The Haematopoietic Stem Cell Niche: New Insights into the Mechanisms Regulating Haematopoietic Stem Cell Behaviour

The concept of the haematopoietic stem cell (HSC) niche was formulated by Schofield in the 1970s, as a region within the bone marrow containing functional cell types that can maintain HSC potency throughout life. Since then, ongoing research has identified numerous cell types and a plethora of signals that not only maintain HSCs, but also dictate their behaviour with respect to homeostatic requirements and exogenous stresses. It has been proposed that there are endosteal and vascular niches within the bone marrow, which are thought to regulate different HSC populations. However, recent data depicts a more complicated picture, with functional crosstalk between cells in these two regions. In this review, recent research into the endosteal/vascular cell types and signals regulating HSC behaviour are considered, together with the possibility of a single subcompartmentalised niche

Extreme asteroids in the Pan-STARRS 1 Survey

Using the first 18 months of the Pan-STARRS 1 survey we have identified 33 candidate high-amplitude objects for follow-up observations and carried out observations of 22 asteroids. 4 of the observed objects were found to have observed amplitude $A_{obs}\geq 1.0$ mag. We find that these high amplitude objects are most simply explained by single rubble pile objects with some density-dependent internal strength, allowing them to resist mass shedding even at their highly elongated shapes. 3 further objects although below the cut-off for 'high-amplitude' had a combination of elongation and rotation period which also may require internal cohesive strength, depending on the density of the body. We find that none of the 'high-amplitude asteroids' identified here require any unusual cohesive strengths to resist rotational fission. 3 asteroids were sufficiently observed to allow for shape and spin pole models to be determined through light curve inversion. 45864 was determined to have retrograde rotation with spin pole axes $\lambda=218\pm 10^{\circ}, \beta=-82\pm 5^{\circ}$ and asteroid 206167 was found to have best fit spin pole axes $\lambda= 57 \pm 5^{\circ}$, $\beta=-67 \pm 5^{\circ}$. An additional object not initially measured with $A_{obs}>1.0$ mag, 49257, was determined to have a shape model which does suggest a high-amplitude object. Its spin pole axes were best fit for values $\lambda=112\pm 6^{\circ}, \beta=6\pm 5^{\circ}$. In the course of this project to date no large super-fast rotators ($P_{rot} < 2.2$ h) have been identified.Comment: 31 pages; accepted by A

The Statistical Approach to Quantifying Galaxy Evolution

Studies of the distribution and evolution of galaxies are of fundamental importance to modern cosmology; these studies, however, are hampered by the complexity of the competing effects of spectral and density evolution. Constructing a spectroscopic sample that is able to unambiguously disentangle these processes is currently excessively prohibitive due to the observational requirements. This paper extends and applies an alternative approach that relies on statistical estimates for both distance (z) and spectral type to a deep multi-band dataset that was obtained for this exact purpose. These statistical estimates are extracted directly from the photometric data by capitalizing on the inherent relationships between flux, redshift, and spectral type. These relationships are encapsulated in the empirical photometric redshift relation which we extend to z ~ 1.2, with an intrinsic dispersion of dz = 0.06. We also develop realistic estimates for the photometric redshift error for individual objects, and introduce the utilization of the galaxy ensemble as a tool for quantifying both a cosmological parameter and its measured error. We present deep, multi-band, optical number counts as a demonstration of the integrity of our sample. Using the photometric redshift and the corresponding redshift error, we can divide our data into different redshift intervals and spectral types. As an example application, we present the number redshift distribution as a function of spectral type.Comment: 40 pages (LaTex), 21 Figures, requires aasms4.sty; Accepted by the Astrophysical Journa

Effective out-of-plane g-factor in strained-Ge/SiGe quantum dots

Recently, lithographic quantum dots in strained-Ge/SiGe have become a promising candidate for quantum computation, with a remarkably quick progression from demonstration of a quantum dot to qubit logic demonstrations. Here we present a measurement of the out-of-plane $g$-factor for single-hole quantum dots in this material. As this is a single-hole measurement, this is the first experimental result that avoids the strong orbital effects present in the out-of-plane configuration. In addition to verifying the expected $g$-factor anisotropy between in-plane and out-of-plane magnetic ($B$)-fields, variations in the $g$-factor dependent on the occupation of the quantum dot are observed. These results are in good agreement with calculations of the $g$-factor using the heavy- and light-hole spaces of the Luttinger Hamiltonian, especially the first two holes, showing a strong spin-orbit coupling and suggesting dramatic $g$-factor tunability through both the $B$-field and the charge state

