Gains from the upgrade of the cold neutron triple-axis spectrometer FLEXX at the BER-II reactor

The upgrade of the cold neutron triple-axis spectrometer FLEXX is described. We discuss the characterisation of the gains from the new primary spectrometer, including a larger guide and double focussing monochromator, and present measurements of the energy and momentum resolution and of the neutron flux of the instrument. We found an order of magnitude gain in intensity (at the cost of coarser momentum resolution), and that the incoherent elastic energy widths are measurably narrower than before the upgrade. The much improved count rate should allow the use of smaller single crystals samples and thus enable the upgraded FLEXX spectrometer to continue making leading edge measurements.Comment: 8 pages, 7 figures, 5 table

The size-star formation relation of massive galaxies at 1.5<z<2.5

We study the relation between size and star formation activity in a complete sample of 225 massive (M > 5 x 10^10 Msun) galaxies at 1.5<z<2.5, selected from the FIREWORKS UV-IR catalog of the CDFS. Based on stellar population synthesis model fits to the observed restframe UV-NIR SEDs, and independent MIPS 24 micron observations, 65% of galaxies are actively forming stars, while 35% are quiescent. Using sizes derived from 2D surface brightness profile fits to high resolution (FWHM_{PSF}~0.45 arcsec) groundbased ISAAC data, we confirm and improve the significance of the relation between star formation activity and compactness found in previous studies, using a large, complete mass-limited sample. At z~2, massive quiescent galaxies are significantly smaller than massive star forming galaxies, and a median factor of 0.34+/-0.02 smaller than galaxies of similar mass in the local universe. 13% of the quiescent galaxies are unresolved in the ISAAC data, corresponding to sizes <1 kpc, more than 5 times smaller than galaxies of similar mass locally. The quiescent galaxies span a Kormendy relation which, compared to the relation for local early types, is shifted to smaller sizes and brighter surface brightnesses and is incompatible with passive evolution. The progenitors of the quiescent galaxies, were likely dominated by highly concentrated, intense nuclear star bursts at z~3-4, in contrast to star forming galaxies at z~2 which are extended and dominated by distributed star formation.Comment: 6 pages, 4 figures, accepted for publication in Ap

Measuring Extinction Curves of Lensing Galaxies

We critique the method of constructing extinction curves of lensing galaxies using multiply imaged QSOs. If one of the two QSO images is lightly reddened or if the dust along both sightlines has the same properties then the method works well and produces an extinction curve for the lensing galaxy. These cases are likely rare and hard to confirm. However, if the dust along each sightline has different properties then the resulting curve is no longer a measurement of extinction. Instead, it is a measurement of the difference between two extinction curves. This "lens difference curve'' does contain information about the dust properties, but extracting a meaningful extinction curve is not possible without additional, currently unknown information. As a quantitative example, we show that the combination of two Cardelli, Clayton, & Mathis (CCM) type extinction curves having different values of R(V) will produce a CCM extinction curve with a value of R(V) which is dependent on the individual R(V) values and the ratio of V band extinctions. The resulting lens difference curve is not an average of the dust along the two sightlines. We find that lens difference curves with any value of R(V), even negative values, can be produced by a combination of two reddened sightlines with different CCM extinction curves with R(V) values consistent with Milky Way dust (2.1 < R(V) < 5.6). This may explain extreme values of R(V) inferred by this method in previous studies. But lens difference curves with more normal values of R(V) are just as likely to be composed of two dust extinction curves with R(V) values different than that of the lens difference curve. While it is not possible to determine the individual extinction curves making up a lens difference curve, there is information about a galaxy's dust contained in the lens difference curves.Comment: 15 pages, 4 figues, ApJ in pres

Sub-millimeter galaxies as progenitors of compact quiescent galaxies

Three billion years after the big bang (at redshift z=2), half of the most massive galaxies were already old, quiescent systems with little to no residual star formation and extremely compact with stellar mass densities at least an order of magnitude larger than in low redshift ellipticals, their descendants. Little is known about how they formed, but their evolved, dense stellar populations suggest formation within intense, compact starbursts 1-2 Gyr earlier (at 3<z<6). Simulations show that gas-rich major mergers can give rise to such starbursts which produce dense remnants. Sub-millimeter selected galaxies (SMGs) are prime examples of intense, gas-rich, starbursts. With a new, representative spectroscopic sample of compact quiescent galaxies at z=2 and a statistically well-understood sample of SMGs, we show that z=3-6 SMGs are consistent with being the progenitors of z=2 quiescent galaxies, matching their formation redshifts and their distributions of sizes, stellar masses and internal velocities. Assuming an evolutionary connection, their space densities also match if the mean duty cycle of SMG starbursts is 42 (+40/-29) Myr (consistent with independent estimates), which indicates that the bulk of stars in these massive galaxies were formed in a major, early surge of star-formation. These results suggests a coherent picture of the formation history of the most massive galaxies in the universe, from their initial burst of violent star-formation through their appearance as high stellar-density galaxy cores and to their ultimate fate as giant ellipticals.Comment: ApJ (in press

