The Carnegie Planet Finder Spectrograph (PFS) has been commissioned for use with the 6.5 meter Magellan Clay telescope at Las Campanas Observatory in Chile. PFS is optimized for high precision measurements of stellar radial velocities to support an ongoing search for extrasolar planets. PFS uses an R4 echelle grating and a prism cross-disperser in a Littrow arrangement to provide complete wavelength coverage between 388 and 668 nm distributed across 64 orders. The spectral resolution is 38,000 with a 1 arcsecond wide slit. An iodine absorption cell is used to superimpose well-defined absorption features on the stellar spectra, providing a fiducial wavelength reference. Several uncommon features have been implemented in the pursuit of increased velocity stability. These include enclosing the echelle grating in a vacuum tank, actively controlling the temperature of the instrument, providing a time delayed integration mode to improve flatfielding, and actively controlling the telescope guiding and focus using an image of the target star on the slit. Data collected in the first five months of scientific operation indicate that velocity precision better than 1 m s(-1) RMS is being achieved.

We present new radial velocity (RV) measurements of the ultra-cool dwarf VB 10, which was recently announced to host a giant planet detected with astrometry. The new observations were obtained using optical spectrographs (MIKE/Magellan and ESPaDOnS/CFHT) and cover 65% of the reported period of 270 days. The nominal precision of the new Doppler measurements is about 150 m s(-1) while their standard deviation is 250 m s(-1). However, there are indications that such a larger variation is due to uncontrolled systematic errors. We apply least-squares periodograms to identify the most significant signals and evaluate their false alarm probabilities (FAPs). We show that this method is the proper generalization to astrometric data because (1) it mitigates the coupling of the orbital parameters with the parallax and proper motion, and (2) it permits a direct generalization to include nonlinear Keplerian parameters in a combined fit to astrometry and RV data. Our analysis of the astrometry alone uncovers the reported 270 day period and an even stronger signal at similar to 50 days. We estimate the uncertainties in the parameters using a Markov chain Monte Carlo approach. Although the new data alone cannot rule out the presence of a candidate, when combined with published RV measurements, the FAPs of the best solutions grow to unacceptable levels strongly suggesting that the observed astrometric wobble is not due to an unseen companion. The new measurements put an upper limit of m sin i similar to 2.5 m(jup) for a companion with a period shorter than one year and moderate eccentricities.

We report results from a survey of MgII absorbers in the spectra of background quasi-stellar objects (QSOs) that are within close angular distances to a foreground galaxy at z < 0.5, using the Magellan Echellette Spectrograph. We have established a spectroscopic sample of 94 galaxies at a median redshift of < z > = 0.24 in fields around 70 distant background QSOs (z(QSO) > 0.6), 71 of which are in an "isolated" environment with no known companions and located at rho less than or similar to 120 h(-1) kpc from the line of sight of a background QSO. The rest-frame absolute B-band magnitudes span a range from M(B) - 5 log h = -16.4 to M(B) - 5 log h = -21.4 and rest-frame B(AB) - R(AB) colors range from B(AB) - R(AB) approximate to 0 to B(AB) - R(AB) approximate to 1.5. Of these "isolated" galaxies, we find that 47 have corresponding MgII absorbers in the spectra of background QSOs and rest-frame absorption equivalent width W(r)(2796) = 0.1-2.34 angstrom, and 24 do not give rise to MgII absorption to sensitive upper limits. Our analysis shows that (1) W(r) (2796) declines with increasing distance from "isolated" galaxies but shows no clear trend in "group" environments; (2) more luminous galaxies possess more extended MgII absorbing halos with the gaseous radius scaled by B-band luminosity according to R(gas) = 75 x (L(B)/L(B))((0.35 +/- 0.03)) h(-1) kpc; (3) there is little dependence between the observed absorber strength and galaxy intrinsic colors; and (4) within R(gas), we find a mean covering fraction of approximate to 70% for absorbers of W(r)(2796) >= 0.3 angstrom and approximate to 80% for absorbers of W(r) (2796) >= 0.1 angstrom. The results confirm that extended MgII absorbing halos are a common and generic feature around ordinary galaxies and that the gaseous radius is a fixed fraction of the dark matter halo radius. The lack of correlation between W(r) (2796) strength and galaxy colors suggests a lack of physical connection between the origin of extended MgII halos and recent star formation history of the galaxies. Finally, we discuss the total gas mass in galactic halos as traced by MgII absorbers. We also compare our results with previous studies.

We study the connections between ongoing star formation, galaxy mass, and extended halo gas, in order to distinguish between starburst-driven outflows and infalling clouds that produce the majority of observed Mg II absorbers at large galactic radii (greater than or similar to 10 h(-1) kpc) and to gain insights into halo gas contents around galaxies. We present new measurements of total stellar mass (M-star), H alpha emission line strength (EW(H alpha)), and specific starformation rate (sSFR) for the 94 galaxies described by Chen et al.'s 2010 paper. We find that the extent of Mg II absorbing gas, R-Mg (II), scales with M-star and sSFR, following R-Mg (II) alpha M-star(0.28) x sSFR(0.11). The strong dependence of R-MgII on M-star is most naturally explained, if more massive galaxies possess more extended halos of cool gas and the observed Mg II absorbers arise in infalling clouds which will subsequently fuel star formation in the galaxies. The additional scaling relation of R-Mg (II) with sSFR can be understood either as accounting for extra gas supplies due to starburst outflows or as correcting for suppressed cool gas content in high-mass halos. The latter is motivated by the well-known sSFR-M-star inverse correlation in field galaxies. Our analysis shows that a joint study of galaxies and Mg II absorbers along common sight lines provides an empirical characterization of halo gaseous radius versus halo mass. A comparison study of R-Mg (II) around red- and blue-sequence galaxies may provide the first empirical constraint for resolving the physical origin of the observed sSFR-M-star relation in galaxies.

