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Register a new userThe Munich Near-Infrared Cluster Survey - I. Field selection, object extraction, and photometry
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N. Drory
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The Munich Near-IR Cluster Survey (MUNICS) is a wide-area, medium-deep, photometric survey selected in the K band. It covers an area of roughly one square degree in the K and J near-IR pass-bands. The survey area consists of 16 6 x 6 fields targeted at QSOs with redshifts 0.5 < z < 2 and 7 28 x 13 stripes targeted at `random high Galactic latitude fields. Ten of the QSO fields were additionally imaged in R and I, and 0.6 square degrees of the randomly selected fields were also imaged in the V, R, and I bands. The resulting object catalogues were strictly selected in K, having a limiting magnitude (50 per cent completeness) of K ~ 19.5 mag and J ~ 21 mag, sufficiently deep to detect passively evolving systems up to a redshift of z ~ 1.5 and luminosity of 0.5 L*. The optical data reach a depth of roughly R ~ 23.5 mag. The projects main scientific aims are the identification of galaxy clusters at redshifts around unity and the selection of a large sample of field early-type galaxies at 0 < z < 1.5 for evolutionary studies. In this paper - the first in a series - we describe the surveys concept, the selection of the survey fields, the near-IR and optical imaging and data reduction, object extraction, and the construction of photometric catalogues. Finally, we show the J-K vs. K colour-magnitude diagramme and the R-J vs. J-K, V-I vs. J-K, and V-I vs. V-R colour-colour diagrammes for MUNICS objects, together with stellar population-synthesis models for different star-formation histories, and conclude that the data set presented is suitable for extracting a catalogue of massive field galaxies in the redshift range 0.5 < z < 1.5 for evolutionary studies and follow-up observations.
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The Munich Near-IR Cluster Survey (MUNICS) is a K selected survey covering 1 square degree in the K and J NIR bands with complementary optical photometry in the V, R, and I bands covering a subarea of 0.35 square degrees. The 3-sigma limiting magnitude is 19.5 in K. The main goals of the project are the identification of clusters of galaxies at redshifts 0.6<z<1.0 and the study of the evolution of the early-type field population at similar redshifts. Here we present first results regarding color distributions and the surface densities of EROs as well as photometric redshifts and a first clustering analysis of the sample.
(Abriged) We present a measurement of the evolution of the rest-frame K-band luminosity function to z ~ 1.2 using a sample of more than 5000 K-selected galaxies drawn from the MUNICS dataset. Distances and absolute K-band magnitudes are derived using photometric redshifts from spectral energy distribution fits to BVRIJK photometry. These are calibrated using >500 spectroscopic redshifts. We obtain redshift estimates having a rms scatter of 0.055 and no mean bias. We use Monte-Carlo simulations to investigate the influence of the errors in distance associated with photometric redshifts on our ability to reconstruct the shape of the luminosity function. Finally, we construct the rest-frame K-band LF in four redshift bins spanning 0.4<z<1.2 and compare our results to the local luminosity function. We discuss and apply two different estimators to derive likely values for the evolution of the number density, Phi*, and characteristic luminosity, M*, with redshift. While the first estimator relies on the value of the luminosity function binned in magnitude and redshift, the second estimator uses the individually measured {M,z} pairs alone. In both cases we obtain a mild decrease in number density by ~ 25% to z=1 accompanied by brightening of the galaxy population by 0.5 to 0.7 mag. These results are fully consistent with an analogous analysis using only the spectroscopic MUNICS sample. The total K-band luminosity density is found to scale as dlog(rho_L)/dz = 0.24. We discuss possible sources of systematic errors and their influence on our parameter estimates.
We present a measurement of the evolution of the stellar mass function in four redshift bins at 0.4 < z < 1.2 using a sample of more than 5000 K-selected galaxies drawn from the MUNICS dataset. Our data cover the stellar mass range 10^10 < M/Msun < 10^12. We derive K-band mass-to-light ratios by fitting a grid of composite stellar population models of varying star formation history, age, and dust extinction to BVRIJK photometry. We discuss the evolution of the average mass-to-light ratio as a function of galaxy stellar mass in the K-band and in the B-band. We compare our stellar mass function at z > 0 to estimates obtained similarly at z=0. We find that the mass-to-light ratios in the K-band decline with redshift. This decline is similar for all stellar masses above $10^10 Msun. Lower mass galaxies have lower mass-to-light ratios at all redshifts. The stellar mass function evolves significantly to z = 1.2. The total normalization decreases by a factor of ~2, the characteristic mass (the knee) shifts towards lower masses and the bright end therefore steepens with redshift. The amount of number density evolution is a strong function of stellar mass, with more massive systems showing faster evolution than less massive systems. We discuss the total stellar mass density of the universe and compare our results to the values from the literature both at lower and higher redshift. We find that the stellar mass density at z~1 is roughly 50% of the local value. Our results imply that the mass assembly of galaxies continues well after $z sim 1$. Our data favor a scenario in which the growth of the most massive galaxies is dominated by accretion and merging rather than star formation which plays a larger role in the growth of less massive systems.
