Posts Tagged correlation

Recent Postings from correlation

Probing the diffuse baryon distribution with the lensing-tSZ cross-correlation

Approximately half of the Universe’s baryons are in a form that has been hard to detect directly. However, the missing component can be traced through the cross-correlation of the thermal Sunyaev-Zeldovich (tSZ) effect with weak gravitational lensing. We build a model for this correlation and use it to constrain the extended baryon component, employing data from the Canada France Hawaii Lensing Survey and the Planck satellite. The measured correlation function is consistent with an isothermal $\beta$-model for the halo gas pressure profile, and the 1- and 2- halo terms are both detected at the 4$\sigma$ level. The effective virial temperature of the gas is found to be in the range ($7\times10^{5}$–$3 \times10^{8}$) K, with approximately $50%$ of the baryons appearing to lie beyond the virial radius of the halos, consistent with current expectations for the warm-hot intergalactic medium.

Jet correlations - opportunities and pitfalls

The simplest observables used to probe the interaction of hard partons with a QCD medium in ultrarelativistic heavy ion collisions measure disappearance, such as the nuclear modification factor R_AA. The information content of such observables is however limited. More differential information is obtained from triggered correlation observables where a trigger condition ensures that a hard event has taken place and the correlation of other objects in the event with the trigger contains information about the nature of parton-medium interaction. By construction, triggered correlation observables are conditional probabilities, i.e. they measure events biased by the trigger condition. The presence of this bias makes the interpretation of observables non-intuitive, but at the same time represents an opportunity to design future measurements to selectively probe particular physics. In this work, an overview over the four types of biases occuring in triggered hard correlation observables is given, followed by a study of current jet correlation phenomenology in the light of the preceding discussion.

$D$ and $D^{\ast}$ meson mixing in cold nuclear matter

We propose to study the mass spectrum of the heavy-light mesons to probe the structure of the spin-isospin correlation in the nuclear medium. We point out that the spin-isospin correlation in the nuclear medium generates a mixing among the heavy-light mesons carrying different spins and isospins such as $D^+$, $D^0$, $D^{\ast +}$ and $D^{\ast 0}$ mesons. We use two types of correlation motivated by the skyrmion crystal and the chiral density wave as typical examples to obtain the mass modification caused by the mixing. Our result shows that the structure of the mixing reflects the pattern of the correlation, i.e. the remaining symmetry. Furthemore, the size of the mass modification provides an information of the strength of the correlation.

On the possible correlation of Galactic VHE source locations and enhancements of the surface density in the Galactic plane

The association of very-high energy sources with regions of the sky rich in dust and gas has been noticed in the study of individual VHE sources. However, the statistical significance of such correlation for the whole population of TeV detections has not been assessed yet. Here we present a study of the association of VHE sources in the central Galactic region with positions of enhanced material content. We obtain estimates of the material content through two classical tracers: dust emission and intensity of the $^\textrm{12}$CO(1$\rightarrow$0) line. We make use of the recently released all-sky maps of astrophysical foregrounds of the Planck Collaboration and of the extensive existing CO mapping of the Galactic sky. In order to test the correlation, we construct randomized samples of VHE source positions starting from the inner Galactic plane survey sources detected by the H.E.S.S. array. We find hints of a positive correlation between positions of VHE sources and regions rich in molecular material, which in the best of cases reaches the 3.9sigma level. The latter confidence is however decreased if variations in the selection criteria are considered, what lead us to conclude that a positive correlation cannot be firmly established yet. Forthcoming VHE facilities will be needed in order to firmly establish the correlation.

Stop on Top

The most natural supersymmetric solution to the hierarchy problem prefers the scalar top partner to be close in mass to the top quark. Experimental searches exclude top squarks across a wide range of masses, but a gap remains when the difference between the masses of the stop and the lightest supersymmetric particle is close to the top mass. We propose to search for stops in this regime by exploiting the azimuthal angular correlation of forward tagging jets in (s)top pair production. As shown in earlier work, this correlation is sensitive to the spin of the heavy states, allowing one to distinguish between top and stop pair production. Here, we demonstrate that this angular information can give a statistically significant stop pair production signal in the upcoming LHC run. While the appropriate simulation including parton showering and detector simulation requires some care, we find stable predictions for the angular correlation using multi-jet merging.

On the impact of correlation information on the orientation parameters between celestial reference frame realizations

In this study, we compared results of determination of the orientation angles between celestial reference frames realized by radio source position catalogues using three methods of accounting for correlation information: using the position errors only, using additionally the correlations be-tween the right ascension and declination (RA/DE correlations) reported in radio source position catalogues published in the IERS format, and using the full covariance matrix. The computations were performed with nine catalogues computed at eight analysis centres. Our analysis has shown that using the RA/DE correlations only slightly influences the computed rotational angles, whereas using the full correlation matrices leads to substantial change in the orientation parameters be-tween the compared catalogues.

Solar Energetic Particle Events in the 23rd Solar Cycle: Interplanetary Magnetic Field Configuration and Statistical Relationship with Flares and CMEs

We study the influence of the large-scale interplanetary magnetic field configuration on the solar energetic particles (SEPs) as detected at different satellites near Earth and on the correlation of their peak intensities with the parent solar activity. We selected SEP events associated with X and M-class flares at western longitudes, in order to ensure good magnetic connection to Earth. These events were classified into two categories according to the global interplanetary magnetic field (IMF) configuration present during the SEP propagation to 1AU: standard solar wind or interplanetary coronal mass ejections (ICMEs). Our analysis shows that around 20% of all particle events are detected when the spacecraft is immersed in an ICME. The correlation of the peak particle intensity with the projected speed of the SEP-associated coronal mass ejection is similar in the two IMF categories of proton and electron events, $\approx 0.6$. The SEP events within ICMEs show stronger correlation between the peak proton intensity and the soft X-ray flux of the associated solar flare, with correlation coefficient $r=\,$0.67$\pm$0.13, compared to the SEP events propagating in the standard solar wind, $r=\,$0.36$\pm$0.13. The difference is more pronounced for near-relativistic electrons. The main reason for the different correlation behavior seems to be the larger spread of the flare longitude in the SEP sample detected in the solar wind as compared to SEP events within ICMEs. We discuss to which extent observational bias, different physical processes (particle injection, transport, etc.), and the IMF configuration can influence the relationship between SEPs and coronal activity.

Modelling the `outliers' track of the radio--X-ray correlation in X-ray binaries based on disc-corona model

The universal radio–X-ray correlation (F_R \propto F_X^{b}, b~0.5-0.7) has been found for a sample of black-hole X-ray binaries (BHBs) in their low/hard states, which can roughly be explained by the coupled model of jet and radiatively inefficient advection dominated accretion flow. However, more and more `outliers’ were found in last few years, which evidently deviate from the universal radio-X-ray correlation and usually show a much steeper correlation with an index of ~1.4. Based on simple physical assumptions, the radiatively efficient accretion flows are speculated to exist in these `outliers’. In this work, we test this issue by modelling the `outliers’ track based on the radiatively efficient disc-corona model and the hybrid jet model. We find that our model predicts a steeper radio–X-ray correlation with slopes >~1.2 for the typical viscosity parameter of \alpha~0.05-0.2. In particular, the slope is ~1.4 for the case of \alpha~0.1, which is consistent with the observational results of H1743-322 very well. Our results suggest that the `outliers’ track may be regulated by the disc-corona model.

