Clustering of Gamma-Ray bursts through kernel principal component analysis

We consider the problem related to clustering of gamma-ray bursts (from "BATSE" catalogue) through kernel principal component analysis in which our proposed kernel outperforms results of other competent kernels in terms of clustering accuracy and we obtain three physically interpretable groups of gamma-ray bursts. The effectivity of the suggested kernel in combination with kernel principal component analysis in revealing natural clusters in noisy and nonlinear data while reducing the dimension of the data is also explored in two simulated data sets.Comment: 30 pages, 10 figure

Multivariate Approaches to Classification in Extragalactic Astronomy

Clustering objects into synthetic groups is a natural activity of any science. Astrophysics is not an exception and is now facing a deluge of data. For galaxies, the one-century old Hubble classification and the Hubble tuning fork are still largely in use, together with numerous mono-or bivariate classifications most often made by eye. However, a classification must be driven by the data, and sophisticated multivariate statistical tools are used more and more often. In this paper we review these different approaches in order to situate them in the general context of unsupervised and supervised learning. We insist on the astrophysical outcomes of these studies to show that multivariate analyses provide an obvious path toward a renewal of our classification of galaxies and are invaluable tools to investigate the physics and evolution of galaxies.Comment: Open Access paper. http://www.frontiersin.org/milky\_way\_and\_galaxies/10.3389/fspas.2015.00003/abstract\>. \<10.3389/fspas.2015.00003 \&g

Cosmic history of integrated galactic stellar initial mass function : a simulation study

Theoretical and indirect observational evidences suggest that stellar initial mass function (IMF) increases with redshift. On the other hand star formation rates (SFR) may be as high as 100 $M_{\odot}$ yr$^{-1}$ in star burst galaxies. These may lead to formation of massive clusters hence massive stars to make the integrated galactic stellar initial mass function (IGIMF) top heavy (i.e. proportion of massive stars is higher than less massive stars). We investigate the joint effect of evolving IMF and several measures of SFR in dependence of galaxy wide IMF. The resulting IGIMF have slopes $\alpha_{2,IGIMF}$ in the high mass regime, which is highly dependent on the minimum mass of the embedded cluster ($M_{ecl,min}$), star formation rates and mass spectrum indices of embedded clusters (viz. $\beta$). It is found that for z $\sim$ 0 - 2, $\alpha_{2,IGIMF}$ becomes steeper (i.e. bottom heavy), for z $\sim$ 2 - 4, $\alpha_{2,IGIMF}$ becomes flatter (i.e. top heavy ) and from z $\sim$ 4 onwards $\alpha_{2,IGIMF}$ becomes again steeper. The effects are faster for higher values of $\beta$. $\alpha_{2,IGIMF}$ is flatter also for higher values of $M_{ecl,min}$. All these effects might be counted for the joint effect of increasing temperature of the ambient medium as well as varying SFR with increasing redshift.Comment: 46 pages, 11 figure

Pola Interaksi Sosial Masyarakat Multietnik Di Tomoni, Kabupaten Luwu Timur

Penelitian ini bertujuan untuk mengetahui pola interaksi sosial masyarakat multietnik di Kelurahan Tomoni, Kecamatan Tomoni, Kabupaten Luwu Timur. Metode penelitian yang digunakan adalah deskriptif kualitatif. Teknik pengumpulan data yang digunakan adalah teknik observasi, wawancara, dokumentasi dan diskusi terpumpun (Focus Group Discussion/FGD), sedangkan alat pengumpulan data adalah panduan observasi, pedoman wawancara, dan dokumentasi. Hasil penelitian menunjukkan bahwa pola interaksi sosial yang terjadi antara masyarakat multietnik berlangsung harmonis. Hal tersebut terlihat dengan adanya hubungan kerjasama di antara mereka, seperti gotong royong dan kerja bakti di lingkungan tempat tinggal, membersihkan tempat ibadah, membantu dalam setiap musibah, saling mengunjungi dalam kegiatan hajatan perkawinan atau aqiqah, saling membantu dalam setiap pembangunan rumah baru, dan lain-lain. Hal lain yang ditemui adalah menghadiri setiap undangan rapat di balai desa atau mengadakan pertemuan untuk menyelesaikan konflik jika terjadi kesalahpahaman antaretnik

Penggunaan Diksi dalam Lagu Mandar

Lirik lagu Mandar merupakah salah satu karya sastra yang ada di Sulawesi Barat yang perlu dilestarikan. Lirik dalam lagu Mandar perlu ditelusuri melalui kajian stilistika dengan pusat perhatian pada penggunaan diksi atau pilihan kata. Pilihan kata berkaitan dengan memilih kata yang tepat untuk menyatakan sesuatu yang dipikirkan dan dirasakan. Penelitian ini merupakan penelitian kepustakaan, sehingga dilaksanakan dengan teknik pengumpulan data berupa baca-simak dan pencatatan. Lirik lagu tersebut dibaca dan disimak dengan saksama, lalu dicatat pada kartu data, dan diklasifikasikan berdasarkan jenis diksinya. Dalam penelitian ini, ada empat lagu Mandar yang dianalisis penggunaan diksinya. Hasil analisis menunjukkan bahwa penggunaan diksi dalam lagu Mandar dapat dilakukan melalui empat bagian, yaitu autosemantis, sinsemantis, kata dasar, dan kata yang mengalami proses morfologis