The radio luminosity function of radio-loud quasars from the 7C Redshift Survey

We present a complete sample of 24 radio-loud quasars (RLQs) from the new 7C Redshift Survey. Every quasar with a low-frequency (151 MHz) radio flux-density S_151 > 0.5 Jy in two regions of the sky covering 0.013 sr is included; 23 of these have sufficient extended flux to meet the selection criteria, 18 of these have steep radio spectra (hereafter denoted as SSQs). The key advantage of this sample over most samples of RLQs is the lack of an optical magnitude limit. By combining the 7C and 3CRR samples, we have investigated the properties of RLQs as a function of redshift z and radio luminosity L_151. We derive the radio luminosity function (RLF) of RLQs and find that the data are well fitted by a single power-law with slope alpha_1=1.9. We find that there must be a break in the RLQ RLF at log_10(L_151 / W Hz^-1 sr^-1) < 27, in order for the models to be consistent with the 7C and 6C source counts. The z-dependence of the RLF follows a one-tailed gaussian which peaks at z=1.7. We find no evidence for a decline in the co-moving space density of RLQs at higher redshifts. A positive correlation between the radio and optical luminosities of SSQs is observed, confirming a result of Serjeant et al. (1998). We are able to rule out this correlation being due to selection effects or biases in our combined sample. The radio-optical correlation and best-fit model RLF enable us to estimate the distribution of optical magnitudes of quasars in samples selected at low radio frequencies. We conclude that for samples with S_151 < 1 Jy one must use optical data significantly deeper than the POSS-I limit (R approx 20), in order to avoid severe incompleteness.Comment: 28 pages with 13 figures. To appear in MNRA

Galaxy Formation Through Filamentary Accretion at z=6.1

We present ALMA observations of the dust continuum and [C II] 158um line emission from the z=6.0695 Lyman Break Galaxy WMH5. These observations at 0.3" spatial resolution show a compact (~3kpc) main galaxy in dust and [C II] emission, with a 'tail' of emission extending to the east by about 5kpc (in projection). The [C II] tail is comprised predominantly of two distinct sub-components in velocity, separated from the core by ~100 and 250km/s, with narrow intrinsic widths of about 80km/s, which we call 'sub-galaxies'. The sub-galaxies themselves are extended east-west by about 3kpc in individual channel images. The [C II] tail joins smoothly into the main galaxy velocity field. The [C II] line to continuum ratios are comparable for the main and sub-galaxy positions, within a factor 2. In addition, these ratios are comparable to z~5.5 LBGs. We conjecture that the WMH5 system represents the early formation of a galaxy through the accretion of smaller satellite galaxies, embedded in a smoother gas distribution, along a possibly filamentary structure. The results are consistent with current cosmological simulations of early galaxy formation, and support the idea of very early enrichment with dust and heavy elements of the accreting material.Comment: 10 pages, 9 figures, Accepted for publication in Ap

The Canada-France High-z Quasar Survey: 1.2mm Observations

We report 250 GHz (1.2 mm) observations of a sample of 20 QSOs at redshifts 5.8<z<6.5 from the the Canada-France High-z Quasar Survey (CFHQS), using the Max-Planck Millimeter Bolometer (MAMBO) array at the IRAM 30-metre telescope. A rms sensitivity <~ 0.6 mJy was achieved for 65% of the sample, and <~ 1.0 mJy for 90%. Only one QSO, CFHQS J142952+544717, was robustly detected with S_250GHz = 3.46 +/-0.52 mJy. This indicates that one of the most powerful known starbursts at z~6 is associated with this radio loud QSO. On average, the other CFHQS QSOs, which have a mean optical magnitude fainter than previously studied SDSS samples of z~6 QSOs, have a mean 1.2 mm flux density = 0.41 +/-0.14 mJy; such a 2.9-sigma average detection is hardly meaningful. It would correspond to ~ 0.94+/-0.32 10^12 Lo, and an average star formation rate of a few 100's Mo/yr, depending on the IMF and a possible AGN contribution to . This is consistent with previous findings of Wang et al. (2011) on the far-infrared emission of z~6 QSOs and extends them toward optically fainter sources.Comment: 6 pages, 1 figure, A&A in pres

