The Giant Magellan Telescope (GMT) is a 24.5m diameter optical/infrared telescope. Its seven 8.4m primary mirrors give it a collecting area equivalent to a 21.4m filled aperture. The nine GMT partners are constructing the telescope at the Las Campanas Observatory in Chile with first light planned for the end of 2018. In this paper, we describe the plans for the first-generation focal plane instrumentation for the telescope. The GMTO Corporation has solicited studies for instruments capable of carrying out the broad range of objectives outlined in the GMT Science Case. Six instruments have been selected for 14 month long conceptual design studies. We briefly describe the features of these instruments and give examples of the major science questions that they can address.

Exploring the origin of Ly alpha nebulae ("blobs") at high redshift requires measurements of their gas kinematics that are impossible with only the resonant, optically thick Ly alpha line. To define gas motions relative to the systemic velocity of the blob, the Ly alpha line must be compared with an optically thin line like H alpha lambda 6563, which is not much altered by radiative transfer effects and is more concentrated about the galaxies embedded in the nebula's core. We obtain optical and near-IR (NIR) spectra of the two brightest Ly alpha blobs (CDFS-LAB01 and CDFS-LAB02) from the Yang et al. sample using the Magellan/Magellan Echellette Spectrograph optical and Very Large Telescope/SINFONI NIR spectrographs. Both the Ly alpha and H alpha lines confirm that these blobs lie at the survey redshift, z similar to 2.3. Within each blob, we detect several H alpha sources, which roughly correspond to galaxies seen in Hubble Space Telescope rest-frame UV images. The H alpha detections show that these galaxies have large internal velocity dispersions (sigma(upsilon) = 130-190 km s(-1)) and that, in the one system (LAB01), where we can reliably extract profiles for two H alpha sources, their velocity difference is Delta upsilon similar to 440 km s(-1). The presence of multiple galaxies within the blobs, and those galaxies' large velocity dispersions and large relative motion, is consistent with our previous finding that Ly alpha blobs inhabit massive dark matter halos that will evolve into those typical of present-day rich clusters and that the embedded galaxies may eventually become brightest cluster galaxies. To determine whether the gas near the embedded galaxies is predominantly infalling or outflowing, we compare the Ly alpha and H alpha line centers, finding that Ly alpha is not offset (Delta upsilon(Ly alpha) = +0 km s(-1)) in LAB01 and redshifted by only +230 km s(-1) in LAB02. These offsets are small compared to those of Lyman break galaxies, which average +450 km s(-1) and extend to about +700 km s(-1). In LAB02, we detect C II lambda 1334 and Si II lambda 1526 absorption lines, whose blueward shifts of similar to 200 km s(-1) are consistent with the small outflow implied by the redward shift of Ly alpha. We test and rule out the simplest infall models and those outflow models with super/hyperwinds, which require large outflow velocities. Because of the unknown geometry of the gas distribution and the possibility of multiple sources of Ly alpha emission embedded in the blobs, a larger sample and more sophisticated models are required to test more complex or a wider range of infall and outflow scenarios.

We present a conceptual design for a moderate resolution optical spectrograph for the Giant Magellan Telescope (GMT). The spectrograph is designed to make use of the large field-of-view of the GMT and be suitable for observations of very faint objects across a wide range of optical wavelengths. We show some details of the optical and mechanical design of the instrument.

We describe the conceptual optomechanical design for GMACS, a wide-field, multi-object, moderate-resolution optical spectrograph for the Giant Magellan Telescope (GMT). GMACS is a candidate first-light instrument for the GMT and will be one of several instruments housed in the Gregorian Instrument Rotator (GIR) located at the Gregorian focus. The instrument samples a 9 arcminute x 18 arcminute field of view providing two resolution modes (i.e, low resolution, R similar to 2000, and moderate resolution, R similar to 4000) over a 3700 angstrom to 10200 angstrom wavelength range. To minimize the size of the optics, four fold mirrors at the GMT focal plane redirect the full field into four individual "arms", that each comprises a double spectrograph with a red and blue channel. Hence, each arm samples a 4.5 arcminute x 9 arcminute field of view. The optical layout naturally leads to three separate optomechanical assemblies: a focal plane assembly, and two identical optics modules. The focal plane assembly contains the last element of the telescope's wide-field corrector, slit-mask, tent-mirror assembly, and slit-mask magazine. Each of the two optics modules supports two of the four instrument arms and houses the aft-optics (i.e. collimators, dichroics, gratings, and cameras). A grating exchange mechanism, and articulated gratings and cameras facilitate multiple resolution modes. In this paper we describe the details of the GMACS optomechanical design, including the requirements and considerations leading to the design, mechanism details, optics mounts, and predicted flexure performance.

We review a conceptual design for a moderate resolution optical spectrograph for the Giant Magellan Telescope (GMT). The spectrograph is designed to make use of the large field-of-view of the GMT and be suitable for observations of very faint objects across a wide range of wavelengths. We also review the status of the instrument and on-going trade studies designed to update the instrument science objectives and technical requirements.

