Rotation curves of galaxies probe their total mass distributions, including dark matter. Dwarf galaxies are excellent systems to investigate the dark matter density distribution, as they tend to have larger fractions of dark matter compared to higher mass systems. The core-cusp problem describes the discrepancy found in the slope of the dark matter density profile in the centres of galaxies (beta*) between observations of dwarf galaxies (shallower cores) and dark matter-only simulations (steeper cusps). We investigate beta* in six nearby spiral dwarf galaxies for which high-resolution CO J = 1-0 data were obtained with ALMA (Atacama Large Millimeter/submillimeter Array). We derive rotation curves and decompose the mass profile of the dark matter using our CO rotation curves as a tracer of the total potential and 4.5 mu m photometry to define the stellar mass distribution. We find = 0.6 with a standard deviation of +/- 0.1 among the galaxies in this sample, in agreement with previous measurements in this mass range. The galaxies studied are on the high stellar mass end of dwarf galaxies and have cuspier profiles than lower mass dwarfs, in agreement with other observations. When the same definition of the slope is used, we observe steeper slopes than predicted by the FIRE and NIHAO simulations. This may signal that these relatively massive dwarfs underwent stronger gas inflows towards their centres than predicted by these simulations, that these simulations overpredict the frequency of accretion or feedback events, or that a combination of these or other effects are at work.

Ly alpha tomography surveys have begun to produce 3D maps of the intergalactic medium opacity at z similar to 2.5 with megaparsec resolution. These surveys provide an exciting new way to discover and characterize high-redshift overdensities, including the progenitors of today's massive groups and clusters of galaxies, known as protogroups and protoclusters. We use the IllustrisTNG-300 hydrodynamical simulation to build mock maps that realistically mimic those observed in the Ly alpha Tomographic IMACS Survey. We introduce a novel method for delineating the boundaries of structures detected in 3D Ly alpha flux maps by applying the watershed algorithm. We provide estimators for the dark matter masses of these structures (at z similar to 2.5), their descendant halo masses at z = 0, and the corresponding uncertainties. We also investigate the completeness of this method for the detection of protogroups and protoclusters. Compared to earlier work, we apply and characterize our method over a wider mass range that extends to massive protogroups. We also assess the widely used fluctuating Gunn-Peterson approximation applied to dark-matter-only simulations; we conclude that while it is adequate for estimating the Ly alpha absorption signal from moderate-to-massive protoclusters (greater than or similar to 10(14.2) h (-1) M (circle dot)), it artificially merges a minority of lower-mass structures with more massive neighbors. Our methods will be applied to current and future Ly alpha tomography surveys to create catalogs of overdensities and study environment-dependent galactic evolution in the Cosmic Noon era.

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).