The faint low-frequency radio universe in continuum: exploitation of the pre-SKA deepest survey

This thesis presents a thorough and significant work on the properties of radio sources as derived from deep 610-MHz GMRT data and ancillary multi-wavelength data. The faint radio sources at 610-MHz are found out to distances such that the objects are seen as they were when the universe was less than half its current age. These data provide a first look at the faint radio sky at sensitivities that will soon be achieved by key programs on the South African MeerKAT radio telescope, and thus take a first step in the exploration of the radio universe that will be made by the Square Kilometre Array. I report deep 610-MHz GMRT observations of the EN1 field, a region of 1.86 deg2 . We achieve a nominal sensitivity of 7.1µ Jy beam−1 . From our 610 MHz mosaic image, we recover 4290 sources after accounting for multiple component sources down to a 5σ flux density limit of 35.5 µ Jy. From this data, I derive the 610 MHz source counts applying corrections for completeness, resolution bias and Eddington bias. The 610- MHz source counts show a flattening at flux densities below 1 mJy. The source counts are higher than previous observations at this frequency below this break. However, they are generally consistent with recent models of the low-frequency source population. Using ancillary multi-wavelength data in the field, I investigate the key issue of source population classification using the deepest data at an intermediate-low frequency (higher than LOFAR and lower than JVLA), where previous work has not been sensitive enough to reach the µJy population. By cross-matching against the multi-wavelength data, I identify 72% of the radio sample having reliable redshifts, of which 19% of the redshifts are based on spectroscopy. From the classification, I obtain 1685 sources as Star-Forming Galaxies (SFGs), 281 sources Radio-Quiet (RQ) and 339 sources Radio-Loud (RL) Active Galactic Nuclei (AGN) for the sub-sample with redshifts and at least one multi-wavelength AGN diagnostic. SFGs are mostly low-power radio sources, i.e L610 MHz 1025 W Hz−1 . From cross-matching my sample with other radio surveys (GMRT at 325-MHz, FIRST at 1.4-GHz and JVLA at 5-GHz), I obtain the median spectral index from 325-MHz to 610-MHz to be −0.80 ± 0.29, 610-MHz to 1.4-GHz to be −0.83 ± 0.31 and 1.4-GHz to 5-GHz to be −1.12 ± 0.15. The main result is that the median spectral index appears to steepen at the highest frequency. With the above catalogue in hand, I use the non-parametric V/Vmax test and the radio luminosity function to investigate the cosmic evolution of different source populations. I study SFGs and derive their IR-radio correlation and luminosity function as a function of redshift. By integrating the evolving SFG luminosity functions I also derive the cosmic star formation rate density out to z = 1.5. I address the long standing question about the origin of radio emission in RQ AGN. I compare the star formation rate (SFR) derived from their far-infrared luminosity, as traced by Herschel, with the SFR computed from their radio emission. I find evidence that the main contribution to the radio emission of RQ AGN is the star formation activity in their host galaxies. At high luminosities, however, both SFGs and 1 RQ AGN display a radio excess when comparing radio and infrared star formation rates. The vast majority of our sample lie along the SFR − M? ”main sequence” at all redshifts when using infrared star formation rates. This result opens the possibility of using the radio band to estimate the SFR even in the hosts of bright AGN where the optical-to-mid-infrared emission can be dominated by the AGN. I investigate the evolution of radio AGN out to z ∼ 1.5 with continuous models of pure density and pure luminosity evolution with Φ? ∝ ( 1 + z)(2.25±0.38)−(0.63±0.35)z and L610 MHz ∝ ( 1 + z)(3.45±0.53)−(0.55±0.29)z respectively. I also constrain the evolution of RQ AGN and RL AGN separately with a continuous model of pure luminosity evolution. For the RQ and RL AGN, we find a fairly mild evolution with redshift best fitted by pure luminosity evolution with L610 MHz ∝ ( 1 + z)(2.81±0.43)−(0.57±0.30)z for RQ AGN and L610 MHz ∝ ( 1 + z)(3.58±0.54)−(0.56±0.29)z for RL AGN. The results reveal that the 610 MHz radio AGN population thus comprises two differently evolving populations whose radio emission is mostly SF-driven or AGN-driven respectively. Finally, I probe the infrared-radio correlation and radio spectral indices of the faint radio population using stacking. I stack infrared sources in the EN1 field using the MIPS 24 micron mid-infrared survey and radio surveys created at 325 MHz, 610 MHz and 1.4 GHz. The stacking experiment shows a variation in the absolute strength of the infrared-radio correlation between these three different frequencies and the MIPS 24 micron band. I find tentative evidence of a small deviation from the correlation at the faintest infrared flux densities. The stacked radio spectral index analyses reveal that the majority of the median stacked sources exhibit steep spectra, with a spectral index that steepens with frequency between α 325 610 and α 610 1400. This work is particularly useful to pave the way for upcoming radio surveys with SKA pathfinders and precursors