Short Gamma Ray Burst Formation Rate from BATSE data using E_p-L_p correlation and the minimum gravitational wave event rate of coalescing compact binary

Using 72 Short Gamma Ray Bursts (SGRBs) with well determined spectral data observed by BATSE, we determine their redshift and the luminosity by applying $E_p$–$L_p$ correlation for SGRBs found by Tsutsui et al. (2013). For 53 SGRBs with the observed flux brighter than $4 \times 10^{-6}~{\rm erg~cm^{-2}s^{-1}}$, the cumulative redshift distribution up to $z=1$ agrees well with that of 22 Swift SGRBs. Especially good agreement is seen for $z < 0.4$ with the KS chance probability of 5.3\%. This suggests that the redshift determination by the $E_p$–$L_p$ correlation for SGRBs works very well. The minimum event rate at $z=0$ is estimated as $R_{\rm on-axis}^{\rm min} = 2 \times 10^{-10}~{\rm events~Mpc^{-3}yr^{-1}}$ so that the minimum beaming angle is $0.57^\circ-3.6^\circ$ assuming the merging rate of $10^{-7}-4\times 10^{-6}~{\rm events~yr^{-1}galaxy^{-1}}$ suggested from the binary pulsar data. Interestingly, this angle is consistent with that for SGRB~130603B of $\sim 4^\circ-8^\circ$ (Fong et al. 2013). On the other hand, if we assume the beaming angle of $\sim 6^\circ$ suggested from four SGRBs, the minimum event rate including off-axis SGRBs is estimated as $R_{\rm all}^{\rm min}\sim 4\times 10^{-8}~{\rm events~Mpc^{-3}yr^{-1}}$. If SGRBs are induced by coalescence of binary neutron stars (NSs) and/or black holes (BHs), this event rate leads to the minimum gravitational-wave detection rate of $\rm 1.3 (50)~events~yr^{-1}$ for NS-NS (NS-BH) binary, respectively, by KAGRA, adv-LIGO, adv-Virgo and GEO network.

Short Gamma Ray Burst Formation Rate from BATSE data using E_p-L_p correlation and the minimum gravitational wave event rate of coalescing compact binary [Cross-Listing]

Using 72 Short Gamma Ray Bursts (SGRBs) with well determined spectral data observed by BATSE, we determine their redshift and the luminosity by applying $E_p$–$L_p$ correlation for SGRBs found by Tsutsui et al. (2013). For 53 SGRBs with the observed flux brighter than $4 \times 10^{-6}~{\rm erg~cm^{-2}s^{-1}}$, the cumulative redshift distribution up to $z=1$ agrees well with that of 22 Swift SGRBs. Especially good agreement is seen for $z < 0.4$ with the KS chance probability of 5.3\%. This suggests that the redshift determination by the $E_p$–$L_p$ correlation for SGRBs works very well. The minimum event rate at $z=0$ is estimated as $R_{\rm on-axis}^{\rm min} = 2 \times 10^{-10}~{\rm events~Mpc^{-3}yr^{-1}}$ so that the minimum beaming angle is $0.57^\circ-3.6^\circ$ assuming the merging rate of $10^{-7}-4\times 10^{-6}~{\rm events~yr^{-1}galaxy^{-1}}$ suggested from the binary pulsar data. Interestingly, this angle is consistent with that for SGRB~130603B of $\sim 4^\circ-8^\circ$ (Fong et al. 2013). On the other hand, if we assume the beaming angle of $\sim 6^\circ$ suggested from four SGRBs, the minimum event rate including off-axis SGRBs is estimated as $R_{\rm all}^{\rm min}\sim 4\times 10^{-8}~{\rm events~Mpc^{-3}yr^{-1}}$. If SGRBs are induced by coalescence of binary neutron stars (NSs) and/or black holes (BHs), this event rate leads to the minimum gravitational-wave detection rate of $\rm 1.3 (50)~events~yr^{-1}$ for NS-NS (NS-BH) binary, respectively, by KAGRA, adv-LIGO, adv-Virgo and GEO network.

Constraints on Gauge Field Production during Inflation

In order to gain new insights into the gauge field couplings in the early universe, we consider the constraints on gauge field production during inflation imposed by requiring that their effect on the CMB anisotropies are subdominant. In particular, we calculate systematically the bispectrum of the primordial curvature perturbation induced by the presence of vector gauge fields during inflation. Using a model independent parametrization in terms of magnetic non-linearity parameters, we calculate for the first time the contribution to the bispectrum from the cross correlation between the inflaton and the magnetic field defined by the gauge field. We then demonstrate that in a very general class of models, the bispectrum induced by the cross correlation between the inflaton and the magnetic field can be dominating compared with the non-Gaussianity induced by magnetic fields when the cross correlation between the magnetic field and the inflaton is ignored.

Constraints on Gauge Field Production during Inflation [Replacement]

In order to gain new insights into the gauge field couplings in the early universe, we consider the constraints on gauge field production during inflation imposed by requiring that their effect on the CMB anisotropies are subdominant. In particular, we calculate systematically the bispectrum of the primordial curvature perturbation induced by the presence of vector gauge fields during inflation. Using a model independent parametrization in terms of magnetic non-linearity parameters, we calculate for the first time the contribution to the bispectrum from the cross correlation between the inflaton and the magnetic field defined by the gauge field. We then demonstrate that in a very general class of models, the bispectrum induced by the cross correlation between the inflaton and the magnetic field can be dominating compared with the non-Gaussianity induced by magnetic fields when the cross correlation between the magnetic field and the inflaton is ignored.

Constraints on Gauge Field Production during Inflation [Replacement]

In order to gain new insights into the gauge field couplings in the early universe, we consider the constraints on gauge field production during inflation imposed by requiring that their effect on the CMB anisotropies are subdominant. In particular, we calculate systematically the bispectrum of the primordial curvature perturbation induced by the presence of vector gauge fields during inflation. Using a model independent parametrization in terms of magnetic non-linearity parameters, we calculate for the first time the contribution to the bispectrum from the cross correlation between the inflaton and the magnetic field defined by the gauge field. We then demonstrate that in a very general class of models, the bispectrum induced by the cross correlation between the inflaton and the magnetic field can be dominating compared with the non-Gaussianity induced by magnetic fields when the cross correlation between the magnetic field and the inflaton is ignored.

Constraints on Gauge Field Production during Inflation [Replacement]

In order to gain new insights into the gauge field couplings in the early universe, we consider the constraints on gauge field production during inflation imposed by requiring that their effect on the CMB anisotropies are subdominant. In particular, we calculate systematically the bispectrum of the primordial curvature perturbation induced by the presence of vector gauge fields during inflation. Using a model independent parametrization in terms of magnetic non-linearity parameters, we calculate for the first time the contribution to the bispectrum from the cross correlation between the inflaton and the magnetic field defined by the gauge field. We then demonstrate that in a very general class of models, the bispectrum induced by the cross correlation between the inflaton and the magnetic field can be dominating compared with the non-Gaussianity induced by magnetic fields when the cross correlation between the magnetic field and the inflaton is ignored.

