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Measurements of magnetic susceptibility, heat capacity and thermal expansion are reported for single crystalline CuSb$_{2}$O$_{6}$ in the temperature range $5

We present a measure of the hard (2-8 keV) X-ray luminosity function (XLF) of Active Galactic Nuclei up to z~5. At high redshifts, the wide area coverage of the Chandra Multiwavength Project is crucial to detect rare and luminous (Lx > 10^44 erg s^-1) AGN. The inclusion of samples from deeper published surveys, such as the Chandra Deep Fields, allows us to span the lower Lx range of the XLF. Our sample is selected from both the hard (z < 3; f(2-8 keV) > 6.3x10^-16 erg cm^-2 s^-1) and soft (z > 3; f(0.5-2.0 keV) > 1.0x10^-16 erg cm^-2 s^-1) energy band detections. Within our optical magnitude limits (r',i' < 24), we achieve an adequate level of completeness (>50%) regarding X-ray source identification (i.e., redshift). We find that the luminosity function is similar to that found in previous X-ray surveys up to z~3 with an evolution dependent upon both luminosity and redshift. At z > 3, there is a significant decline in the numbers of AGN with an evolution rate similar to that found by studies of optically-selected QSOs. Based on our XLF, we assess the resolved fraction of the Cosmic X-ray Background, the cumulative mass density of Supermassive Black Holes (SMBHs), and the comparison of the mean accretion rate onto SMBHs and the star formation history of galaxies as a function of redshift. A coevolution scenario up to z~2 is plausible though at higher redshifts the accretion rate onto SMBHs drops more rapidly. Finally, we highlight the need for better statistics of high redshift AGN at z > 3, which is achievable with the upcoming Chandra surveys., Comment: Accepted for publication in ApJ; 25 pages, 18 figures

We present a survey of serendipitous extended X-ray sources and optical cluster candidates from the Chandra Multi-wavelength Project (ChaMP). Our main goal is to make an unbiased comparison of X-ray and optical cluster detection methods. In 130 archival Chandra pointings covering 13 square degrees, we use a wavelet decomposition technique to detect 55 extended sources, of which 6 are nearby single galaxies. Our X-ray cluster catalog reaches a typical flux limit of about ~10^-14 erg s^-1 cm^-2, with a median cluster core radius of 21 arcsec. For 56 of the 130 X-ray fields, we use the ChaMP's deep NOAO/4m MOSAIC g, r, and i imaging to independently detect cluster candidates using a Voronoi tessellation and percolation (VTP) method. Red-sequence filtering decreases the galaxy fore/background contamination and provides photometric redshifts to z~0.7. From the overlapping 6.1 square degree X-ray/optical imaging, we find 115 optical clusters (of which 11% are in the X-ray catalog) and 28 X-ray clusters (of which 46% are in the optical VTP catalog). The median redshift of the 13 X-ray/optical clusters is 0.41, and their median X-ray luminosity (0.5-2 keV) is L_X=(2.65\pm0.19)x10^43 ergs s^-1. The clusters in our sample that are only detected in our optical data are poorer on average (~4sigma) than the X-ray/optically matched clusters, which may partially explain the difference in the detection fractions., Comment: 64 pages, 20 figures, accepted for publication in ApJ

For measurement of the AGN luminosity function and its evolution, X-ray selection samples all types of AGN and provides reduced obscuration bias in comparison with UV-excess or optical surveys. The apparent decline in optically-selected quasars above z~3 may be strongly affected by such a bias. The Chandra Multiwavelength Project (ChaMP) is characterizing serendipitously detected X-ray sources in a large number of fields with archival Chandra imaging. We present a preliminary measure of the co-moving space density using a sample of 311 AGN found in 23 ChaMP fields (~1.8 deg^2) supplemented with 57 X-ray bright AGN from the CDF-N and CDF-S. Within our X-ray flux (f(0.3-8.0 keV) > 4x10^-15 erg cm^-2 s^-1) and optical magnitude (r' < 22.5) limits, our sample includes 14 broad emission line AGN at z > 3. Using this X-ray selected sample, we detect a turnover in the co-moving space density of luminous type 1 AGN (log Lx > 44.5; units erg s^-1; measured in the 0.3-8.0 keV band and corrected for Galactic absorption) at z > 2.5. Our X-ray sample is the first to show a behavior similar to the well established evolution of the optical quasar luminosity function. A larger sample of high redshift AGN and with a greater fraction of identified sources, either spectroscopic or photometric, at faint optical magnitudes (r' > 22.5) are required to remove the remaining uncertainty in our measure of the X-ray luminosity function. We confirm that for z < 1, lower luminosity AGN (log Lx < 44.5) are more prevalent by more than an order of magnitude than those with high luminosity. We have combined the Chandra sample with AGN from the ROSAT surveys to present a measure of the space density of luminous type 1 AGN in the soft X-ray band (0.5-2.0 keV) which confirms the broad band turnover described above., Comment: 8 pages, 9 figures, 1 color figure, Expanded version accepted by ApJ

The BTC40 Survey for high-redshift quasars is a multicolor search using images obtained with the Big Throughput Camera (BTC) on the CTIO 4-m telescope in V, I, and z filters to search for quasars at redshifts of 4.8 < z < 6. The survey covers 40 sq. deg. in B, V, & I and 36 sq. deg. in z. Limiting magnitudes (3 sigma) reach to V = 24.6, I = 22.9 and z = 22.9. We used the (V-I) vs. (I-z) two-color diagram to select high-redshift quasar candidates from the objects classified as point sources in the imaging data. Follow-up spectroscopy with the AAT and CTIO 4-m telescopes of candidates having I < 21.5 has yielded two quasars with redshifts of z = 4.6 and z = 4.8 as well as four emission line galaxies with z = 0.6. Fainter candidates have been identified down to I = 22 for future spectroscopy on 8-m class telescopes., Comment: 27 pages, 8 figures; Accepted for publication in the Astronomical Journal