We present radial velocities for 14 stars on the California and Carnegie Planet Search target list that reveal new companions. One star, HD 167665, was fit with a definitive Keplerian orbit leading to a minimum mass for the companion of 50.3 M-Jup at a separation from its host of similar to 5.5 AU. Incomplete or limited phase coverage for the remaining 13 stars prevents us from assigning to them unique orbital parameters. Instead, we fit their radial velocities with Keplerian orbits across a grid of fixed values for M sin i and period P, and use the resulting chi(2)(v) surface to place constraints on M sin i, P, and semimajor axis a. This technique allowed us to restrict M sin i below the brown dwarf- stellar mass boundary for an additional four companions ( HD 150554, HD 8765, HD 72780, HD 74014). If the combined five companions are confirmed as brown dwarfs, these results would comprise the first major catch of such objects from our survey beyond similar to 3 AU.

We study the structural evolution of massive galaxies by linking progenitors and descendants at a constant cumulative number density of n(c) = 1.4 x 10(-4) Mpc(-3) to z similar to 3. Structural parameters were measured by fitting Sersic profiles to high-resolution CANDELS HST WFC3 J(125) and H-160 imaging in the UKIDSS-UDS at 1 < z < 3 and ACS I-814 imaging in COSMOS at 0.25 < z < 1. At a given redshift, we selected the HST band that most closely samples a common rest-frame wavelength so as to minimize systematics from color gradients in galaxies. At fixed n(c), galaxies grow in stellar mass by a factor of similar to 3 from z similar to 3 to z similar to 0. The size evolution is complex: galaxies appear roughly constant in size from z similar to 3 to z similar to 2 and then grow rapidly to lower redshifts. The evolution in the surface mass density profiles indicates that most of the mass at r < 2 kpc was in place by z similar to 2, and that most of the new mass growth occurred at larger radii. This inside-out mass growth is therefore responsible for the larger sizes and higher Sersic indices of the descendants toward low redshift. At z < 2, the effective radius evolves with the stellar mass as r(e) proportional to M-2.0, consistent with scenarios that find dissipationless minor mergers to be a key driver of size evolution. The progenitors at z similar to 3 were likely star-forming disks with r(e) similar to 2 kpc, based on their low Sersic index of n similar to 1, low median axis ratio of b/a similar to 0.52, and typical location in the star-forming region of the U-V versus V-J diagram. By z similar to 1.5, many of these star-forming disks disappeared, giving rise to compact quiescent galaxies. Toward lower redshifts, these galaxies continued to assemble mass at larger radii and became the local ellipticals that dominate the high-mass end of the mass function at the present epoch.

We follow the structural evolution of star-forming galaxies (SFGs) like the Milky Way by selecting progenitors to z similar to 1.3 based on the stellar mass growth inferred from the evolution of the star-forming sequence. We select our sample from the 3D-HST survey, which utilizes spectroscopy from the HST/WFC3 G141 near-IR grism and enables precise redshift measurements for our sample of SFGs. Structural properties are obtained from S ' ersic profile fits to CANDELS WFC3 imaging. The progenitors of z = 0 SFGs with stellar mass M = 10(10.5)M(circle dot) are typically half as massive at z similar to 1. This late-time stellar mass growth is consistent with recent studies that employ abundance matching techniques. The descendant SFGs at z similar to 0 have grown in half-light radius by a factor of similar to 1.4 since z similar to 1. The half-light radius grows with stellar mass as r(e) proportional to M-0.29. While most of the stellar mass is clearly assembling at large radii, the mass surface density profiles reveal ongoing mass growth also in the central regions where bulges and pseudobulges are common features in present day late-type galaxies. Some portion of this growth in the central regions is due to star formation as recent observations of H alpha maps for SFGs at z similar to 1 are found to be extended but centrally peaked. Connecting our lookback study with galactic archeology, we find the stellar mass surface density at R = 8 kpc to have increased by a factor of similar to 2 since z similar to 1, in good agreement with measurements derived for the solar neighborhood of the Milky Way.

