The stellar mass function of galaxies to z ~ 5 in the Fors Deep and GOODS-S fields

We present a measurement of the evolution of the stellar mass function (MF) of galaxies and the evolution of the total stellar mass density at 0<z<5. We use deep multicolor data in the Fors Deep Field (FDF; I-selected reaching I_AB=26.8) and the GOODS-S/CDFS region (K-selected reaching K_AB=25.4) to estimate stellar masses based on fits to composite stellar population models for 5557 and 3367 sources, respectively. The MF of objects from the GOODS-S sample is very similar to that of the FDF. Near-IR selected surveys hence detect the more massive objects of the same principal population as do I-selected surveys. We find that the most massive galaxies harbor the oldest stellar populations at all redshifts. At low z, our MF follows the local MF very well, extending the local MF down to 10^8 Msun. The faint end slope is consistent with the local value of alpha~1.1 at least up to z~1.5. Our MF also agrees very well with the MUNICS and K20 results at z<2. The MF seems to evolve in a regular way at least up to z~2 with the normalization decreasing by 50% to z=1 and by 70% to z=2. Objects having M>10^10 Msun which are the likely progenitors of todays L* galaxies are found in much smaller numbers above z=2. However, we note that massive galaxies with M>10^11 Msun are present even to the largest redshift we probe. Beyond z=2 the evolution of the mass function becomes more rapid. We find that the total stellar mass density at z=1 is 50% of the local value. At z=2, 25% of the local mass density is assembled, and at z=3 and z=5 we find that at least 15% and 5% of the mass in stars is in place, respectively. The number density of galaxies with M>10^11 Msun evolves very similarly to the evolution at lower masses. It decreases by 0.4 dex to z=1, by 0.6 dex to z=2, and by 1 dex to z=4.Comment: Accepted for publication in ApJ

On the Relation between Solar Activity and Clear-Sky Terrestrial Irradiance

The Mauna Loa Observatory record of direct-beam solar irradiance measurements for the years 1958-2010 is analysed to investigate the variation of clear-sky terrestrial insolation with solar activity over more than four solar cycles. The raw irradiance data exhibit a marked seasonal cycle, extended periods of lower irradiance due to emissions of volcanic aerosols, and a long-term decrease in atmospheric transmission independent of solar activity. After correcting for these effects, it is found that clear-sky terrestrial irradiance typically varies by about 0.2 +/- 0.1% over the course of the solar cycle, a change of the same order of magnitude as the variations of the total solar irradiance above the atmosphere. An investigation of changes in the clear-sky atmospheric transmission fails to find a significant trend with sunspot number. Hence there is no evidence for a yet unknown effect amplifying variations of clear-sky irradiance with solar activity.Comment: 16 pages, 7 figures, in press at Solar Physics; minor changes to the text to match final published versio

The Kormendy relation of massive elliptical galaxies at z~1.5. Evidence for size evolution ?

We present the morphological analysis based on HST-NIC2 (0.075 arcsec/pixel) images in the F160W filter of a sample of 9 massive field (> 10^{11} M_\odot) galaxies spectroscopically classified as early-types at 1.2<z<1.7. Our analysis shows that all of them are bulge dominated systems. In particular, 6 of them are well fitted by a de Vaucouleurs profile (n=4) suggesting that they can be considered pure elliptical galaxies. The remaining 3 galaxies are better fitted by a Sersic profile with index 1.9<n<2.3 suggesting that a disk-like component could contribute up to 30% to the total light of these galaxies. We derived the effective radius R_e and the mean surface brightness within R_e of our galaxies and we compared them with those of early-types at lower redshifts. We find that the surface brightness of our galaxies should get fainter by 2.5 mag from z~1.5 to z~0 to match the surface brightness of the local ellipticals with comparable R_e, i.e. the local Kormendy relation. Luminosity evolution without morphological changes can only explain half of this effect, as the maximum dimming expected for an elliptical galaxy is ~1.6 mag in this redshift range. Thus, other parameters, possibly structural, may undergo evolution and play an important role in reconciling models and observations. Hypothesizing an evolution of the effective radius of galaxies we find that R_e should increase by a factor 1.5 from z~1.5 to z~0.Comment: Accepted for publication in MNRAS, 15 pages, 8 figure

Extremely compact massive galaxies at z~1.4

The optical rest-frame sizes of 10 of the most massive (~5x10^{11}h_{70}^{-2}M_sun) galaxies found in the near-infrared MUNICS survey at 1.2<z<1.7 are analysed. Sizes were estimated both in the J and K' filters. These massive galaxies are at least a factor of 4_{-1.0}^{+1.9} (+-1 sigma) smaller in the rest-frame V-band than local counterparts of the same stellar mass. Consequently, the stellar mass density of these objects is (at least) 60 times larger than massive ellipticals today. Although the stellar populations of these objects are passively fading, their structural properties are rapidly changing since that redshift. This observational fact disagrees with a scenario where the more massive and passive galaxies are fully assembled at z~1.4 (i.e. a monolithic scenario) and points towards a dry merger scenario as the responsible mechanism for the subsequent evolution of these galaxies.Comment: 5 pages, 2 figures, 1 table, accepted for publication in MNRAS letter

