A wide field survey at the Northern Ecliptic Pole

Abstract

Abstract. We present a medium deep survey carried out in the three filters Bj, R and K. The survey covers homogeneously the central square degree around the Northern Ecliptic Pole (NEP) down to a completeness limit (95%) of 24.25, 23.0 and 17.5 mag in Bj, R and K, respectively. While the near infrared data have been presented in the first paper of this series, here we concentrate on the optical data and the results based on the combined BjRK-data. The unique combination of area and depth in our survey allows to perform a variety of investigations based on homogeneous material covering more than ten magnitudes in apparent brightness. We analyze the number counts for point-like and extended sources in Bj and R to determine the slopes in d log N/dm and to test for possible breaks therein. While we can confirm the slopes found in previous works with a higher statistical significance, the largest uncertainty remaining for the amplitudes is galactic extinction. We determine the colour distributions of galaxies in Bj − R and R − K down to Bj = 24.0 and K = 18.0 mag, respectively. The distributions in both colours are modeled using galaxy spectral evolution synthesis. We demonstrate that the standard models of galaxy evolution are unable to reproduce the steady reddening trend in R − K despite flawless fits to the colour distributions in the optical (Bj −R). The BjRK data collected over a large area provides the opportunity to select rare objects like candidates for high-redshift galaxies and extremely red objects (EROs, R − K > 5.0) and to determine their surface density. Our EROs are selected at an intermediate magnitude range and contain contribution from both galactic as well as extragalactic sources. At K < 16.5 mag, where a morphological classification is possible, the stellar component dominates the sample.

J- andKs-Band Galaxy Counts and Color Distributions in theAKARINorth Ecliptic Pole Field

“…Figure 5 shows a comparison of pointlike star counts. The diamonds represent our star counts, and the squares represent those of Kümmel & Wagner (2000). Our star counts at 16:5 < K s < 17:0 are lower than those of Kümmel & Wagner (2000) because our star counts are classified on the basis of the optical image profiles and some saturated pointlike objects are removed from the catalog.…”

“…The bump is also seen in recent results from wide and deep surveys, although the fainter counts of wide-field surveys (e.g., 7.1 deg 2 ; Elston et al 2006) require a correction for completeness, while the brighter counts of deep surveys (e.g., Roche et al 2003;Caputi et al 2005;Förster Schreiber et al 2006) have large errors due to the lower number of galaxies. It was also reported that galaxy populations below the turning point of the K-band count slope tend to have bluer optical-NIR colors (e.g., Gardner et al 1993;Gardner 1995;Djorgovski et al 1995;Saracco et al 1997Saracco et al , 1999Bershady et al 1998;McCracken et al 2000;Huang et al 2001;Kümmel & Wagner 2001). On the other hand, papers describing the J-band galaxy counts published to date number only a few.…”

The VIRMOS deep imaging survey

“…We compare our total sample estimate of the amplitude, A ω at 1 deg, of the angular correlation function with a compilation of results from the literature. We include mesurements from: Daddi et al (2000), Kümmel & Wagner (2001), McCracken et al (2000b), Daddi et al (2003) and Roche et al (2003). The continous, dotted and dashed lines show, for reference, the models of PLE from Roche et al (1998), with scaling from local galaxy clustering.…”

Supernovae without host galaxies?

“…Each SN site was observed for 2 h in total, divided into ten exposures with 720 s each. To find even very faint objects, we chose to observe with an exceptionally wide filter available at CAHA: the BV Roeser filter (Kümmel & Wagner 2001). In comparison to standard Johnson filters (e.g.…”

“…Kümmel & Wagner 2001). We adjusted the photometric zero-point SExtractor uses for magnitude computation in an iterative process such that the extracted magnitudes agree to within the < ∼ 0.2 mag scatter with those of the reference stars selected Notes.…”