Outflows from active galactic nuclei: The BLR-NLR metallicity correlation

The metallicity of active galactic nuclei (AGNs), which can be measured by emission line ratios in their broad and narrow line regions (BLRs and NLRs), provides invaluable information about the physical connection between the different components of AGNs. From the archival databases of the International Ultraviolet Explorer, the Hubble Space Telescope and the Sloan Digital Sky Survey, we have assembled the largest sample available of AGNs which have adequate spectra in both the optical and ultraviolet bands to measure the narrow line ratio [N II]/H{\alpha} and also, in the same objects, the broad-line N V/C IV ratio. These permit the measurement of the metallicities in the NLRs and BLRs in the same objects. We find that neither the BLR nor the NLR metallicity correlate with black hole masses or Eddington ratios, but there is a strong correlation between NLR and BLR metallicities. This metallicity correlation implies that outflows from BLRs carry metal-rich gas to NLRs at characteristic radial distances of ~ 1.0 kiloparsec. This chemical connection provides evidence for a kinetic feedback of the outflows to their hosts. Metals transported into the NLR enhance the cooling of the ISM in this region, leading to local star formation after the AGNs turn to narrow line LINERs. This post-AGN star formation is predicted to be observable as an excess continuum emission from the host galaxies in the near infrared and ultraviolet, which needs to be further explored.

Relationship Between the Kinetic Power and Bolometric Luminosity of Jets: limitation from black hole X-ray binaries, active galactic nuclei, and gamma-ray bursts

The correlation between the kinetic power $P_{\rm jet}$ and intrinsic bolometric luminosity $L_{\rm jet}$ of jets may reveal the underlying jet physics in various black hole systems. Based on the recent work by Nemmen et al. (2012), we re-investigate this correlation with additional sources of black-hole X-ray binaries (BXBs) in hard/quiescent states and low-luminosity active galactic nuclei (LLAGNs). The new sample includes 29 sets of data from 7 BXBs and 20 LLAGNs, with $P_{\rm jet}$ and $L_{\rm jet}$ being derived from spectral modeling of the quasi-simultaneous multi-band spectra under the accretion-jet scenario. Compared to previous works, the range of luminosity is now enlarged to more than $20$ decades, i.e. from $10^{31}{\rm erg/s}$ to $10^{52}{\rm erg/s}$, which is possible to better constrain the correlation. One notable result is that the jets in BXBs and LLAGNs almost follow the same $P_{\rm jet} – L_{\rm jet}$ correlation that was obtained from blazars and gamma-ray bursts (GRBs). The slope indices we derived are $1.03\pm0.01$ for the whole sample, $0.85\pm0.06$ for BXB subsample, $0.71\pm0.11$ for LLAGN subsample, and $1.01\pm0.05$ for the LLAGN-blazar subsample, respectively. The correlation index about unit implies the independence of jet efficiency on the luminosity or kinetic power. Our results may further support the hypothesis that similar physical processes exist in the jets of various black hole systems.

Relationship Between the Kinetic Power and Bolometric Luminosity of Jets: limitation from black hole X-ray binaries, active galactic nuclei, and gamma-ray bursts [Replacement]

The correlation between the kinetic power $P_{\rm jet}$ and intrinsic bolometric luminosity $L_{\rm jet}$ of jets may reveal the underlying jet physics in various black hole systems. Based on the recent work by Nemmen et al. (2012), we re-investigate this correlation with additional sources of black-hole X-ray binaries (BXBs) in hard/quiescent states and low-luminosity active galactic nuclei (LLAGNs). The new sample includes 29 sets of data from 7 BXBs and 20 LLAGNs, with $P_{\rm jet}$ and $L_{\rm jet}$ being derived from spectral modeling of the quasi-simultaneous multi-band spectra under the accretion-jet scenario. Compared to previous works, the range of luminosity is now enlarged to more than $20$ decades, i.e. from $10^{31}{\rm erg/s}$ to $10^{52}{\rm erg/s}$, which allows for better constraining of the correlation. One notable result is that the jets in BXBs and LLAGNs almost follow the same $P_{\rm jet} – L_{\rm jet}$ correlation that was obtained from blazars and gamma-ray bursts (GRBs). The slope indices we derived are $1.03\pm0.01$ for the whole sample, $0.85\pm0.06$ for BXB subsample, $0.71\pm0.11$ for LLAGN subsample, and $1.01\pm0.05$ for the LLAGN-blazar subsample, respectively. The correlation index around unit implies the independence of jet efficiency on the luminosity or kinetic power. Our results may further support the hypothesis that similar physical processes exist in the jets of various black hole systems.

Lensing and time-delay contributions to galaxy correlations

Galaxy clustering on very large scales can be probed via the 2-point correlation function in the general case of wide and deep separations, including all the lightcone and relativistic effects. Using our recently developed formalism, we analyze the behavior of the local and integrated contributions for a baseline future survey and how these depend on redshift range, linear and angular separations and luminosity function. Relativistic corrections to the local part of the correlation can be non-negligible but they remain generally sub-dominant. On the other hand, the additional correlations arising from lensing convergence and time-delay effects can become very important and even dominate the observed total correlation function. We investigate different configurations formed by the observer and the pair of galaxies, and we find that the case of near-radial large-scale separations is where these effects will be the most important.

On the long-term correlation between the flux in the Ca II H & K and Halpha lines for FGK stars

The re-emission in the cores of the Ca II H & K and H$\alpha$ lines, are well known proxies of stellar activity. However, these activity indices probe different activity phenomena, the first being more sensitive to plage variation, while the other one being more sensitive to filaments. In this paper we study the long-term correlation between $\log R’_{HK}$ and $\log I_{H\alpha}$, two indices based on the Ca II H & K and H$\alpha$ lines respectively, for a sample of 271 FGK stars using measurements obtained over a $\sim$9 year time span. Because stellar activity is one of the main obstacles to the detection of low-mass and long-period planets, understanding further this activity index correlation can give us some hints about the optimal target to focus on, and ways to correct for these activity effects. We found a great variety of long-term correlations between $\log R’_{HK}$ and $\log I_{H\alpha}$. Around 20% of our sample has strong positive correlation between the indices while about 3% show strong negative correlation. These fractions are compatible with those found for the case of early-M dwarfs. Stars exhibiting a positive correlation have a tendency to be more active when compared to the median of the sample, while stars showing a negative correlation are more present among higher metallicity stars. There is also a tendency for the positively correlated stars to be more present among the coolest stars, a result which is probably due to the activity level effect on the correlation. Activity level and metallicity seem therefore to be playing a role on the correlation between $\log R’_{HK}$ and $\log I_{H\alpha}$. Possible explanations based on the influence of filaments for the diversity in the correlations between these indices are discussed in this paper.

On the Sodium versus Iron Correlation in Late B-Type Stars

With an aim to study whether the close correlation between [Na/H] and [Fe/H] recently found in A-type stars further persists in the regime of B-type stars, the abundances of Na were determined for 30 selected sharp-lined late B-type stars (10000K < T_eff < 14000K) from the Na I 5890/5896 doublet. These Na abundances were then compared with the O and Fe abundances (derived from the O I 6156-8 and Fe II 6147/6149 lines) showing anti-correlated peculiarities. It turned out that, unlike the case of A-type stars, [Na/H] is roughly constant at a slightly subsolar level ([Na/H] ~ -0.2 (+/-0.2)) without any significant correlation with [Fe/H] which shows considerable dispersion ranging from ~ -0.6 to ~ +1.0. This may serve as an important observational constraint for understanding the abundance peculiarities along with the physical mechanism of atomic diffusion in upper main-sequence stars of late A through late B-type including Am and HgMn stars.

Cosmology from cross correlation of CMB lensing and galaxy surveys

In recent years cross correlation of lensing of the Cosmic Microwave Background (CMB) with other large scale structure (LSS) tracers has been used as a method to detect CMB lensing. Current experiments are also becoming sensitive enough to measure CMB lensing without the help of auxiliary tracers. As data quality improves rapidly, it has been suggested that the CMB lensing-LSS cross correlation may provide new insights into parameters describing cosmological structure growth. In this work we perform forecasts that combine the lensing potential auto power spectrum from various future CMB experiments, the galaxy power spectrum from galaxy surveys, as well as the cross power spectrum between the two, marginalizing over a number galactic and non-galactic cosmological parameters. We find that the CMB lensing-LSS cross correlation contains significant information on parameters such as the redshift distribution and bias of LSS tracers. We also find that the cross correlation information will lead to independent probes of cosmological parameters such as neutrino mass and the reionization optical depth.

