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.
119357334
Dense gas and star formation: characteristics of cloud cores associated with water masers
We have observed 150 regions of massive star formation, selected originally by the presence of an H2O maser, in the J = 5 → 4, 3 → 2, and 2 → 1 transitions of CS, and 49 regions in the same transitions of C34S. Over 90% of the 150 regions were detected in the J = 2 → 1 and 3 → 2 transitions of CS, and 75% were detected in the J = 5 → 4 transition. We have combined the data with the J = 7 → 6 data from our original (1992) survey to determine the density by analyzing the excitation of the rotational levels. Using large velocity gradient models, we have determined densities and column densities for 71 of these regions. The gas densities are very high (log n = 5.9), but much less than the critical density of the J = 7 → 6 line. Small maps of 25 of the sources in the J = 5 → 4 line yield a mean diameter of 1.0 pc. Several estimates of the mass of dense gas were made for the sources for which we had sufficient information. The mean virial mass is 3800 M☉. The mean ratio of bolometric luminosity to virial mass (L/M) is 190, about 50 times higher than estimates made using CO emission, suggesting that star formation is much more efficient in the dense gas probed in this study. The depletion time for the dense gas is ~1.3 × 107 yr, comparable to the timescale for gas dispersal around open clusters and OB associations. We find no statistically significant line width-size or density-size relationships in our data. Instead, both line width and density are greater for a given size than would be predicted by the usual relationships. We find that the line width increases with density, the opposite of what would be predicted by the usual arguments. We estimate that the luminosity of our Galaxy (excluding the inner 400 pc) in the CS J = 5 → 4 transition is 15-23 L☉, considerably less than the luminosity in this line within the central 100 pc of NGC 253 and M82. In addition, the ratio of far-infrared luminosity to CS luminosity is higher in M82 than in any cloud in our sample.
17554708
Far-Infrared Observations of the Very Low Luminosity Embedded Source L1521F-IRS in the Taurus Star-Forming Region
We investigate the environment of the very low luminosity object L1521F-IRS using data from the Taurus Spitzer Legacy Survey. The MIPS 160 μm image shows both extended emission from the Taurus cloud and emission from multiple cold cores over a 1° × 2° region. Analysis shows that the cloud dust temperature is 14.2 ± 0.4 K and the extinction ratio is A_(160)/A_K = 0.010 ± 0.001 up to A_V ~ 4 mag. We find κ_(160) = 0.23 ± 0.046 cm^2 g^(–1) for the specific opacity of the gas-dust mixture. Therefore, for dust in the Taurus cloud we find that the 160 μm opacity is significantly higher than that measured for the diffuse interstellar medium, but not too different from dense cores, even at modest extinction values. Furthermore, the 160 μm image shows features that do not appear in the IRAS 100 μm image. We identify six regions as cold cores, i.e., colder than 14.2 K, all of which have counterparts in extinction maps or C^(18)O maps. Three of the six cores contain embedded young stellar objects, which demonstrates the cores are sites of current star formation. We compare the effects of L1521F-IRS on its natal core and find there is no evidence for dust heating at 160 or 100 μm by the embedded source. From the infrared luminosity L_(TIR) = 0.024 L_⊙ we find L_(bol_int) = 0.034 - 0.046 L_⊙, thus confirming the source's low luminosity. Comparison of L1521F-IRS with theoretical simulations for the very early phases of star formation appears to rule out the first core collapse phase. The evolutionary state appears similar to or younger than the class 0 phase, and the estimated mass is likely to be substellar.
8016228
Indications of Inflow Motions in Regions Forming Massive Stars
Observational evidence of inflowing motions in massive star-forming regions has been extremely rare. We have made a spectroscopic survey of a sample of 28 massive star-forming cores associated with water masers. An optically thick line of HCN (3-2) was used in combination with optically thin lines [H13CN (3-2) or C34S (5-4), (3-2), and (2-1)] to identify "blue" line profiles that can indicate inflow. Comparing intensities for 18 double-peaked line profiles yields 11 blue and three red profiles that are statistically significant. In the full sample of 28 sources, 12 show blue profiles, and six show red profiles that are statistically significant based on the velocity offsets of lines that are optically thick from those that are optically thin. These results indicate that HCN (3-2) emission may trace inflow in regions forming high-mass stars.
14925292
A PARAMETER STUDY OF THE DUST AND GAS TEMPERATURE IN A FIELD OF YOUNG STARS
We model the thermal effect of young stars on their surrounding environment in order to understand clustered star formation. We take radiative heating of dust, dust-gas collisional heating, cosmic-ray heating, and molecular cooling into account. Using DUSTY, a spherical continuum radiative transfer code, we model the dust temperature distribution around young stellar objects with various luminosities and surrounding gas and dust density distributions. We have created a grid of dust temperature models, based on our modeling with DUSTY, which we can use to calculate the dust temperature in a field of stars with various parameters. We then determine the gas temperature assuming energy balance. Our models can be used to make large-scale simulations of clustered star formation more realistic.
