14 research outputs found
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
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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
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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)