Dust Scattering In Turbulent Media: Correlation Between The Scattered Light and Dust Column Density

Radiative transfer models in a spherical, turbulent interstellar medium (ISM) in which the photon source is situated at the center are calculated to investigate the correlation between the scattered light and the dust column density. The medium is modeled using fractional Brownian motion structures that are appropriate for turbulent ISM. The correlation plot between the scattered light and optical depth shows substantial scatter and deviation from simple proportionality. It was also found that the overall density contrast is smoothed out in scattered light. In other words, there is an enhancement of the dust-scattered flux in low-density regions, while the scattered flux is suppressed in high-density regions. The correlation becomes less significant as the scattering becomes closer to be isotropic and the medium becomes more turbulent. Therefore, the scattered light observed in near-infrared wavelengths would show much weaker correlation than the observations in optical and ultraviolet wavelengths. We also find that the correlation plot between scattered lights at two different wavelengths shows a tighter correlation than that of the scattered light versus the optical depth.

The Metal-Rich Stars Get Richer in Planets For All But Planets With R_P <= 2 R_E

The metallicity of exoplanet systems serves as a critical diagnostic of planet formation mechanisms. Previous studies have obtained followup observations to measure the metallicity of Kepler planet candidates host stars and show that the planet-metallicity correlation holds for large planets (R_P >= 4 R_E); however, this correlation is not found for smaller planets. Here we define a sample of 1166 multi-planet candidates from Kepler Objects of Interest and use the host star metallicities from Kepler In- put Catalog to study the planet-metallicity correlation. This sample is a factor of 3-5 larger than those used in previous studies. We compare the fraction of sub-solar and super-solar metallicity stars with transiting planets. Although any sample of stars will have incompleteness in the number of detected transiting planets, we expect that these incompleteness factors essentially affect metal-poor and metal-rich stars equally. For orbital period less than 100 days, we confirm a strong planet-metallicity correlation for gas giant planets (5 R_E < R_P <= 22 R_E). The gas giant planet occurrence rate is 2.6 times higher around stars with super-solar metallicity than around stars with the sub-solar metallicity. For Neptune-like planets (2 R_E < RP <= 5 R_E), the planet occurrence rate for the super-solar metallicity sample is 1.4 times higher than the sub- solar metallicity sample. No correlation of planet occurrence rate with metallicity exists for small-radii planets (R_P <= 2 R_E).

Detection of warm and diffuse baryons in large scale structure from the cross-correlation of gravitational lensing and the thermal Sunyaev-Zeldovich effect [Replacement]

We report the first detection of a correlation between gravitational lensing by large scale structure and the thermal Sunyaev-Zeldovich (tSZ) effect. Using the mass map from the Canada France Hawaii Telescope Lensing Survey (CFHTLenS) and a newly-constructed tSZ map from Planck, we measure a non-zero correlation between the two maps out to one degree angular separation on the sky, with an overall significance of 6 sigma. The tSZ maps are formed in a manner that removes primary cosmic microwave background fluctuations and minimizes residual contamination by galactic and extragalactic dust emission, and by CO line emission. We perform numerous tests to show that our measurement is immune to these residual contaminants. The resulting correlation function is consistent with the existence of a warm baryonic gas tracing the large scale structure with a bias b_gas. Given the shape of the lensing kernel, our signal sensitivity peaks at a redshift z~0.4, where half a degree separation on the sky corresponds to a physical scale of ~10 Mpc. The amplitude of the signal constrains the product (b_gas/1)(T_e / 1 keV)(n_e / 1 m^-3)=2.01\pm 0.31\pm 0.21, at redshift zero. Our study suggests that a substantial fraction of the "missing" baryons in the universe may reside in a low density warm plasma that traces dark matter.

Detection of warm and diffuse baryons in large scale structure from the cross-correlation of gravitational lensing and the thermal Sunyaev-Zeldovich effect [Replacement]

We report the first detection of a correlation between gravitational lensing by large scale structure and the thermal Sunyaev-Zeldovich (tSZ) effect. Using the mass map from the Canada France Hawaii Telescope Lensing Survey (CFHTLenS) and a newly-constructed tSZ map from Planck, we measure a non-zero correlation between the two maps out to one degree angular separation on the sky, with an overall significance of 6 sigma. The tSZ maps are formed in a manner that removes primary cosmic microwave background fluctuations and minimizes residual contamination by galactic and extragalactic dust emission, and by CO line emission. We perform numerous tests to show that our measurement is immune to these residual contaminants. The resulting correlation function is consistent with the existence of a warm baryonic gas tracing the large scale structure with a bias b_gas. Given the shape of the lensing kernel, our signal sensitivity peaks at a redshift z~0.4, where half a degree separation on the sky corresponds to a physical scale of ~10 Mpc. The amplitude of the signal constrains the product (b_gas/1)(T_e / 0.1 keV)(n_e / 1 m^-3)=2.01\pm 0.31\pm 0.21, at redshift zero. Our study suggests that a substantial fraction of the "missing" baryons in the universe may reside in a low density warm plasma that traces dark matter.

Detection of warm and diffuse baryons in large scale structure from the cross-correlation of gravitational lensing and the thermal Sunyaev-Zeldovich effect [Replacement]

We report the first detection of a correlation between gravitational lensing by large scale structure and the thermal Sunyaev-Zeldovich (tSZ) effect. Using the mass map from the Canada France Hawaii Telescope Lensing Survey (CFHTLenS) and a newly-constructed tSZ map from Planck, we measure a non-zero correlation between the two maps out to one degree angular separation on the sky, with an overall significance of 6 sigma. The tSZ maps are formed in a manner that removes primary cosmic microwave background fluctuations and minimizes residual contamination by galactic and extragalactic dust emission, and by CO line emission. We perform numerous tests to show that our measurement is immune to these residual contaminants. The resulting correlation function is consistent with the existence of a warm baryonic gas tracing the large scale structure with a bias b_gas. Given the shape of the lensing kernel, our signal sensitivity peaks at a redshift z~0.4, where half a degree separation on the sky corresponds to a physical scale of ~10 Mpc. The amplitude of the signal constrains the product (b_gas/1)(T_e / 0.1 keV)(n_e / 1 m^-3)=2.01\pm 0.31\pm 0.21, at redshift zero. Our study suggests that a substantial fraction of the "missing" baryons in the universe may reside in a low density warm plasma that traces dark matter.

Detection of warm and diffuse baryons in large scale structure from the cross-correlation of gravitational lensing and the thermal Sunyaev-Zeldovich effect

We report the first detection of a correlation between gravitational lensing by large scale structure and the thermal Sunyaev-Zeldovich (tSZ) effect. Using the mass map from the Canada France Hawaii Telescope Lensing Survey (CFHTLenS) and a newly-constructed tSZ map from Planck, we measure a non-zero correlation between the two maps out to one degree angular separation on the sky, with an overall significance of 6 sigma. The tSZ maps are formed in a manner that removes primary cosmic microwave background fluctuations and minimizes residual contamination by galactic and extragalactic dust emission, and by CO line emission. We perform numerous tests to show that our measurement is immune to these residual contaminants. The resulting correlation function is consistent with the existence of a warm baryonic gas tracing the large scale structure with a bias $b_{\rm gas}$. Given the shape of the lensing kernel, our signal sensitivity peaks at a redshift z~0.4, where half a degree separation on the sky corresponds to a physical scale of ~10 Mpc. The amplitude of the signal constrains the product (b_gas/1)(T_e / 1 keV)(n_e / 1 m^-3)=2.01\pm 0.31\pm 0.21, at redshift zero. Our study suggests that a substantial fraction of the "missing" baryons in the universe may reside in a low density warm plasma that traces dark matter.

