Uv-to-fir analysis of spitzer/irac sources in the extended groth strip i: Multi-wavelength photometry and spectral energy distributions

We present an IRAC 3.6+4.5 microns selected catalog in the Extended Groth Strip (EGS) containing photometry from the ultraviolet to the far-infrared and stellar parameters derived from the analysis of the multi-wavelength data. In this paper, we describe the method used to build coherent spectral energy distributions (SEDs) for all the sources. In a companion paper, we analyze those SEDs to obtain robust estimations of stellar parameters such as photometric redshifts, stellar masses, and star formation rates. The catalog comprises 76,936 sources with [3.6]<23.75 mag (85% completeness level of the IRAC survey in the EGS) over 0.48 square degrees. For approximately 16% of this sample, we are able to deconvolve the IRAC data to obtain robust fluxes for the multiple counterparts found in ground-based optical images. Typically, the SEDs of the IRAC sources in our catalog count with more than 15 photometric data points, spanning from the UV to the FIR. Approximately 95% and 90% of all IRAC sources are detected in the deepest optical and near-infrared bands. Only 10% of the sources have optical spectroscopy and redshift estimations. Almost 20% and 2% of the sources are detected by MIPS at 24 and 70 microns, respectively. We also cross-correlate our catalog with public X-ray and radio catalogs. Finally, we present the Rainbow Navigator public web-interface utility designed to browse all the data products resulting from this work, including images, spectra, photometry, and stellar parameters.

On the nature of the extragalactic number counts in the K-band

We investigate the causes of the different shape of the $K$-band number counts when compared to other bands, analyzing in detail the presence of a change in the slope around $Ksim17.5$. We present a near-infrared imaging survey, conducted at the 3.5m telescope of the Calar Alto Spanish-German Astronomical Center (CAHA), covering two separated fields centered on the HFDN and the Groth field, with a total combined area of $sim0.27$deg$^{2}$ to a depth of $Ksim19$ ($3sigma$,Vega). We derive luminosity functions from the observed $K$-band in the redshift range [0.25-1.25], that are combined with data from the references in multiple bands and redshifts, to build up the $K$-band number count distribution. We find that the overall shape of the number counts can be grouped into three regimes: the classic Euclidean slope regime ($dlog N/dmsim0.6$) at bright magnitudes; a transition regime at intermediate magnitudes, dominated by $M^{ast}$ galaxies at the redshift that maximizes the product $phi^{ast}frac{dV_{c}}{dOmega}$; and an $alpha$ dominated regime at faint magnitudes, where the slope asymptotically approaches -0.4($alpha$+1) controlled by post-$M^{ast}$ galaxies. The slope of the $K$-band number counts presents an averaged decrement of $sim50%$ in the range $15.5<K<18.5$ ($dlog N/dmsim0.6-0.30$). The rate of change in the slope is highly sensitive to cosmic variance effects. The decreasing trend is the consequence of a prominent decrease of the characteristic density $phi^{ast}_{K,obs}$ ($sim60%$ from $z=0.5$ to $z=1.5$) and an almost flat evolution of $M^{ast}_{K,obs}$ (1$sigma$ compatible with $M^{ast}_{K,obs}=-22.89pm0.25$ in the same redshift range).