H I Content and Optical Properties of Field Galaxies From the Alfalfa Survey. Ii. Multivariate Analysis of a Galaxy Sample in Low-Density Environments

Abstract

This is the second paper of two reporting results from a study of the H I content and stellar properties of nearby galaxies detected by the Arecibo Legacy Fast ALFA blind 21-cm line survey and the Sloan Digital Sky Survey in a 2160 square degree region of high galactic latitude sky covered by both surveys, in the general Virgo direction. Here we analyze a complete H I flux-limited subset of 1624 objects with homogeneously measured 21-cm and multi-wavelength optical attributes extracted from the control sample of H I emitters in environments of low local galactic density assembled by Toribio et al. (2010). Strategies of multivariate data analysis are applied to this dataset in order to: i) investigate the correlation structure of the space defined by an extensive set of potentially independent observables describing gas-rich systems; ii) identify the intrinsic parameters that best define their neutral gas content; and iii) explore the scaling 1 The correlation analysis carried out in this work requires that we ignore any possible curvature in the relationships investigated.

Galaxy and Mass Assembly (GAMA): merging galaxies and their properties

“…Obviously, we have no knowledge of the gas content of these galaxies, but we can use the u − r colour to separate quiescent and actively star-forming galaxies, with the dividing line at u − r = 2.2 (e.g., Strateva et al 2001;Baldry et al 2004). This is acceptable for our purposes, as there is a moderate degree of correlation between colour and gas content, in the sense of red galaxies being more gas-poor (Toribio et al 2011). Here 'dry' mergers are between two 'red' galaxies, 'wet' mergers between two 'blue' galaxies and 'damp' mergers contain one member of each.…”

Optical and HI properties of isolated galaxies in the 2MIG catalog. I. General relationships

“…There have been many studies [4,[20][21][22][23][24] of the scale relationships between the global parameters of galaxies (luminosity, size, rotation amplitude, neutral hydrogen mass, etc.). Data on the parameters of the scale relationships for different sources often differ substantially.…”

“…Various way of detecting isolated galaxies in 2D and 3D spaces have been developed [1]. These have been applied to different surveys of the sky in various wavelengths [2][3][4]. The methods for selecting isolated galaxies often are applied to small segments of the sky or to different volumes.…”

Full stellar kinematical profiles of central parts of nearby galaxies

“…HI-blind surveys based solely on the presence of neutral hydrogen were used frequently in the past to reveal correlations between various properties of galaxies and also to find fundamental features through principal component analysis (Disney et al 2008;Toribio et al 2011). The HI window is unbiased with respect to galaxy luminosity, selecting all the galaxies with a measurable gas content.…”

“…Such a sample is required to address important issues in the field of galaxy formation and evolution. To obtain galaxy properties through the wide wavelength range, we cross-matched our sample with the spectroscopy available from the Sloan Digital Sky Survey (SDSS) with available catalogs adding ultraviolet photometry to near-infrared (NIR) and optical photometry, extending the work of Toribio et al (2011).…”