The 3-D clustering of radio galaxies in the TONS survey

We present a clustering analysis of the Texas-Oxford NVSS Structure (TONS) radio galaxy redshift survey. This complete flux-limited survey consists of 268 radio galaxies with spectroscopic redshifts in three separate regions of the sky covering a total of 165 deg^2. By going to faint radio flux densities (s_1.4>3 mJy) but imposing relatively bright optical limits (E R 19.5), the TONS sample is optimised for looking at the clustering properties of low luminosity radio galaxies in a region of moderate (0 < z < 0.5) redshifts. We use the two point correlation function to determine the clustering strength of the combined TONS08 and TONS12 sub-samples and find a clustering strength of r_0(z)=8.7+/-1.6 Mpc (h=0.7). If we assume growth of structure by linear theory and that the median redshift is 0.3, this corresponds to r_0(0)=11.0+/-2.0 Mpc which is consistent with the clustering strength of the underlying host galaxies (~ 2.5 Lstar ellipticals) of the TONS radio galaxy population.Comment: 18 pages, MNRAS accepted. Full paper including all spectra can be found at http://www.noao.edu/noao/staff/brand/brand_corr_fn.ps.g

The Triggering and Bias of Radio Galaxies

We present new results on the clustering and three-dimensional distribution of radio galaxies from the Texas-Oxford NVSS Structure (TONS) survey. The TONS survey was constructed to look at the distribution of radio galaxies in a region of moderate (0 < z < 0.5) redshifts by matching NVSS sources with objects in APM catalogues to obtain a sample of optically bright (R < 19.5), radio faint (1.4-GHz flux density S_1.4 > 3 mJy) radio galaxies over large areas on the sky. We find that redshift spikes, which represent large concentrations of radio galaxies which trace (~ 100 Mpc^3) super-structures are a common phenomena in these surveys. Under the assumption of quasi-linear structure formation theory and a canonical radio galaxy bias, the structures represent ~ 4-5 sigma peaks in the primordial density field and their expected number is low. The most plausible explanation for these low probabilities is an increase in the radio galaxy bias with redshift. To investigate potential mechanisms which have triggered the radio activity in these galaxies - and hence may account for an increase in the bias of this population, we performed imaging studies of the cluster environment of the radio galaxies in super-structure regions. Preliminary results show that these radio galaxies may reside preferentially at the edges of rich clusters. If radio galaxies are preferentially triggered as they fall towards rich clusters then they would effectively adopt the cluster bias.Comment: 4 pages to be published in the proceedings of "Multiwavelength AGN Surveys", Cozumel, Dec 8-12, 200

Using radio galaxies to find super-structures

Radio galaxies are excellent at tracing large-scale structure due to their high bias. We present new results from the TONS08 radio galaxy redshift survey. We find unequivocal evidence for a huge (at least 80 x 80 x 100 Mpc^3) super-structure at redshift z=0.27, confirming tentative evidence for such a structure from the 7C redshift survey (7CRS). A second, newly discovered super-structure is also tentatively found at redshift 0.35 (of dimensions at least 100 x 100 x 100 Mpc^3). Out of the total sample size of 84 radio galaxies, at least 25 are associated with the two super-structures. We use quasi-linear structure formation theory to estimate the number of such structures expected in the TONS08 volume if the canonical value for radio galaxy bias is assumed. Under this assumption, the structures represent ~ 4-5 sigma peaks in the primordial density field and their expected number is low (10^{-2}-10^{-4}). Fortunately, there are several plausible explanations (many of which are testable) for these low probabilities in the form of potential mechanisms for boosting the bias on large scales. These include: the association of radio galaxies with highly biased rich clusters in super-structures, enhanced triggering by group/group mergers, and enhanced triggering and/or redshift space distortion in collapsing systems as the growth of super-structures moves into the non-linear regime. Similar structures could have been missed in previous surveys because of the effects of Poisson-sampling fluctuations.Comment: 6 pages, 3 figures. To appear in "Radio galaxies: past, present and future", eds M. Jarvis et al., Leiden, Nov 200

Managing complex medication regimens: perspectives of consumers with osteoarthritis and healthcare professionals

BACKGROUND: Managing medications is complex, particularly for consumers with multiple coexisting conditions for whom benefits and adverse effects are unpredictable and health priorities may be variable. OBJECTIVE: To investigate perceptions of and experiences with managing drug regimens from the perspectives of consumers with osteoarthritis and coexisting chronic conditions and of healthcare professionals from diverse backgrounds. METHODS: Using an exploratory research design, focus groups were formed with 34 consumers and 19 healthcare professionals. Individual interviews were undertaken with 3 community medical practitioners. RESULTS: Consumers\u27 management of medications was explored in terms of 3 themes: administration of medications, provision of information, and the perceived role of healthcare professionals. In general, consumers lacked understanding regarding the reason that they were prescribed certain medications. Since all consumer participants had at least 2 chronic conditions, they were taking many drugs to relieve undesirable symptoms. Some consumers were unable to achieve improved pain relief and were reluctant to take analgesics prescribed on an as - needed basis. Healthcare professionals discussed the importance of using non-pharmacologic measures to improve symptoms; however, consumers stated that physicians encourage them to continue using medications, often for prolonged periods, even when these agents are not helpful. CONCLUSIONS: Consumers were dissatisfied about the complexity of their medication regimens and also lacked understanding as to how to take their drugs effectively. Dedicated time should be devoted during medical consultations to facilitate verbal exchange of information about medications. Pharmacists must communicate regularly with physicians about consumers\u27 medication needs to help preempt any problems that may arise. Instructions need to be revised through collaboration between physicians and pharmacists so that &quot;as needed&quot; directions provide more explicit advice about when and how to use such drugs. Future research, using large, generalizable samples, should examine trends related to consumers\u27 experiences of symptomatic relief from chronic conditions and their understandings about medications. <br /

