119498034
Submillimeter Dust Continuum Studies of Low and High Mass Star Formation
Studying the physical environments of low mass and high mass cores using dust continuum emission provides important observational constraints on theoretical models of star formation. The motivation and procedure for modeling dust continuum emission is reviewed and the results of recent surveys towards low mass and high mass star forming regions are compared.
29731360
Submillimeter Follow-up of WISE-selected Hyperluminous Galaxies
We have used the Caltech Submillimeter Observatory (CSO) to follow-up a sample of Wide-field Infrared Survey Explorer (WISE) selected, hyperluminous galaxies, the so-called W1W2-dropout galaxies. This is a rare (∼1000 all-sky) population of galaxies at high redshift (peaks at z = 2–3), which are faint or undetected by WISE at 3.4 and 4.6 μm, yet are clearly detected at 12 and 22 μm. The optical spectra of most of these galaxies show significant active galactic nucleus activity. We observed 14 high-redshift ( z> 1.7) W1W2-dropout galaxies with SHARC-II at 350–850 μm, with nine detections, and observed 18 with Bolocam at 1.1 mm, with five detections. Warm Spitzer follow-up of 25 targets at 3.6 and 4.5 μm, as well as optical spectra of 12 targets, are also presented in the paper. Combining WISE data with observations from warm Spitzer and CSO, we constructed their mid-IR to millimeter spectral energy distributions (SEDs). These SEDs have a consistent shape, showing significantly higher mid-IR to submillimeter ratios than other galaxy templates, suggesting a hotter dust temperature. We estimate their dust temperatures to be 60–120 K using a single-temperature model. Their infrared luminosities are well over 10 13 L� . These SEDs are not well fitted with existing galaxy templates, suggesting they are a new population with very high luminosity and hot dust. They are likely among the most luminous galaxies in the universe. We argue that they are extreme cases of luminous, hot dust-obscured galaxies (DOGs), possibly representing a short evolutionary phase during galaxy merging and evolution. A better understanding of their long-wavelength properties needs ALMA as well as Herschel data.
119371049
Evolutionary Signatures in the Formation of Low-Mass Protostars
We present an evolutionary picture of a forming star. We assume a singular isothermal sphere as the initial state of the core that undergoes collapse, as described by Shu. We include the evolution of a first hydrostatic core at early times and allow a disk to grow, as predicted by Adams & Shu. We use a one-dimensional radiative transfer code to calculate the spectral energy distribution for the evolving protostar from the beginning of collapse to the point when all envelope material has accreted onto the star + disk system. Then, we calculate various observational signatures (Tbol, Lbol/Lsmm, and infrared colors) as a function of time. As defined by the bolometric temperature criterion, the Class 0 stage should be very short, while the Class I stage persists for much of the protostar's early life. We present physical distinctions among the classes of forming stars and calculate the observational signatures for these classes. Finally, we present models of infrared color-magnitude diagrams, as observed by the Spitzer Space Telescope, that should be strong discriminators in determining the stage of evolution for a protostar.
16588244
MAMBO mapping of Spitzer c2d small clouds and cores
Aims. To study the structure of nearby (<500 pc) dense starless and star-forming cores with the particular goal to identify and understand evolutionary trends in core properties, and to explore the nature of Very Low Luminosity Objects (<0.1 L ⊙ ; VeLLOs). Methods. Using the MAMBO bolometer array, we create maps unusually sensitive to faint (few mJy per beam) extended (≈5') thermal dust continuum emission at 1.2 mm wavelength. Complementary information on embedded stars is obtained from Spitzer, IRAS, and 2MASS. Results. Our maps are very rich in structure, and we characterize extended emission features ("subcores") and compact intensity peaks in our data separately to pay attention to this complexity. We derive, e.g., sizes, masses, and aspect ratios for the subcores, as well as column densities and related properties for the peaks. Combination with archival infrared data then enables the derivation of bolometric luminosities and temperatures, as well as envelope masses, for the young embedded stars. Conclusions. Starless and star-forming cores occupy the same parameter space in many core properties; a picture of dense core evolution in which any dense core begins to actively form stars once it exceeds some fixed limit in, e.g., mass, density, or both, is inconsistent with our data. A concept of necessary conditions for star formation appears to provide a better description: dense cores fulfilling certain conditions can form stars, but they do not need to, respectively have not done so yet. Comparison of various evolutionary indicators for young stellar objects in our sample (e.g., bolometric temperatures) reveals inconsistencies between some of them, possibly suggesting a revision of some of these indicators. Finally, we challenge the notion that VeLLOs form in cores not expected to actively form stars, and we present a first systematic study revealing evidence for structural differences between starless and candidate VeLLO cores.