Quark-Novae Ia in the Hubble diagram: Implications For Dark Energy [Replacement]

The accelerated expansion of the Universe was proposed through the use of Type-Ia SNe as standard candles. The standardization depends on an empirical correlation between the stretch/color and peak luminosity of the light curves. The use of Type Ia SN as standard candles rests on the assumption that their properties (and this correlation) do not vary with red-shift. We consider the possibility that the majority of Type-Ia SNe are in fact caused by a Quark-Nova detonation in a tight neutron-star-CO-white-dwarf binary system; a Quark-Nova Ia. The spin-down energy injected by the Quark Nova remnant (the quark star) contributes to the post-peak light curve and neatly explains the observed correlation between peak luminosity and light curve shape. We demonstrate that the parameters describing Quark-Novae Ia are NOT constant in red-shift. Simulated Quark-Nova Ia light curves provide a test of the stretch/color correlation by comparing the true distance modulus with that determined using SN light curve fitters. We determine a correction between the true and fitted distance moduli which when applied to Type-Ia SNe in the Hubble diagram recovers the Omega_M = 1 cosmology. We conclude that Type-Ia SNe observations do not necessitate the need for an accelerating expansion of the Universe (if the observed SNe-Ia are dominated by QNe-Ia) and by association the need for Dark Energy.

Quark-Novae Ia in the Hubble diagram: Implications For Dark Energy

The accelerated expansion of the Universe was proposed through the use of Type-Ia SNe as standard candles. The standardization depends on an empirical correlation between the stretch/color and peak luminosity of the light curves. The use of Type Ia SN as standard candles rests on the assumption that their properties (and this correlation) do not vary with red-shift. We consider the possibility that the majority of Type-Ia SNe are in fact caused by a Quark-Nova detonation in a tight neutron-star-CO-white-dwarf binary system; a Quark-Nova Ia. The spin-down energy injected by the Quark Nova remnant (the quark star) contributes to the post-peak light curve and neatly explains the observed correlation between peak luminosity and light curve shape. We demonstrate that the parameters describing Quark-Novae Ia are NOT constant in red-shift. Simulated Quark-Nova Ia light curves provide a test of the stretch/color correlation by comparing the true distance modulus with that determined using SN light curve fitters. We determine a correction between the true and fitted distance moduli which when applied to Type-Ia SNe in the Hubble diagram recovers the Omega_M = 1 cosmology. We conclude that Type-Ia SNe observations do not necessitate the need for an accelerating expansion of the Universe (if the observed SNe-Ia are dominated by QNe-Ia) and by association the need for Dark Energy.

Mg II h+k Flux - Rotational Period Correlation for G-type stars

We present an analysis of the correlation between the mid-UV Mg II h and k emission lines and measured rotational periods of G-type stars. Based on IUE and HST high resolution spectra of a sample of 36 stars, we derive an exponential function that best represents the correlation. We found that the variation of the Mg II h + k fluxes is about a factor of 2.5 larger than that of Ca II H+K, indicating that the UV features are more sensitive to the decline of rotational period. The comparison of UV-predicted rotational periods with those derived from empirical Prot – Ca II H+K flux calibrations are consistent, with some scatter at large periods, where the emission are less intense. We present newly derived rotational periods for 15 G-type stars.

Mg II h+k Flux - Rotational Period Correlation for G-type stars [Replacement]

We present an analysis of the correlation between the mid-UV Mg II h and k emission lines and measured rotational periods of G-type stars. Based on IUE and HST high resolution spectra of a sample of 36 stars, we derive an exponential function that best represents the correlation. We found that the variation of the Mg II h + k fluxes is about a factor of 2.5 larger than that of Ca II H+K, indicating that the UV features are more sensitive to the decline of rotational period. The comparison of UV-predicted rotational periods with those derived from empirical Prot – Ca II H+K flux calibrations are consistent, with some scatter at large periods, where the emission are less intense. We present newly derived rotational periods for 15 G-type stars.

Predictions for the relation between strong HI absorbers and galaxies at redshift 3 [Replacement]

We combine cosmological, hydrodynamical simulations with accurate radiative transfer corrections to investigate the relation between strong HI absorbers (N_HI >~ 10^17 /cm^2) and galaxies at redshift z = 3. We find a strong anti-correlation between the column density and the impact parameter that connects the absorber to the nearest galaxy. The median impact parameters for Lyman Limit (LL) and Damped Lyman-{\alpha} (DLA) systems are ~10 and ~1 proper kpc, respectively. If normalized to the size of the halo of the nearest central galaxy, the median impact parameters for LL and DLA systems become ~1 and ~10^-1 virial radii, respectively. At a given HI column density, the impact parameter increases with the mass of the closest galaxy, in agreement with observations. We predict most strong HI absorbers to be most closely associated with extremely low-mass galaxies, M_star < 10^8 M_sun and star formation rate <10^-1 M_sun/yr. We also find a correlation between the column density of absorbers and the mass of the nearest galaxy. This correlation is most pronounced for DLAs with N_HI > 10^21 /cm^2 which are typically close to galaxies with M_star >~ 10^9 M_sun. Similar correlations exist between column density and other properties of the associated galaxies such as their star formation rates, halo masses and HI content. The galaxies nearest to HI absorbers are typically far too faint to be detectable with current instrumentation, which is consistent with the high rate of (often unpublished) non-detections in observational searches for the galaxy counterparts of strong HI absorbers. Moreover, we predict that the detected nearby galaxies are typically not the galaxies that are most closely associated with the absorbers, thus causing the impact parameters, star formation rates and stellar masses of the observed counterparts to be biased high.

Predictions for the relation between strong HI absorbers and galaxies at redshift 3

We combine cosmological, hydrodynamical simulations with accurate radiative transfer corrections to investigate the relation between strong HI absorbers (N_HI >~ 10^17 /cm^2) and galaxies at redshift z = 3. We find a strong anti-correlation between the column density and the impact parameter that connects the absorber to the nearest galaxy. The median impact parameters for Lyman Limit (LL) and Damped Lyman-{\alpha} (DLA) systems are ~10 and ~1 proper kpc, respectively. If normalized to the size of the halo of the nearest central galaxy, the median impact parameters for LL and DLA systems become ~1 and ~10^-1 virial radii, respectively. At a given HI column density, the impact parameter increases with the mass of the closest galaxy, in agreement with observations. We predict most strong HI absorbers to be most closely associated with extremely low-mass galaxies, M_star < 10^8 M_sun and star formation rate <10^-1 M_sun/yr. We also find a correlation between the column density of absorbers and the mass of the nearest galaxy. This correlation is most pronounced for DLAs with N_HI > 10^21 /cm^2 which are typically close to galaxies with M_star >~ 10^9 M_sun. Similar correlations exist between column density and other properties of the associated galaxies such as their star formation rates, halo masses and HI content. The galaxies nearest to HI absorbers are typically far too faint to be detectable with current instrumentation, which is consistent with the high rate of (often unpublished) non-detections in observational searches for the galaxy counterparts of strong HI absorbers. Moreover, we predict that the detected nearby galaxies are typically not the galaxies that are most closely associated with the absorbers, thus causing the impact parameters, star formation rates and stellar masses of the observed counterparts to be biased high.