10821126
Modeling Spitzer Observations of VV Ser. I. The Circumstellar Disk of a UX Orionis Star
We present mid-infrared Spitzer IRS spectra of the UX Orionis star VV Ser, combined with interferometric and spectroscopic data from the literature covering UV to submillimeter wavelengths. The full set of data are modeled by an axisymmetric Monte Carlo radiative transfer code to test the prediction of Dullemond et al. that disks around UX Orionis stars are self-shadowed and seen nearly edge-on. Our model is consistent with all the available observational constraints, providing strong support for this interpretation. The mid-infrared SED is declining and exhibits weak silicate emission features, consistent with a self-shadowed geometry. MIPS imaging shows that the disk has a small grain dust mass as low as 0.8 × 10^(-7) M_⊙, which may be due to strong grain growth and settling. The grains in the upper layers of the puffed-up inner rim must be small (0.01-0.4 μm) to reproduce the colors (R_V ~ 3.6) of the optical light curve, while the silicate emission features indicate that grains in the outer disk (>1-2 AU) are somewhat larger (0.3-3.0 μm). If grains in the inner disk are small, the location of the puffed-up inner rim is estimated to be at 0.7-0.8 AU. This is almost twice the rim radius estimated from near-infrared interferometry. Since larger (more gray) grains are able to penetrate closer to the star for the same dust sublimation temperature, we suggest a model in which large grains in the disk midplane reach to within 0.25 AU of the star, while small grains in the disk surface create a puffed-up rim at ~0.7-0.8 AU.
15147744
Majorana neutrino masses can save one-family technicolour models
We make non-perturbative estimates of the electroweak radiative correction parameter S in dynamical symmetry breaking models with Majorana neutrino masses. The Majorana masses are treated as perturbations to a non-local chiral model of the strong interactions. We argue that parameter ranges exist that would allow realistic values of S and T in one-family technicolour models.
17520420
Gauge invariant regularization in the AdS/CFT correspondence and ghost D-branes
A field theoretic understanding of how the radial direction in the AdS/CFT correspondence plays the role of a gauge invariant measure of energy scale has long been missing. In SU(N) Yang–Mills, a realization of a gauge invariant cutoff has been achieved by embedding the theory in spontaneously broken SU(N|N) gauge theory. With the recent discovery of ghost D-branes an AdS/CFT correspondence version of this scheme is now possible. We show that a very simple construction precisely ties the two pictures together providing a concrete understanding of the radial RG flow on the field theory side.
6689021
Flavor Physics and Fine-Tuning in Theory Space
Recently a new class of composite Higgs models have been developed which give rise to naturally light Higgs bosons without supersymmetry. Based on the chiral symmetries of “theory space,” involving replicated gauge groups and appropriate gauge symmetry breaking patterns, these models allow the scale of the underlying strong dynamics giving rise to the composite particles to be as large as of order 10 TeV, without any fine tuning to prevent large corrections to Higgs boson mass(es) of order 100 GeV. In this paper we show that the size of flavor violating interactions arising generically from underlying flavor dynamics constrains the scale of the Higgs boson compositeness to be greater than of order 75 TeV, implying that significant fine-tuning is required. Without fine-tuning, the low-energy structure of the composite Higgs model alone is not sufficient to eliminate potential problems with flavor-changing neutral currents or excessive CP violation; solving those problems requires additional information or assumptions about the symmetries of the underlying flavor or strong dynamics. We also consider the weaker, but more model-independent, bounds which arise from limits on weak isospin violation.
4001005
Topological charge and U(1)A symmetry in the high temperature phase of QCD
Abstract We discuss the global symmetries of the high temperature phase of QCD with N f massless quarks. We show that the U ( N f ) × U ( N f ) symmetries are only violated by operators of dimension ≥ 3 N f . For N f > 2 this implies that the thermal two-point correlation functions of the η′ and π a 's are identical. We discuss the implications of this for the chiral phase transition at finite temperature.
15006058
An Effective field theory approach to color superconductivity at high quark density
Abstract We investigate the Fermi Liquid theory of high density QCD. Using the renormalization group (RG), we determine the behavior of effective fermion interactions near the Fermi surface. At sufficiently high densities the matching between the Fermi Liquid theory and QCD can be accomplished in perturbation theory and a reliable calculation of Cooper pair formation performed, modulo the existence of screening masses for the gluon. The presence of a chemical potential leads to different RG flows for sub-components of the effective interactions which would ordinarily be linked by Lorentz invariance. We also study instanton-induced operators and find that near the Fermi surface they are likely to be subdominant relative to operators induced by perturbative gluon exchange. We discuss the implications of our results for the phase structure of QCD at finite baryon density and temperature.