209907524
Photon - dominated regions in low UV fields : a study of the peripheral regions of L1204 /S140
119355247
Studying Infall
The study of protostellar collapse or infall has proven unusually difficult and controversial. Some historical context will be provided, against which recent advances can be measured. We now have a substantial number of objects with signatures that can be interpreted in terms of collapse, but a number of issues remain. One issue is the effect of chemical variations, especially depletion in the dense, cold interiors of cores that are likely to form low mass stars. Strategies for dealing with this issue depend on using dust emission to constrain the density and temperature distribution, leaving molecular line observations to constrain dynamics and abundance distributions. Recent progress in this area will be described and we will consider the next challenges to be overcome. Interferometeric observations, especially with future instruments, will provide a powerful tool. In combination with chemical studies coupled with dynamical models, the observations made possible by interferometers should finally put this subject on a firm foundation.
17882244
Triviality and the precision bound on the Higgs mass
Abstract The triviality of the scalar sector of the standard one-doublet Higgs model implies that this model is only an effective low-energy theory valid below some cut-off scale Λ . For a heavy Higgs this scale must be relatively low (10 TeV or less). Additional interactions coming from the underlying theory, and suppressed by the scale Λ , give rise to model-dependent corrections to precisely measured electroweak quantities. Dimension six operators arising from the underlying physics naturally contribute to the S and T parameters, and their effects should be included in a global fit to the precision data that determines any limit on the Higgs mass. Using dimensional analysis, we estimate the expected size of these corrections in a custodially-symmetric strongly-interacting underlying theory. Taking these operators' coefficients to be of natural size gives sufficiently large contributions to the T parameter to reconcile Higgs masses as large as 400–500 GeV with the precision data.
8365482
Non-equilibrium physics at a holographic chiral phase transition
The D3/D7 system holographically describes an $ \mathcal{N} = 2 $ gauge theory which spontaneously breaks a chiral symmetry by the formation of a quark condensate in the presence of a magnetic field. At finite temperature it displays a first order phase transition. We study out of equilibrium dynamics associated with this transition by placing probe D7 branes in a geometry describing a boost-invariant expanding or contracting plasma. We use an adiabatic approximation to track the evolution of the quark condensate in a heated system and reproduce the phase structure expected from equilibrium dynamics. We then study solutions of the full partial differential equation that describes the evolution of out of equilibrium configurations to provide a complete description of the phase transition including describing aspects of bubble formation.
11037353
Lattice tests of supersymmetric Yang-Mills theory?
Supersymmetric Yang Mills theory is directly accessible to lattice simulations using current methodology, and can provide a non-trivial check of recent exact results in SQCD. In order to tune the lattice simulation to the supersymmetric point it is neccessary to understand the behavior of the theory with a small supersymmetry breaking gaugino mass. We introduce a soft breaking gaugino mass in a controlled fashion using a spurion analysis. We compute the gluino condensate, vacuum energy and bound-state masses as a function of the gaugino mass, providing more readily accessible predictions which still test the supersymmetric results. Finally we discuss diagnostics for obtaining the bare lattice parameters that correspond to the supersymmetric continuum limit.
14538317
Field theory operator encoding in N = 2 geometries
We investigate supergravity solutions describing D5-branes wrapped on a two cycle which are dual to = 2 super Yang Mills theory. Brane probing these solutions allows the moduli space of the field theory to be identified. There are a unique set of coordinates in which the field theory on the probe takes an = 2 form and in these coordinates the running coupling of the gauge theory may be identified. We show that the geometry, when restricted to the moduli space, takes a very simple form involving only two functions. One is the running gauge coupling whilst the other parametrizes the scalar operators of the field theory. The D5-brane distributions, for the full set of solutions in the literature, can be determined by assuming the field theory's form for the running coupling as a function of scalar vevs. We show that the resulting distributions also correctly reproduce the scalar operators parametrized elsewhere providing the first non-trivial consistency check on the duality.
56474092
Holographic description of the QCD phase diagram and out of equilibrium dynamics
Holography provides a powerful tool to model QCD and other strongly coupled gauge dynamics. As examples of its power to compute in novel environments I review some recent results: these include models of the phase structure of QCD at finite temperature and chemical potential; and computation of time dependent processes at strongly coupled phase transitions.