The QUEST Data Processing Software Pipeline

A program that we call the QUEST Data Processing Software Pipeline has been written to process the large volumes of data produced by the QUEST camera on the Samuel Oschin Schmidt Telescope at the Palomar Observatory. The program carries out both aperture and PSF photometry, combines data from different repeated observations of the same portion of sky, and produces a Master Object Catalog. A rough calibration of the data is carried out. This program, as well as the calibration procedures and quality checks on the output are described.Comment: 17 pages, 1 table, 8 figure

Dust and the Infrared Kinematic Properties of Early-Type Galaxies

We have obtained spectra and measured the stellar kinematics in a sample of 25 nearby early-type galaxies (with velocity dispersions from less than 100 km/s to over 300 km/s) using the near-infrared CO absorption bandhead at 2.29 microns. Our median uncertainty for the dispersions is ~10%. We examine the effects of dust on existing optical kinematic measurements. We find that the near-infrared velocity dispersions are in general smaller than optical velocity dispersions, with differences as large as 30%. The median difference is 11% smaller, and the effect is of greater magnitude for higher dispersion galaxies. The lenticular galaxies (18 out of 25) appear to be causing the shift to lower dispersions while the classical ellipticals (7 out of 25) are consistent between the two wavelength regimes. If uniformly distributed dust causes these differences, we would expect to find a correlation between the relative amount of dust in a galaxy and the fractional change in dispersion, but we do not find such a correlation. We do see correlations both between velocity dispersion and CO bandhead equivalent width, and velocity dispersion and Mg2 index. The differences in dispersion are not well explained by current models of dust absorption. The lack of correlation between the relative amount of dust and shift in dispersion possibly suggets that dust does not have a similar distribution from galaxy to galaxy. The CO equivalent widths of these galaxies are quite high (>10 angstroms for almost all), requiring the light at these wavelengths to be dominated by very cool stars.Comment: 17 pages, 14 figures, accepted to The Astronomical Journa

Sweep the dust away: infrared kinematics of nearby galaxies

textIn this dissertation, I have conducted a study of the near-infrared kinematics of a well-defined sample of nearby galaxies. I use the CO bandhead at 2.29 microns to measure the internal stellar kinematics of this sample. Observing in the near-infrared allows us to address possible biases or problems in our current kinematic understanding of galaxies (based on optical kinematics alone) and extend our knowledge to galaxies often excluded from kinematic analyses. This spectral region minimizes the effects of dust in galaxies; it is long enough to minimize dust absorption but short enough to avoid dilution of the continuum by emission from vii hot dust. Also, observing at these longer wavelengths traces the older, redder stellar population and minimizes effects due to recent star formation. I have chosen a sample of nearby early-type galaxies which are well-studied in optical wavelengths to first calibrate the CO bandhead for kinematic analysis, finding that for the galaxies which have the least dust and are the best-studied, optical and near-IR kinematics are consistent. I then apply this observational treatment to study the Fundmental Plane (FP) of galaxies in an unbiased way, as well as to measure the central black hole (BH) mass of Centaurus A, a galaxy so dusty that it is inaccessible to optical kinematic techniques. For a sample of early-type galaxies, I find a FP scaling relation different from the optical relation, indicating that systematic variation in mass-to-light ratio is important in the shape of the FP. For a sample of bulge galaxies, I find a FP scaling relation moderately different from the early-type FP, pointing to relative structural differences between these families of galaxies. I find a high value for the central BH of Centaurus A, five to ten times higher than that predicted by correlations between BH mass and global galaxy properties. This result implies that galaxy bulge growth and central BH growth are not coeval. Together, these results illustrate the power of using near-infrared kinematics.Astronom

Text mining with R: a tidy approach

Much of the data available today is unstructured and text-heavy, making it challenging for analysts to apply their usual data wrangling and visualization tools. With this practical book, you'll explore text-mining techniques with tidytext, a package that authors Julia Silge and David Robinson developed using the tidy principles behind R packages like ggraph and dplyr. You'll learn how tidytext and other tidy tools in R can make text analysis easier and more effective. The authors demonstrate how treating text as data frames enables you to manipulate, summarize, and visualize characteristics of text. You'll also learn how to integrate natural language processing (NLP) into effective workflows. Practical code examples and data explorations will help you generate real insights from literature, news, and social media. Learn how to apply the tidy text format to NLP Use sentiment analysis to mine the emotional content of text Identify a document's most important terms with frequency measurements Explore relationships and connections between words with the ggraph and widyr packages Convert back and forth between R's tidy and non-tidy text formats Use topic modeling to classify document collections into natural groups Examine case studies that compare Twitter archives, dig into NASA metadata, and analyze thousands of Usenet message

Rekyt/funrar

funrar is a package to compute functional rarity indices, it quantifies how species are rare both from a functional and an extent point of view. Following the different facets of rarity proposed by Rabinowitz (1981)

tidytext: tidytext v0.1.1

Added documentation for n-grams, skip n-grams, and regex Added codecov and appveyor Added tidiers for LDA objects from topicmodels and a vignette on topic modeling Added function to calculate tf-idf of a tidy text dataset and a tf-idf vignette Fixed a bug when tidying by line/sentence/paragraph/regex and there are multiple non-text columns Fixed a bug when unnesting using n-grams and skip n-grams (entire text was not being collapsed) Added ability to pass a (custom tokenizing) function to token. Also added a collapse argument that makes the choice whether to combine lines before tokenizing explicit. Changed tidy.dictionary to return a tbl_df rather than a data.frame Updated cast_sparse to work with dplyr 0.5.0 Deprecated the pair_count function, which has been moved to pairwise_count in the widyr package. This will be removed entirely in a future version