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New Wide Field J- and K-band Galaxy Counts and the Extragalactic Background

Published online by Cambridge University Press:  13 May 2016

P. Väisänen
Affiliation:
Helsinki University Observatory, Helsinki 00014, Finland
E. V. Tollestrup
Affiliation:
Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA
S. P. Willner
Affiliation:
Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA
Martin Cohen
Affiliation:
Radio Astronomy Laboratory, 601 Campbell Hall, University of California, Berkeley, CA 94720, USA

Abstract

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We present new medium-deep wide field galaxy counts at J- and K-bands, performed in the ELAIS fields. The source detection limits are at J = 19.5 and K = 18.0 magnitudes. The sky coverage is 1 degree2, making our survey the largest to date at these wavelengths and magnitudes. Counts in this brightness range are critical for normalization of models when explaining the deepest galaxy counts. In our survey fields we find evidence for a higher than expected local galaxy density. If normalized to our counts, galaxy models do not need strong brightness evolution or exotic populations to be explained even at the faintest levels. We measure clearly sub-Euclidean slopes of d log N(m)/dm ~ 0.45 to 0.50 at 13 < K < 17.5 and 14.5 < J < 19. Normal, passively evolving stellar populations along with a high normalization of the local luminosity function and an open cosmological model best fit both the slope and amplitude of our number counts. We report a preliminary value, ~ 30 n Wm−2sr−1, for the K-band extragalactic background light using zodi-subtracted DIRBE-data and our observed star counts. The value is consistent with, e.g., Matsumoto (these Proceedings 2001) and Gorjian, V., Wright, E. L., & Chary, R. R. 2000, ApJ, 536, 550, but is considerably higher than extrapolations from faint galaxy counts.

Type
Research Article
Copyright
Copyright © Astronomical Society of the Pacific 2001