14 research outputs found
Strong Gravitational Lensing with SKA
The advent of new observational facilities in the last two decades has
allowed the rapid discovery and high-resolution optical imaging of many strong
lens systems from galaxy to cluster scales, as well as their spectroscopic
follow-up. Radio telescopes have played the dominant role in the systematic
detection of dozens of new arcsec-scale lens systems. For the future, we expect
nothing less! The next major ground- and space-based facilities, especially the
Square Kilometer Array can discover tens of thousands of new lens systems in
large sky surveys. For optical imaging and spectroscopic follow-up a strong
synergy with planned optical facilities is needed. Here, we discuss the field
where strong gravitational lensing is expected to play the dominant role and
where SKA can have a major impact: The study of the internal mass structure and
evolution of galaxies and clusters to z~1. In addition, studies of more exotic
phenomena are contemplated. For example, milli- and microlensing can provide a
way to measure the mass-functions of stars and CDM substructure at cosmological
distances. All-sky radio monitoring will also rapidly develop the field of
time-domain lensing.Comment: 9 pages, 3 figures; to appear in "Science with the Square Kilometer
Array," eds. C. Carilli and S. Rawlings, New Astronomy Reviews (Elsevier:
Amsterdam
Gravitational Lensing by Cosmic Strings in the Era of Wide-Field Surveys
Motivated by the recent claim for gravitational lensing by a cosmic string,
we reinvestigate the probability of finding such an event with upcoming
wide-field surveys. If an observed lensing event is suspected to be due to a
string, observations of the vicinity of the event in a circle of diameter L
centered on the observed lens should reveal several additional lensing events.
For a string located nearby (z\lesssim 0.5), we find that observations in a
region of size \approx 1 arcmin^2 will see \sim 100 objects, of which \sim 5
would be lensed by the string, compared to \sim 0.1 lensed by conventional
sources.Comment: 4 pages, 3 figures, to be submitted to PRD Rapid
SMILE: Search for MIlli-LEnses
ABSTRACTDark matter (DM) haloes with masses below ∼108 M⊙, which would help to discriminate between DM models, may be detected through their gravitational effect on distant sources. The same applies to primordial black holes, considered as an alternative scenario to DM particle models. However, there is still no evidence for the existence of such objects. With the aim of finding compact objects in the mass range of ∼106–109 M⊙, we search for strong gravitational lenses on milliarcsec scales (</p
The sub-arcsecond structure of 4C39.25
Wetensch. publicatieFaculteit der Wiskunde en Natuurwetenschappe
The CLASS Gravitational Lens Survey : Survey Selection and Early Results for 3271 Radio Sources
First Results from the CLASS Gravitational Lens Survey: Two New Compact Radio Lenses with Arc-Second Separations
Baryon acoustic oscillations from Integrated Neutral Gas Observations: Broadband corrugated horn construction and testing
International audienceThe Baryon acoustic oscillations from Integrated Neutral Gas Observations (BINGO) telescope is a 40-m class radio telescope under construction that has been designed to measure the large-angular-scale intensity of Hi emission at 980–1260 MHz and hence to constrain dark energy parameters. A large focal plane array comprising of 1.7-metre diameter, 4.3-metre length corrugated feed horns is required in order to optimally illuminate the telescope. Additionally, very clean beams with low sidelobes across a broad frequency range are required, in order to facilitate the separation of the faint Hi emission from bright Galactic foreground emission. Using novel construction methods, a full-sized prototype horn has been assembled. It has an average insertion loss of around − 0.15 dB across the band, with a return loss around 25 dB. The main beam is Gaussian with the first sidelobe at around − 25 dB. A septum polariser to separate the signal into the two hands of circular polarization has also been designed, built and tested
SMILE
Publisher Copyright: © 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.Dark matter (DM) haloes with masses below ∼108 M·, which would help to discriminate between DM models, may be detected through their gravitational effect on distant sources. The same applies to primordial black holes, considered as an alternative scenario to DM particle models. However, there is still no evidence for the existence of such objects. With the aim of finding compact objects in the mass range of ∼106-109 M·, we search for strong gravitational lenses on milliarcsec scales (<150 mas). For our search, we used the Astrogeo very long baseline interferometry (VLBI) fits image data base - the largest publicly available data base, containing multifrequency VLBI data of 13 828 individual sources. We used the citizen science approach to visually inspect all sources in all available frequencies in search for images with multiple compact components on mas scales. At the final stage, sources were excluded based on the surface brightness preservation criterion. We obtained a sample of 40 sources that passed allsteps and therefore are judged to be mas lens candidates. These sources are currently followed up with ongoing European VLBI network observations at 5 and 22 GHz. Based on spectral index measurements, we suggest that two of our candidates have a higher probability to be associated with gravitational lenses.Peer reviewe