SED Type Research Articles

Linear and nonlinear optical properties of M@C59X (M = Li, Na and X = B, N) cage

By applying the density functional theory (DFT) combined with sum-over-orbital (SOO) approach, the static and frequency dependent nonlinear optical (NLO) properties of the C60 and M@C59X cages have been studied. The NLO properties of the C60 cage have been investigated by considering effects of substitution of one B or N atom at one of C sites and Li or Na atoms encapsulation in the C60 cage (SED). The numerical results show that the polarizabilities and second hyperpolarizabilities values of the C60 cage can greatly vary with respect to SED type. As, highest peak value of second hyperpolarizabilities for Na@C59N is about 34, 1.8 and 1.1 times larger than that of the C60, Li@C59X and Na@C59B cages, respectively. These results can be important to experimentalists for designing new NLO materials with large NLO responses.

The low-mass stellar population in the young cluster Tr 37

We present a study of accretion and protoplanetary disks around M-type stars in the 4 Myr-old cluster Tr37. With a well-studied solar-type population, Tr37 is a benchmark for disk evolution. We used low-resolution spectroscopy to identify 141 members (78 new) and 64 probable members, mostly M-type stars. H\alpha\ emission provides information about accretion. Optical, 2MASS, Spitzer, and WISE data are used to trace the SEDs. We construct radiative transfer models to explore the structures of full-disks, pre-transition, transition, and dust-depleted disks. Including the new and previously known members, we confirm that a substantial fraction (~2/5) of disks show signs of evolution, either as radial dust evolution (transition/pre-transition disks) or as a more global evolution (low small-dust masses, dust settling, and weak/absent accretion signatures). Accretion is strongly dependent on the SED type. About half of the transition objects are consistent with no accretion, and dust-depleted disks have weak (or undetectable) accretion signatures, especially among M-type stars. The analysis of accretion and disk structure suggests a parallel evolution of dust and gas. We find several distinct classes of evolved disks, based on SED type and accretion, pointing to different disk dispersal mechanisms and probably different evolutionary paths. Dust depletion and opening of inner holes appear to be independent processes: most transition disks are not dust-depleted, and most dust-depleted disks do not require inner holes. The differences in disk structure between M-type and solar-type stars in Tr37 (4 Myr) are not as remarkable as in the young, sparse, Coronet cluster (1-2 Myr), suggesting that other factors, like the environment/interactions, are likely to play a role in the disk evolution and dispersal. Finally, we also find some evidence of clumpy star formation or mini-clusters within Tr37.

CFHTLenS: higher order galaxy–mass correlations probed by galaxy–galaxy–galaxy lensing

We present the first direct measurement of the galaxy-matter bispectrum as a function of galaxy luminosity, stellar mass, and SED type. Our analysis uses a galaxy-galaxy-galaxy lensing technique (G3L), on angular scales between 9 arcsec to 50 arcmin, to quantify (i) the excess surface mass density around galaxy pairs (excess mass hereafter) and (ii) the excess shear-shear correlations around single galaxies, both of which yield a measure of two types of galaxy-matter bispectra. We apply our method to the state-of-the-art Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS), spanning 154 square degrees. This survey allows us to detect a significant change of the bispectra with lens properties. Measurements for lens populations with distinct redshift distributions become comparable by a newly devised normalisation technique. That will also aid future comparisons to other surveys or simulations. A significant dependence of the normalised G3L statistics on luminosity within -23<M_r<-18 and stellar mass within 5x10^9 M_sol<M_star<2x10^11 M_sol is found (h=0.73). Both bispectra exhibit a stronger signal for more luminous lenses or those with higher stellar mass (up to a factor 2-3). This is accompanied by a steeper equilateral bispectrum for more luminous or higher stellar mass lenses for the excess mass. Importantly, we find the excess mass to be very sensitive to galaxy type as recently predicted with semi-analytic galaxy models: luminous (M_r<-21) late-type galaxies show no detectable signal, while all excess mass detected for luminous galaxies seems to be associated with early-type galaxies. We also present the first observational constraints on third-order stochastic galaxy biasing parameters.