Mid-infrared sources in the ELAIS Deep X-ray Survey

We present a cross‐correlation of the European Large Area Infrared Space Observatory (ISO) survey (ELAIS) with the ELAIS Deep X‐ray Survey of the N1 and N2 fields. There are seven Chandra point sources with matches in the ELAIS Final Analysis 15‐μm catalogue, out of a total of 28 extragalactic ISO sources present in the Chandra fields. Five of these are consistent with active galactic nuclei (AGN) giving an AGN fraction of ∼19 per cent in the 15‐μm flux range 0.8–6 mJy. We have co‐added the hard X‐ray fluxes of the individually undetected ISO sources and find a low significance detection consistent with star formation in the remaining population. We combine our point source cross‐correlation fraction with the XMM–Newton observations of the Lockman Hole and Chandra observations of the Hubble Deep Field North to constrain source count models of the mid‐infrared galaxy population. The low dust‐enshrouded AGN fraction in ELAIS implied by the number of cross‐identifications between the ELAIS mid‐infrared sample and the Chandra point sources is encouraging for the use of mid‐infrared surveys to constrain the cosmic star formation history, provided there are not further large undetected populations of Compton‐thick AGN

Medical students as global citizens: a qualitative study of medical students' views on global health teaching within the undergraduate medical curriculum

Background: There is increasing interest in global health teaching among medical schools and their students. Schools in the UK and internationally are considering the best structure, methods and content of global health courses. Academic work in this area, however, has tended to either be normative (specifying what global health teaching ought to look like) or descriptive (of a particular intervention, new module, elective, etc.). Methods: While a number of studies have explored student perspectives on global health teaching, these have often relied on tools such as questionnaires that generate little in-depth evidence. This study instead used qualitative methods to explore medical student perspectives on global health in the context of a new global health module established in the core medical curriculum at a UK medical school. Results: Fifth year medical students participated in a structured focus group session and semi-structured interviews designed to explore their knowledge and learning about global health issues, as well as their wider perspectives on these issues and their relevance to professional development. While perspectives on global health ranged from global health ‘advocate’ to ‘sceptic’, all of the students acknowledged the challenges of prioritising global health within a busy curriculum. Conclusions: Students are highly alert to the diverse epistemological issues that underpin global health. For some students, such interdisciplinarity is fundamental to understanding contemporary health and healthcare. For others, global health is merely a topic of geographic relevance. Furthermore, some students appeared to accept global health as a specialist area only relevant to professionals working overseas, while others considered it to be an essential part of working in the globalised world and therefore relevant to all medical professionals. Students also clearly noted that including ‘soft’ subjects and more discursive approaches to teaching and learning often sits awkwardly in a programme where ‘harder’ forms of knowledge and didactic methods tend to dominate. This suggests that more work needs to be done to explain the relevance of global health to medical students at the very beginning of their studies

The ELAIS deep X-ray survey - I. Chandra source catalogue and first results

We present an analysis of two deep (75 ks) Chandra observations of the European Large Area Infrared Space Observatory (ISO) Survey (ELAIS) fields N1 and N2 as the first results from the ELAIS deep X-ray survey. This survey is being conducted in well-studied regions with extensive multiwavelength coverage. Here we present the Chandra source catalogues along with an analysis of source counts, hardness ratios and optical classifications. A total of 233 X-ray point sources are detected in addition to two soft extended sources, which are found to be associated with galaxy clusters. An overdensity of sources is found in N1 with 30 per cent more sources than N2, which we attribute to large-scale structure. A similar variance is seen between other deep Chandra surveys. The source count statistics reveal an increasing fraction of hard sources at fainter fluxes. The number of galaxy-like counterparts also increases dramatically towards fainter fluxes, consistent with the emergence of a large population of obscured sources

The ultracool-field dwarf luminosity-function and space density from the Canada-France Brown Dwarf Survey

