Comparing Stellar Populations of Galaxies across the Hubble Sequence: Reduction of PISCES Near-Infrared Images

To better understand the properties of high redshift galaxies and improve models of galaxy formation, we are investigating color radial profiles to study the stellar age, dust and metallicity distribution of galaxies of varying lumi-nosities and morphological types. Current data obtained in the optical and UV have shown that early-type galaxies have a flat color profile, or are bluer at larger radii, while late-type spirals are redder with increasing radius. These trends are believed to be linked with stellar population ages or dust. To break the age-dust degeneracy as well as to avoid the metallicity dependence, we have obtained near-infrared images of Nearby Field Galaxy Survey (NFGS) galax-ies taken with the PISCES Wide-field Infrared Camera on the 90-inch Bok Telescope. Combined with the optical and UV data, these new, near-infrared images will help better constrain these parameters and determine the ages of the stellar components of the galaxies. We discuss the method used to process and reduce the data and present the radial profile of the surface brightness and color of one particular galaxy in the sample, UGC 439

Relationships between HI Gas Mass, Stellar Mass and Star Formation Rate of HICAT+WISE (HI-WISE) Galaxies

We have measured the relationships between HI mass, stellar mass and star formation rate using the HI Parkes All Sky-Survey Catalogue (HICAT) and the Wide-field Infrared Survey Explorer (WISE). Of the 3,513 HICAT sources, we find 3.4 micron counterparts for 2,896 sources (80%) and provide new WISE matched aperture photometry for these galaxies. For our principal sample of spiral galaxies with W1 $\le$ 10 mag and z $\le$ 0.01, we identify HI detections for 93% of the sample. We measure lower HI-stellar mass relationships that HI selected samples that do not include spiral galaxies with little HI gas. Our observations of the spiral sample show that HI mass increases with stellar mass with a power-law index 0.35; however, this value is dependent on T-type, which affects both the median and the dispersion of HI mass. We also observe an upper limit on the HI gas fraction, which is consistent with a halo spin parameter model. We measure the star formation efficiency of spiral galaxies to be constant 10$^{-9.57}$ yr$^{-1}$ $\pm$ 0.4 dex for 2.5 orders of magnitude in stellar mass, despite the higher stellar mass spiral showing evidence of quenched star formation.Comment: 20 pages, 13 figures; accepted for publication by Ap

HI galaxies with little star formation: an abundance of LIERs

We present a sample of 91 HI galaxies with little or no star formation and discuss the analysis of the integral field unit (IFU) spectra of 28 of these galaxies. We identified HI galaxies from the HI Parkes All-Sky Survey Catalog (HICAT) with Wide-field Infrared Survey Explorer (WISE) colours consistent with low specific star formation (< 10$^{-10.4}$ yr$^{-1}$), and obtained optical IFU spectra with the Wide-Field Spectrograph (WiFeS). Visual inspection of the PanSTARRS, Dark Energy Survey, and Carnegie-Irvine imaging of 62 galaxies reveals that at least 32 galaxies in the sample have low levels of star formation, primarily in arms/rings. New IFU spectra of 28 of these galaxies reveal 3 galaxies with central star formation, 1 galaxy with low-ionisation nuclear emission-line regions (LINERs), 20 with extended low-ionisation emission-line regions (LIERs) and 4 with high excitation Seyfert (Sy) emission. From the spectroscopic analysis of HI-selected galaxies with little star formation, we conclude that 75% of this population are LINERs/LIERs

A systematic survey for z< 0.04 CLAGNs

We have conducted a systematic survey for z < 0.04 active Galactic nuclei (AGNs) that may have changed spectral class over the past decade. We use SkyMapper, Pan-STARRS and the Véron-Cetty & Véron catalogue to search the entire sky for these ‘changing-look’ AGNs (CLAGNs) using a variety of selection methods, where Pan-STARRS has a coverage of 3π steradians (sky north of Declination −30○) and SkyMapper has coverage of ∼21000  deg2 (sky south of Declination 0○). We use small aperture photometry to measure how colour and flux have changed over time, where a change may indicate a change in spectral type. Optical colour and flux are used as a proxy for changing Hα equivalent width, while WISE 3.4 μm flux is used to look for changes in the hot dust component. We have identified four AGNs with varying spectra selected using our optical colour selection method. Three AGNs were confirmed from recent observations with WiFeS on the 2.3 m telescope at Siding Spring and the other was identified from archival spectra alone. From this, we identify two new CLAGNs; NGC 1346 and 2MASX J20075129–1108346. We also recover Mrk 915 and Mrk 609, which are known to have varying spectra in the literature, but they do not meet our specific criteria for CLAGNs