KINKS AND DENTS IN PROTOPLANETARY DISKS: RAPID INFRARED VARIABILITY AS EVIDENCE FOR LARGE STRUCTURAL PERTURBATIONS

We report on synoptic observations at 3.6 and 4.5micron of young stellar objects in IC 348 with 38 epochs covering 40 days. We find that among the detected cluster members, 338 at [3.6] and 269 at both [3.6] and [4.5], many are variable on daily to weekly timescales with typical fluctuations of ~0.1 mag. The fraction of variables ranges from 20% for the diskless pre-main sequence stars to 60% for the stars still surrounded by infalling envelopes. We also find that stars in the exposed cluster core are less variable than the stars in the dense, slightly younger, south-western ridge. This trend persists even after accounting for the underlying correlation with infrared SED type, suggesting that the change in variable fraction is not simply a reflection of the change in relative fraction of class I vs. class II sources across the cloud, but instead reflects a change in variability with age. We also see a strong correlation between infrared variability and X-ray luminosity among the class II sources. The observed variability most likely reflects large changes in the structure of the inner wall located at the dust sublimation radius. We explore the possibility that these structural perturbations could be caused by a hot spot on the star heating dust above the sublimation temperature, causing it to evaporate rapidly, and increasing the inner radius for a portion of the disk. Under a number of simplifying assumptions we show that this model can reproduce the size and timescale of the 3.6 and 4.5micron fluctuations. Regardless of its source, the infrared variability indicates that the inner disk is not a slowly evolving entity, but instead is a bubbling, warped, dented mass of gas and dust whose global size and shape fluctuate in a matter of days.

Automated measurement of redshifts from mid-infrared low-resolution spectroscopy

We present a new SED-fitting based routine for redshift determination that is optimised for mid-infrared (MIR) low-resolution spectroscopy. Its flexible template scaling increases the sensitivity to slope changes and small scale features in the spectrum, while a new selection algorithm called Maximum Combined Pseudo-Likelihood (MCPL) provides increased accuracy and a lower number of outliers compared to the standard maximum-likelihood (ML) approach. Unlike ML, MCPL searches for local (instead of absolute) maxima of a 'pseudo-likelihood' (PL) function, and combines results obtained for all the templates in the library to weed out spurious redshift solutions. The capabilities of MCPL are demonstrated by comparing its results to those of regular ML and to the optical spectroscopic redshifts of a sample of 491 Spitzer/IRS spectra from sources at 0<z<3.7. MCPL achieves a redshift accuracy dz/(1+z)<0.005 for 78% of the galaxies in the sample compared to 68% for ML. The rate of outliers (dz/(1+z)>0.02) is 14% for MCPL and 22% for ML. chi^2 values for ML solutions are found to correlate with the SNR of the spectra, but not with redshift accuracy. By contrast, the peak value of the normalised combined PL (gamma) is found to provide a good indication on the reliability of the MCPL solution for individual sources. The accuracy and reliability of the redshifts depends strongly on the MIR SED. Sources with significant polycyclic aromatic hydrocarbon emission obtain much better results compared to sources dominated by AGN continuum. Nevertheless, for a given gamma the frequency of accurate solutions and outliers is largely independent on their SED type. This reliability indicator for MCPL solutions allows to select subsamples with highly reliable redshifts. In particular, a gamma>0.15 threshold retains 79% of the sources with dz/(1+z)<0.005 while reducing the outlier rate to 3.8% (abridged).