The nature of the microjy source population

Masters of ScienceThe study of the faint radio universe and of its properties has recently become a very active field of research not only because of the much improved capabilities of the SKA pathfinders but also because of the need to better plan for SKA surveys. These new facilities will map large areas of the sky to unprecedented depths and transform radio astronomy into the leading technique for investigating the complex processes which govern the formation and evolution of galaxies. This thesis combines multi-wavelength techniques, highly relevant to future deep radio surveys, to study the properties of faint radio sources. The nature of the faint radio sources is presented, over a large GMRT survey area of an area of 1.2 deg2 comprising 2800 sources. Utilising multi-wavelength data we have matched 85% of the radio population to Spitzer/IRAC and obtained a redshift estimate for 63%. The redshift associations are a combination of photometric and spectroscopic redshift estimates. This study investigates several multi-wavelength diagnostics used to identify AGN, using radio, infrared, optical and x-ray data . This analysis shows that various diagnostics (from the radio through the X-ray ones) select fairly different types of AGNs, with an evidence of a disagreement in the number of AGNs selected by each individual diagnostics. For the sources with redshift we use a classification scheme based on radio luminosity, x-ray emission, BOSS/SDSS spectroscopy, IRAC colors satisfying the Donley criterion, and MIPS 24ɥm radio-loud AGN criteria to separate them into AGNs and SFGs. On the basis of this classification, we find that at least 12.5% of the sources with redshifts are AGNs while the remaining 87.5% are adopted as SFGs. We explore the nature of the classified sources through the far-infrared radio correlation. We measure a median qIR value of 2:45± 0:01 for the SFGs and qIR value of 2:27 ± 0:05 for the AGNs. The decrease in the median value of qIR for the AGNs is a result of the additional AGN component to radio emission for the AGN-powered sources and find tentative evidence of an evolution of the qIR with redshift

LITURGICAL CHANGES IN THE REPERTORY OF THE METHODIST CHURCH GHANA

……………………………………………………………………………………………………… Abstract: The growth of Christianity in Ghana has led to the proliferation of liturgical changes leading to conflict of religious ideologies within the traditional (orthodox) and the modern (charismatic) churches. These liturgical modifications are seen not only in their worship, prayers and offerings but also in their music. This paper explores the changes that have taken place in the musical liturgy of the Methodist Church, Ghana. Through qualitative data collection, the paper investigates the factors leading to these changes and brings out the impact made in the Methodist church in general. It uses two epistemological frameworks: The separatism and the syncretism. The former looks at the liturgy in retrospect whereas the latter dwells on the changes culminating different beliefs as a result of the different movements in the Christendom in Ghana. To satisfy the varied congregational taste in this modern world, it is important that the shift in the musical liturgy of the Methodist church is well embraced by all

5TH applied research conference in Africa

Abstract: Please refer to full text to view abstrac

Haematological and Biochemical Reference Values for Healthy Adults in the Middle Belt of Ghana

BACKGROUND: Reference values are very important in clinical management of patients, screening participants for enrollment into clinical trials and for monitoring the onset of adverse events during these trials. The aim of this was to establish gender-specific haematological and biochemical reference values for healthy adults in the central part of Ghana. METHODS: A total of 691 adults between 18 and 59 years resident in the Kintampo North Municipality and South District in the central part of Ghana were randomly selected using the Kintampo Health and Demographic Surveillance System and enrolled in this cross-sectional survey. Out of these, 625 adults made up of 316 males and 309 females were assessed by a clinician to be healthy. Median values and nonparametric 95% reference values for 16 haematology and 22 biochemistry parameters were determined for this population based on the Clinical Laboratory and Standards Institute guidelines. Values established in this study were compared with the Caucasian values being used currently by our laboratory as reference values and also with data from other African and western countries. RESULTS: REFERENCE VALUES ESTABLISHED INCLUDE: haemoglobin 113-164 g/L for males and 88-144 g/L for females; total white blood cell count 3.4-9.2 × 10(9)/L; platelet count 88-352 × 10(9)/L for males and 89-403 × 10(9)/L for females; alanine aminotransferase 8-54 U/L for males and 6-51 U/L for females; creatinine 56-119 µmol/L for males and 53-106 µmol/L for females. Using the haematological reference values based on the package inserts would have screened out up to 53% of potential trial participants and up to 25% of the population using the biochemical parameters. CONCLUSION: We have established a panel of locally relevant reference parameters for commonly used haematological and biochemical tests. This is important as it will help in the interpretation of laboratory results both for clinical management of patients and safety monitoring during a trial

Haematology reference values for Kintampo.

<p>Med: Median.</p>*<p>Mann-Whitney test for differences in between males and females.</p

Biochemistry out of range (OOR) values based on comparison with values from Elitech reagent inserts.

<p>NA: Not available.</p

Map of study communities.

<p>Map of study communities.</p

Analytical precision for haematology assays.

<p>Analytical precision for haematology assays.</p

Haematology out of range (OOR) values based on comparison with ABX values.

<p>NA: Not available.</p