In this CHANG-ES IV paper, we present all the VLA D-configuration observations and results of the 35 edge-on CHANG-ES galaxies in two frequency bands, C and L. These data products (including intensity maps, spectral index maps, polarization maps) areall be part of our Data Release 1, located at http://www.queensu.ca/changes. Apart from presenting each galaxy in a range of maps for two different weightings of each band, we also investigate deeper the in-band spectral index maps, primary beam corrections, flux densities and star formation rates.
Spectral index maps presented have a) been primary beam corrected, b) cut off below 5σ, c) cut off wherever the formal error > 1.0, and been convolved with a Gaussian to smooth over the pixel-to-pixel variations within any clean beam. No changes in spatial resolution results from this process.
Spectral index uncertainties have been thoroughly investigated. Apart from extreme values near the edges "edge-effect" which should be ignored, there are effects of the primary beam corrections. Our tests on two pointing data show that results outside the half-power level of the primary beam model used in CASA need be treated with caution. The true error in α is typically underestimated by 20% in the formal error maps. In regions of high signal-to-noise, they may even underestimate the error by a factor ∼ 5. The latter affects C-band more than L-band, since the galaxies do not extend beyond the half-power point of the primary beam for L-band.
Galaxies with flatter α values at the centres often have indications of central activity. In some cases, such as NGC 2820, NGC 3556 and NGC 5775 and others, α is flatter at C-band than in L-band, suggesting a higher contribution from thermal emission at the higher frequency.
Star formation rates were derived via WISE-WERGA images, and potential AGN contamination of the SFR results investigated. Many candidates may have starburst nuclei, with the exceptions of NGC 660, NGC 3735 and NGC 4388 who may indeed harbour an AGN. Lower limit SFR are calculated for these and used for the two latter galaxies.
We scaled, rotated and ordered the L-band images of the CHANG-ES galaxies by SFR surface density in order to be able to compare the galaxies on equal footing and get a snap shot of potential correlations between SFR and halo size. We produced two maps, one scaled by distance (to 10 Mpc), the other by the 22 µm WISE-WERGA sizes, and the second one does reveal a trend of galaxies harbouring larger halos having higher SFR densities.
The L-band images from the previous point were medianed to bring forth the median edge-on galaxy, which harbours a compelling halo.
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities inc.
T.W, J.I., A.M., P.S. and C.M. thank the VLA staff for excellent assistance for these observations and reductions during their respective visits to Soccorro.
We are greatly indebted to T. Jarrett for running the WISE WERGA process on our sample and providing us with the resulting images.
The work at Ruhr-University Bochum has been supported by DFG through FOR1048.
We acknowledge the support of the Computer Center of the Max-Planck Institute (RZG) in Garching, Germany for the use of archiving facilities.
We are grateful to A. Vladimirov, for graciously providing time at a Stanford computer cluster for some of our imaging. In extension, we acknowledge support via NASA grants NNX10AE78G and NNX13AC47G.
This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.
SDSS and DSS2 images were used to create the optical images in panel d) of the appendix images. Funding for the Sloan Digital Sky Survey (SDSS) and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the U.S. Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, and the Max Planck Society, and the Higher Education Funding Council for England. The SDSS Web site is http://www.sdss.org/. The SDSS is managed by the Astrophysical Research Consortium (ARC) for the Participating Institutions. The Participating Institutions are the American Museum of Natural History, Astrophysical Institute Potsdam, University of Basel, University of Cambridge, Case Western Reserve University, The University of Chicago, Drexel University, Fermilab, the Institute for Advanced Study, the Japan Participation Group, The Johns Hopkins University, the Joint Institute for Nuclear Astrophysics, the Kavli Institute for Particle Astrophysics and Cosmology, the Korean Scientist Group, the Chinese Academy of Sciences (LAMOST), Los Alamos National Laboratory, the Max-Planck-Institute for Astronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University, Ohio State University, University of Pittsburgh, University of Portsmouth, Princeton University, the United States Naval Observatory, and the University of Washington.
The Digitized Sky Surveys were produced at the Space Telescope Science Institute under U.S. Government grant NAG W-2166. The images of these surveys are based on photographic data obtained using the Oschin Schmidt Telescope on Palomar Mountain and the UK Schmidt Telescope. The plates were processed into the present compressed digital form with the permission of these institutions.
This work is based [in part] on observations made with the Spitzer Space Telescope and has made use of the NASA/ IPAC Infrared Science Archive, which are operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by NASA.
This research made use of APLpy, an open-source plotting package for Python hosted at http://aplpy.github.com.
Facilities: VLA, Spitzer.