The star formation rate history in the FORS Deep and GOODS South Fields

We measure the star formation rate (SFR) as a function of redshift z up to z \~4.5, based on B, I and (I+B) selected galaxy catalogues from the FORS Deep Field (FDF) and the K-selected catalogue from the GOODS-South field. Distances are computed from spectroscopically calibrated photometric redshifts accurate to (Delta_z / (z_spec+1)) ~0.03 for the FDF and ~0.056 for the GOODS-South field. The SFRs are derived from the luminosities at 1500 Angstroem. We find that the total SFR estimates derived from B, I and I+B catalogues agree very well (\lsim 0.1 dex) while the SFR from the K catalogue is lower by ~0.2 dex. We show that the latter is solely due to the lower star-forming activity of K-selected intermediate and low luminosity (L<L_*) galaxies. The SFR of bright (L>L_*) galaxies is independent of the selection band, i.e. the same for B, I, (I+B), and K-selected galaxy samples. At all redshifts, luminous galaxies (L>L_*) contribute only ~1/3 to the total SFR. There is no evidence for significant cosmic variance between the SFRs in the FDF and GOODs-South field, ~0.1 dex, consistent with theoretical expectations. The SFRs derived here are in excellent agreement with previous measurements provided we assume the same faint-end slope of the luminosity function as previous works (alpha ~ -1.6). However, our deep FDF data indicate a shallower slope of alpha=-1.07, implying a SFR lower by ~0.3 dex. We find the SFR to be roughly constant up to z ~4 and then to decline slowly beyond, if dust extinctions are assumed to be constant with redshift.Comment: 6 pages, 2 figures, Accepted for publication in ApJ

Exploring local immunological adaptation of two stickleback ecotypes by experimental infection and transcriptome-wide digital gene expression analysis

Understanding the extent of local adaptation in natural populations and the mechanisms that allow individuals to adapt to their native environment is a major avenue in molecular ecology research. Evidence for the frequent occurrence of diverging ecotypes in species that inhabit multiple ecological habitats is accumulating, but experimental approaches to understanding the biological pathways as well as the underlying genetic mechanisms are still rare. Parasites are invoked as one of the major selective forces driving evolution and are themselves dependent on the ecological conditions in a given habitat. Immunological adaptation to local parasite communities is therefore expected to be a key component of local adaptation in natural populations. Here, we use next-generation sequencing technology to compare the transcriptome-wide response of experimentally infected three-spined sticklebacks from a lake and a river population, which are known to evolve under selection by distinct parasite communities. By comparing overall gene expression levels as well as the activation of functional pathways in response to parasite exposure, we identified potential differences between the two stickleback populations at several levels. Our results suggest locally adapted patterns of gene regulation in response to parasite exposure, which may reflect different local optima in the trade-off between the benefits and the disadvantages of mounting an immune response because of quantitative differences of the local parasite communities

The Comoving Infrared Luminosity Density: Domination of Cold Galaxies across 0<z<1

In this paper we examine the contribution of galaxies with different infrared (IR) spectral energy distributions (SEDs) to the comoving infrared luminosity density, a proxy for the comoving star formation rate (SFR) density. We characterise galaxies as having either a cold or hot IR SED depending upon whether the rest-frame wavelength of their peak IR energy output is above or below 90um. Our work is based on a far-IR selected sample both in the local Universe and at high redshift, the former consisting of IRAS 60um-selected galaxies at z<0.07 and the latter of Spitzer 70um selected galaxies across 0.1<z<1. We find that the total IR luminosity densities for each redshift/luminosity bin agree well with results derived from other deep mid/far-IR surveys. At z<0.07 we observe the previously known results: that moderate luminosity galaxies (L_IR<10^11 Lsun) dominate the total luminosity density and that the fraction of cold galaxies decreases with increasing luminosity, becoming negligible at the highest luminosities. Conversely, above z=0.1 we find that luminous IR galaxies (L_IR>10^11 Lsun), the majority of which are cold, dominate the IR luminosity density. We therefore infer that cold galaxies dominate the IR luminosity density across the whole 0<z<1 range, hence appear to be the main driver behind the increase in SFR density up to z~1 whereas local luminous galaxies are not, on the whole, representative of the high redshift population.Comment: 5 pages, 3 figures, accepted for publication in MNRA

Transcriptome profiling of immune tissues reveals habitat-specific gene expression between lake and river sticklebacks

The observation of habitat-specific phenotypes suggests the action of natural selection. The three-spined stickleback (Gasterosteus aculeatus) has repeatedly colonized and adapted to diverse freshwater habitats across the northern hemisphere since the last glaciation, while giving rise to recurring phenotypes associated with specific habitats. Parapatric lake and river populations of sticklebacks harbour distinct parasite communities, a factor proposed to contribute to adaptive differentiation between these ecotypes. However, little is known about the transcriptional response to the distinct parasite pressure of those fish in a natural setting. Here, we sampled wild-caught sticklebacks across four geographical locations from lake and river habitats differing in their parasite load. We compared gene expression profiles between lake and river populations using 77 whole-transcriptome libraries from two immune-relevant tissues, the head kidney and the spleen. Differential expression analyses revealed 139 genes with habitat-specific expression patterns across the sampled population pairs. Among the 139 differentially expressed genes, eight are annotated with an immune function and 42 have been identified as differentially expressed in previous experimental studies in which fish have been immune challenged. Together, these findings reinforce the hypothesis that parasites contribute to adaptation of sticklebacks in lake and river habitats

Genomics of Divergence along a Continuum of Parapatric Population Differentiation

MM received funding from the Max Planck innovation funds for this project. PGDF was supported by a Marie Curie European Reintegration Grant (proposal nr 270891). CE was supported by German Science Foundation grants (DFG, EI 841/4-1 and EI 841/6-1)