Black Hole Mass of the Ultraluminous X-ray source M82 X-1

We report the first clear evidence for the simultaneous presence of a low frequency break and a QPO in the fluctuation power spectrum of a well known ultraluminous X-ray source (ULX) in M82 using long XMM-Newton observations. The break occurs at a frequency of 34.2_{-3}^{+6}mHz. The QPO has a centroid at 114.3\pm1.5mHz, a coherence Q~3.5 and an amplitude (rms) of 19% in the 2-10keV band. The power spectrum is approximately flat below the break frequency and then falls off above the break frequency as a power law with the QPO superimposed. This form of the power spectrum is characteristic of the Galactic X-ray binaries (XRBs) in their high or intermediate states. M82 X-1 was likely in an intermediate state during the observation. The EPIC PN spectrum is well described by a model comprising an absorbed power-law (Gamma~2) and an iron line at ~6.6keV with a width sigma~0.2keV and an equivalent width of ~180eV. Using the well established correlations between the power and energy spectral parameters for XRBs, we estimate a black hole mass for M82 X-1 in the range of 25-520Msun including systematic errors that arise due to the uncertainty in the calibration of the photon spectral index versus QPO frequency relation.Comment: Final version, accepted for publication in ApJ Letter

Cosmic Gravitational Shear from the HST Medium Deep Survey

We present a measurement of cosmic shear on scales ranging from 10\arcsec to 2\arcmin in 347 WFPC2 images of random fields. Our result is based on shapes measured via image fitting and on a simple statistical technique; careful calibration of each step allows us to quantify our systematic uncertainties and to measure the cosmic shear down to very small angular scales. The WFPC2 images provide a robust measurement of the cosmic shear signal decreasing from $5.2$ at 10\arcsec to $2.2$ at 130\arcsec .Comment: 4 pages 2 Postscript figures, uses emulateapj.cls Astrophysical Journal Letters, December 1, 200

Wildlife Population Cycles: Implications for Damage Control Planning

Animal population cycles are not a newly discovered phenomena. References to irruptions (sic, Leopold 1933 p. 50) of small rodents can be found in the Old Testament, the writings of Aristotle and in European histories (Orr 1963 p. 360). The wildlife literature is filled with descriptions and studies of the population fluctuations of numerous species. Despite the vast amounts of data collected and speculation engaged in, biologists only partially understand the reasons for these fluctuations (Archibald 1977, Chitty 1952, Christian 1950, Cole 1951, Frank 1957, Hoffman 1958 Swinton 1883 and many others)

The toxic sheep collar for control of sheep-killing coyotes: A progress report

The toxic sheep collar is the most selective method known for killing coyotes that prey on domestic sheep. The concept dates back to the early 1900's and has been studied at the Denver Wildlife Research Center (DWRC) since 1974. Field tests with sodium cyanide (NaCN) in 1975 were unsuccessful due to repellent properties of the toxicant and to the apparent reluctance of coyotes to attack tethered lambs wearing bulky collars. Coyotes attacked one or more tethered, collared lambs in 7 of the 19 test pastures. In all, 14 collared lambs were attacked. Eight of the collars were punctured but no dead coyotes were recovered. A smaller collar containing diphacinone was field tested in 1976. The diphacinone-filled collars were readily accepted by coyotes and lethal to them, but the slow action (5-16 days between dosing and death) of diphacinone made it difficult to assess the effectiveness of these collars under field conditions. Target flocks containing 1 to 12 collared lambs plus uncollared ewes were placed in 15 fenced pastures from which the larger ranch flocks had been removed after repeated coyote predation. One or more collared lambs were attacked in 11 of the 15 tests. An unknown number of coyotes were killed, and in most tests the subsequent incidence of predation was lower than that before the test. Captive coyotes continued to kill sheep for 4 or 5 days after they received a lethal dose of diphacinone; therefore a faster-acting toxicant is needed. This research has shown that problem coyotes can be killed with toxic collars, but further studies are needed to determine the feasibility of this approach compared with traditional means of control. In most tests to date the frequency of coyote predation has been too low and too irregular to permit effective use of the collar; target flocks were in the field for an average of 10 days before being attacked. The known disadvantages of the method include the need to sacrifice live lambs, the human hazards associated with the use of toxicants under field conditions, and the costs of managing target flocks and other sheep in the problem areas

The Contribution of Late-type/Irregulars to the Faint Galaxy Counts from HST Medium Deep Survey Images

We present a complete morphologically classified sample of 144 faint field galaxies from the HST Medium Deep Survey with 20.0 < I <22.0 mag. We compare the global properties of the ellipticals, early and late-type spirals, and find a non-negligible fraction (13/144) of compact blue [(V-I) < 1.0 mag] systems with $r^{1/4}$-profiles. We give the differential galaxy number counts for ellipticals and early-type spirals independently, and find that the data are consistent with no-evolution predictions based on conventional flat Schechter luminosity functions (LF's) and a standard cosmology. Conversely, late-type/Irregulars show a steeply rising differential number count with slope $(\frac{\delta log N}{\delta m}) = 0.64\pm 0.1$. No-evolution models based on the Loveday et al. (1992) and Marzke et al. (1994b) {\it local} luminosity functions under-predict the late-type/Irregular counts by 1.0 and 0.5 dex, respectively, at I = 21.75 mag. Examination of the Irregulars alone shows that $\sim 50$% appear inert and the remainder have multiple cores. If the inert galaxies represent a non-evolving late-type population, then a Loveday-like LF ($\alpha\simeq -1.0$) is ruled out for these types, and a LF with a steep faint-end ($\alpha\simeq -1.5$) is suggested. If multiple core structure indicates recent star-formation, then the observed excess of faint blue field galaxies is likely due to {\it evolutionary} processes acting on a {\it steep} field LF for late-type/Irregulars. The evolutionary mechanism is unclear, but 60% of the multiple-core Irregulars show close companions. To reconcile a Marzke-like LF with the faint redshift surveys, this evolution must be preferentially occurring in the brightest late-type galaxies with z > 0.5 at I = 21.75 mag.Comment: 29 pages, 1 catalog and 10 figures. The figures and catalog can be found at http://www.phys.unsw.edu.au/~spd/bib.htm