Wide and deep near-UV (360 nm) galaxy counts and the extragalactic background light with the Large Binocular Camera

Abstract

Context. Deep multicolour surveys are the main tool for exploring the formation and evolution of the very faint galaxies that are beyond the spectroscopic limit of present technology. The photometric properties of these faint galaxies are usually compared with current renditions of semianalytical models to provide constraints on the detailed treatment of the fundamental physical processes involved in galaxy formation and evolution, namely the mass assembly and the star formation. Aims. Galaxy counts over large sky areas in the 360 nm near-UV band are particularly difficult to obtain given the low efficiency of near-UV instrumentation, even at 8 m class telescopes. Observing in the near-UV bands can provide a first assessment of the distribution of star formation activity in distant (up to z ∼ 3) galaxies. A relatively large instrumental field of view helps to minimize the biases caused by cosmic variance. Methods. We obtained deep images in the 360 nm U band provided by the blue channel of the Large Binocular Camera at the prime focus of the Large Binocular Telescope. Over an area of 0.4 sq. deg., we derived the galaxy number counts down to U = 27 in the Vega system (corresponding to U = 27.86 in the AB system) at a completeness level of 30% reaching the faintest current limit for this wavelength and sky area. Results. The shape of the galaxy number counts in the U band can be described by a double power-law, the bright side being consistent with the shape of shallower surveys of comparable or greater areas. The slope bends over significantly at U > 23.5 ensuring the convergence of the contribution by star-forming galaxies to the extragalactic background light in the near-UV band to a value that is more than 70% of the most recent upper limits derived for this band. We jointly compared our near-UV and K band counts collected from the literature with a few selected hierarchical CDM models, concentrating on specific critical issues in the physical description of the galaxy formation and evolution.

DeepR-band counts ofz≈ 3 Lyman-break galaxy candidates with the LBT

“…Number counts of galaxies per 0.5 mag per arcmin 2 in the U band for the fields in our survey, which have been derived by singlemode photometry. We see that there is very good agreement between our estimates and previous studies (Capak et al 2004;Eliche-Moral et al 2006;Rovilos et al 2009;Grazian et al 2009). Grazian et al (2009).…”

“…We see that there is very good agreement between our estimates and previous studies (Capak et al 2004;Eliche-Moral et al 2006;Rovilos et al 2009;Grazian et al 2009). Grazian et al (2009). Again, our results are in agreement with all the aforementioned surveys, and the field-to-field variations are relatively small at U ≥ 22.0.…”

“…The brightest part of this sample can be used for spectroscopic followup, and this new spectroscopic sample would help refine the color-selection criterion for LBGs further. Part of this dataset has already been used by Grazian et al (2009) to present deep U-band counts in the Q0933 field, while the extended dataset was used by Boutsia et al (2011) to derive a stringent upper limit to the escape fraction of ionizing photons of LBGs at z ∼ 3.3. By adding new spectroscopically confirmed candidates, an even more accurate estimate of the escape fraction could be obtained based on this sample.…”

THE HUBBLE SPACE TELESCOPE WIDE FIELD CAMERA 3 EARLY RELEASE SCIENCE DATA: PANCHROMATIC FAINT OBJECT COUNTS FOR 0.2-2 μm WAVELENGTH

“…Figure 11(a) the panchromatic GAMA survey (Driver et al 2009) counts in NUV+ugrizY J H , which cover AB = 10-21 mag (Xu et al 2005;Hill et al 2010). At the faint end, we added the WHT U band and HDF-North and South F300W counts of Metcalfe et al (2001), the deep LBT U-band counts of Grazian et al (2009), as well as the deep HST STIS counts of Gardner et al (2000). Best-fit luminosity and number density evolution models cover AB 10-30 mag (see Driver et al 1998;Hill et al 2010).…”

“…At the faint end in Figures 12(d)- (j), we added the HUDF counts in BV iz from Beckwith et al (2006), which cover AB = 24-30 mag, and the HUDF counts from the Bouwens et al (2010b) data in the F105W, F125W, and F160W filters (hereafter YJH), as compiled by Yan et al (2011b), which cover AB = 24-30 mag. In the UV, we added the William Herschel Telescope (WHT) U-band counts and the HDF-North and South F300W counts as compiled by Metcalfe et al (2001), the deep Large Binocular Telescope (LBT) U-band counts of Grazian et al (2009), as well as the deep HST STIS UV counts of Gardner et al (2000).…”