Day 512

Sunday.  

1309.3847
Alignments of galaxies within cosmic filaments from SDSS DR7
Zhang, Yang, Wang, Wang, Mo, van den Bosch

Find that the major axes of galaxies in filaments tend to be preferentially aligned with the directions of the filaments, while galaxies in sheets have their major axes preferentially aligned parallel to the plane of the sheets.  The Strength of this alignment signal is strongest for red, central galaxies, and in good agreement with that of DM haloes in N-body simulations.  This suggests that red, central galaxies are well aligned with their host haloes, in quantitative agreement with previous studies based on the spatial distribution of satellite galaxies.  There is a luminosity and mass dependence that brighter and more massive galaxies in filaments and sheets have stronger alignment signals.  Also find that the orientation of galaxies is aligned with the eigenvector associated with the smallest eigenvalue of the tidal tensor.  These observational results provide direct evidence that galaxy formation is affected by large-scale environments, and strongly suggests that galaxies are aligned with each other over scales comparable to those of sheets and filaments in the cosmic web.

1309.3869
Gamma-ray burst afterglow theory
van Eerten

Established that gamma-ray  burst afterglows result from initially relativistic outflows interacting with the medium surrounding the burster and emitting non-thermal radiation ranging from radio to X-rays.  However, many big and small questions remain about after glows, with the accumulating amount of observational data at the various frequencies raising as many questions as they answer.  In this review, highlight a number of current theoretical issues and how they fit or do not fit within the basic theoretical framework.  In addition to theoretical progress, also emphasize the increasing role and usefulness of numerical studies of afterglow blast waves and their radiation.

1309.3878
Simulating galaxy evolution with a non-universal stellar initial mass function
Bekki

Incorporate a NUIMF (non-uniform IMF) model into galaxy-scale chemodynamical simulations in order to investigate the differences in chemical and dynamical evolution of disk galaxies between the NUIMF and universal IMF (UIMF) models.  In the adopted NUIMF model, the 3 slopes of the Kroupa IMF depend independently on densities and metallicities [Fe/H] of molecular gas clouds, and production rates of metals and dust from massive and AGB stars can vary according to the time evolution of the 3 IMF slopes.  The preliminary results of the simulations are:  SFRs in actively SF disk galaxies can be significantly lower in the NUIMF model than in the UIMF model, and the differences between the two models can be more remarkable in galaxies with higher SFRs.  Chemical enrichment can proceed more rapidly in the NUIMF model and [Mg/Fe] for a given metallicity is higher in the NUIMF model.  The evolution of H2 fraction (f_H2) and dust-to-gas ratio (D) is more rapid in the NUIMF model so that the final f_H2 and D can be higher in the NUIMF model.  Formation of massive stellar clumps in gas-rich disks is more strongly suppressed owing to the stronger SN feedback effect in the NUIMF model.  The radial density profiles of new stars within the central 1kpc are shallower in the NUIMF model.  

1309.3891
Weak lensing calibrated M-T scaling relation of galaxy groups in the COSMOS field
Kettula, Finoguenov, Massey, Rhodes, Hoekstra, Taylor, Spinelli, Tanaka, Ilbert, Capak, McCracken, Koekemoer

Calibrate scaling relation between WL mass and X-ray spectroscopic temperature for 10 galaxy groups in the COSMOS field, combined with 55 higher mass clusters from the literature.  The COSMOS data includes HST imaging and redshift measurements of 46 source galaxies per square arcmin, enabling WL measurements of low mass systems.  Sample extends the mass range of the lensing calibrated M-T relation an order of magnitude lower than any previous study, resulting in a power-law slope of 1.48p0.13m0.09.  The slope is consistent with the self-similar model, predictions from simulations, and observations of clusters.  However, Xray observations relying on mass measurements derived under the assumption of hydrostatic equilibrium have indicated that masses at group scales are lower than expected.  Both simulations and observations suggest that hydrostatic mass measurements can be biased low.  This external WL masses provides the first observational support for hydrostatic mass bias at group level, showing an increasing bias with decreasing temperature and reaching a level of 30-50% at 1 keV.