Spectroscopic + photometric redshifts, stellar mass estimates, and rest-frame colors from the 3D-HST survey are combined with structural parameter measurements from CANDELS imaging to determine the galaxy size-mass distribution over the redshift range 0 < z < 3. Separating early-and late-type galaxies on the basis of star-formation activity, we confirm that early-type galaxies are on average smaller than late-type galaxies at all redshifts, and we find a significantly different rate of average size evolution at fixed galaxy mass, with fast evolution for the early-type population, R-eff proportional to (1 + z)(-1.48), and moderate evolution for the late-type population, R-eff proportional to (1 + z)(-0.75). The large sample size and dynamic range in both galaxy mass and redshift, in combination with the high fidelity of our measurements due to the extensive use of spectroscopic data, not only fortify previous results but also enable us to probe beyond simple average galaxy size measurements. At all redshifts the slope of the size-mass relation is shallow, R-eff proportional to M-*(0.22) , for late-type galaxies with stellar mass >3 x 10(9) M-circle dot, and steep, R-eff proportional to M-*(0.75), for early-type galaxies with stellar mass >2 x 10(10) M-circle dot. The intrinsic scatter is less than or similar to 0.2 dex for all galaxy types and redshifts. For late-type galaxies, the logarithmic size distribution is not symmetric but is skewed toward small sizes: at all redshifts and masses, a tail of small late-type galaxies exists that overlaps in size with the early-type galaxy population. The number density of massive (similar to 10(11)M(circle dot)), compact (R-eff < 2 kpc) early-type galaxies increases from z = 3 to z 1.5-2 and then strongly decreases at later cosmic times.

We investigate star formation rates (SFRs) of quiescent galaxies at high redshift (0.3 < z < 2.5) using 3D-HST WFC3 grism spectroscopy and Spitzer mid-infrared data. We select quiescent galaxies on the basis of the widely used UVJ color-color criteria. Spectral energy distribution (SED) fitting (rest-frame optical and near-IR) indicates very low SFRs for quiescent galaxies (sSFR similar to 10(-12) yr(-1)). However, SED fitting can miss star formation if it is hidden behind high dust obscuration and ionizing radiation is re-emitted in the mid-infrared. It is therefore fundamental to measure the dust-obscured SFRs with a mid-IR indicator. We stack the MIPS 24 mu m images of quiescent objects in five redshift bins centered on z = 0.5, 0.9, 1.2, 1.7, 2.2 and perform aperture photometry. Including direct 24 mu m detections, we find sSFR similar to 10(-11.9) x (1 + z)(4) yr(-1). These values are higher than those indicated by SED fitting, but at each redshift they are 20-40 times lower than those of typical star-forming galaxies. The true SFRs of quiescent galaxies might be even lower, as we show that the mid-IR fluxes can be due to processes unrelated to ongoing star formation, such as cirrus dust heated by old stellar populations and circumstellar dust. Our measurements show that star formation quenching is very efficient at every redshift. The measured SFR values are at z > 1.5 marginally consistent with the ones expected from gas recycling (assuming that mass loss from evolved stars refuels star formation) and well below that at lower redshifts.

The Magellan Telescopes are a set of twin 6.5 meter ground based optical/near-IR telescopes operated by the Carnegie Institution for Science at the Las Campanas Observatory (LCO) in Chile. The primary mirrors are f/1.25 paraboloids made of borosilicate glass and a honeycomb structure. The secondary mirror provides both f/11 and f/5 focal lengths with two Nasmyth, three auxiliary, and a Cassegrain port on the optical support structure (OSS).

We study the nature of the faint radio source population detected in the MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) Early Science data in the COSMOS field, focusing on the properties of the radio-loud active galactic nuclei (AGNs). Using the extensive multiwavelength data available in the field, we are able to classify 88 per cent of the 5223 radio sources in the field with host galaxy identifications as AGNs (35 per cent) or star-forming galaxies (54 per cent). We select a sample of radio-loud AGNs with redshifts out to z similar to 6 and radio luminosities 10(20) < L-1.4 GHz/W Hz(-1) < 10(27) and classify them as high-excitation and low-excitation radio galaxies (HERGs and LERGs). The classification catalogue is released with this work. We find no significant difference in the host galaxy properties of the HERGs and LERGs in our sample. In contrast to previous work, we find that the HERGs and LERGs have very similar Eddington-scaled accretion rates; in particular we identify a population of very slowly accreting AGNs that are formally classified as HERGs at these low radio luminosities, where separating into HERGs and LERGs possibly becomes redundant. We investigate how black hole mass affects jet power, and find that a black hole mass greater than or similar to 10(7.8) M-circle dot is required to power a jet with mechanical power greater than the radiative luminosity of the AGN (L-mech/L-bol > 1). We discuss that both a high black hole mass and black hole spin may be necessary to launch and sustain a dominant radio jet.

