1203.1032
Spitzer observations of the HH 1/2 system. The discovery of the counter jet
Noriega-Crespo, Raga
* Herbig-Haro object: small patches of nebulosity associated with newly born stars, and are formed when gas ejected b young stars collides with clouds of gas and dust nearby at speeds of several hundred km/s. Ubiquitous in SF regions; several often seen around a single stars, aligned along its rotational axis. Transient phenomena, not lasting more than few thousand years. Highly ionized emission nebula (but no star within--no IR emission). Has jet-like nature, highly collimated (polar jets). 1-20 M_Earth ejected, T=8k to 12k K, 20-30% ionized (but decreases with distance), quite dense (few~tens thousands particles / cm^3), mostly H and He, over 400 HH objects known, in SF HII regions, found in large groups, often found near Bok globules, most lie within 0.5 pc of their parent star.
Spitzer IRAC mid-IR observation with 0.6"-0.8" seeing. Optically invisible counter jet found in IR. Dominated by collisionally excited H2 pure rotational lines from a medium with a neutral Hydrogen gas density of 1-2k cm^-3 and a temperature of 1500K. Consistent with symmetric outflow with extinction from a dense, circumstellar structure of 6" size along the outflow axis; mean visual extinction of Av=11 mag.
1203.1033
Non-gaussian features of primordial magnetic fields in power-law inflation
Motta, Caldwell
* conformal geometry: study of the set of angle-preserving (conformal) transformations on a space.
Show: conformal-invariance violating coupling of the inflaton to EM produces a cross correlation between curvature fluctuations and a spectrum of primordial magnetic fields. In this model, primordial magnetic field is generated in the case of power-law inflation. Study correlation (3pt function of the curvature perturbation and two powers of the magnetic field). Signal can be stronger than from pure scalar perturbation from inflation.
1203.1034
General complex polynomial root solver and its further optimization for binary micro lenses
Skowron, Gould
Present new algorithm to solve polynomial equations, 1.6 to 3x faster than ZROOTS subroutine from NR. Largest improvement does from fail-safe procedure that permits skipping the majority of calculations in the great majority of cases without risking catastrophic failure in the few cases when these are actually required. Identify a discriminant that enables a rational choice between Laguerre's method and newton's method on a case-by-case basis. Briefly review history of root solving ("Newton's method" discovered by Simpson). Argue that NR should voluntarily surrender its copyright protection for non-profit applications.
1203.1037
Multi-dimensional, compressible viscous flow on a moving Voronoi mesh
Munoz, Springel, Marcus, Vogelsberger, Hernquist
Moving mesh algorithm for numerical schemes of Euler and Navier-Stokes equations. Various benefits. Realized for AREPO code, both in 2d and 3d. Good accuracy with geometric flexibility, competitive with other highly refined Eulerian methods. Allow astrophysical applications of the AREPO code where physical viscosity is important, such as hot plasma in galaxy clusters, or for viscous accretion disk models.
1203.1038
Galactic winds driven by CR streaming
Uhlig, Pfrommer, Sharma, Nath, Ensslin, Sprngel
* Advection: transport mechanism of a substance (or a conserved property) by a fluid, due to fluid's bulk motion in a particular direction.
Galactic winds: observed in many spiral galaxies from dwarfs up to the MW, and sometimes carry mass in excess of that of newly formed stars by up to a factor of ten. Multiple driving processes of such winds proposed: e.g., thermal pressure due to SNe heating, UV radiation pressure on dust grains, or CR pressure. Here, study CR pressure using numerical model that accounts for CR acceleration by SNe, CR thermalization, and advective CR transport. Introduce a novel implementation of CR streaming relative to the rest frame of the gas. Find CR streaming drives powerful and sustained winds in galaxies with virial masses 1e11 Msun. CR streaming is able to drive fountain flows that excite turbulence. For halo masses >1e10 Msun, predict an observable level of Halpha and X-ray emission from the heated halo gas. Conclude that CR-driven winds should be crucial in suppressing and regulating the first epoch of galaxy formation, expelling a large fraction of baryons, and aid in shaping the faint end of the galaxy luminosity function. They should then also be responsible for much of the metal enrichment of the IGM.
1203.1039
Cosmological implications of a stellar IMF that varies with the jeans mass in galaxies
Narayanan, Dave
Observations of SF galaxies at high-z has problems with SFR, either between data and models, or between complementary measures of SFR. These putative discrepancies could all be alleviated if the stellar IMF is systematically weighted toward more high-mass star formation in rapidly SF galaxies. Explore how the IMF might vary under the central assumption that the turnover mass in the IMF, Mc, scales wit hthe Jeans mass in gian molecular clouds (GMCs), M_J. Enploy hydro and radiative transfer sims of galaxies to predict how the typical GMC Jeans mass (and hence the IMF) varies with galaxy property. Then study the impact of such an IMF on the SF law, SFR-M* relation, sub millimeter galaxies (SMGs) and the cosmic SFR density. Results: The H2 mass-weighted Jeans mass in a galaxy scales with the SFR when the SFR is greater than a few Msun/yr. Stellar population synthesis modeling shows that this results in a nonlinear relation between SFR propto L_bol^0.88. Using this model results in a lowered normalization of the SFR-M* relation in better agreement with models, a reduced discrepancy between the observed cosmic SFR density and stellar mass density evolution, and SMG SFRs that are easier to accommodate in current hierarchical structure formation models. It further results in a Schmidt relation with slope of 1.6 when utilising a physically motivated form for the CO-H2 conversion factor. While each of the discrepancies considered here could be alleviated without appealing to a varying IMF, the modest variation implied by assuming Mc propto M_J is a plausible solution that simultaneously addresses numerous thorny issues regarding the SFRs of high-z galaxies.