1309.4087
Direct detection of SDSS J0926+3624 orbital expansion with ARCONS
Szypryt ... Marsden, et al

AM Canum Venaticorum (AM CVn) stars belong to a class of ultra-compact, short period binaries with spectra dominated largely by helium.  SDSS J0926+3624 is of particular interest as it is the first observed eclipsing AM CVn system.  Observed SDSS J0926+3624 with ARCONS at the Palomar 200" telescope.  ARCONS uses a relatively new type of energy-resolved photon counters called Microwave Kinetic Inductance Detectors (MKIDs).  ARCONS, sensitive to radiation from 350 to 1100 nm, has a time resolution of several microseconds and can measure the energy of a photon to ~10 [units?].  Present the light curves for these observations and examine changes in orbital period from prior observations.  [Why would you need ARCONS?]  Using a quadratic ephemeris model, measure a period rate of change dot(P)=3e-13 [!  for the time resolution, I guess?].  In addition, use the high timing resolution of ARCONS to examine the system's high frequency variations and search for possible quasi-periodic oscillations (QPOs).  Finally, use the instrument's spectral resolution to examine the light curves in various wavelength bands.  Do not find any high frequency QPOs or significant spectral variability throughout an eclipse.  

1309.4093
The intrinsic scatter along the main sequence of star-f0rming galaxies at z~0.7
Guo, Zheng, Fu

A sample of 12614 SF galaxies (SFGs) with M* >1e9.5Msun, 0.6<z<08 from COSMOS selected to study the intrinsic scatter of the correlation between SFR and stellar mass.  Drive SFR from UV and IR luminosities; stacking technique adopted to measure IR emission for galaxies undetected at 24 micron.  Confirm that the slope of the mass-SFR relation is close to unity.  Examine the distributions of sSFRs in 4 equally spaced mass bins from 1e9.5 to 1e11.5 Msun; different models are used to constrain the scatter of sSFR for lower mass galaxies that are mostly undetected at 24 um.  The SFR scatter is dominated by the scatter of UV luminosity and gradually that of IR luminosity at increasing stellar mass.  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.  The scatter of the mass-SFR relation seems not constant  (scatter in sSFR is smaller for SFGs of 1e10.5Msun).  If confirmed, this suggests that the physical processes governing SF become systematically less violent [does "violence" (mergers) equate to more scatter?  I guess so] for less massive galaxies.  The sSFR distribution for SFGs with intermediate mass 1e10-10.5 Msun is characterized by a prominent excess of intense starbursts in comparison with other mass bins.  Argue that this feature reflects that both violent (e.g., major/minor mergers) and quiescent processes are important in regulating SF in this intermediate mass regime.

1309.4118
Astroseismology, standard candles and the Hubble Constant: what is the role of astroseismology in the era of precision cosmology?
Neilson etal

Classical Cepheids form one of the funcations of modern cosmology and the extragalactic distance scale, however, CMB observations measure cosmological parameters and indirectly the Hubble Constant, H0, to unparalleled precision.  THe coming decade will provide opportunities to measure H0 to 2% uncertainty thanks to GAIA satellite, JWST, ELTs and other telescopes using Cepheids and other standard candles.  In this work, discuss the upcoming role for variable stars and astroseismology in calibrating the distance scale and measuring H0 and what problems exist in understanding these stars that will feedback on these measurements.

1309.4120
Red bulgeless galaxies in SDSS DR7.  Are there any AGN hosts?
Coelho et al

With the main goal of finding bulgeless galaxies harboring SMBHs and showing, at most, just residual SF activity, selected a sample of massive bulgeless red sequence galaxies, based on the NYU-VAGC catalog.  Multiwavelength data were retrieved using EURO-VO tools, and the objects are characterized in terms of degree of SF and the presence of AGN.  Found 7 objects that are quenched massive galaxies, that have no prominent bulge and that show signs of extra activity in their nuclei, five of them being central in their halo.  These objects are rather robust candidates for rare systems that, though devoid of a significant bulge, harbor a SMBH with an activity level likely capable of having halted the SF through feedback.

1309.4224
Bad pixel modified interpolation for astronomical images
Popowicz, Kurek, Filus

New method of interpolation for the pixel brightness estimation in astronomical images; is simple and easily implementable.  Show the comparison of this method with the widely used linear interpolation and other interpolation algorithms using 1000 astronomical images obtained from SDSS.  Comparison shows that this method improves bad pixels brightness estimation with 4x lower mean error than the presently most popular linear interpolation and has a better performance than any other examined method [what exactly is the improvement?].  The presented idea is flexible and can be also applied to presently used and future interpolation methods.  The proposed method is especially useful for large sky surveys image reduction but can be also applied to single image correction.