A parameter study of self-consistent disk models around Herbig AeBe stars

We present a parameter study of self-consistent models of protoplanetary disks around Herbig AeBe stars. We use the code developed by Dullemond and Dominik, which solves the 2D radiative transfer problem including an iteration for the vertical hydrostatic structure of the disk. This grid of models will be used for several studies on disk emission and mineralogy in follow-up papers. In this paper we take a first look on the new models, compare them with previous modeling attempts and focus on the effects of various parameters on the overall structure of the SED that leads to the classification of Herbig AeBe stars into two groups, with a flaring (group I) or self-shadowed (group II) SED. We find that the parameter of overriding importance to the SED is the total mass in grains smaller than 25 μm, confirming the earlier results by Dullemond and Dominik. All other parameters studied have only minor influences, and will alter the SED type only in borderline cases. We find that there is no natural dichotomy between group I and II. From a modeling point of view, the transition is a continuous function of the small dust mass. We also show that moderate grain growth produces spectra with weak or no 10 μm feature, both for flaring (Group I) and non-flaring (Group II) sources. The fact that sources with weak features have been found mostly in Group I sources is therefore surprising and must be due to observational biases or evolutionary effects.

Large Structures and Galaxy Evolution in COSMOS at z &lt; 1.1

We present the first identification of large-scale structures (LSSs) at z < 1.1 in the Cosmic Evolution Survey (COSMOS). The structures are identified from adaptive smoothing of galaxy counts in the pseudo-3D space (α, δ, z) using the COSMOS photometric redshift catalog. The technique is tested on a simulation including galaxies distributed in model clusters and a field galaxy population—recovering structures on all scales from 1' to 20' without a priori assumptions for the structure size or density profile. The COSMOS photometric redshift catalog yields a sample of 1.5 × 105 galaxies with redshift accuracy, ΔzFWHM/(1 + z) ≤ 0.1 at z < 1.1 down to IAB ≤ 25 mag. Using this sample of galaxies, we identify 42 LSSs and clusters. Projected surface-density maps for the structures indicate multiple peaks and internal structure in many of the most massive LSSs. The stellar masses (determined from the galactic SEDs) for the LSSs range from M* ~ 1011 up to ~3 × 1013 M☉. Five LSSs have total stellar masses exceeding 1013 M☉. (Total masses including nonstellar baryons and dark matter are expected to be ~50-100 times greater.) The derived mass function for the LSSs is consistent (within the expected Poisson and cosmic variances) with those derived from optical and X-ray studies at lower redshift. To characterize structure evolution and for comparison with simulations, we compute a new statistic: the area filling factor as a function of the overdensity value compared to the mean at surface overdensity (fA ). The observationally determined fA has less than 1% of the surface area (in each redshift slice) with overdensities exceeding 10:1, and evolution to higher overdensities is seen at later epochs (lower z); both characteristics are in good agreement with what we find using similar processing on the Millennium Simulation. Although similar variations in the filling factors as a function of overdensity and redshift are seen in the observations and simulations, we do find that the observed distributions reach higher overdensities than the simulation, perhaps indicating overmerging in the simulation. All of the LSSs show a dramatic preference for earlier SED type galaxies in the denser regions of the structures, independent of redshift. The SED types in the central 1 and 1-5 Mpc regions of each structure average about one SED type earlier than the mean type at the same redshift, corresponding to a stellar population age difference of ~2-4 Gyr at z = 0.3-1. We also investigate the evolution of key galactic properties—mass, luminosity, SED, and star formation rate (SFR)—with redshift and environmental density as derived from overdensities in the full pseudo-3D cube. Both the maturity of the stellar populations and the "downsizing" of star formation in galaxies vary strongly with redshift (epoch) and environment. For a very broad mass range (1010-1012 M☉), we find that galaxies in dense environments tend to be older; this is not just restricted to the most massive galaxies. And in low-density environments, the most massive galaxies appear to have also been formed very early (z > 2), compared to the lower mass galaxies there. Over the range z < 1.1, we do not see evolution in the mass of galaxies by more than a factor of ~2 separating active and inactive star-forming galaxy populations.

