What shapes the far-infrared spectral energy distributions of galaxies?

To explore the connection between the global physical properties of galaxies and their far-infrared (FIR) spectral energy distributions (SEDs), we study the variation in the FIR SEDs of a set of hydrodynamically simulated galaxies that are generated by performing dust radiative transfer in post-processing. Our sample includes both isolated and merging systems at various stages of the merging process and covers infrared (IR) luminosities and dust masses that are representative of both low- and high-redshift galaxies. We study the FIR SEDs using principle component analysis (PCA) and find that 97\% of the variance in the sample can be explained by two principle components (PCs). The first PC characterizes the wavelength of the peak of the FIR SED, and the second encodes the breadth of the SED. We find that the coefficients of both PCs can be predicted well using a double power law in terms of the IR luminosity and dust mass, which suggests that these two physical properties are the primary determinants of galaxies' FIR SED shapes. Incorporating galaxy sizes does not significantly improve our ability to predict the FIR SEDs. Our results suggest that the observed redshift evolution in the effective dust temperature at fixed IR luminosity is not driven by geometry: the SEDs of $z \sim 2-3$ ultraluminous IR galaxies (ULIRGs) are cooler than those of local ULIRGs not because the high-redshift galaxies are more extended but rather because they have higher dust masses at fixed IR luminosity. Finally, based on our simulations, we introduce a two-parameter set of SED templates that depend on both IR luminosity and dust mass.Comment: Submitted to ApJ, comments welcom

Steadily Increasing Star Formation Rates in Galaxies Observed at 3 <~ z <~ 5 in the CANDELS/GOODS-S Field

We investigate the star formation histories (SFHs) of high redshift (3 <~ z <~ 5) star-forming galaxies selected based on their rest-frame ultraviolet (UV) colors in the CANDELS/GOODS-S field. By comparing the results from the spectral-energy-distribution-fitting analysis with two different assumptions about the SFHs --- i.e., exponentially declining SFHs as well as increasing ones, we conclude that the SFHs of high-redshift star-forming galaxies increase with time rather than exponentially decline. We also examine the correlations between the star formation rates (SFRs) and the stellar masses. When the galaxies are fit with rising SFRs, we find that the trend seen in the data qualitatively matches the expectations from a semi-analytic model of galaxy formation. The mean specific SFR is shown to increase with redshift, also in agreement with the theoretical prediction. From the derived tight correlation between stellar masses and SFRs, we derive the mean SFH of star-forming galaxies in the redshift range of 3 <~ z <~ 5, which shows a steep power-law (with power alpha = 5.85) increase with time. We also investigate the formation timescales and the mean stellar population ages of these star-forming galaxies. Our analysis reveals that UV-selected star-forming galaxies have a broad range of the formation redshift. The derived stellar masses and the stellar population ages show positive correlation in a sense that more massive galaxies are on average older, but with significant scatter. This large scatter implies that the galaxies' mass is not the only factor which affects the growth or star formation of high-redshift galaxies.Comment: 31 pages, 8 figures, 2 table

Effects of tall fescue and lactate dehydrogenase genetic polymorphisms on dairy heifer growth and immune function

Objectives of this project were to evaluate polymorphisms in upstream elements of the lactate dehydrogenase B (LDHB) gene in crossbred dairy heifers (n = 27) and their effects on immune function and heifer growth when grazing endophyte-infected tall fescue. Two cultivars of tall fescue were utilized: Kentucky 31 (KY31), a wild-type endophyte-infected tall fescue, and HiMag 4 (HiMag), a domesticated non-toxic endophyte-infected tall fescue. Crossbred dairy heifers (Holstein × Jersey) were stratified by weight and randomly allotted to forage. The LDHB gene codes for one subunit of lactate dehydrogenase (LDH), an enzyme that catalyzes pyruvate to lactate and back to pyruvate. Forward primer used for amplification was 5’-ACACACCAGCAGCATCTCAG-3’ and reverse primer was 5’- GATAAGGGCTGCACGAAGAC-3’. The amplicon size for this LDHB primer set was 457 base pairs. Sequenced amplicons were aligned with Clustal2W for polymorphism detection and genotype assignment. Heifers that had a heterozygous genotype and grazed HiMag were heavier when compared with other heifer groups. Number of red blood cells and hemoglobin concentrations for heifers grazing KY31 were greater when compared to heifers grazing HiMag. Distribution of white blood cells was affected by LDHB genotype. Two dairy heifer management tools, stockpiled tall fescue and LDHB genotyping, were assessed in this study, both of which impacted heifer growth and immune function as assessed by blood cell differentials

Access and Use of Records Through the Cadastre System at the Ministry of Mining Headquarters, Nairobi

The Mining Cadastre System is a tool that facilitates easy access and use of information on mining license granting process and mineral resources in Kenya. The purpose of this study was to investigate the access and use of records through Cadastre System at the Ministry of Mining headquarters in Nairobi, Kenya. The specific objectives of the study were to: examine the extent to which the features of Cadastre System capture record-keeping functionalities and facilitates access and use of records at the Ministry of Mining Headquarters, Nairobi; establish the extent to which users access and utilize the system to meet their information needs; examine the opportunities and threats associated with Cadastre System in accessing and use of records and propose measures of enhancing its use. This study was guided by the Records Continuum model by Upward (2005) and the Design and Implementation of Record-keeping System (DIRKS) model by the National Archives of Australian (2001). The research study applied descriptive survey design and used both qualitative and quantitative approaches. The target population was 152 respondents. The researcher used three sampling techniques namely; stratified sampling, simple random sampling and purposive sampling. The sample size was made up of 66 respondents. The study used interviews and questionnaires as methods of collecting data. The interview was used to collect data from the two Directors from Mines and Geology Directorate. Questionnaires were used to collect data from the staff of the Ministry who use the system. The pilot study was done in the Ministry of Mining Directorate at Community Area in Upper Hill Nairobi to test the data collection instruments. The researcher used 3 members of Registry Staff and tested the interview schedule with 2 Administrators to test the study. Quantitative data was analyzed using Statistical Package for Social Sciences (SPSS version 23) while discourse analysis was used for analyzing qualitative data. Data was presented in tables and pie-charts. Textual data presentation was presented through discourse analysis. The main results from the research were that; the Cadastre System helps in the management of the mineral resources in the Ministry of Mining; users use the system to access mineral information allowing smooth and efficient document transactions; Cadastre system maximized revenue collection from the mineral sector and enhanced investor confidence. However, there were regulatory challenges affecting Cadastre system processes because of the new Mining Act 2016. The System required skilled experts in record-keeping as a measure to improve the Cadastre System operations. The study concludes that the Cadastral System in the Ministry of Mining needs adequate funding to maintain its operations. Trained personnel with records management skills should be involved in the Cadastre System development and maintenance alongside the mining engineers and cadastral staff for better service delivery. Therefore, the study recommends for allocation of adequate funds in its budget to facilitate the system’s operations and involvement of adequate skilled record’s management staff to enhance Cadaster System operations alongside the mining engineers/staff possibly through departmental trainings. Cadastral system enhancement would be beneficial to policy makers, staff and investors in the ministry of Mining. Policy makers will assess the Cadastre System performance with a view of upgrading it where need be. The staff will use the system to enhance service delivery while investors will get the information they are seeking for better returns in their mining investments. There is therefore need to allocate more budget to maintenance Cadastre System and the infrastructure so as to be accessed remotely at all times. Keywords: Access and use of records, Record-keeping, Cadastre System, Mining, Information needs. DOI: 10.7176/IKM/10-2-03 Publication date: February 29th 202