Context. The radial variations of the stellar populations properties within passive galaxies at high redshift contain information about their assembly mechanisms, based on which galaxy formation and evolution scenarios may be distinguished.

The stellar initial mass function (IMF) is a fundamental property in the measurement of stellar masses and galaxy star formation histories. In this work, we focus on the most massive galaxies in the nearby universe log(M*/M-circle dot) > 11.2. We obtain high-quality Magellan/LDSS-3 long-slit spectroscopy with a wide wavelength coverage of 0.4-1.01 mu m for 41 early-type galaxies (ETGs) in the MASSIVE survey and derive high signal-to-noise spectra within an aperture of R-e/8. Using detailed stellar synthesis models, we constrain the elemental abundances and stellar IMF of each galaxy through full spectral modeling. All the ETGs in our sample have an IMF that is steeper than a Milky Way (Kroupa) IMF. The best-fit IMF mismatch parameter, alpha(IMF) = (M/L)/(M/L)(MW), ranges from 1.1 to 3.1, with an average of = 1.84, suggesting that on average, the IMF is more bottom heavy than Salpeter. Comparing the estimated stellar masses with the dynamical masses, we find that most galaxies have stellar masses that are smaller than their dynamical masses within the 1 sigma uncertainty. We complement our sample with lower-mass galaxies from the literature and confirm that log(alpha(IMF)) is positively correlated with log(sigma), log(M*), and log(M-dyn). From the combined sample, we show that the IMF in the centers of more massive ETGs is more bottom heavy. In addition, we find that log(alpha(IMF)) is positively correlated with both [Mg/Fe] and the estimated total metallicity [Z/H]. We find suggestive evidence that the effective stellar surface density Sigma(Kroupa) might be responsible for the variation of alpha(IMF). We conclude that sigma, [Mg/Fe], and [Z/H] are the primary drivers of the global stellar IMF variation.

Galaxy protoclusters, which will eventually grow into the massive clusters we see in the local Universe, are usually traced by locating overdensities of galaxies(1). Large spectroscopic surveys of distant galaxies now exist, but their sensitivity depends mainly on a galaxy's star-formation activity and dust content rather than its mass. Tracers of massive protoclusters that do not rely on their galaxy constituents are therefore needed. Here we report observations of Lyman-a absorption in the spectra of a dense grid of background galaxies(2,3), which we use to locate a substantial number of candidate protoclusters at redshifts 2.2 to 2.8 through their intergalactic gas. We find that the structures producing the most absorption, most of which were previously unknown, contain surprisingly few galaxies compared with the dark-matter content of their analogues in cosmological simulations(4,5). Nearly all of the structures are expected to be protoclusters, and we infer that half of their expected galaxy members are missing from our survey because they are unusually dim at rest-frame ultraviolet wavelengths. We attribute this to an unexpectedly strong and early influence of the protocluster environment(6,7) on the evolution of these galaxies that reduced their star formation or increased their dust content.

We present the latest precision radial velocity results from the Anglo Australian Planet Search. These include new planet mass companions to HD 216437, HD 196050, HD 30177, HD 73526, and HD 2039, as well as evidence for a second companion to HD 160691 residing in a long period orbit. The results come from a sample of similar to 200 nearby inactive FGKM dwarfs with V<7.5 and a subsample of 20 more distant metal rich stars. At least 25 +/- 11% of metal rich stars appear to have planets within 2.5 AU, somewhat more than the 8% of stars which appear to have planets within 3.5 AU.