1309.4270
New distances to RAVE stars
Binney et al

Probability density functions are determined from new stellar parameters for the distance moduli of stars for which the RAdial Velocity Experiment (RAVE) has obtained spectra with S/N>=10.  The expectation value of distance is larger than the distance implied by the expectation of distance modulus; the latter is itself larger than the distance implied by the expectation value of the parallax.  RAVE parallaxes of Hipparcos stars agree well with that of Hipparcos', so the expectation of parallax is the most reliable distance indicator.  The latter are improved by taking extinction into account.  Provide one- two- or three-Gaussian fits to the distance pdfs.  The effective temperature absolute-magnitude diagram of the stars is significantly improved when these pdfs are used to make the diagram.  Use the method of kinematic corrections devised by Schoenrich, Binney & Asplund to check for systematic errors in the estimators for ordinary stars and confirm the conclusion reached from the Hipparcos stars that the most reliable distance indicator is the expectation of parallax.  There is an indication that for cool dwarfs and low-gravity giants <varpi> [?  apparently some indicator of parallax] tends to be larger than the true distance by up to 30 percent.  The most satisfactory distances are for dwarfs hotter than 5500K.  Compare distances to stars in 13 open clusters with cluster distance from the literature and find excellent agreement for the dwarfs and indications that we [RAVE?] are over-estiamting distances to giants, especially in young clusters.  Taking extinction into account slightly improves results for cluster stars even through derived extinctions scatter significantly within a cluster and in four clusters the mean extinction of clusters stars do not agree with the cluster's literature value.  Noise in the spectra dominates neither the uncertainty in distance nor the uncertainty in extinction.

1309.4284
The RAdial Velocity Experiment (RAVE): fourth data release
Kordopatis et al

Present the stellar atmospheric parameters (effective temperature, surface gravity, overall metallicity), radial velocities, individual abundances and distances determined for 425 561 stars, which constitute the 4th data release of RAVE.  The stellar atmospheric parameters are computed using a new pipeline, based on the algorithms of MATISSE and DEGAS.  The spectral degeneracies and the 2MASS photometric information are now better taken into considerations, improving the parameter determination compared to the previous RAVE data releases.  The individual abundances for six elements (Mg, Al, Si, Ti, Fe and Ni) are also given, based on a special-purpose pipeline which is also improved compared to that available for the RAVE DR3 and Chemical DR1 data releases.  Together with photometric information and proper motions, these data can be retrieved from the RAVE collaboration website and the Vizier database.

1309.4285
Galactic kinematics and dynamics from RAVE stars
Binney et al

1309.4293
The RAVE survey: the Galactic escape speed and the mass of the Milky Way
Piffl et al

1309.4325
A RAVE Investigation on galactic open clusters I. Radial velocities and metllicities
Conrad et al

... several RAVE papers out this day, as seen above.


1309.4296
An anisotropic distribution of spin vectors in asteroid families
Hanuš et al

Present the spin-vector distributions for 8 astroidal families.  Use combined orbital- and spin-evolution model to explain the observed spin-vector properties of objects among collisional families.  In general, observe for studied families similar trends in the (a_p, beta) space: (i) larger astroids are situated in the proximity of the center of the family, (ii) asteroids with beta>0deg are usually found to the right from the family center; (iii) asteroids with beta<0 to the left from the center (iv) majority of the astroids have large pole-ecliptic latitudes (|beta|>~30 deg); and (v) some families have a statistically significant excess of asteroids with beta>0 or beta<0.  Numerical simulation of the long-term evolution of a collisional family is capable of reproducing well the observed spin-vector properties.  Using this simulation, also independently constrain the age of families Flora and Koronis.  

1309.4448
SATMC: spectral energy distribution analysis through Markov chains
Johnson, Wilson, Tang, Scott

Present general purpose SED fitting tool SATMC: use MCMC algorithms, SATMC fits an observed SED to SED templates or models of the user's choice to infer intrinsic parameters, generate confidence levels and produce the posterior parameter distribution.  Describe the key features of SATMC from the underlying MCMC engine to specific features for handling SED fitting.  Detail several test cases of SATMC, comparing results obtained to traditional least-squares methods, which highlight its accuracy, robustness and wide range of possible applications.  Also present sample of submillimeter galaxies that have been fitted using the SED synthesis routine GRASIL as input.  In general, these SMGs are shown to occupy a large volume of parameter space, particularly in regards to their star formation rates which range from ~30-3000 Msun/yr and stellar masses which range from ~1e10-12 Msun.  Taking advantage of the Bayesian formalism inherent to SATMC, also show how the fitting results may change under different parameterizations (i.e., different initial mass functions) and through additional or improved photometry, the latter being crucial to the study of high-redshift galaxies.  [can this be also used for photo-z?]