An Empirical Connection between the UV Color of Early Type Galaxies and the Stellar Initial Mass Function

Using new UV magnitudes for a sample of early-type galaxies, ETGs, with published stellar mass-to-light ratios, Upsilon_*, we find a correlation between UV color and Upsilon_* that is tighter than those previously identified between Upsilon_* and either the central stellar velocity dispersion, metallicity, or alpha enhancement. The sense of the correlation is that galaxies with larger Upsilon_* are bluer in the UV. We conjecture that differences in the lower mass end of the stellar initial mass function, IMF, are related to the nature of the extreme horizontal branch populations that are generally responsible for the UV flux in ETGs. If so, then UV color can be used to identify ETGs with particular IMF properties and to estimate Upsilon_*.

Stellar clusters in the inner Galaxy and their correlation with cold dust emission

Stars are born within dense clumps of giant molecular clouds, constituting young stellar agglomerates known as embedded clusters, which only evolve into bound open clusters under special conditions. We statistically study all embedded clusters (ECs) and open clusters (OCs) known so far in the inner Galaxy, investigating particularly their interaction with the surrounding molecular environment and the differences in their evolution. We first compiled a merged list of 3904 clusters from optical and infrared clusters catalogs in the literature, including 75 new (mostly embedded) clusters discovered by us in the GLIMPSE survey. From this list, 695 clusters are within the Galactic range |l| < 60 deg and |b| < 1.5 deg covered by the ATLASGAL survey, which was used to search for correlations with submm dust continuum emission tracing dense molecular gas. We defined an evolutionary sequence of five morphological types: deeply embedded cluster (EC1), partially embedded cluster (EC2), emerging open cluster (OC0), OC still associated with a submm clump in the vicinity (OC1), and OC without correlation with ATLASGAL emission (OC2). Together with this process, we performed a thorough literature survey of these 695 clusters, compiling a considerable number of physical and observational properties in a catalog that is publicly available. We found that an OC defined observationally as OC0, OC1, or OC2 and confirmed as a real cluster is equivalent to the physical concept of OC (a bound exposed cluster) for ages in excess of ~16 Myr. Some observed OCs younger than this limit can actually be unbound associations. We found that our OC and EC samples are roughly complete up to ~1 kpc and ~1.8 kpc from the Sun, respectively, beyond which the completeness decays exponentially. Using available age estimates for a few ECs, we derived an upper limit of 3 Myr for the duration of the embedded phase… (Abridged)

The state of globular clusters at birth: emergence from the gas-embedded phase

In this paper, we discuss the origin of the observed correlation between cluster concentration c and present-day mass function (PDMF) slope {\alpha} reported by De Marchi, Paresce & Pulone. This relation can either be reproduced from universal initial conditions combined with some dynamical mechanism(s) that alter(s) the cluster structure and mass function over time, or it must arise early on in the cluster lifetime, such as during the gas-embedded phase of cluster formation. Using a combination of Monte Carlo and N-body models for globular cluster evolution performed with the MOCCA and NBODY6 codes, respectively, we explore a number of dynamical mechanisms that could affect the observed relation. For the range of initial conditions considered here, our results are consistent with an universal initial binary fraction \approx 10% (which does not, however, preclude 100%) and an universal initial stellar mass function resembling the standard Kroupa distribution. Most of the dispersion observed in the c-{\alpha} relation can be attributed to two-body relaxation and Galactic tides. However, dynamical processes alone could not have reproduced the dispersion in concentration, and we require at least some correlation between the initial concentration and the total cluster mass. We argue that the origin of this trend could be connected to the gas-embedded phase of cluster evolution.

Star Formation Sites toward the Galactic Center Region: The Correlation of CH3OH Masers, H2O Masers, and Near-IR Green Sources

We present a study of star formation in the Central Molecular Zone (CMZ) of our Galaxy through the association of three star formation indicators: 6.7 GHz CH3OH masers, 22 GHz H2O masers, and enhanced 4.5 micron emission (`green’) sources. We explore how star formation in the Galactic center (l < 1.3 deg, |b| < 10′, where l and b are Galactic longitude and Galactic latitude) compares with that of the Galactic disk (6 deg < l < 345 deg, |b| < 2 deg). Using an automated algorithm, we search for enhanced 4.5 micron emission sources toward 6.7 GHz CH3OH masers detected in the Parkes Methanol Multibeam Survey. We combine these results with our 22 GHz H2O maser survey of the CMZ carried out with the Mopra telescope. We find that the correlation of CH3OH masers with green sources is a function of Galactic latitude, with a minimum close to b=0 and increasing with |b| (toward the central part of the Galaxy, 6 deg < l < 345 deg, |b| < 2 deg). We find no significant difference between the correlation rate of CH3OH masers with green sources in the CMZ and the disk. This suggests that although the physical conditions of the gas are different in the Galactic center from that of the Galactic disk, once gravitational instability sets in at sufficiently high densities, signatures of star formation appear to be similar in both regions. Moreover, the detection of green sources, even at the distance of the Galactic center, shows that our technique can easily identify the early stages of star formation, especially in low extinction regions of the Galaxy. Through the association of H2O and CH3OH masers, we identify 15 star-forming sites in the CMZ. We find no coincident H2O and CH3OH masers outside the CMZ (with limited H2O maser survey coverage outside the CMZ), possibly indicating a difference in the maser evolutionary sequence for star-forming cores in the Galactic center region and the disk.

The role of fast magnetic reconnection in acceleration zones of microquasars and AGNs

Fast magnetic reconnection events can be a very powerful mechanism operating at the jet launching region of microquasars and AGNs. We have recently found that the power released by reconnection between the magnetic field lines of the coronal inner disk region and the lines anchored into the black hole is able to accelerate relativistic particles through a first-order Fermi process and produce the observed radio luminosity from both microquasars and low luminous AGNs (LLAGNs). We also found that the observed correlation between the radio luminosity and the mass of these sources, spanning 10^9 orders of magnitude in mass, is naturally explained by this process. In this work, assuming that the gamma-ray emission is probably originated in the same acceleration zones that produce the radio emission, we have applied the scenario above to investigate the origin of the high energy outcomes from an extensive number of sources including high (HLAGNs) and LLAGNs, microquasars and GRBs. We find correlation of our model with the gamma emission only for microquasars and a few LLAGNs, while none of the HLAGNs or GRBs are fitted, neither in radio nor in gamma. We attribute the lack of correlation of the gamma emission for most of the LLAGNs to the fact that this processed emission doesn’t depend only on the local magnetic field activity around the source/accretion disk, but also on other environmental factors like the photon and density fields. We conclude that the emission from the LLAGNs and microquasars comes from the nuclear region of their sources and therefore, can be driven by nuclear magnetic activity. However, in the case of the HLAGNs and GRBs, the nuclear emission is blocked by the surrounding density and photon fields and therefore, we can only see the jet emission further out.