Two extrasolar planets, HD 209458b and TrES-1, are currently known to transit bright parent stars for which physical properties can be accurately determined. The two transiting planets have very similar masses and periods and hence invite detailed comparisons between their observed and theoretically predicted properties. In this paper, we carry out these comparisons. We first report photometric and spectroscopic follow-up observations of TrES-1, and we use these observations to obtain improved estimates for the planetary radius, R-pl = (1.08 +/- 0.05)R-J, and the planetary mass, M-pl (0.729 +/- 0.036)M-J. We also confirm that the inclination estimate of the planetary orbit as i = 88.degrees 2. These values agree with those obtained by Alonso et al. in their discovery paper, but the uncertainty in the planet radius has been improved as a result of both high-cadence photometry of two full transits and from independent radius determinations for the V 11.8 K0 V parent star. We derive estimates for the TrES-1 stellar parameters of R-*/R-circle dot = 0.83 +/- 0.03 (by combining independent estimates from stellar models, high-resolution spectra, and transit light curve fitting) M-*/M-circle dot = 0.87 +/- 0.05 (via fitting to evolutionary tracks), T-eff = 5214 +/- 23 K, [Me/H] = 0.001 +/- 0.04, rotational velocity V sin (i) 1.08 +/- 0.3 km s(-1), log g 4.52 +/- 0.05 dex, log L-*/L-circle dot = -0.32, d = 157 +/- 6 pc, and an age of tau = 4 +/- 2 Gyr. These estimates of the physical properties of the system allow us to compute evolutionary models for the planet that result in a predicted radius of R-pl = 1.05R(J) for a model that contains an incompressible 20 M-circle plus core and a radius R-pl = 1.09R(J) for a model without a core. We use our grids of planetary evolution models to show that, with standard assumptions, our code also obtains good agreement with the observed radii of the other recently discovered transiting planets, including OGLE-TR-56b, OGLE-TR-111b, OGLE-TR113b, and OGLE-TR-132b. We report an updated radius for HD 209458b of R-pl = (1.32 +/- 0.05)R-J, based on a new radius estimate of R-* = 1.12 R-circle dot for the parent star. Our theoretical predictions for the radius of HD 209458b are R-pl = 1.05R(J) and 1.09R(J) for models with and without cores. HD 209458b is therefore the only transiting planet whose radius does not agree well with our theoretical models. We argue that tidal heating stemming from dynamical interaction with a second planet is currently the most viable explanation for its inflated size.

Doppler measurements from Subaru and Keck have revealed radial velocity variations in the V 8.15, G0 IV star HD 149026 consistent with a Saturn-mass planet in a 2.8766 day orbit. Photometric observations at Fairborn Observatory have detected three complete transit events with depths of 0.003 mag at the predicted times of conjunction. HD 149026 is now the second-brightest star with a transiting extrasolar planet. The mass of the star, based on interpolation of stellar evolutionary models, is 1.3 +/- 0.1 M-circle dot; together with the Doppler amplitude K-1 = 43.3 m s(-1), we derive a planet mass M sin i = 0.36M(J) and orbital radius 0.042 AU. HD 149026 is chromospherically inactive and metal-rich with spectroscopically derived [Fe/H] = +0.36, T-eff 6147 K, log g 4.26, and v sin i 6.0 km s(-1). Based on Teff and the stellar luminosity of 2.72 L-circle dot, we derive a stellar radius of 1.45 R-circle dot. Modeling of the three photometric transits provides an orbital inclination of 85 degrees.3 +/- 1 degrees.0 and ( including the uncertainty in the stellar radius) a planet radius of (0.725 +/- 0.05) R-J. Models for this planet mass and radius suggest the presence of a similar to 67 M-circle dot core composed of elements heavier than hydrogen and helium. This substantial planet core would be difficult to construct by gravitational instability.

We report 35 radial velocity measurements of HD 149026 taken with the Keck Telescope. Of these measurements, 15 were made during the transit of the companion planet HD 149026b, which occurred on 2005 June 25. These velocities provide a high-cadence observation of the Rossiter-McLaughlin effect, the shifting of photospheric line profiles that occurs when a planet occults a portion of the rotating stellar surface. We combine these radial velocities with previously published radial velocity and photometric data sets and derive a composite best-fit model for the star-planet system. This model confirms and improves previously published orbital parameters, including the remarkably small planetary radius, the planetary mass, and the orbital inclination, found to be R-p/R-Jup 0.718 +/- 0.065, M-p/M-Jup 0.352 +/- 0.025, and I = 86.1 degrees +/- 1.4 degrees, respectively. Together the planetary mass and radius determinations imply a mean planetary density of 1.18(-0.30)(+0.38) g cm(-3). The new data also allow for the determination of the angle between the apparent stellar equator and the orbital plane, which we constrain to be lambda = 12 degrees +/- 15 degrees.