Mid‐Infrared Properties of X‐Ray Sources in the Extended Groth Strip

Mid-infrared observations of Active Galactic Nuclei (AGN) are important for understanding of the physical conditions around the central accretion engines. Chandra and XMM-Newton X-ray observations of a 300 arcmin^2 region in the Extended Groth Strip are used to select a sample of~150 AGN. The Spitzer instruments IRAC and MIPS detect 68-80% of these sources, which show a wide range of mid-infrared properties. About 40% of the sources have red power-law spectral energy distributions (f_nu ~ nu^alpha, alpha<0) in the 3.6-8 um IRAC bands. In these sources the central engine dominates the emission at both X-ray and IR wavelengths. Another 40% of the sources have blue mid-IR spectral energy distributions (alpha>0) with their infrared emission dominated by the host galaxy; the remaining 20% are not well-fit by a power law. Published IRAC color criteria for AGN select most of the red sources, but only some of the blue sources. As with all other known methods, selecting AGN with mid-IR colors will not produce a sample that is simultaneously complete and reliable. The IRAC SED type does not directly correspond to X-ray spectral type (hard/soft). The mid-IR properties of X-ray-detected Lyman-break, radio, submillimeter, and optically-faint sources vary widely and, for the most part, are not distinct from those of the general X-ray/infrared source population. X-ray sources emit 6-11% of the integrated mid--IR light, making them significant contributors to the cosmic infrared background.

The evolution of the luminosity functions in the FORS deep field from low to high redshift

Received -; accepted - Abstract. We present the redshift evolution of the restframe galaxy luminosity function (LF) in the red r', i', and z' bands as derived from the FORS Deep Field (FDF), thus extending the results published in Gabasch et al. (2004a) to longer wavelengths. Using the deep and homogeneous I-band selected dataset of the FDF we are able to follow the red LFs over the redshift range 0.5 < z < 3.5. The results are based on photometric redshifts for 5558 galaxies derived from the photometry in 9 filters achieving an accuracy ofz/(zspec + 1) ≤ 0.03 with only ∼ 1% outliers. A comparison with results from the literature shows the reliability of the derived LFs. Because of the depth of the FDF we can give relatively tight constraints on the faint-end slopeof the LF: The faint-end of the red LFs does not show a large redshift evolution and is compatible within 1� to 2� with a constant slope over the redshift range 0.5 ∼ < z ∼ < 2.0. Moreover, the slopes in r', i', and z' are very similar with a best fitting value of � = −1.33 ± 0.03 for the combined bands. There is a clear trend ofto steepen with increasing wavelength: �UV &u' = −1.07 ± 0.04 → �g'&B = −1.25 ± 0.03 → �r'&i'&z' = −1.33 ± 0.03. We subdivide our galaxy sample into four SED types and determine the contribution of a typical SED type to the overall LF. We show that the wavelength dependence of the LF slope can be explained by the relative contribution of different SED-type LFs to the overall LF, as different SED types dominate the LF in the blue and red bands. Furthermore we also derive and analyze the luminosity density evolution of the different SED types up to z ∼ 2. We investigate the evolution of Mand � � by means of the redshift parametrization M � (z) = M �

Normal and Starburst Galaxies in Deep X-ray Surveys

This paper reviews the nature of normal and starburst galaxies in deep X-ray surveys, focusing on the observational issues. Normal and starburst galaxies may be divided from AGN via X-ray/optical flux ratios, optical spectroscopic identification, hardness ratio, and X-ray luminosity. Each of these is discussed, including the possible impact on derived X-ray-Star Formation Rate (X-ray/SFR) correlations. The measured differences in the normal galaxy X-ray Luminosity Functions (XLFs) by SED type at ). The paper closes with a discussion of normal galaxy studies with future X-ray missions such as Constellation-X, XEUS, and Generation-X.