Distant red galaxies in the Hubble Ultra Deep Field

We take advantage of the Hubble Ultra Deep Field (UDF) data to study the restframe optical and ultra violet (UV) morphologies of the novel population of Distant Red Galaxies (DRGs). Six galaxies with J-Ks > 2.3 are found to Ks=21.5, five of which have photometric redshifts z_phot > 2, corresponding to a surface density of 0.9/arcmin^2. The surface brightness distributions of the z_phot > 2 galaxies are better represented by exponential disks than R^{1/4}-laws. Two of the z_phot > 2 galaxies are extended, while three have compact morphologies. The restframe optical morphology of the z_phot > 2 galaxies is quite different from the restframe UV morphology: all the galaxies have red central components which dominate in the NICMOS H_{160}-band images, and distinct off-center blue features which show up in (and often dominate) the ACS images. The mean measured effective radius of the z_phot > 2 galaxies is =1.9+/-1.4 kpc, similar (within the errors) to the mean size of LBGs at similar redshifts. All the DRGs are resolved in the ACS images, while four are resolved in the NICMOS images. Two of the z_phot > 2 galaxies are bright X-ray sources and hence host AGN. The diverse restframe optical and UV morphological properties of DRGs derived here suggest that they have complex stellar populations, consisting of both evolved populations that dominate the mass and the restframe optical light, and younger populations, which show up as patches of star formation in the restframe UV light; in many ways resembling the properties of normal local galaxies. This interpretation is supported by fits to the broadband SEDs, which for all five z_phot > 2 are best represented by models with extended star formation histories and substantial amounts of dust.Comment: Accepted for publication in APJ

Direct Measurements of the Stellar Continua and Balmer/4000 Angstrom Breaks of Red z>2 Galaxies: Redshifts and Improved Constraints on Stellar Populations

We use near-infrared (NIR) spectroscopy obtained with GNIRS on Gemini, NIRSPEC on KECK, and ISAAC on the VLT to study the rest-frame optical continua of three `Distant Red Galaxies' (having Js - Ks > 2.3) at z>2. All three galaxy spectra show the Balmer/4000 Angstrom break in the rest-frame optical. The spectra allow us to determine spectroscopic redshifts from the continuum with an estimated accuracy dz/(1+z) ~ 0.001-0.04. These redshifts agree well with the emission line redshifts for the 2 galaxies with Halpha emission. This technique is particularly important for galaxies that are faint in the rest-frame UV, as they are underrepresented in high redshift samples selected in optical surveys and are too faint for optical spectroscopy. Furthermore, we use the break, continuum shape, and equivalent width of Halpha together with evolutionary synthesis models to constrain the age, star formation timescale, dust content, stellar mass and star formation rate of the galaxies. Inclusion of the NIR spectra in the stellar population fits greatly reduces the range of possible solutions for stellar population properties. We find that the stellar populations differ greatly among the three galaxies, ranging from a young dusty starburst with a small break and strong emission lines to an evolved galaxy with a strong break and no detected line emission. The dusty starburst galaxy has an age of 0.3 Gyr and a stellar mass of 1*10^11 Msun. The spectra of the two most evolved galaxies imply ages of 1.3-1.4 Gyr and stellar masses of 4*10^11 Msun. The large range of properties seen in these galaxies strengthens our previous much more uncertain results from broadband photometry. Larger samples are required to determine the relative frequency of dusty starbursts and (nearly) passively evolving galaxies at z~2.5.Comment: Accepted for publication in the Astrophysical Journal. 12 pages, 6 figure

Multiplication and Composition in Weighted Modulation Spaces

We study the existence of the product of two weighted modulation spaces. For this purpose we discuss two different strategies. The more simple one allows transparent proofs in various situations. However, our second method allows a closer look onto associated norm inequalities under restrictions in the Fourier image. This will give us the opportunity to treat the boundedness of composition operators.Comment: 49 page

Understanding the limits to ethnic change: lessons from Uganda's “lost counties”

The historically constructed nature of ethnicity has become a widely accepted paradigm in the social sciences. Scholars have especially have focused on the ways modern states have been able to create and change ethnic identities, with perhaps the strongest case studies coming from colonial Africa, where the gap between strong states and weak societies has been most apparent. I suggest, however, that in order to better understand how and when ethnic change occurs it is important to examine case studies where state-directed ethnic change has failed. To rectify this oversight I examine the case of the “lost counties” of Uganda, which were transferred from the Bunyoro kingdom to the Buganda kingdom at the onset of colonial rule. I show that British attempts to assimilate the Banyoro residents in two of the lost counties were an unmitigated failure, while attempts in the other five counties were successful. I claim that the reason for these differing outcomes lies in the status of the two lost counties as part of the historic Bunyoro homeland, whereas the other five counties were both geographically and symbolically peripheral to Bunyoro. The evidence here thus suggests that varying ethnic attachments to territory can lead to differing outcomes in situations of state-directed assimilation and ethnic change