Near- infrared observations of more than a dozen 'hot-Jupiter' extrasolar planets have now been reported(1-5). These planets display a wide diversity of properties, yet all are believed to have had their spin periods tidally spin- synchronized with their orbital periods, resulting in permanent star- facing hemispheres and surface flow patterns that are most likely in equilibrium. Planets in significantly eccentric orbits can enable direct measurements of global heating that are largely independent of the details of the hydrodynamic flow(6). Here we report 8-mu m photometric observations of the planet HD 80606b during a 30- hour interval bracketing the periastron passage of its extremely eccentric 111.4- day orbit. As the planet received its strongest irradiation ( 828 times larger than the flux received at apastron) its maximum 8- mm brightness temperature increased from 800 K to 1,500K over a six- hour period. We also detected a secondary eclipse for the planet, which implies an orbital inclination of i approximate to 90 degrees, fixes the planetary mass at four times the mass of Jupiter, and constrains the planet's tidal luminosity. Our measurement of the global heating rate indicates that the radiative time constant at the planet's 8- mu m photosphere is similar to 4.5 h, in comparison with 3 - 5 days in Earth's stratosphere(7).

We present high-resolution High Resolution Echelle Spectrometer (HIRES)/Keck spectra of HD 209458, and a Monte Carlo variation on the basic method used by other workers, to look for the excess in-transit absorption in the NaD doublet at 5893 angstrom due to the extrasolar planet. The HIRES data, binned by bandpass, allow a direct comparison with previous results. We find >3 sigma results in most test bandpasses around the NaD doublet, including relative absorption of (-108.8 +/- 25.7) x 10(-5) in the "narrow" bandpass used by other workers. This is approximate to 4.7 times larger than the "narrow" results reported by Charbonneau et al. for HD 209458b. However, >2 sigma absorption is detected in some weak Fe I and Ni I lines that were tested for comparison, raising concern about the uncertainties introduced by continuum-fitting and terrestrial atmosphere subtraction.

We investigate the possibility that the large orbital eccentricity of the transiting Neptune-mass planet Gliese 436b (Gl 436b) is maintained in the face of tidal dissipation by a second planet in the system. We find that the currently observed configuration can be understood if Gl 436b and a putative companion have evolved to a quasi-stationary fixed point in which the planets' orbital apses are co-linear and in which secular variations in the orbital eccentricities of the two planets have been almost entirely damped out. In our picture, the two planets are currently experiencing a long period of gradual orbital circularization. Specifically, if Gl 436b has a tidal Q similar to 300,000, similar to both the Jovian Q and to the upper limit for the Neptunian Q, then this circularization timescale can be of order tau similar to 8 Gyr given the presence of a favorably situated perturber. We adopt an octopole-order secular theory based on a Legendre expansion in the semimajor axis ratio a(1)/a(2) to delineate well-defined regions of (P-c, M-c, e(c)) space that can be occupied by a perturbing companion. This description includes the leading-order effects of general relativity, and retains accuracy for perturbing companion planets that have high eccentricity. We incorporate the evolutionary effect of tidal dissipation into our secular model of the system, and solve the resulting initial value problems for a large sample of the allowed configurations. We find a locus of apsidally aligned configurations that are (1) consistent with the currently published radial velocity data, (2) consistent with the current lack of observed transit timing variations (TTVs), (3) subject to rough constraint on dynamical stability, and which (4) have damping timescales consistent with the current multi-Gyr age of the star. We then polish the stationary configurations derived from secular theory with full numerical integrations, and compute the TTVs and radial velocity half-amplitudes induced by the resulting configurations. We present our results in the form of candidate companion planets to Gl 436b. For these candidates, radial velocity half-amplitudes, K-c, are of order 3 m s(-1), and the maximum amplitude of orbit-to-orbit TTVs are of order Delta t = 1 s to Delta t = 5 s. For the particular example case of a perturber with orbital period, P-c = 40d, mass, M-c = 8.5 M-circle plus, and eccentricity, e(c) = 0.58, we confirm our semianalytic calculations with a full numerical three-body integration of the orbital decay that includes tidal damping and spin evolution. Additionally, we discuss the possibility of many-perturber stationary configurations, utilizing modified Laplace-Lagrange secular theory. We then perform a proof-of-concept tidally dissipated numerical integration with three planets, which shows the system approaching a triply circular state.