Baade's red sheet resolved into stars with HST in the Blue Compact Dwarf Galaxy VII Zw 403

HST WFPC2 observations of the nearby Blue Compact Dwarf Galaxy VII~Zw~403 (= UGC 6456) resolve single stars down to M$_I$$\approx$-2.5, deep enough to identify red giants. This population has a more uniform spatial distribution than the young main-sequence stars and supergiants, forming the structure known as "Baade's red sheet". We conclude that VII~Zw~403 is not a primeval galaxy.Comment: submitted to: ApJ Letter

Surface photometry of new nearby dwarf galaxies

We present CCD surface photometry of 16 nearby dwarf galaxies, many of which were only recently discovered. Our sample comprises both isolated galaxies and galaxies that are members of nearby galaxy groups. The observations were obtained in the Johnson B and V bands (and in some cases in Kron-Cousins I). We derive surface brightness profiles, total magnitudes, and integrated colors. For the 11 galaxies in our sample with distance estimates the absolute B magnitudes lie in the range of -10>Mb>-13. The central surface brightness ranges from 22.5 to 27.0 mag/sq.arcsec. Most of the dwarf galaxies show exponential light profiles with or without a central light depression. Integrated radial color gradients, where present, appear to indicate a more centrally concentrated younger population and a more extended older population.Comment: accepted by A&

Novel Synthetic Biomaterials for Kidney-Derived Progenitor / Stem Cell Differentiation

End-stage kidney disease is increasing in prevalence and is associated with high levels of morbidity and mortality. At present, the only treatment options are dialysis or renal transplantation. However, dialysis is very costly and is associated with high levels of morbidity, whereas the problem with transplantation is that there is a shortage of organ donors. For these reasons, over recent years, there has been an increasing interest in developing novel therapies in the field of regenerative medicine including stem cell based therapies and tissue engineering. Stem cells could be used in a number of ways to develop new therapies for kidney disease. Firstly, they could be administered as cell therapies to patients with kidney disease, and secondly, they could be used to generate specific types of renal cells in vitro that could be used for understanding disease mechanisms and for drug discovery programmes. The barriers to the development of novel stem cell therapies include the difficulties in expanding kidney-derived stem cells in culture without altering their phenotype, and directing their differentiation to specific types of renal cells. These issues could be addressed by developing biomaterial substrates that provide an appropriate microenvironment for the successful culture and differentiation of stem cells. Within this study we interrogated a wide range of biomaterial substrates for their capability to direct the differentiation of kidney derived progenitor / stem cells. These materials were thoroughly characterised in terms of their physicochemical properties, such as surface chemistry, nanotopography and wettability by employing a wide range of analytic techniques, including X-Ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), colorimetry and contact angle measurements. We firstly investigated a range of polyacrylates. These substrates were novel in that, they were precisely designed to mimic cell binding motifs of the extracellular matrix stereochemically by using monomeric precursors that display particular chemical functional group chemistries, namely amine, hydroxyl, carboxyl groups or aliphatic spacer groups. We found that these materials differed strongly in the presence and distribution of surface functional group chemistries and topographical features, including the distribution of surface artefacts on a macroscale. Moreover, some of these materials were able to direct the differentiation into specialised renal cell lines. Two substrates, namely ESP 003 and ESP 004, directed the differentiation of kidney derived stem cells into podocytes and two further substrates, namely ESP 007 and BTL 15, directed differentiation into functional proximal tubule cells. These four substrates stimulated cell differentiation to an extent of about 40 to 50% after only 96 h in cell culture. We were moreover able to identify surface physicochemical cues, including surface micro- and nanoscale topography and surface functional group chemistries that are important to stimulate the differentiation process. In addition, we investigated a range of plasma polymer coatings composed of allylamine and octadiene that were provided as homo-or copolymers and in form of chemical gradients, the latter one differing in the amount of nitrogen functional group chemistries across the surfaces. We found that substrates with higher allylamine content displayed a greater amount of nitrogen functional groups and therefore increased in wettability. Moreover, those plasma polymer substrates with higher amine functionality directed kidney progenitor cell differentiation into podocytes, whereas substrates with higher octadiene concentration directed cell differentiation into functional proximal tubule cells, both to an extent of 35 to 45% after only 96 h in culture. To further study cell differentiation, we then incorporated gold nanoparticles underneath these plasma coatings, either in form of homogeneous coatings or in form of a nanoparticle density gradient. We found that surface topographic gradients increased cell differentiation into podocytes 3- to 4-fold, whereas differentiation into proximal tubule cells was only dependent on surface chemistry. Our studies on plasma polymer substrates highlighted not only the great potential of plasma polymers to modify surface functionality of a wide range of surfaces, but also emphasized the great capabilities of surface gradients, whether chemical or topographical in nature, to effect cellular fate. In summary, the results of this study include the identification of biomaterial substrates that have the potential to differentiate kidney-derived progenitor/stem cells in vitro and of the cues that are necessary to assist in the differentiation process. In the future, these biomaterials could be useful for directing the differentiation of pluripotent stem cell-derived renal progenitors to specific types of renal cells that could be used for applications in regenerative medicine and drug discovery programmes