Context. Thanks to recent and ongoing large scale surveys, hundreds of brown dwarfs have been discovered in the last decade. The Canada-France Brown Dwarf Survey is a wide-field survey for cool brown dwarfs conducted with the MegaCam camera on the Canada-France-Hawaii Telescope telescope. Aims. Our objectives are to find ultracool brown dwarfs and to constrain the field brown-dwarf luminosity function and the mass function from a large and homogeneous sample of L and T dwarfs. Methods. We identify candidates in CFHT/MegaCam i' and z' images and follow them up with pointed near infrared (NIR) imaging on several telescopes. Halfway through our survey we found ~50 T dwarfs and ~170 L or ultra cool M dwarfs drawn from a larger sample of 1400 candidates with typical ultracool dwarfs i' - z' colours, found in 780 square degrees. Results. We have currently completed the NIR follow-up on a large part of the survey for all candidates from mid-L dwarfs down to the latest T dwarfs known with utracool dwarfs' colours. This allows us to draw on a complete and well defined sample of 102 ultracool dwarfs to investigate the luminosity function and space density of field dwarfs. Conclusions. We found the density of late L5 to T0 dwarfs to be 2.0pm0.8 x 10-3 objects pc-3, the density of T0.5 to T5.5 dwarfs to be 1.4pm0.3 x 10-3 objects pc-3, and the density of T6 to T8 dwarfs to be 5.3pm3.1 x 10-3 objects pc-3 . We found that these results agree better with a flat substellar mass function. Three latest dwarfs at the boundary between T and Y dwarfs give the high density 8.3p9.0m5.1 x 10-3 objects pc-3. Although the uncertainties are very large this suggests that many brown dwarfs should be found in this late spectral type range, as expected from the cooling of brown dwarfs, whatever their mass, down to very low temperature.Comment: Accepted for publication in A&

The ELAIS Deep X-ray Survey

We present initial follow-up results of the ELAIS Deep X-ray Survey which is being undertaken with the Chandra and XMM-Newton Observatories. 235 X-ray sources are detected in our two 75 ks ACIS-I observations in the well-studied ELAIS N1 and N2 areas. 90% of the X-ray sources are identified optically to R=26 with a median magnitude of R=24. We show that objects which are unresolved optically (i.e. quasars) follow a correlation between their optical and X-ray fluxes, whereas galaxies do not. We also find that the quasars with fainter optical counterparts have harder X-ray spectra, consistent with absorption at both wavebands. Initial spectroscopic follow-up has revealed a large fraction of high-luminosity Type 2 quasars. The prospects for studying the evolution of the host galaxies of X-ray selected Type 2 AGN are considered.Comment: 9 pages, 5 figures, To appear in Proceedings of XXI Moriond Conference: "Galaxy Clusters and the High Redshift Universe Observed in X-rays", edited by D. Neumann, F.Durret, & J. Tran Thanh Va

Redshifts and Neutral Hydrogen Observations of Compact Symmetric Objects in the COINS Sample

Compact Symmetric Objects (CSOs) are young radio galaxies whose jet axes lie close to the plane of the sky, and whose appearance is therefore not dominated by relativistic beaming effects. The small linear sizes of CSOs make them valuable for studies of both the evolution of radio galaxies and testing unified schemes for active galactic nuclei (AGN). A parsec-scale region of gas surrounding the central engine is predicted by both accretion and obscuration scenarios. Working surfaces, or ``hot spots,'' and the radio jets of CSOs are close enough to the central engines that this circumnuclear gas can be seen in absorption. The CSOs Observed in the Northern Sky (COINS) sample is comprised of 52 CSO candidates identified in three VLBI surveys. Of these, 27 have now been confirmed as CSOs. Optical redshifts are available in the literature for 28 of the CSO candidates, and HI absorption has been detected toward four. We present new optical spectroscopic redshifts for three of the candidates and summarize the current status of optical identifications. We further report on the discovery of HI in absorption towards the CSO J1816+3457 and summarize the results of neutral hydrogen absorption studies of the sources in this sample.Comment: 12 pages, Accepted for publication in Ap