Massive Ellipticals at High Redshift: NICMOS Imaging of Z~1 Radio Galaxies

We present deep, continuum images of eleven high-redshift (0.811 < z < 1.875) 3CR radio galaxies observed with NICMOS. Our images probe the rest-frame optical light where stars are expected to dominate the galaxy luminosity. The rest-frame UV light of eight of these galaxies demonstrates the well-known ``alignment effect''. Most of the radio galaxies have rounder, more symmetric morphologies at rest-frame optical wavelengths. Here we show the most direct evidence that in most cases the stellar hosts are normal elliptical galaxies with de Vaucouleurs law light profiles. For a few galaxies very faint traces of the UV-bright aligned component are also visible in the infrared images. We derive both the effective radius and surface-brightness for nine of eleven sample galaxies by fitting surface-brightness models to them. We find their sizes are similar to those of local FRII radio source hosts and are in general larger than other local galaxies. The derived host galaxy luminosities are very high and lie at the bright end of luminosity functions constructed at similar redshifts. The galaxies in our sample are also brighter than the rest-frame size--surface-brightness locus defined by the low-redshift sources. Passive evolution roughly aligns the z ~ 1 galaxies with the low-redshift samples. The optical host is sometimes centered on a local minimum in the rest-frame UV emission, suggesting the presence of substantial dust obscuration. We also see good evidence of nuclear point sources in three galaxies. Overall, our results are consistent with the hypothesis that these galaxies have already formed the bulk of their stars at redshifts greater than z >~ 2, and that the AGN phenomenon takes place within otherwise normal, perhaps passively evolving, galaxies. (abridged)Comment: 28 pages, 14 figures, accepted to ApJ. Uses AASTEX and emulateapj

The Detection of Inside-out Disk Growth in M33

We present resolved stellar photometry of 4 fields along the major axis of the M33 disk from images taken with the Advanced Camera for Surveys aboard the Hubble Space Telescope. The photometry provides a detailed census of the red clump in all fields and reaches the ancient main sequence in the outermost field. Through detailed modeling of the color-magnitude diagrams, we find that the percentage of the stellar mass formed prior to z=1 changes from 71 +/- 9% in the innermost field to 16 +/- 6% in the outermost field. The disk shows a clear trend of increasing scale-length with time, evolving from 1.0 +/- 0.1 kpc 10 Gyr ago to 1.8 +/- 0.1 kpc at times more recent than 5 Gyr ago, in agreement with analytical predictions for disk growth. Beyond the disk truncation radius, however, the stellar density profile steepens with time and the age gradient reverses, in agreement with recent simulations. The late and slow growth of the stellar disk may be due in part to the low mass of M33.Comment: 7 pages, 4 figures, accepted for publication in ApJ Letter

Chandra Detection of a TypeII Quasar at z=3.288

We report on observations of a TypeII quasar at redshift z=3.288, identified as a hard X-ray source in a 185 ks observation with the Chandra X-ray Observatory and as a high-redshift photometric candidate from deep, multiband optical imaging. CXOJ084837.9+445352 (hereinafter CXO52) shows an unusually hard X-ray spectrum from which we infer an absorbing column density N(H) = (4.8+/-2.1)e23 / cm2 (90% confidence) and an implied unabsorbed 2-10 keV rest-frame luminosity of L(2-10) = 3.3e44 ergs/s, well within the quasar regime. Hubble Space Telescope imaging shows CXO52 to be elongated with slight morphological differences between the WFPC2 F814W and NICMOS F160W bands. Optical and near-infrared spectroscopy of CXO52 show high-ionization emission lines with velocity widths ~1000 km/s and flux ratios similar to a Seyfert2 galaxy or radio galaxy. The latter are the only class of high-redshift TypeII luminous AGN which have been extensively studied to date. Unlike radio galaxies, however, CXO52 is radio quiet, remaining undetected at radio wavelengths to fairly deep limits, f(4.8GHz) < 40 microJy. High-redshift TypeII quasars, expected from unification models of active galaxies and long-thought necessary to explain the X-ray background, are poorly constrained observationally with few such systems known. We discuss recent observations of similar TypeII quasars and detail search techniques for such systems: namely (1) X-ray selection, (2) radio selection, (3) multi-color imaging selection, and (4) narrow-band imaging selection. Such studies are likely to begin identifying luminous, high-redshift TypeII systems in large numbers. We discuss the prospects for these studies and their implications to our understanding of the X-ray background.Comment: 28 pages, 5 figures; to appear in The Astrophysical Journa