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

Exploring Cluster Ellipticals as Cosmological Standard Rods

We explore the possibility to calibrate massive cluster ellipticals as cosmological standard rods using the Fundamental Plane relation combined with a correction for luminosity evolution. Though cluster ellipticals certainly formed in a complex way, their passive evolution out to redshifts of about 1 indicates that basically all major merging and accretion events took place at higher redshifts. Therefore, a calibration of their luminosity evolution can be attempted. We propose to use the Mg$-\sigma$ relation for that purpose because it is independent of distance and cosmology. We discuss a variety of possible caveats, ranging from dynamical evolution to uncertainties in stellar population models and evolution corrections to the presence of age spread. Sources of major random and systematic errors are analysed as well. We apply the described procedure to nine elliptical galaxies in two clusters at $z=0.375$ and derive constraints on the cosmological model. For the best fitting $\Lambda$-free cosmological model we obtain: $q_o \approx 0.1$, with 90% confidence limits being $0 < q_o < 0.7$ (the lower limit being due to the presence of matter in the Universe). If the inflationary scenario applies (i.e. the Universe has flat geometry), then, for the best fitting model, matter and $\Lambda$ contribute about equally to the critical cosmic density (i.e. $\Omega_m \approx \Omega_\Lambda \approx 0.5$). With 90% confidence $\Omega_\Lambda$ should be smaller than 0.9.Comment: 21 pages, including 5 eps-figures, Latex, uses aasms4.sty, accepted by ApJ main journa

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

The Hamburg/SAO Survey for Emission-Line Galaxies. III. The Third List of 81 Galaxies

We present the third list with results {Tables 2 to 6 are available only in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html. Figures A1 to A9 will be made available only in the electronic version of the journal.} of the Hamburg/SAO Survey for Emission-Line Galaxies (HSS therein, SAO - Special Astrophysical Observatory, Russia). This survey is based on the digitized objective-prism photoplate database of the Hamburg Quasar Survey (HQS). Here, we present new spectroscopic results of candidates which were obtained in 1998 with the 2.1 m KPNO and the 2.2 m Calar Alto telescopes. All candidates are selected in the declination band +35$^{\circ}$ to +40$^{\circ}$. The follow-up spectroscopy with the 2 m class telescopes confirmed 85 emission-line objects out of 113 observed candidates and allowed their quantitative spectral classification. For 80 of them, the redshifts are determined for the first time. For 5 previously known ELGs, line ratios are presented for the first time. We could classify 55 out of the 85 emission-line objects as BCG/H{\sc ii} galaxies or probable BCGs, 4 - as QSOs, 6 - as Seyfert galaxies, 1 - as super-association in a subluminous spiral galaxy, and 11 are low-excitation objects - either starburst nuclear (SBN), or dwarf amorphous nuclear starburst galaxies (DANS). We could not classify 8 ELGs. Further, for 8 more galaxies we did not detect any significant emission lines.Comment: A&A latex file with 8 tables and one figure. Astron. Astrophys. Suppl. accepted 200