HIRES Dust Imaging of the NGC 6334 Star Forming Complex

We present here our final report for the NASA grant "HIRES Dust Imaging of the NGC 6334 Star Forming Complex." This project was designed to study the photodissociation regions surrounding several OB stars in this cloud complex. NGC 6334 is unique in having at least seven distinct massive star forming regions in the same molecular cloud complex. The obvious advantage of studying young stars in the same molecular complex is that the stars all formed in the same global environment. Consequently, global factors like density waves, abundances, global magnetic field strength, and age of the parental molecular cloud cannot contribute to the differences among the star forming regions. Instead, the differences must arise only from local effects such as the mass, age, and UV fields of the individual stars. A study of NGC 6334 will greatly simplify the general problem of comparing different star formation regions by eliminating global effects

Dense gas and HII regions in the starburst galaxy NGC 253

The energetic activity in the nuclear barred region of NGC 253 is attributable to a burst of star formation. NGC 253 is in many ways a twin of the prototypical starburst galaxy M82; the strong non-thermal radio continuum, high far-infrared luminosity, and bright molecular emission of the central 1 Kpc parallel the morphology of the M82 starburst. Furthermore, the filamentary low ionization optical emission and extended x ray emission along the minor axis in NGC 253 is similar to a scaled down version of the well developed galactic bipolar wind in M82. The infrared luminosity of NGC 253, 3(exp 10) solar luminosity, is comparable to M82 but is emitted from a smaller region (Telesco and Harper 1980). This suggests that the NGC 253 starburst may be more intense and at an earlier evolutionary stage than M82. However, the presence of a non-stellar AGN in NGC 253 may complicate the comparison (Turner and Ho, 1985). Researchers used the Hat Creek millimeter interferometer to map emission from the J = 1 to 0 transitions of HCN and HCO(+) as well as 3 mm continuum emission, toward the nuclear region of NGC 253. The HCO(+) and continuum observations are sensitive to spatial scales from 6 to 45 seconds. The 2 minute field of view comfortably includes the entire starburst region (about 40 seconds; 650 pc). Because the longer baseline HCN observations are not yet complete, they are only sensitive to spatial scales from 15 to 45 seconds

Impacts of AIDS on marriage patterns, customs and practices in Uganda

Uganda has one of the highest numbers of reported AIDS cases in sub-Saharan Africa. This is mainly due to a number of historical and political factors. The government of Uganda has openly dealt with the AIDS crisis since 1986 but before that the socio-economic and political chaos in the country created an ideal situation for HIV to spread widely in both rural and urban areas. The HIV infection rate varies among different population subgroups: the 1987/88 sero-survey showed variations among regions and between rural and urban areas. In the most urbanized central region, 21.1 per cent of urban and 12.1 per cent of rural residents were estimated to be HIV-positive. In Western Region which is less developed than Central, 29 per cent of urban and 5.7 per cent of rural residents were infected. In contrast, in the remote and rural West Nile Region, 7.7 per cent of urban and 6.6 per cent of rural residents were HIV-positive (Asedri 1989). There is now a sizeable body of research in Uganda on sexual behaviour, social networking and HIV transmission, including sexual partner studies and studies of changing sexual behaviour in response to the epidemic (e.g. Berkley et al. 1990; Serwadda et al. 1992; Konde-Lule, Musagara and Musgrave 1993; Mulder et al. 1994). However, there is a need for more research on the impact of AIDS on the individual, the family and the community. Little is currently known about changes in households, extended families and their coping mechanisms, and the impact of AIDS on future productivity at the family level and within the community. The household is the basic unit of subsistence production in Uganda, and its existence and that of the extended family system within which it is embedded has enabled the society to weather the many stresses of war and social dislocation which have occurred in the country for over two decades. It is anticipated, however, that the increased stress occasioned by AIDS will be too much for the extended family systems to bear in the long run

Hard Gamma Ray Emission from the Starburst Galaxy NGC 253

We have completed the study to search for hard gamma ray emission from the starburst galaxy NGC 253. Since supernovae are thought to provide the hard gamma ray emission from the Milky Way, starburst galaxies, with their extraordinarily high supernova rates, are prime targets to search for hard gamma ray emission. We conducted a careful search for hard gamma ray emission from NGC 253 using the archival data from the EGRET experiment aboard the CGRO. Because this starburst galaxy happens to lie near the South Galactic Pole, the Galactic gamma ray background is minimal. We found no significant hard gamma ray signal toward NGC 253, although a marginal signal of about 1.5 sigma was found. Because of the low Galactic background, we obtained a very sensitive upper limit to the emission of greater than 100 MeV gamma-rays of 8 x 10(exp -8) photons/sq cm s. Since we expected to detect hard gamma ray emission, we investigated the theory of gamma ray production in a dense molecular medium. We used a leaky-box model to simulate diffusive transport in a starburst region. Since starburst galaxies have high infrared radiation fields, we included the effects of self-Compton scattering, which are usually ignored. By modelling the expected gamma-ray and synchrotron spectra from NGC 253, we find that roughly 5 - 15% of the energy from supernovae is transferred to cosmic rays in the starburst. This result is consistent with supernova acceleration models, and is somewhat larger than the value derived for the Galaxy (3 - 10%). Our calculations match the EGRET and radio data very well with a supernova rate of 0.08/ yr, a magnetic field B approx. greater than 5 x 10(exp -5) G, a density n approx. less than 100/sq cm, a photon density U(sub ph) approx. 200 eV/sq cm, and an escape time scale tau(sub 0) approx. less than 10 Myr. The models also suggest that NGC 253 should be detectable with only a factor of 2 - 3 improvement in sensitivity. Our results are consistent with the standard picture of gamma-ray acceleration by supernovae

