Dynamics of putative raft-associated proteins at the cell surface

Lipid rafts are conceptualized as membrane microdomains enriched in cholesterol and glycosphingolipid that serve as platforms for protein segregation and signaling. The properties of these domains in vivo are unclear. Here, we use fluorescence recovery after photobleaching to test if raft association affects a protein's ability to laterally diffuse large distances across the cell surface. The diffusion coefficients (D) of several types of putative raft and nonraft proteins were systematically measured under steady-state conditions and in response to raft perturbations. Raft proteins diffused freely over large distances (>4 μm), exhibiting Ds that varied 10-fold. This finding indicates that raft proteins do not undergo long-range diffusion as part of discrete, stable raft domains. Perturbations reported to affect lipid rafts in model membrane systems or by biochemical fractionation (cholesterol depletion, decreased temperature, and cholesterol loading) had similar effects on the diffusional mobility of raft and nonraft proteins. Thus, raft association is not the dominant factor in determining long-range protein mobility at the cell surface

DSA-10: A prototype array for localizing fast radio bursts

The Deep Synoptic Array 10 dish prototype is an instrument designed to detect and localise fast radio bursts with arcsecond accuracy in real time. Deployed at Owens Valley Radio Observatory, it consists of ten 4.5m diameter dishes, equipped with a 250MHz bandwidth dual polarisation receiver, centered at 1.4GHz. The 20 input signals are digitised and field programmable gate arrays are used to transform the data to the frequency domain and transmit it over ethernet. A series of computer servers buffer both raw data samples and perform a real time search for fast radio bursts on the incoherent sum of all inputs. If a pulse is detected, the raw data surrounding the pulse is written to disk for coherent processing and imaging. The prototype system was operational from June 2017 - February 2018 conducting a drift scan search. Giant pulses from the Crab pulsar were used to test the detection and imaging pipelines. The 10-dish prototype system was brought online again in March 2019, and will gradually be replaced with the new DSA-110, a 110-dish system, over the next two years to improve sensitivity and localisation accuracy.Comment: 10 pages, 13 figures, accepted by MNRA

A fast radio burst localised to a massive galaxy

Intense, millisecond-duration bursts of radio waves have been detected from beyond the Milky Way [1]. Their extragalactic origins are evidenced by their large dispersion measures, which are greater than expected for propagation through the Milky Way interstellar medium alone, and imply contributions from the intergalactic medium and potentially host galaxies [2]. Although several theories exist for the sources of these fast radio bursts, their intensities, durations and temporal structures suggest coherent emission from highly magnetised plasma [3,4]. Two sources have been observed to repeat [5,6], and one repeater (FRB 121102) has been localised to the largest star-forming region of a dwarf galaxy at a cosmological redshift of 0.19 [7, 8]. However, the host galaxies and distances of the so far non-repeating fast radio bursts are yet to be identified. Unlike repeating sources, these events must be observed with an interferometer with sufficient spatial resolution for arcsecond localisation at the time of discovery. Here we report the localisation of a fast radio burst (FRB 190523) to a few-arcsecond region containing a single massive galaxy at a redshift of 0.66. This galaxy is in stark contrast to the host of FRB 121102, being a thousand times more massive, with a greater than hundred times lower specific star-formation rate. The properties of this galaxy highlight the possibility of a channel for FRB production associated with older stellar populations

Deep Synoptic Array Science: First FRB and Host Galaxy Catalog

Fast Radio Bursts (FRBs) are a powerful and mysterious new class of transient that are luminous enough to be detected at cosmological distances. By associating FRBs to host galaxies, we can measure intrinsic and environmental properties that test FRB origin models, in addition to using them as precise probes of distant cosmic gas. The 110-antenna Deep Synoptic Array (DSA-110) is a radio interferometer built to maximize the rate at which it can simultaneously detect and localize FRBs. Here, we present the first sample of FRBs and host galaxies discovered by the DSA-110. This sample of 11 FRBs is the largest uniform sample of localized FRBs to date and is selected based on association to host galaxies identified in optical imaging by Pan-STARRS1 and follow-up spectroscopy at the Palomar and Keck observatories. These FRBs have not been observed to repeat and their radio properties (dispersion, temporal scattering, energy) are similar to that of the known non-repeating FRB population. Most host galaxies have ongoing star formation, as has been identified before for FRB hosts. In contrast to prior work, a large fraction (four of eleven) of the new sample are more massive than 10$^{11}$\ M$_{\odot}$ and most had elevated star formation rates more than 100 Myr in their past. The distribution of star-formation history across this host-galaxy sample shows that the delay-time distribution is wide, spanning from $\sim100$\,Myr to $\sim10$\,Gyr. This requires the existence of one or more progenitor formation channels associated with old stellar populations, such as the binary evolution of compact objects.Comment: 21 pages. Submitted to AAS Journal

DSA-10: A Prototype Array for Localizing Fast Radio Bursts

The Deep Synoptic Array 10-dish prototype (DSA-10) is an instrument designed to detect and localize fast radio bursts with arcsecond accuracy in real time. Deployed at Owens Valley Radio Observatory, it consists of ten 4.5-m diameter dishes, equipped with a 250-MHz bandwidth dual polarization receiver, centred at 1.4 GHz. The 20 input signals are digitized and field programmable gate arrays are used to transform the data to the frequency domain and transmit it over ethernet. A series of computer servers buffer both raw data samples and perform a real time search for fast radio bursts on the incoherent sum of all inputs. If a pulse is detected, the raw data surrounding the pulse are written to disc for coherent processing and imaging. The prototype system was operational from 2017 June to 2018 February conducting a drift scan search. Giant pulses from the Crab Pulsar were used to test the detection and imaging pipelines. The 10-dish prototype system was brought online again in 2019 March, and will gradually be replaced with the new DSA-110, a 110-dish system, over the next 2 yr to improve sensitivity and localization accuracy