An analysis of the quality of property-management principles in the South African public sector - a focus on residential property

Die doel van hierdie artikel is om die toepaslikheid van openbare sektor residensiële eiendomsbestuur op nasionale vlak, soos geïmplementeer deur die Departement van Openbare Werke (DOW), se huidige verhuringspraktyke te ondersoek. Die artikel ondersoek huidige beste praktyk in die verhuring van residensiële eiendom en evalueer die toepaslikheid van hierdie praktyke wanneer die DOW surplus residensiële eiendomme verhuur. Die bevindings dui daarop dat die DOW se residensiële verhuringsbestuur nie op standard is met aanvaarde praktyk nie en tesame met onvoldoende kapasiteit in terme van die grootte van die portefeulje asook die nodige kundigheid, kan hulle nie effektiewe huurkontrakbestuur van surplus staatsbeheerde residensiële eiendom implementeer nie. Die DOW eiendomsverhuringfunksie moet dus onderwerp word aan ‘n hersiening en verandering van die huidige status quo onder die leiding van ‘n onafhanklike eiendomsbestuur raadgewende komitee of verwysingsgroep.The aim of this paper is to investigate the applicability of public-sector residential property management as implemented by the Department of Public Works (DPW) at national level to current leasing management practices. The article investigates current best practice in leasing of residential property and evaluates the applicability of these practices to the DPW, as the landlord, when letting out surplus residential properties. The findings indicate that the DPW residential leasing management is not in line with best practices, together with inadequate capacity in terms of the size of the portfolio and the requisite expertise to adopt and implement effective lease management of surplus state-owned residential property. Thus the DPW property-leasing function should be subjected to a review and re-engineering of the current status quo with guidance from an independent property-management advisory committee or reference group.http://reference.sabinet.co.za/sa_epublication/structam201

Spitzer Mid-Infrared Spectroscopy of 70um-Selected Distant Luminous Infrared Galaxies

We present mid-infrared spectroscopy obtained with the Spitzer Space Telescope of a sample of 11 optically faint, infrared luminous galaxies selected from a Spitzer MIPS 70um imaging survey of the NDWFS Bootes field. These are the first Spitzer IRS spectra presented of distant 70um-selected sources. All the galaxies lie at redshifts 0.3<z<1.3 and have very large infrared luminosities of L_IR~ 0.1-17 x 10^12 solar luminosities. Seven of the galaxies exhibit strong emission features attributed to polycyclic aromatic hydrocarbons (PAHs). The average IRS spectrum of these sources is characteristic of classical starburst galaxies, but with much larger infrared luminosities. The PAH luminosities of L(7.7) ~ 0.4 - 7 x 10^11 solar luminosities imply star formation rates of ~ 40 - 720 solar masses per year. Four of the galaxies show deep 9.7um silicate absorption features and no significant PAH emission features (6.2um equivalent widths < 0.03um). The large infrared luminosities and low f70/f24 flux density ratios suggests that these sources have AGN as the dominant origin of their large mid-infrared luminosities, although deeply embedded but luminous starbursts cannot be ruled out. If the absorbed sources are AGN-dominated, a significant fraction of all far-infrared bright, optically faint sources may be dominated by AGN.Comment: 8 Pages, ApJ accepte

Redshift Distribution of Extragalactic 24 micron Sources

We present the redshift distribution of a complete, unbiased sample of 24 micron sources down to fnu(24 micron) = 300 uJy (5-sigma). The sample consists of 591 sources detected in the Bootes field of the NOAO Deep Wide-Field Survey. We have obtained optical spectroscopic redshifts for 421 sources (71%). These have a redshift distribution peaking at z~0.3, with a possible additional peak at z~0.9, and objects detected out to z=4.5. The spectra of the remaining 170 (29%) exhibit no strong emission lines from which to determine a redshift. We develop an algorithm to estimate the redshift distribution of these sources, based on the assumption that they have emission lines but that these lines are not observable due to the limited wavelength coverage of our spectroscopic observations. The redshift distribution derived from all 591 sources exhibits an additional peak of extremely luminous (L(8-1000 micron) > 3 x 10^{12} Lsun) objects at z~2, consisting primarily of sources without observable emission lines. We use optical line diagnostics and IRAC colors to estimate that 55% of the sources within this peak are AGN-dominated. We compare our results to published models of the evolution of infrared luminous galaxies. The models which best reproduce our observations predict a large population of star-formation dominated ULIRGs at z > 1.5 rather than the AGN-dominated sources we observe.Comment: 21 pages, 11 figures; accepted for publication in Ap

