Role of galaxy mergers in cosmic star formation history

We present a morphology study of intermediate-redshift (0.2 < z < 1.2) luminous infrared galaxies (LIRGs) and general field galaxies in the GOODS fields using a revised asymmetry measurement method optimized for deep fields. By taking careful account of the importance of the underlying sky-background structures, our new method does not suffer from systematic bias and offers small uncertainties. By redshifting local LIRGs and low-redshift GOODS galaxies to different higher redshifts, we have found that the redshift dependence of the galaxy asymmetry due to surface-brightness dimming is a function of the asymmetry itself, with larger corrections for more asymmetric objects. By applying redshift-, infrared (IR)-luminosity- and optical-brightness-dependent asymmetry corrections, we have found that intermediate-redshift LIRGs generally show highly asymmetric morphologies, with implied merger fractions ~50% up to z = 1.2, although they are slightly more symmetric than local LIRGs. For general field galaxies, we find an almost constant relatively high merger fraction (20%-30%). The B-band luminosity functions (LFs) of galaxy mergers are derived at different redshifts up to z = 1.2 and confirm the weak evolution of the merger fraction after breaking the luminosity-density degeneracy. The IR LFs of galaxy mergers are also derived, indicating a larger merger fraction at higher IR luminosity. The integral of the merger IR LFs indicates a dramatic evolution of the merger-induced IR energy density [(1 + z)^~(5-6)], and that galaxy mergers start to dominate the cosmic IR energy density at z greater than or ~ 1.

The challenges of safeguarding and securing cultural heritage materials during violent conflict in Nigeria.

Almost every community, country and continent is experiencing a form of conflict, war or disaster. These wars have claimed lives, antiquities, heritage materials, contemporary Arts, Galleries, Museums, Archives, Monuments andHeritage sites. The aim of this study is to explore the challenges of safeguarding cultural heritage material during violent conflict in Nigeria bearing in mind the two UNESCO world heritage sites in Nigeria: Sukur kingdom and Osun Oshogbo sacred Grove. The outcome of this study will help the policy makers to address the challenges of safeguarding cultural heritage materials in times of conflicts, bridge the gap on the existing literature concerning the safeguarding of cultural heritage materials in times of conflict and to make a modest contribution to the existing body of knowledge on cultural heritage protection in Nigeria in particular and other parts of the world in general. This study relies on both primary and secondary sources using questionnaire and oral interview to elicit information from selected relevant cultural agencies, journalists and scholars in the field of art and culture. Relevant literature and documents on the challenges of safeguarding and securing of cultural heritage materials during conflicts were reviewed. The data gathered from the questionnaires and the oral interview is presented in frequency tabular form to give precise and comprehensive insight into the study findings. Notable among the challenges were insecurity and lack of professionalism in the field of cultural heritage profession. The study also revealed that governments are not enforcing the global laws and conventions for the protection of cultural heritage materials in times of violent conflict. The communities where these materials are located have little or no knowledge about the import of these materials and do not take part in securing them in the event of conflict. It is crucial that we place high value on heritage materials since they are inextricably linked with our identity and where we come from. It is strongly recommended that Cultural Heritage Institutions should involve as much as possible the local communities living around the sites by creating awareness educating and encouraging them to take ownership of the Sites located within their communities. They must ensure that the site is safeguarded against all forms of threat. Items of heritage value are not often considered in most disaster management plans therefore there is the need to consider heritage as priority just as the protection of lives and property.