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Register a new userThe rest-frame $K$-band luminosity function of galaxies in clusters to $z=1.3$
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We derive the rest-frame $K$-band luminosity function for galaxies in 32 clusters at $0.6 < z < 1.3$ using deep $3.6mu$m and $4.5mu$m imaging from the Spitzer Space Telescope InfraRed Array Camera (IRAC). The luminosity functions approximate the stellar mass function of the cluster galaxies. Their dependence on redshift indicates that massive cluster galaxies (to the characteristic luminosity $M^*_K$) are fully assembled at least at $z sim 1.3$ and that little significant accretion takes place at later times. The existence of massive, highly evolved galaxies at these epochs is likely to represent a significant challenge to theories of hierarchical structure formation where such objects are formed by the late accretion of spheroidal systems at $z < 1$.
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We present results on the rest-frame $H$-band luminosity functions (LF) of red sequence galaxies in seven clusters at 1.0 < z < 1.3 from the Gemini Observations of Galaxies in Rich Early Environments Survey (GOGREEN). Using deep GMOS-z and IRAC $3.6 mu$m imaging, we identify red sequence galaxies and measure their LFs down to $M_{H} sim M_{H}^{*} + (2.0 - 3.0)$. By stacking the entire sample, we derive a shallow faint end slope of $ alpha sim -0.35^{+0.15}_{-0.15} $ and $ M_{H}^{*} sim -23.52^{+0.15}_{-0.17} $, suggesting that there is a deficit of faint red sequence galaxies in clusters at high redshift. By comparing the stacked red sequence LF of our sample with a sample of clusters at z~0.6, we find an evolution in the faint end of the red sequence over the ~2.6 Gyr between the two samples, with the mean faint end red sequence luminosity growing by more than a factor of two. The faint-to-luminous ratio of our sample ($0.78^{+0.19}_{-0.15}$) is consistent with the trend of decreasing ratio with increasing redshift as proposed in previous studies. A comparison with the field shows that the faint-to-luminous ratios in clusters are consistent with the field at z~1.15 and exhibit a stronger redshift dependence. Our results support the picture that the build up of the faint red sequence galaxies occurs gradually over time and suggest that faint cluster galaxies, similar to bright cluster galaxies, experience the quenching effect induced by environment already at z~1.15.
We present the rest-frame J- and H-band luminosity function (LF) of field galaxies, based on a deep multi-wavelength composite sample from the MUSYC, FIRES and FIREWORKS survey public catalogues, covering a total area of 450 arcmin^2. The availability of flux measurements in the Spitzer IRAC 3.6, 4.5, 5.8, and 8 um channels allows us to compute absolute magnitudes in the rest-frame J and H bands up to z=3.5 minimizing the dependence on the stellar evolution models. We compute the LF in the four redshift bins 1.5<z<2.0, 2.0<z<2.5, 2.5<z<3.0 and 3.0<z<3.5. Combining our results with those already available at lower redshifts, we find that (1) the faint end slope is consistent with being constant up to z=3.5, with alpha=-1.05+/-0.03 for the rest-frame J band and alpha=-1.15+/-0.02 for the rest-frame H band; (2) the normalization phi* decreases by a factor of 6 between z=0 and z~1.75 and by a factor 3 between z~1.75 and z=3.25; (3) the characteristic magnitude M* shows a brightening from z=0 to z~2 followed by a slow dimming to z=3.25. We finally compute the luminosity density (LD) in both rest-frame J and H bands. The analysis of our results together with those available in the literature shows that the LD is approximately constant up to z~1, and it then decreases by a factor of 6 up to z=3.5.
We present $K$-band luminosity functions for galaxies in a heterogeneous sample of 38 clusters at $0.1 < z < 1$. Using infrared-selected galaxy samples which generally reach 2 magnitudes fainter than the characteristic galaxy luminosity $L^*$, we fit Schechter functions to background-corrected cluster galaxy counts to determine $K^*$ as a function of redshift. Because of the magnitude limit of our data, the faint-end slope $alpha$ is fixed at -0.9 in the fitting process. We find that $K^*(z)$ departs from no-evolution predictions at $z > 0.4$, and is consistent with the behavior of a simple, passive luminosity evolution model in which galaxies form all their stars in a single burst at $z_f = 2 (3)$ in an $H_0 = 65 km/s Mpc^{-1}, Omega_M = 0.3, Omega_{Lambda}=0.7 (0)$ universe. This differs from the flat or negative infrared luminosity evolution which has been reported for high redshift field galaxy samples. We find that the observed evolution appears to be insensitive to cluster X-ray luminosity or optical richness, implying little variation in the evolutionary history of galaxies over the range of environmental densities spanned by our cluster sample. These results support and extend previous analyses based on the color evolution of high redshift cluster E/S0 galaxies, indicating not only that their stellar populations formed at high redshift, but that the assembly of the galaxies themselves was largely complete by $z approx 1$, and that subsequent evolution down to the present epoch was primarily passive.
We present early results from the Faint InfraRed Extragalactic Survey (FIRES) at the VLT, the main goal of which is to study galaxy evolution in a deep, K-band selected sample. With our NIR selection, we select galaxies based on their rest-frame optical light at all redshifts z<3. Our seven band photometry, coupled with an accurate and reliable photometric redshift technique, gives us the ability to study galaxies at the same rest-frame wavelength across a large range in redshift. We present here the rest-frame V-band luminosity of objects in our sample as a function of redshift and demonstrate the importance of near infrared data in measuring the correct photometric redshift and rest-frame optical luminosity.
We present the rest-frame optical (B, V, and R band) luminosity functions (LFs) of galaxies at 2<z<3.5, measured from a K-selected sample constructed from the deep NIR MUSYC, the ultradeep FIRES, and the GOODS-CDFS. This sample is unique for its combination of area and range of luminosities. The faint-end slopes of the LFs at z>2 are consistent with those at z~0. The characteristic magnitudes are significantly brighter than the local values (e.g., ~1.2 mag in the R band), while the measured values for Phi_star are typically ~5 times smaller. The B-band luminosity density at z~2.3 is similar to the local value, and in the R band it is ~2 times smaller than the local value. We present the LF of Distant Red Galaxies (DRGs), which we compare to that of non-DRGs. While DRGs and non-DRGs are characterized by similar LFs at the bright end, the faint-end slope of the non-DRG LF is much steeper than that of DRGs. The contribution of DRGs to the global densities down to the faintest probed luminosities is 14%-25% in number and 22%-33% in luminosity. From the derived rest-frame U-V colors and stellar population synthesis models, we estimate the mass-to-light ratios (M/L) of the different subsamples. The M/L ratios of DRGs are ~5 times higher (in the R and V bands) than those of non-DRGs. The global stellar mass density at 2<z<3.5 appears to be dominated by DRGs, whose contribution is of order ~60%-80% of the global value. Qualitatively similar results are obtained when the population is split by rest-frame U-V color instead of observed J-K color.
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