1203.1045
The evolution of the Compton thick fraction and the nature of obscuration for AGN in the Chandra Deep Field South
Brightman, Ueda
* Compton scattering: non-eleastic scattering of photons off of electrons.
X-ray spectral analysis of high-z AGN in the CDFS, with spectral models that account for Compton scattering and the geometry of the circumnuclear material. Goal: ascertain to what extent the torus paradigm of local AGN is applicable at earlier epochs, and to evaluate the evolution of the Compton thick fraction (f_CT) with z, important for XRB synthesis models and understanding the accretion history of the universe. The scattered nuclear light (known to be dependent on the covering factor of the circumnuclear material) used to aid in understanding of geometry. Covering factor of the circumnuclear material is correlated with NH, and as such the most heavily obscured AGN are in fact also the most geometrically buried (scatter decreases as NH increases). Find significant fraction of sources (20%) in the CDFS are likely to be buried in material with close to 4pi coverage. Find 41 CT AGN using the new torus models, 29 reported for the first time. Bin sample by z in order to investigate the volition of f_CT. Find signifiant increase in the intrinsic f_CT from 20% local to 40% at z=1-4.
1203.1051
Variability in quasar broad absorption line outflows II. Multi-epoch monitoring of Si IV and C IV variability
Capellupo, Hamann, Shields, Hidalgo, Barlow
Variability studies of BALs help illuminate the structure, evolution, and basic physical properties of the outflows. PResent results from ongoing BAL monitoring campaign of 24 quasars at 1.2<z<2.9. Directly compare the variabilities in C IV (1549) and Si IV (1400) absorption. Si IV BALs more likely to vary. For speeds >2e4 m/s, 47% had Si variability, while 31% had C variability. 50% of Si regions did not have corresponding C variability at the same velocities, while nearly all occurrences of C variability had corresponding changes in Si. Do not find any correlation between the absolute change in strength in C and Si, but the fractional change in strength ... characteristic time-scale for significant line variation and for structural changes in the outflows is less than a few years. Coordinated variabilities between absorption regions at different velocities in individual quasars: favor changing ionization of the outflowing gas as the cause of the observed BAL variability.
nature10778
Biosignatures as revealed by spectropolarimetry of Earthshine
Sterzik, Bagnulo, Palle
"Biosignatures" == signatures of life, a.k.a. 'red edge' (i.e. green foliage), surface concentrations of molecular oxygen, methane far from equilibrium. Atmosphere polarizes the light. Signatures of oxygen, ozone and water. Apply to exoplanets: constrain properties of atmosphere and surfaces with spectropolarimetry. Report disk integrated polarization of Earthshine from the Moon. Find fractional contribution of clouds and ocean surface; sensitive to visible areas of vegetation (down to 10%).
1203.1057
Constraints on the ICM velocity power spectrum from the X-ray lines width and shift
Zhuravleva, Churazov, Kravtsov, Sunyaev
Spatially resolved measurements of the energy and width for the brightest emission lines in ICM (future X-ray observations). Use this to constrain velocity power spectrum in galaxy clusters. Variations of these quantities with the projected distance R in cool core clusters has info on velocity field length scales in the ICM. Effective length increases with R, allowing one to probe the amplitude of the velocity variations at different spatial scales; closely related to the structure function of the 3d velocity field. Projected velocity field can be converted to 3d velocity field, especially for clusters like Coma with an extended flat core in the surface brightness. Assuming isotropic Gaussian 3d velocity field, simple expressions relate the power spectrum of the 3d velocity field and the observables. Uncertainties in the observables. If large scale motions present in the ICM, uncertainties may dominate the statistical errors of line width.
1203.1059
The prompt-afterglow connection in gamma-ray bursts: a comprehensive statistical analysis of Swift x-ray light-curves
Margutti et al
In a 2 parameter x-ray to prompt gamma-ray relations, short GRBs are outliers. Existence of a universal 3 parameter scaling that inks x-ray and gamma-ray energy for both long and short GRBs.
1203.1073
A note on solar cycle length during the medieval climate anomaly
Vaquero, Trigo
* Medieval climate anomaly (MCA): time of warm climate in the north Atlantic region from AD 950 to 1250. It was followed by a cooler period in the North Atlantic termed the LIttle Ice Age.