We present Stroemgren-NIR photometry of NGC6528 and its surroundings in the Baades Window. uvby images were collected with EFOSC2@NTT, while NIR catalogs are based on VIRCAM@VISTA and SOFI@NTT data. The matching with HST photometry allowed us to obtain proper-motion-cleaned samples of cluster and bulge stars. The huge color sensitivity of Stroemgren-NIR CMDs helped us in disentangling age and metallicity effects. The RGB of NGC6528 is reproduced by scaled-solar isochrones with solar abundance or alpha-enhanced isochrones with the same iron content, and an age of t = 11+/-1 Gyr. These findings support literature age estimates for NGC6528. We also performed a theoretical metallicity calibration based on the Stroemgren index m1 and on visual-NIR colors for RGs, by adopting scaled-solar and alpha-enhanced models. We applied the calibration to estimate the metallicity of NGC6528, finding [Fe/H] = -0.04+/-0.02, with an intrinsic dispersion of 0.27 dex (by averaging abundances based on the scaled-solar [m], y - J and [m], y - K Metallicity-Index-Color relations), and of -0.11+/-0.01 (sig = 0.27 dex), by using the m1, y - J and m1, y - K relations. These findings support the results of Zoccali et al. (2004) which give [Fe/H] = -0.10+/-0.2, and a low alpha-enhancement, [alpha/Fe] = 0.1, and of Carretta et al. (2001), that find [Fe/H] = 0.07+/-0.01, with [alpha/Fe] = 0.2. By applying the scaled-solar MIC relations to Baades window RGs, we find a metallicity distribution extending from [Fe/H] ~ -1.0 to ~ 1 dex, with peaks at [Fe/H] ~ -0.2 and +0.55 ([m], y - J and [m], y - K relations), and [Fe/H] ~ -0.25 and +0.4 (m1, y - J and m1, y - K relations). These findings are in good agreement with the spectroscopic studies of Hill et al. (2011) for the Baades window, of Uttenthaler et al. (2012) for a region centered at (l,b) = (0, -10), and with the results of the ARGOS survey (Ness et al. 2013a).
The NGVS-IR project (Next Generation Virgo Survey - Infrared) is a contiguous near-infrared imaging survey of the Virgo cluster of galaxies. It complements the optical wide-field survey of Virgo (NGVS). The current state of NGVS-IR consists of Ks-band imaging of 4 deg^2 centered on M87, and J and Ks-band imaging of 16 deg^2 covering the region between M49 and M87. In this paper, we present the observations of the central 4 deg^2 centered on Virgos core region. The data were acquired with WIRCam on the Canada-France-Hawaii Telescope and the total integration time was 41 hours distributed in 34 contiguous tiles. A survey-specific strategy was designed to account for extended galaxies while still measuring accurate sky brightness within the survey area. The average 5sigma limiting magnitude is Ks=24.4 AB mag and the 50% completeness limit is Ks=23.75 AB mag for point source detections, when using only images with better than 0.7 seeing (median seeing 0.54). Star clusters are marginally resolved in these image stacks, and Virgo galaxies with mu_Ks=24.4 AB mag arcsec^-2 are detected. Combining the Ks data with optical and ultraviolet data, we build the uiK color-color diagram which allows a very clean color-based selection of globular clusters in Virgo. This diagnostic plot will provide reliable globular cluster candidates for spectroscopic follow-up campaigns needed to continue the exploration of Virgos photometric and kinematic sub-structures, and will help the design of future searches for globular clusters in extragalactic systems. Equipped with this powerful new tool, future NGVS-IR investigations based on the uiK diagram will address the mapping and analysis of extended structures and compact stellar systems in and around Virgo galaxies.
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