We present coarse but robust star-formation histories (SFHs) derived from spectrophotometric data of the Carnegie-Spitzer-IMACS Survey, for 22,494 galaxies at 0.3 < z < 0.9 with stellar masses of 10(9)M(circle dot) to 10(12)M(circle dot). Our study moves beyond "average" SFHs and distribution functions of specific star-formation rates (sSFRs) to individually measured SFHs for tens of thousands of galaxies. By comparing star-formation rates (SFRs) with timescales of 10(10), 10(9), and 10(8) years, we find a wide diversity of SFHs: "old galaxies" that formed most or all of their stars early,. galaxies that formed stars with declining or constant SFRs over a Hubble time, and genuinely "young galaxies" that formed most of their stars since z = 1 This sequence is one of decreasing stellar mass, but remarkably, each type is found over a mass range of a factor of 10. Conversely, galaxies at any given mass follow a wide range of SFHs, leading us to conclude that. (1) halo mass does not uniquely determine SFHs,. (2) there is no "typical" evolutionary track, and (3) "abundance matching" has limitations as a tool for inferring physics. Our observations imply that SFHs are set at an early epoch, and that-for most galaxies-the decline and cessation of star formation occurs over a Hubble time, without distinct "quenching" events. SFH diversity is inconsistent with models where galaxy mass, at any given epoch, grows simply along relations between SFR and stellar mass, but is consistent with a two-parameter lognormal form, lending credence to this model from a new and independent perspective.

We report the discovery of eight new giant planets, and updated orbits for four known planets, orbiting dwarf and subgiant stars using the CORALIE, HARPS, and MIKE instruments as part of the Calan-Hertfordshire Extrasolar Planet Search. The planets have masses in the range 1.1-5.4 M-J's, orbital periods from 40 to 2900 d, and eccentricities from 0.0 to 0.6. They include a double-planet system orbiting the most massive star in our sample (HD147873), two eccentric giant planets (HD128356b and HD154672b), and a rare 14 Herculis analogue (HD224538b). We highlight some population correlations from the sample of radial velocity detected planets orbiting nearby stars, including the mass function exponential distribution, confirmation of the growing body of evidence that low-mass planets tend to be found orbiting more metal-poor stars than giant planets, and a possible period-metallicity correlation for planets with masses > 0.1 M-J, based on a metallicity difference of 0.16 dex between the population of planets with orbital periods less than 100 d and those with orbital periods greater than 100 d.

We describe a new method to derive clean, iodine-free spectra directly from observations acquired using high-resolution echelle spectrographs equipped with iodine cells. The main motivation to obtain iodine-free spectra is to use portions of the spectrum that are superimposed with the dense forest of iodine absorption lines, in order to retrieve lines that can be used to monitor the magnetic activity of the star, helping to validate candidate planets. In short, we provide a straightforward methodology to clean the spectra using the forward model used to derive radial velocities, the line spread function information plus the stellar spectrum without iodine to reconstruct and subtract the iodine spectrum from the observations. We show our results using observations of the star tau Ceti acquired with the Planet Finder Spectrograph (PFS), High Resolution Echelle Spectrometer (HIRES), and University College London Echelle Spectrograph (UCLES), reaching an iodine-free spectrum correction at the similar to 1% rms level. We additionally discuss the limitations and further applications of the method.

In the first part of this paper, four different Cassegrain optical systems with their correctors are designed and studied for multi-object fiber slit spectroscopic survey. The aperture in 6.5 m and field of view 3 degrees are taken for these optical systems. Assuming observation wavelength range is 0.365-0.95 mu m, the maximum zenith distance for observing is 60 degrees, the maximum diameter of these lenses is 1.66 m, the altitude of the telescope site is 2500 m, two correctors are composed of 4-piece lenses and the other two are 5-piece lenses. The results obtained are: f-ratio about 3.7, the image quality for all four systems with EE80D <= 0.60 '', the linear diameter of the focal surface is about 1.2 m and 11 000 fibers can be set on it. Considering the limit of size of fused silica and optical glass, the maximum diameter for lens is about 1.7 m. Such a 6.5 m telescope is about the largest one if using the above correctors. Considering the multi-object spectroscopic survey is greatly important, we also studied some telescope optical systems having their aperture near or larger than 10 m used for the multi-object fiber spectroscopic survey. Such ideas are introduced in the last section of this paper.

We present a new in situ, multiple electron-multiplier LA-ICP-MS technique for the analysis of boron isotopes (delta(11)B) at < I parts per thousand 2sigma precision and at the nanogram level. Sample materials analyzed were all natural and synthetic glasses, spanning a range of boron concentrations from 0.39 to 30.2 ppm and B-11/B-10 values from 4.0254 to 4.0799 (delta(11)B - 6.08 parts per thousand to + 7.35 parts per thousand). The in situ analyses were duplicated at higher concentrations by solution analyses of chemically separated boron using conventional nebulization on the same ICP-MS system.