Aims. We report on the first spectroscopic search for quiescent degenerate binaries in globular clusters.

The globular cluster M15 is unique in its display of star-to-star variations in the neutron-capture elements. Comprehensive abundance surveys have been previously conducted for handfuls of M15 red giant branch (RGB) and red horizontal branch (RHB) stars. No attempt has been made to perform a single, self-consistent analysis of these stars, which exhibit a wide range in atmospheric parameters. In the current effort, a new comparative abundance derivation is presented for three RGB and six RHB members of the cluster. The analysis employs an updated version of the line transfer code MOOG, which now appropriately treats coherent, isotropic scattering. The apparent discrepancy in the previously reported values for the metallicity of M15 RGB and RHB stars is addressed and a resolute disparity of Delta(RHB-RGB) approximate to 0.1 dex in the iron abundance was found. The anti-correlative behavior of the light neutron-capture elements (Sr, Y, Zr) is clearly demonstrated with both Ba and Eu, standard markers of the s- and r-process, respectively. No conclusive detection of Pb was made in the RGB targets. Consequently for the M15 cluster, this suggests that the main component of the s-process has made a negligible contribution to those elements normally dominated by this process in solar system material. Additionally for the M15 sample, a large Eu abundance spread is confirmed, which is comparable to that of the halo field at the same metallicity. These abundance results are considered in the discussion of the chemical inhomogeneity and nucleosynthetic history of M15.

We have derived the absolute proper motion (PM) of the globular cluster M55 using a large set of CCD images collected with the du Pont telescope between 1997 and 2008. We find (mu(alpha) cos delta, mu(delta)) = (-3.31 +/- 0.10, -9.14 +/- 0.15) mas yr(-1) relative to background galaxies. Membership status was determined for 16 945 stars with 14 < V < 21 from the central part of the cluster. The PM catalogue includes 52 variables, of which 43 are probable members of M55. This sample not only is dominated by pulsating blue straggler stars, but also includes five eclipsing binaries, three of which are main-sequence objects. The survey also identified several candidate blue, yellow and red straggler stars belonging to the cluster. We detected 15 likely members of the Sgr dSph galaxy located behind M55. The average PM for these stars was measured to be (mu(alpha) cos delta, mu(delta)) = (-2.23 +/- 0.14, -1.83 +/- 0.24) mas yr(-1).

Type Ia supernovae are key tools for measuring distances on a cosmic scale. They are generally thought to be the thermonuclear explosion of an accreting white dwarf in a close binary system. The nature of the mass donor is still uncertain. In the single-degenerate model it is a main-sequence star or an evolved star, whereas in the double-degenerate model it is another white dwarf. We show that the velocity structure of absorbing material along the line of sight to 35 type Ia supernovae tends to be blueshifted. These structures are likely signatures of gas outflows from the supernova progenitor systems. Thus, many type Ia supernovae in nearby spiral galaxies may originate in single-degenerate systems.

We present precise radial-velocity (RV) measurements of WASP-1 and WASP-2 throughout transits of their giant planets. Our goal was to detect the Rossiter-McLaughlin (RM) effect, the anomalous RV observed during eclipses of rotating stars, which can be used to study the obliquities of planet-hosting stars. For WASP-1, a weak signal of a prograde orbit was detected with approximate to 2 sigma confidence, and for WASP-2 no signal was detected. The resulting upper bounds on the RM amplitude have different implications for these two systems because of the contrasting transit geometries and the stellar types. Because WASP-1 is an F7V star, and such stars are typically rapid rotators, the most probable reason for the suppression of the RM effect is that the star is viewed nearly pole-on. This implies that the WASP-1 star has a high obliquity with respect to the edge-on planetary orbit. Because WASP-2 is a K1V star, and is expected to be a slow rotator, no firm conclusion can be drawn about the stellar obliquity. Our data and our analysis contradict an earlier claim that WASP-2b has a retrograde orbit, thereby revoking this system's status as an exception to the pattern that cool stars have low obliquities.

We measure a tilt of 86 degrees +/- 6 degrees. between the sky projections of the rotation axis of the WASP-7 star and the orbital axis of its close-in giant planet. This measurement is based on observations of the Rossiter-McLaughlin (RM) effect with the Planet Finder Spectrograph on the Magellan II telescope. The result conforms with the previously noted pattern among hot-Jupiter hosts, namely, that the hosts lacking thick convective envelopes have high obliquities. Because the planet's trajectory crosses a wide range of stellar latitudes, observations of the RM effect can in principle reveal the stellar differential rotation profile; however, with the present data the signal of differential rotation could not be detected. The host star is found to exhibit radial-velocity noise ("stellar jitter") with an amplitude of approximate to 30 m s(-1) over a timescale of days.