The evolution of the luminosity functions in the FORS Deep Field from low to high redshift

We present the redshift evolution of the restframe galaxy luminosity function (LF) in the red r � , i � ,a ndzbands, as derived from the FORS Deep Field (FDF), thus extending our earlier results to longer wavelengths. Using the deep and homogeneous I-band selected dataset of the FDF, we were able to follow the red LFs over the redshift range 0.5 < z < 3.5. The results are based on photometric redshifts for 5558 galaxies derived from the photometry in 9 filters and achieving an accuracy of ∆z/(zspec + 1) ≤ 0.03 with only ∼1% outliers. A comparison with results from the literature shows the reliability of the derived LFs. Because of the depth of the FDF, we can give relatively tight constraints on the faint-end slope α of the LF; the faint-end of the red LFs does not show a large redshift evolution and is compatible within 1σ to 2σ with a constant slope over the redshift range 0.5 < z < 2.0. Moreover, the slopes in r � , i � ,a ndzare very similar to a best-fitting value of α = −1.33 ± 0.03 for the combined bands. There is a clear trend of α to steepen with increasing wavelength: αUV&u� = −1.07 ± 0.04 → αg� &B = −1.25 ± 0.03 → αr� &i� &z� = −1.33 ± 0.03. We subdivided our galaxy sample into four SED types and determined the contribution of a typical SED type to the overall LF. We show that the wavelength dependence of the LF slope can be explained by the relative contribution of different SED-type LFs to the overall LF, as different SED types dominate the LF in the blue and red bands. Furthermore we also derived and analyzed the luminosity density evolution of the different SED types up to z ∼ 2. We investigated the evolution of M ∗ and φ ∗ by means of the redshift parametrization M ∗ (z) = M ∗ + a ln (1 + z )a ndφ ∗ (z) = φ ∗ (1 + z) b . Based on the FDF data, we found only a mild brightening of M ∗ (ar� ∼− 0.8, and ai� ,z� ∼− 0.4) and a decreasing φ ∗ (br� ,i� ,z� ∼− 0.6) with increasing redshift. Therefore, fromz �∼ 0. 5t oz �∼ 3 the characteristic luminosity increases by ∼0.8, ∼0.4, and ∼0.4 mag in the r � , i � ,a ndzbands, respectively. Simultaneously the characteristic density decreases by about 40% in all analyzed wavebands. A comparison of the LFs with semi- analytical galaxy formation models by Kauffmann et al. (1999) shows a similar result to the blue bands: the semi-analytical models predict LFs that describe the data at low redshift very well, but show growing disagreement with increasing redshifts.

Isometric force and maximal shortening velocity of single muscle fibers from elite master runners.

Single chemically permeabilized gastrocnemius fibers from six elite endurance-trained master runners (RUN group) and five age-matched sedentary controls (SED group) were mounted between a force transducer and a position motor, studied under conditions of maximal and submaximal Ca2+ activation, and subsequently electrophoresed on 5% polyacrylamide gels to determine myosin heavy chain (MHC) composition. For the SED group, peak isometric tension (Pzero) averaged 143 +/- 3, 156 +/- 4, and 170 +/- 4 kN/m2 and maximal shortening velocity (Vzero) averaged 0.43 +/- 0.01, 1.90 +/- 0.08, and 5.59 +/- 0.40 fiber lengths/s for fibers expressing type I, IIa, and IIx MHC, respectively (all comparisons, P < 0.05). Hill plot analysis of relative forces during submaximal Ca2+ activation indicated no SED vs. RUN differences in Ca2+ sensitivity or in the cooperativity of Ca2+ activation. However, at maximal Ca2+ activation, RUN type I and IIa fibers produced 15% less peak absolute force than SED fibers (P < 0.05). This reduction in fiber force was a direct result of the smaller diameter of the RUN fibers (P < 0.05), because Pzero, peak elastic modulus (Ezero), and Pzero/Ezero were not different between SED and RUN groups. RUN type I fibers also displayed a mean Vzero that was 19% higher than the average Vzero of the SED type I fibers (P < 0.05). In separate experiments, quantification of relative myosin light chain (MLC) isoform content revealed a 28% greater ratio of MLC3 to MLC2 in single type I fibers from the RUN group (P < 0.05), suggesting that the elevated Vzero of the RUN type I fibers was related to a greater expression of MLC3. In conclusion, the single fibers from the elite master runners displayed specific morphological and contractile properties that may enhance the performance of these athletes during prolonged muscular activity.