarily hampered by the paucity and quality of data. It nevertheless demonstrates the potential of our method, that may be fully realized with the ESA Gaia mission
The AARTFAAC 60 MHz transients survey
We report the experimental setup and overall results of the AARTFAAC
wide-field radio survey, which consists of observing the sky within 50
of Zenith, with a bandwidth of 3.2MHz, at a cadence of 1s, for
545h. This yielded nearly 4 million snapshots, two per second, of on
average 4800 square degrees and a sensitivity of around 60Jy. We find two
populations of transient events, one originating from PSRB095008 and one
from strong ionospheric lensing events, as well as a single strong candidate
for an extragalactic transient, with a peak flux density of Jy and
a dispersion measure of , We also set a strong
upper limit of 1.1 all-sky per day to the rate of any other populations of
fast, bright transients. Lastly, we constrain some previously detected types of
transient sources by comparing our detections and limits with other
low-frequency radio transient surveys.Comment: 10 pages, 8 figures. Published by MNRA
Joint constraints on the Galactic dark matter halo and Galactic Centre from hypervelocity stars
GalaxiesStars and planetary system