CARMA Survey Toward Infrared-bright Nearby Galaxies (STING). III. The Dependence of Atomic and Molecular Gas Surface Densities on Galaxy Properties

We investigate the correlation between CO and HI emission in 18 nearby galaxies from the CARMA Survey Toward IR-Bright Nearby Galaxies (STING) at sub-kpc and kpc scales. Our sample, spanning a wide range in stellar mass and metallicity, reveals evidence for a metallicity dependence of the HI column density measured in regions exhibiting CO emission. Such a dependence is predicted by the equilibrium model of McKee & Krumholz, which balances H_2 formation and dissociation. The observed HI column density is often smaller than predicted by the model, an effect we attribute to unresolved clumping, although values close to the model prediction are also seen. We do not observe HI column densities much larger than predicted, as might be expected were there a diffuse HI component that did not contribute to H_2 shielding. We also find that the H_2 column density inferred from CO correlates strongly with the stellar surface density, suggesting that the local supply of molecular gas is tightly regulated by the stellar disk.

The hard X-ray behavior of Aql X-1 during type-I bursts

We report the discovery of an anti-correlation between the soft and the hard X-ray lightcurves of the X-ray binary Aql X-1 when bursting. This behavior may indicate that the corona is cooled by the soft X-ray shower fed by the type-I X-ray bursts, and that this process happens within a few seconds. Stacking the Aql X-1 lightcurves of type-I bursts, we find a shortage in the 40–50 keV band, delayed by 4.5$\pm$1.4 s with respect to the soft X-rays. The photospheric radius expansion (PRE) bursts are different in that neither a shortage nor an excess shows up in the hard X-ray lightcurve.

Kinematic active region formation in a three-dimensional solar dynamo model

We propose a phenomenological technique for modelling the emergence of active regions within a three-dimensional, kinematic dynamo framework. By imposing localised velocity perturbations, we create emergent flux-tubes out of toroidal magnetic field at the base of the convection zone, leading to the eruption of active regions at the solar surface. The velocity perturbations are calibrated to reproduce observed active region properties (including the size and flux of active regions, and the distribution of tilt angle with latitude), resulting in a more consistent treatment of flux-tube emergence in kinematic dynamo models than artificial flux deposition. We demonstrate how this technique can be used to assimilate observations and drive a kinematic 3D model, and use it to study the characteristics of active region emergence and decay as a source of poloidal field. We find that the poloidal components are strongest not at the solar surface, but in the middle convection zone, in contrast with the common assumption that the poloidal source is located near the solar surface. We also find that, while most of the energy is contained in the lower convection zone, there is a good correlation between the evolution of the surface and interior magnetic fields.

Understanding Trends Associated with Clouds in Irradiated Exoplanets

Unlike previously explored relationships between the properties of hot Jovian atmospheres, the geometric albedo and the incident stellar flux do not exhibit a clear correlation, as revealed by our re-analysis of Q0 to Q14 Kepler data. If the albedo is primarily associated with the presence of clouds in these irradiated atmospheres, a holistic modeling approach needs to relate the following properties: the strength of stellar irradiation (and hence the strength and depth of atmospheric circulation), the geometric albedo (which controls both the fraction of starlight absorbed and the pressure level at which it is predominantly absorbed) and the properties of the embedded cloud particles (which determine the albedo). The anticipated diversity in cloud properties renders any correlation between the geometric albedo and the stellar flux to be weak and characterized by considerable scatter. In the limit of vertically uniform populations of scatterers and absorbers, we use an analytical model and scaling relations to relate the temperature-pressure profile of an irradiated atmosphere and the photon deposition layer and to estimate if a cloud particle will be lofted by atmospheric circulation. We derive an analytical formula for computing the albedo spectrum in terms of the cloud properties, which we compare to the measured albedo spectrum of HD 189733b by Evans et al. (2013). Furthermore, we show that whether an optical phase curve is flat or sinusoidal depends on whether the particles are small or large as defined by the Knudsen number. This may be an explanation for why Kepler-7b exhibits evidence for the longitudinal variation in abundance of condensates, while Kepler-12b shows no evidence for the presence of condensates, despite the incident stellar flux being similar for both exoplanets.

Cosmological Time Dilation in Durations of Swift Long Gamma-Ray Bursts

Cosmological time dilation is a fundamental phenomenon in an expanding universe, which stresses that both the duration and wavelength of the emitted light from a distant object at the redshift $z$ will be dilated by a factor of $1+z$ at the observer. By using a sample of 139 \emph{Swift} long GRBs with known redshift ($z\leq8.2$), we measure the observed duration ($T_{90}$) in the observed energy range between $140/(1+z)$ keV and $350/(1+z)$ keV, corresponding to a fixed energy range of 140-350 keV in the rest frame. We obtain a significant correlation between the duration and the factor $1+z$, i.e., $T_{\rm{90}}=10.5(1+z)^{0.94\pm0.26}$, which is well consistent with that expected from cosmological time dilation effect.

Revisiting the Dichotomy of Early-type Galaxies

We study the relationship among isophotal shapes, central light profiles and kinematic properties of early-type galaxies (ETGs) based on a compiled sample of 184 ETGs. These sample galaxies are included in the Data Release 8 of Sloan Digital Sky Survey (SDSS DR8) and have central light profiles and kinematic properties available from the literature, which were measured based on Hubble Space Telescope ({\it HST}) and \atlas\ integral-field spectrograph (IFS) observations, respectively. We find that there is only a weak correlation between the isophotal shape ($a_{4}/a$) and the central light profile (within $1\,\rm kpc$) of ETGs. About two-fifths of "core" galaxies have disky isophotes, while one-third of "power-law" galaxies are boxy deviated. Our statistical results also show that there are weak correlations between galaxy luminosity and dynamical mass with $a_{4}/a$, but such correlations are tighter with central light profile. Moreover, no clear link has been found between the isophotal shape and the S\’ ersic index. Comparisons show that there are similar correlations between $a_{4}/a$ and ellipticity and between $a_{4}/a$ and specific angular momentum $\lambda_{R_e/2}$ for "power-law" ETGs, but there are no such correlations for "core" ETGs. Therefore, we speculate that the bimodal classifications for ETGs are not as simple as previously thought, though we also find that the most deviated disky ETGs are "power-law", more elongated and fast rotators.

Supernova neutrinos and nucleosynthesis

Observations of metal-poor stars indicate that at least two different nucleosynthesis sites contribute to the production of r-process elements. One site is responsible for the production of light r-process elements Z<~50 while the other produces the heavy r-process elements. We have analyzed recent observations of metal-poor stars selecting only stars that are enriched in light r-process elements and poor in heavy r-process elements. We find a strong correlation between the observed abundances of the N=50 elements (Sr, Y and Zr) and Fe. It suggest that neutrino-driven winds from core-collapse supernova are the main site for the production of these elements. We explore this possibility by performing nucleosynthesis calculations based on long term Boltzmann neutrino transport simulations. They are based on an Equation of State that reproduces recent constrains on the nuclear symmetry energy. We predict that the early ejecta is neutron-rich with Ye ~ 0.48, it becomes proton rich around 4 s and reaches Ye = 0.586 at 9 s when our simulation stops. The nucleosynthesis in this model produces elements between Zn and Mo, including 92Mo. The elemental abundances are consistent with the observations of the metal-poor star HD 12263. For the elements between Ge and Mo, we produce mainly the neutron-deficient isotopes. This prediction can be confirmed by observations of isotopic abundances in metal-poor stars. No elements heavier than Mo (Z=42) and no heavy r-process elements are produced in our calculations.