Impact of AIDS on the family and mortality in Uganda

The profile of the HIV/AIDS epidemic in Uganda can be summarized in the following terms: by December 1993, the cumulative AIDS cases reported by the official health system stood at 43,875 (ACP 1994); with about equal numbers by sex, with 47.7 per cent and 52.3 per cent of male and female cases respectively, the age-sex distribution showing female to male ratios of 4:1 and 2:1 in the age groups 15-19 and 20-24 respectively. This is followed by about equal numbers of both sexes at age-group 25-29 and a slight excess of males in all age groups thereafter. Although all 39 administrative districts had cases reported by that date, there are significant variations in the severity of the epidemic from district to district, with cumulative cases per thousand population in 1993 varying from less than one in some remote districts to more than 144 in Kampala city. The distribution by residence indicates a more severe urban than rural epidemic, with trading centres being in between in severity; nationally, the frequency of AIDS-related deaths is increasing and AIDS is touching most people's lives directly or indirectly. Many researchers have conducted studies of transmission, progression rates, sexual behaviour, patient care and the impact of the disease in Uganda (e.g. Konde-Lule 1992; Serwadda et al. 1992; Barnett and Blaikie 1992; McGrath et al. 1993; Mulder et al. 1994). The findings of these investigations have greatly enhanced the understanding of the disease and its impact on Ugandans. However, most of these studies have been limited in coverage of the country; they have concentrated on Rakai, Masaka and Kampala districts which are most affected by the disease. This paper reports the findings of a study on the impact of AIDS on the family and mortality covering six districts in the west, southwest, south and east of Uganda

Care for AIDS orphans in Uganda: findings from focus group discussions

A few studies have published findings on AIDS orphan care. Perhaps the pioneering study of orphans in Uganda was by Hunter (1990) who was alarmed by the high proportions of orphans in the population. She found that 23 per cent of the children in Rakai district did not have both parents in comparison to 12 per cent in Hoima; she predicted that the usual coping mechanism of the extended family would not be adequate to handle the problem. Another study, by Barnett and Blaikie (1992) in the Rakai district, narrated the experiences of different groups of orphans. Despite the existence of the extended family system in the area, Barnett and Blaikie found some of the orphans stunted and malnourished because they could not cope with orphanhood. The study concluded that most orphans were deprived of education, parental care, nutrition, shelter, clothing and the legal protection of their parents' property. However, these two studies were limited in the coverage of Uganda to the south and central regions and one district in the western region. This paper reports findings of a recent study of the care of AIDS orphans in several regions of Uganda. It is also the purpose of the paper to investigate how the various societies in Uganda have coped with the orphan problem since the onset of the AIDS epidemic. Changes in past and present coping mechanisms are discussed and recommendations for the future are made

Re-examining Larson's Scaling Relationships in Galactic Molecular Clouds

The properties of Galactic molecular clouds tabulated by Solomon etal (1987) (SRBY) are re-examined using the Boston University-FCRAO Galactic Ring Survey of 13CO J=1-0 emission. These new data provide a lower opacity tracer of molecular clouds and improved angular and spectral resolution than previous surveys of molecular line emission along the Galactic Plane. We calculate GMC masses within the SRBY cloud boundaries assuming LTE conditions throughout the cloud and a constant H2 to 13CO abundance, while accounting for the variation of the 12C/13C with Galacto-centric radius. The LTE derived masses are typically five times smaller than the SRBY virial masses. The corresponding median mass surface density of molecular hydrogen for this sample is 42 Msun/pc^2, which is significantly lower than the value derived by SRBY (median 206 Msun/pc^2) that has been widely adopted by most models of cloud evolution and star formation. This discrepancy arises from both the extrapolation by SRBY of velocity dispersion, size, and CO luminosity to the 1K antenna temperature isophote that likely overestimates the GMC masses and our assumption of constant 13CO abundance over the projected area of each cloud. Owing to the uncertainty of molecular abundances in the envelopes of clouds, the mass surface density of giant molecular clouds could be larger than the values derived from our 13CO measurements. From velocity dispersions derived from the 13CO data, we find that the coefficient of the cloud structure functions, vo=sigma_v/R^{1/2}, is not constant, as required to satisfy Larson's scaling relationships, but rather systematically varies with the surface density of the cloud as Sigma^{0.5} as expected for clouds in self-gravitational equlibrium.Comment: Accepted by ApJ. Newest version includes modifications from the refere