We report the discovery of RAVE J203843.2-002333, a bright (V = 12.73), very metal-poor ([Fe/H]= -2.91), r-process-enhanced ([Eu/Fe]= +1.64 and[Ba/Eu]= -0.81) star selected from the RAVE survey. This star was identified as a metal-poor candidate based on its medium-resolution (R similar to 1600) spectrum obtained with the KPNO/Mayall Telescope, and followed up with high-resolution (R similar to 66,000) spectroscopy with the Magellan/Clay Telescope, allowing for the determination of elemental abundances for 24 neutron-capture elements, including thorium and uranium. RAVE J2038-0023 is only the fourth metal-poor star with a clearly measured U abundance. The derived chemical abundance pattern exhibits good agreement with those of other known highly r-process-enhanced stars, and evidence suggests that it is not an actinide-boost star. Age estimates were calculated using U/X abundance ratios, yielding a mean age of 13.0 +/- 1.1 Gyr.

A high-resolution spectroscopic analysis is presented for a new highly r-process-enhanced ([Eu/Fe] - 1.27, [Ba/Eu] = -0.65), very metal-poor ([Fe/H] = -2.09), retrograde halo star, RAVE J153830.9-180424, discovered as part of the R-Process Alliance survey. At V = 10.86, this is the brightest and most metal-rich r-II star known in the Milky Way halo. Its brightness enables high-S/N detections of a wide variety of chemical species that are mostly created by the r-process, including some infrequently detected lines from elements like Ru, Pd, Ag, Tm, Yb, Lu, Hf, and Th, with upper limits on Pb and U. This is the most complete r-process census in a very metal-poor r-II star. J1538-1804 shows no signs of s-process contamination, based on its low [Ba/Eu] and [Pb/Fe]. As with many other r-process-enhanced stars, J1538-1804's r-process pattern matches that of the Sun for elements between the first, second, and third peaks, and does not exhibit an actinide boost. Cosmo-chronometric age-dating reveals the r-process material to be quite old. This robust main r-process pattern is a necessary constraint for r-process formation scenarios (of particular interest in light of the recent neutron star merger, GW170817), and has important consequences for the origins of r-II stars. Additional r-I and r-II stars will be reported by the R-Process Alliance in the near future.

We present results from a medium-resolution (R similar to 2000) spectroscopic follow-up campaign of 1694 bright (V < 13.5), very metal-poor star candidates from the RAdial Velocity Experiment (RAVE). Initial selection of the low-metallicity targets was based on the stellar parameters published in RAVE Data Releases 4 and 5. Follow up was accomplished with the Gemini-N and Gemini-S, the ESO/NTT, the KPNO/Mayall, and the SOAR telescopes. The wavelength coverage for most of the observed spectra allows for the determination of carbon and a-element abundances, which are crucial for considering the nature and frequency of the carbon-enhanced metal-poor (CEMP) stars in this sample. We find that 88% of the observed stars have[Fe H] <= -1.0, 61% have [Fe H] <= -2.0, and 3% have[Fe H] <= -3.0 (with four stars at[Fe H] <= -3.5). There are 306 CEMP star candidates in this sample, and we identify 169 CEMP Group. I, 131 CEMP Group. II, and 6 CEMP Group. III stars from the A(C) versus [Fe/H] diagram. Inspection of the[alpha/C] abundance ratios reveals that five of the CEMP Group. II stars can be classified as "mono-enriched second-generation" stars. Gaia DR1 matches were found for 734 stars, and we show that transverse velocities can be used as a confirmatory selection criteria for low-metallicity candidates. Selected stars from our validated list are being followed-up with high-resolution spectroscopy to reveal their full chemical-abundance patterns for further studies.