1309.4451
Locating the "missing" baryons with extragalactic dispersion measure estimates
McQuinn

Recent confirmation of a class of millisecond radio bursts likely of extragalactic origin that is well-suited for estimating dispersion measures (DMs) [total column density of free electrons between the observer and a pulsar---measured by the fact that low frequency radio waves travel through the medium slower than high frequency waves].  Another showed that DM could be measured even towards non-variable extragalactic synchrotron sources.  Motivated by these results, calculate the probability distribution of DM(z) in different models for how the cosmic baryons are distributed (both analytically and with cosmological simulations).  Show that the distribution of DM is quite sensitive to whether the "missing" baryons lie around the virial radius of 1e11-13 Msun haloes or further out, which is not easily constrained with other observational techniques.  The intrinsic contribution to DM from each source could complicate studies of the extragalactic contributions.  This difficulty is avoided by stacking based on the impact parameter to foreground galaxies.  Show that a stacking analysis using a sample of ~100 DM measurements from arcminute-localized, z>~0.5 sources would place interesting constraints at 0.2-2 halo virial radii on the baryonic mass profile surrounding different galaxy types.  Conveniently for intergalactic studies, sightlines that intersect intervening galactic disks should be easily identified owing to scattering.  A detectable level of scattering may also result from turbulence in the circumgalactic medium.

1309.4459
The role of galaxy interaction in the SFR-M relation: characterizing morphological properties of Herschel-selected galaxies at 0.2<z<1.5
Hung et al

Galaxy interactions/mergers have been shown to dominate the population of IR luminous galaxies (log(LIR)>11.6 Lsun) in the local Universe (z<0.25).  Recent studies based on the relation between galaxies' SFRs and M* (the SFR-M relation or the galaxy main sequence (MS)) have suggested that galaxy interaction/mergers may only become significant when galaxies fall well above the galaxy MS.  Since the typical SFR at given M increase with redshift, the existence of galaxy MS implies that massive, IR-luminous galaxies at high-z may not necessarily be driven by galaxy interactions.  Examine the role of galaxy interactions in the SFR-M relation by carrying out a morphological analysis of 2084 Herschel-selected galaxies at 0.2<z<1.5 in the COSMOS fields.  Herschel-PACS and -SPIRE observations covering the full 2-deg^2 COSMOS field provide one of the largest FIR selected samples of high-z galaxies with well-determined redshifts to date, which sufficient sensitivity at z~1, to sample objects lying on and above the galaxy MS.  Using a detailed visual classification scheme, show that the fraction of "disk galaxies" decreases and the fraction of "irregular" galaxies increases systematically with increasing LIR out to z~1.5 and z~1.0, respectively.  At log (LIR)>11.5 Lsun, >50% of the objects show evident features of strongly interacting/merger systems, where this percentage is similar to the studies of local IR-luminous galaxies.  The fraction of interacting/merger systems also systematically increases with the deviation from the SFR-M relation, supporting the view that galaxies fall above the MS are more dominated by mergers than the MS galaxies.  Meanwhile, find that ~18% of massive IR-luminous MS galaxies are classified as interacting systems, where this population may not evolve through the evolutionary track predicted by a simple gas exhaustion model.  

1309.4460
Cosmology with Minkowski functionals and moments of the weak lensing convergence field
Petri, Haiman, Hui, May, Kratochvil

Compare the efficiency of moments and Minkowski functionals (MFs) in constraining the subset of cosmological parameters (Omega_m, w, sigma_8) using simulated WL convergence maps.  Study an analytic perturbative expansion of the MFs in terms of the moments of the convergence field and of its spatial derivatives.  Show that this perturbations series breaks down on smoothing scales below 5', while it shows a good degree of convergence on larger scales (15').  Most of the cosmological distinguishing power is lost when the maps are smoothed on these larger scales.  Also show that, on scales comparable to 1', where the perturbation series does not converge, cosmological constraints obtained from the MFs are approximately 1.5-2 times better then the ones obtained from the first few moments of the convergence distribution --- provided that the latter include spatial information, either from moments of gradients, or by combining multiple smoothing scales.  Including either a set of these moments or the MFs can significantly tighten constraints on cosmological parameters, compared to the conventional method of using the power spectrum alone.

1309.4729
Astrobiology: an astronomer's perspective
Bergin

Focus on the origin of life in the context of planetary formation, with additional emphasis on tracing the most abundant volatile elements, C, H, O, and N that are used by life on Earth.  First explore the history of life on Earth and outline the current state of our knowledge regarding the delivery of the C, H, O, N elements to Earth.  Then discuss how astronomers track the gaseous and solid molecular carriers of these volatiles throughout the process of star and planet formation.  It is now clear that the early stages of SF fosters the creation of water and simple organic molecules with enrichments of heavy isotopes.  These molecules are found as ice coatings on the solid materials that represent microscopic beginnings of terrestrial worlds.  Based on the meteoritic and cometary record, the process of planet formation, and the local environment, lead to additional increases in organic complexity.  The astronomical connections towards this stage are only now being directly made.  Although the exact details are uncertain, it is likely that the birth process of star and planets likely leads to terrestrial worlds being born with abundant water and organics on the surface.