Mass Extinction And The Structure Of The Milky Way

We use the most up to date Milky Way model and solar orbit data in order to test the hypothesis that the Sun’s galactic spiral arm crossings cause mass extinction events on Earth. To do this, we created a new model of the Milky Way’s spiral arms by combining a large quantity of data from several surveys. We then combined this model with a recently derived solution for the solar orbit to determine the timing of the Sun’s historical passages through the Galaxy’s spiral arms. Our new model was designed with a symmetrical appearance, with the major alteration being the addition of a spur at the far side of the Galaxy. A correlation was found between the times at which the Sun crosses the spiral arms and six known mass extinction events. Furthermore, we identify five additional historical mass extinction events that might be explained by the motion of the Sun around our Galaxy. These five additional significant drops in marine genera that we find include significant reductions in diversity at 415, 322, 300, 145 and 33 Myr ago. Our simulations indicate that the Sun has spent ~60% of its time passing through our Galaxy’s various spiral arms. Also, we briefly discuss and combine previous work on the Galactic Habitable Zone with the new Milky Way model.

Mid-Infrared Atomic Fine-Structure Emission Line Spectra of Luminous Infrared Galaxies: Spitzer/IRS Spectra of the GOALS Sample

We present the data and our analysis of MIR fine-structure emission lines detected in Spitzer/IRS high-res spectra of 202 local LIRGs observed as part of the GOALS project. We detect emission lines of [SIV], [NeII], [NeV], [NeIII], [SIII]18.7, [OIV], [FeII], [SIII]33.5, and [SiII]. Over 75% of our galaxies are classified as starburst (SB) sources in the MIR. We compare ratios of the emission line fluxes to stellar photo- and shock-ionization models to constrain the gas properties in the SB nuclei. Comparing the [SIV]/[NeII] and [NeIII]/[NeII] ratios to the Starburst99-Mappings III models with an instantaneous burst history, the line ratios suggest that the SB in our LIRGs have ages of 1-4.5Myr, metallicities of 1-2Z_sun, and ionization parameters of 2-8e7cm/s. Based on the [SIII]/[SIII] ratios, the electron density in LIRG nuclei has a median electron density of ~300cm-3 for sources above the low density limit. We also find that strong shocks are likely present in 10 SB sources. A significant fraction of the GOALS sources have resolved neon lines and 5 show velocity differences of >200km/s in [NeIII] or [NeV] relative to [NeII]. Furthermore, 6 SB and 5 AGN LIRGs show a trend of increasing line width with ionization potential, suggesting the possibility of a compact energy source and stratified ISM in their nuclei. We confirm a strong correlation between the [NeII]+[NeIII] emission, as well as [SIII]33.5, with both the IR luminosity and the 24um warm dust emission measured from the spectra. Finally, we find no correlation between the hardness of the radiation field or the line width and the ratio of the total IR to 8um emission (IR8). This may be because the IR luminosity and the MIR fine-structure lines are sensitive to different timescales over the SB, or that IR8 is more sensitive to the geometry of the warm dust region than the radiation field producing the HII region emission.

Constraints on the Galactic Bar from the Hercules stream as traced with RAVE across the Galaxy

Non-axisymmetries in the Galactic potential (spiral arms and bar) induce kinematic groups such as the Hercules stream. Assuming that Hercules is caused by the effects of the Outer Lindblad Resonance of the Galactic bar, we model analytically its properties as a function of position in the Galaxy and its dependence on the bar’s pattern speed and orientation. Using data from the RAVE survey we find that the azimuthal velocity of the Hercules structure decreases as a function of Galactocentric radius, in a manner consistent with our analytical model. This allows us to obtain new estimates of the parameters of the Milky Way’s bar. The combined likelihood function of the bar’s pattern speed and angle has its maximum for a pattern speed of Omega_b=(1.89 +- 0.08) x Omega_0 where Omega_0 is the local circular frequency. Assuming a Solar radius of 8.05 kpc and a local circular velocity of 238 km/s, this corresponds to Omega_b=56 +- 2 km/s/kpc. On the other hand, the bar’s orientation phi_b cannot be constrained with the available data. In fact, the likelihood function shows that a tight correlation exists between the pattern speed and the orientation, implying that a better description of our best fit results is given by the linear relation Omega_b/Omega_0=1.905 + 0.0044[phi_b(deg)-47.7], with standard deviation of 0.02. For example, for an angle of phi_b=30deg the pattern speed is 54.0+-0.5km/s/kpc. These results are not very sensitive to the other Galactic parameters such as the circular velocity curve or the peculiar motion of the Sun, and are robust to biases in distance.

Isothermal dust models of Herschel-ATLAS galaxies

We use galaxies from the Herschel-ATLAS survey, and a suite of ancillary simulations based on an isothermal dust model, to study our ability to determine the effective dust temperature, luminosity and emissivity index of 250um selected galaxies in the local Universe (z < 0.5). As well as simple far-infrared SED fitting of individual galaxies based on chi^2 minimisation, we attempt to derive the best global isothermal properties of 13,826 galaxies with reliable optical counterparts and spectroscopic redshifts. Using our simulations, we highlight the fact that applying traditional SED fitting techniques to noisy observational data in the Herschel Space Observatory bands introduces artificial anti-correlation between derived values of dust temperature and emissivity index. This is true even for galaxies with the most robust detections in our sample, making the results hard to interpret. We apply a method to determine the best-fit global values of isothermal effective temperature and emissivity index for z < 0.5 galaxies in H-ATLAS, deriving T = 22.3 +/- 0.1K and Beta = 1.98 +/- 0.02 (or T = 23.5 +/- 0.1K and Beta = 1.82 +/- 0.02 if we attempt to correct for bias by assuming that T and Beta are independent and normally distributed). We use our technique to test for an evolving emissivity index, finding only weak evidence. The median dust luminosity of our sample is log(Ldust/Lsolar) = 10.72 +/- 0.05 which (unlike T) shows little dependence on the choice of Beta used in our analysis, including whether it is variable or fixed. We use a further suite of simulations to emphasise the importance of the H-ATLAS PACS data for deriving dust temperatures at these redshifts, even though they are less sensitive than the SPIRE data. The majority of galaxies detected by H-ATLAS are normal star-forming galaxies, though a substantial minority (~31%) fall in the Luminous Infrared Galaxy category. (Abridged)

The Intrinsic Scatter Along The Main Sequence of Star-Forming Galaxies at z ~ 0.7

A sample of 12614 star-forming galaxies (SFGs) with stellar mass >10^9.5 M_sun between 0.6<z<0.8 from COSMOS is selected to study the intrinsic scatter of the correlation between star formation rate (SFR) and stellar mass. We derive SFR from ultraviolet (UV) and infrared (IR) luminosities. A stacking technique is adopted to measure IR emission for galaxies undetected at 24 micron. We confirm that the slope of the mass-SFR relation is close to unity. We examine the distributions of specific SFRs (SSFRs) in four equally spaced mass bins from 10^9.5 M_sun to 10^11.5 M_sun. Different models are used to constrain the scatter of SSFR for lower mass galaxies that are mostly undetected at 24 micron. The SFR scatter is dominated by the scatter of UV luminosity and gradually that of IR luminosity at increasing stellar mass. We derive SSFR dispersions of 0.18, 0.21, 0.26 and 0.31 dex with a typical measurement uncertainty of <~ 0.01 dex for the four mass bins. Interestingly, the scatter of the mass-SFR relation seems not constant in the sense that the scatter in SSFR is smaller for SFGs of stellar mass <10^10.5 M_sun. If confirmed, this suggests that the physical processes governing star formation become systematically less violent for less massive galaxies. The SSFR distribution for SFGs with intermediate mass 10^10-10^10.5 M_sun is characterized by a prominent excess of intense starbursts in comparison with other mass bins. We argue that this feature reflects that both violent (e.g., major/minor mergers) and quiescent processes are important in regulating star formation in this intermediate mass regime.

 

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