Quantum Instrumentation Control Kit -- Defect Arbitrary Waveform Generator (QICK-DAWG): A Quantum Sensing Control Framework for Quantum Defects

Quantum information communication, sensing, and computation often require complex and expensive instrumentation resulting in a large entry barrier. The Quantum Instrumentation Control Kit (QICK) overcomes this barrier for superconducting qubits with a collection of software and firmware for state-of-the-art radio frequency system on chip (RFSoC's) field programmable gate architecture (FPGA) chips. Here we present a software and firmware extension to QICK, the Quantum Instrumentation Control Kit - Defect Arbitrary Waveform Generator (QICK-DAWG), which is an open-source software and firmware package that supports full quantum control and measurement of nitrogen-vacancy defects in diamond and other quantum defects using RFSoC FPGAs. QICKDAWG extends QICK to the characterization of nitrogen-vacancy defects and other diamond quantum defects by implementing DC-1 GHz readout, AOM or gated laser control, and analog or photon counting readout options. QICK-DAWG also adds pulse sequence programs and data analysis scripts to collect and characterize photoluminescence (PL) intensity, optically detected magnetic resonance (ODMR) spectra, PL readout windows, Rabi oscillations, Ramsay interference spectra, Hahn echo spin-spin relaxation times T$_2$, and spin-lattice relaxation times T$_1$. We demonstrate that QICK-DAWG is a powerful new paradigm of open source quantum hardware that significantly lowers the entry barrier and cost for quantum sensing using quantum defects.Comment: 8 pages, 1 figure, GitHub https://github.com/sandialabs/qick-daw

The DEEP2 Galaxy Redshift Survey: The Voronoi-Delaunay Method Catalog of Galaxy Groups

We present a public catalog of galaxy groups constructed from the spectroscopic sample of galaxies in the fourth data release from the Deep Extragalactic Evolutionary Probe 2 (DEEP2) Galaxy Redshift Survey, including the Extended Groth Strip (EGS). The catalog contains 1165 groups with two or more members in the EGS over the redshift range 0 0.6 in the rest of DEEP2. Twenty-five percent of EGS galaxies and fourteen percent of high-z DEEP2 galaxies are assigned to galaxy groups. The groups were detected using the Voronoi-Delaunay method (VDM) after it has been optimized on mock DEEP2 catalogs following similar methods to those employed in Gerke et al. In the optimization effort, we have taken particular care to ensure that the mock catalogs resemble the data as closely as possible, and we have fine-tuned our methods separately on mocks constructed for the EGS and the rest of DEEP2. We have also probed the effect of the assumed cosmology on our inferred group-finding efficiency by performing our optimization on three different mock catalogs with different background cosmologies, finding large differences in the group-finding success we can achieve for these different mocks. Using the mock catalog whose background cosmology is most consistent with current data, we estimate that the DEEP2 group catalog is 72% complete and 61% pure (74% and 67% for the EGS) and that the group finder correctly classifies 70% of galaxies that truly belong to groups, with an additional 46% of interloper galaxies contaminating the catalog (66% and 43% for the EGS). We also confirm that the VDM catalog reconstructs the abundance of galaxy groups with velocity dispersions above ~300 km s^(–1) to an accuracy better than the sample variance, and this successful reconstruction is not strongly dependent on cosmology. This makes the DEEP2 group catalog a promising probe of the growth of cosmic structure that can potentially be used for cosmological tests