Mid-Infrared Variability from the Spitzer Deep, Wide-Field Survey
Szymon Kozlowski, Christopher S. Kochanek, Daniel Stern, Matthew L. N. Ashby, Roberto J. Assef, J. J. Bock, C. Borys, K. Brand, M. Brodwin, M. J. I. Brown, R. C… 展开作者
Szymon Kozlowski, Christopher S. Kochanek, Daniel Stern, Matthew L. N. Ashby, Roberto J. Assef, J. J. Bock, C. Borys, K. Brand, M. Brodwin, M. J. I. Brown, R. Cool, A. Cooray, S. Croft, Arjun Dey, P. R. Eisenhardt, A. Gonzalez, V. Gorjian, R. Griffith, N. Grogin, R. Ivison, J. Jacob, B. T. Jannuzi, A. Mainzer, L. Moustakas, H. Rottgering, N. Seymour, H. A. Smith, S. A. Stanford, J. R. Stauffer, I. S. Sullivan, W. van Breugel, S. P. Willner, E. L. Wright
We use the multi-epoch, mid-infrared Spitzer Deep, Wide-Field Survey to investigate the variability of 474,179 objects in 8.1 deg^2 of the NDWFS Bootes field. We perform a Difference Image Analysis of the four available epochs between 2004 and 2008, focusing on the deeper 3.6 and 4.5 micron bands. We find that 1.1% of the studied sample meet our standard selection criteria for being classed as a variable source. We require that the 3.6 and 4.5 micron light-curves are strongly correlated (r>0.8) and that their joint variance exceeds that for all sources with the same magnitude by 2 sigma. We then examine the mid-IR colors of the variable sources and match them with X-ray sources from the XBootes survey, radio catalogs, 24 micron-selected AGN candidates, and spectroscopically identified AGNs from the AGN and Galaxy Evolution Survey (AGES). Based on their mid-IR colors, most of the variable sources are AGNs (76%), with smaller contributions from stars (11%), galaxies (6%), and unclassified objects. Most of the stellar, galaxy and unclassified sources are false positives. For our standard selection criteria, 11-12% of the mid-IR counterparts to X-ray sources, 24 micron-selected AGN candidates and spectroscopically identified AGNs show variability. Mid-IR AGN variability can be well described by a single power-law structure function with a power-law index of 0.5 at both 3.6 and 4.5 microns, and an amplitude of 0.1 mag on rest-frame time scales of 2 years. The variability amplitude is higher for shorter rest-frame wavelengths and lower luminosities. (Abridged)
Mid-Infrared Galaxy Morphology from the Spitzer Survey of Stellar Structure in Galaxies (S^4G): The Imprint of the de Vaucouleurs Revised Hubble-Sandage Classification System at 3.6 microns
Probing the Interstellar Medium of z~1 Ultra-luminous Infrared Galaxies through Interferometric Observations of CO and Spitzer Mid-infrared Spectroscopy