The Collimated Jet Source in IRAS 16547-4247: Time Variation, Possible Precession, and Upper Limits to the Proper Motions Along the Jet Axis

The triple radio source detected in association with the luminous infrared source IRAS 16547-4247 has previously been studied with high angular resolution and high sensitivity with the Very Large Array (VLA) at 3.6-cm wavelength. In this paper, we present new 3.6 cm observations taken 2.68 years after the first epoch that allow a search for variability and proper motions, as well as the detection of additional faint sources in the region. We do not detect proper motions along the axis of the outflow in the outer lobes of this source at a 4-$\sigma$ upper limit of $\sim$160 km s$^{-1}$. This suggests that these lobes are probably working surfaces where the jet is interacting with a denser medium. However, the brightest components of the lobes show evidence of precession, at a rate of $0\rlap.^\circ08$ yr$^{-1}$ clockwise in the plane of the sky. It may be possible to understand the distribution of almost all the identified sources as the result of ejecta from a precessing jet. The core of the thermal jet shows significant variations in flux density and morphology. We compare this source with other jets in low and high mass young stars and suggest that the former can be understood as a scaled-up version of the latter.Comment: 26 pages, 9 figure

The Origin of the 24-micron Excess in Red Galaxies

Observations with the Spitzer Space Telescope have revealed a population of red-sequence galaxies with a significant excess in their 24-micron emission compared to what is expected from an old stellar population. We identify 900 red galaxies with 0.15<z<0.3 from the AGN and Galaxy Evolution Survey (AGES) selected from the NOAO Deep Wide-Field Survey Bootes field. Using Spitzer/MIPS, we classify 89 (~10%) with 24-micron infrared excess (f24>0.3 mJy). We determine the prevalence of AGN and star-formation activity in all the AGES galaxies using optical line diagnostics and mid-IR color-color criteria. Using the IRAC color-color diagram from the IRAC Shallow Survey, we find that 64% of the 24-micron excess red galaxies are likely to have strong PAH emission features in the 8-micron IRAC band. This fraction is significantly larger than the 5% of red galaxies with f24<0.3 mJy that are estimated to have strong PAH emission, suggesting that the infrared emission is largely due to star-formation processes. Only 15% of the 24-micron excess red galaxies have optical line diagnostics characteristic of star-formation (64% are classified as AGN and 21% are unclassifiable). The difference between the optical and infrared results suggest that both AGN and star-formation activity is occurring simultaneously in many of the 24-micron excess red galaxies. These results should serve as a warning to studies that exclusively use optical line diagnostics to determine the dominant emission mechanism in the infrared and other bands. We find that ~40% of the 24-micron excess red galaxies are edge-on spiral galaxies with high optical extinctions. The remaining sources are likely to be red galaxies whose 24-micron emission comes from a combination of obscured AGN and star-formation activity.Comment: ApJ, accepted; 11 pages, 7 figures; corrected reference to IRAC Shallow Survey in abstrac

A Significant Population of Very Luminous Dust-Obscured Galaxies at Redshift z ~ 2

Observations with Spitzer Space Telescope have recently revealed a significant population of high-redshift z~2 dust-obscured galaxies (DOGs) with large mid-IR to UV luminosity ratios. These galaxies have been missed in traditional optical studies of the distant universe. We present a simple method for selecting this high-z population based solely on the ratio of the observed mid-IR 24um to optical R-band flux density. In the 8.6 sq.deg Bootes NDWFS Field, we uncover ~2,600 DOG candidates (= 0.089/sq.arcmin) with 24um flux densities F24>0.3mJy and (R-[24])>14 (i.e., F[24]/F[R] > 1000). These galaxies have no counterparts in the local universe, and become a larger fraction of the population at fainter F24, representing 13% of the sources at 0.3~mJy. DOGs exhibit evidence of both star-formation and AGN activity, with the brighter 24um sources being more AGN- dominated. We have measured spectroscopic redshifts for 86 DOGs, and find a broad z distribution centered at ~2.0. Their space density is 2.82E-5 per cubic Mpc, similar to that of bright sub-mm-selected galaxies at z~2. These redshifts imply very large luminosities LIR>~1E12-14 Lsun. DOGs contribute ~45-100% of the IR luminosity density contributed by all z~2 ULIRGs, suggesting that our simple selection criterion identifies the bulk of z~2 ULIRGs. DOGs may be the progenitors of ~4L* present-day galaxies seen undergoing a luminous,short- lived phase of bulge and black hole growth. They may represent a brief evolution phase between SMGs and less obscured quasars or galaxies. [Abridged]Comment: Accepted for publication in the Astrophysical Journa