Remnants from Gamma-Ray Bursts

We model the intermediate time evolution of a "jetted" gamma-ray burst by two blobs of matter colliding with the interstellar medium. We follow the hydrodynamical evolution of this system numerically and calculate the bremsstrahlung and synchrotron images of the remnant. We find that for a burst energy of $10^{51}$ erg the remnant becomes spherical after $\sim 5000$ years when it collects $\sim 50M_\odot$ of interstellar mass. This result is independent of the exact details of the GRB, such as the opening angle. After this time a gamma-ray burst remnant has an expanding sphere morphology. The similarity to a supernova remnant makes it difficult distinguish between the two at this stage. The expected number of non-spherical gamma-ray burst remnants is $\sim0.05$ per galaxy for a beaming factor of 0.01 and a burst energy of $10^{51}$ erg. Our results suggest that that the double-shell object DEM L 316 is not a GRB remnant.Comment: 16 pages, 9 figures, Substantial revisions, Accepted by Ap

The Origin of X-shaped Radio Galaxies: Clues from the Z-symmetric Secondary Lobes

Existing radio images of a few X-shaped radio galaxies reveal Z-symmetric morphologies in their weaker secondary lobes which cannot be naturally explained by either the galactic merger or radio-lobe backflow scenarios, the two dominant models for these X-shaped radio sources. We show that the merger picture can explain these morphologies provided one takes into account that, prior to the coalescence of their supermassive black holes, the smaller galaxy releases significant amounts of gas into the ISM of the dominant active galaxy. This rotating gas, whose angular momentum axis will typically not be aligned with the original jets, is likely to provide sufficient ram pressure at a distance ~10 kpc from the nucleus to bend the extant jets emerging from the central engine, thus producing a Z-symmetry in the pair of radio lobes. Once the two black holes have coalesced some 10^7 yr later, a rapid reorientation of the jets along a direction close to that of the orbital angular momentum of the swallowed galaxy relative to the primary galaxy would create the younger primary lobes of the X-shaped radio galaxy. This picture naturally explains why such sources typically have powers close to the FR I/II break. We suggest that purely Z-symmetric radio sources are often en route to coalescence and the concomitant emission of substantial gravitational radiation, while X-shaped ones have already merged and radiated.Comment: 12 pages, 1 compressed figure; accepted for publication in ApJ Letter

Discovery Of A Molecular Outflow in the Haro 6-10 Star-Forming Region

We present high sensitivity 12CO and 13CO (1-0) molecular line maps covering the full extent of the parsec scale Haro~6-10 Herbig-Haro (HH) flow. We report the discovery of a molecular CO outflow along the axis of parsec-scale HH flow. Previous molecular studies missed the identification of the outflow probably due to their smaller mapping area and the confusing spectral features present towards the object. Our detailed molecular line study of the full 1.6 pc extent of the optical flow shows evidence for both blueshifted and redshifted gas set in motion by Haro~6-10 activity. The molecular outflow is centered at Haro~6-10, with redshifted gas being clumpy and directed towards the northeast, while blueshifted gas is in the southwest direction. The molecular gas terminates well within the cloud, short of the most distant HH objects of the optical flow. Contamination from an unrelated cloud along the same line of sight prevents a thorough study of the blueshifted outflow lobe and the mass distribution at the lowest velocities in both lobes. The cloud core in which Haro~6-10 is embedded is filamentary and flattened in the east-west direction. The total cloud mass is calculated from 13CO(1-0) to be ~200Msun. The lower limit of the mass associated with the outflow is ~0.25Msun.Comment: ApJ Accepted; 9 pages, 8 figures. For high resolution ps file use: http://www.astro.umass.edu/~irena/haro.p

Are ultra-luminous infrared galaxies the dominant extragalactic population at high luminosities?

Based on the recent QSO surveys it is shown that, contrary to the widespread notion, high-luminousity QSOs are at least as numerous in the nearby universe as the ultraluminous far-infrared galaxies (ULIGs). Therefore, the fraction of ULIGs that have got a hidden quasar at the nucleus, for example in the dust shrouded phase, cannot be overwhelmingly large

Was the Cosmic Web of Protogalactic Material Permeated by Lobes of Radio Galaxies During the Quasar Era?

Evidence for extended active lifetimes (> 10^8 yr) for radio galaxies implies that many large radio lobes were produced during the `quasar era', 1.5 < z < 3, when the comoving density of radio sources was 2 -- 3 dex higher than the present level. However, inverse Compton losses against the intense microwave background substantially reduce the ages and numbers of sources that are detected in flux-limited surveys. The realization that the galaxy forming material in those epochs was concentrated in filaments occupying a small fraction of the total volume then leads to the conclusion that radio lobes permeated much of the volume occupied by the protogalactic material during that era. The sustained overpressure in these extended lobes is likely to have played an important role in triggering the high inferred rate of galaxy formation at z > 1.5 and in the magnetization of the cosmic network of filaments.Comment: 5 pages, 0 figures, submitted to ApJ Letters; uses emulateapj

‘Lots of Black people are on meds because they're seen as aggressive’: STOMP, COVID-19 and anti-racism in community learning disability services

Background The STOMP agenda (Stopping Over-Medication of People with learning disabilities, autism, or both) drew focus to individuals with a diagnosis of a learning disability being prescribed psychotropic medication to manage ‘behaviours that challenge’. The following study is an audit of two community learning disability services in the London boroughs of Westminster and Kensington and Chelsea for compliance with national guidance on the use of medication in this population, the impact of the COVID-19 pandemic, and equality, diversity and anti-racism. Method Routinely collected data were audited relating to clients identified in each service, totalling 54 participants. Data were audited against five standards: minimum effective dose, medication reviews, alternative multidisciplinary input, the impact of the COVID-19 pandemic and equality, diversity and anti–racism. Comparisons were made to the overall caseload (N = 365) where appropriate. Results Evidence demonstrated a greater risk of receiving psychotropic medication to manage behaviours that challenge for service users from racialised backgrounds, further evidencing institutional and/or individualised racism within practice for this population. Prescriptions also increased in dosage during the COVID-19 pandemic exacerbated by insufficient provision of alternative input and regular multi-disciplinary review as required by national guidance. Conclusions Community learning disability teams require dedicated, co-produced STOMP pathways to review those at risk of over-medication. Additional research is required to explore individual and systemic factors contributing to ethnic disparities in medication prescription for behaviours that challenge among people with learning disabilities. Further recommendations are considered around developing data collection, service user involvement, and future directions.Accessible summary: - Abuse at care home (Winterbourne View) led the NHS to start a campaign known as STOMP to make sure people with learning disabilities and/or autism got the right medication. - We looked at the medications people with learning disabilities in our area were given. We looked at how often these medications were checked by a doctor. We looked at what other support people were given. - We also looked at how people with learning disabilities were affected by COVID-19. We also looked at differences between people from different racial backgrounds. - We found that some people were given more medications to manage their behaviour. We found that the medications were not checked as often as they should be. This happened most for Black, Brown, and Asian people. - We spoke to a local service user project about our findings. They said they think racism is one of the reasons for more medications. They also said it is bad that people are on too much medication and that people should get more support