* During 1645-1715, in the middle of the Little Ice Age, there was a period of low solar activity known as the Maunder Minimum. (Spörer Minimum also identified with cooling in 1460-1550). Other indicators of low solar activity during this period are levels of 14C and 10Be.
* Maunder minimum: when the sunspots became exceedingly rare, between 1645 to 1715; coincides (along with Dalton Minimum and Spörer Minimum) with a period of lower-than-average global temperatures.
Use observations of sunspot and aurora sightings to reconstruct solar cycle length; an average duration of 10.72 years during the MCA. Thus, solar activity was most probably not exceptionally intense, supporting the view that internal variability of the coupled ocean-atmosphere system was the main driver of MCA.
1203.1087
The SDSS quasar lens search. V. Final catalog from DR7
Inada, Oguri, ... et al
26 lensed quasars i<19.1 and in 0.6<z<2.2 selected from 50k quasar spectra in SDSS DR7; separation restricted to 1"<theta<20" and i-band difference < 1.25 mag. Additional 36 lenses identified with various techniques. 81 pairs (not multiple images) of quasars from follow up spectroscopy, 26 are physically associated. Wide range of image separations, redshifts, and magnitudes. Suitable for systematic studies of cosmological parameters and surveys of the structure and evolution of galaxies and quasars.
1203.1088
The SDSS quasar lens search. VI. constraints on DE and the evolution of massive galaxies
Oguri, Inada, ... et al
Compare 19 lensed quasars, compare with theoretical expectations, paying attention to the selection function. Constrain Omega_Lambda for a flat universe. w constrained combining with BAO and WMAP. Also obtain simultaneous constraints on cosmo params and z evolution of the galaxy velocity function; find no evidence of z evolution at z<1. THe statistics of lensed quasars robustly confirm the accelerated cosmic expansion.
1203.1155
THe effect of ISM turbulence on the gravitational instability of galactic discs
Hoffmann, Romeo
Investigate the gravitational instability of galactic disks, treating stars and interstellar cold gas as two distinct components, and taking into account the phenomenology of ISM turbulence. Analyze a large sample of galaxies from "The HI Neary Galaxy Survey" (THINGS), show in detail how interstellar turbulence affects the discs of SF spirals. Turbulence has significant effect on both the inner and outer regions of the disc; in particular, drives the inner gas disc to a regime of transition between two instability phases and makes the outer disc more prone to star-dominated instabilities.
1203.1164, 1203.1165
Decaying DM: a stacking analysis of galaxy clusters to improve on current limits
Combet, Maurin, Nezri, Pointecouteau, Hinton, White
Nezri, White, Combet, Maruin, Pointecouteau, Hinton
Galaxy cluster stacking can improve current limits on decaying DM by 5x to 100x for gamma-ray observations: angular resolution achievable to 0.1 deg. Mean 80%-ile DM signal is 0.15 deg. Need instruments with resolution better than this. For FermiLAT, improvement is ~2x, due to (i) relatively poor resolution, (ii) larger angles subtended by bright, nearby objects such as Virgo.
1203.1166
Disentangling CR and DM-induced gamma-ray in galaxy clusters?
Maurin, Combet, Nezri, Pointecouteau
Simulate DM decay/annihilation and CR along LoS. Log-N-logF power-law behavior may be a clear signatures to disentangle decaying DM from CR induced gamma-rays (and DM annihilation). Shift between the brightest object and its followers depends on the signal origin, so the the behavior of the cumulative of the signal does depend on it. Also show that stacking a large number of objects can reinforce the discrimination power of angular dependence studies for a CR or DM decay origin, (but not for DM annihilation), provided that the cluster signal is rescaled by the angular size corresponding its DM halo scale radius.
1203.1190
Idealized models for galactic disk formation and evolution in 'realistic' LCDM haloes
Aumer, White
Study the dynamics of galactic disk formation and evolution. Add rotating spheres of hot gas at z=1.3 to two fully cosmological DM-only halo (re)simulations. Gas cools according to an artificial and adjustable cooling function to form a rotationally supported galaxy. Evolve to z=0. Vary: angular momentum and density profiles of the initial gas sphere, the cooling time and the orientation of the angular momentum vector to study the effects on the evolution of the disk. The final disks show realistic structural and kinematic properties. The slower the cooling/accretion processes, the higher the kinematic disk-bulge ratio D/B. Find the initial orientation of the gas angular momentum with respect to the halo gas a major effect on the resulting D/B: most stable systems result from orientations parallel to the halo minor axis, but the sign of the spin can have a strong effect. Despite the spherical and coherently rotating initial gas distribution, the orientation of the central disk and of the outer gas components and the relative angle between the components can all change by more than 90 degrees over several Byr. Disks can form from initial conditions oriented parallel to the major axis, but there is often strong misalignment between inner and outer material. The more the orientation of the baryonic angular momentum changes during the evolution, the lower the final D/B. The behavior varies strongly from halo to halo. Even simple initial conditions can lead to strong bars, dominant bulges, massive, misaligned rings and counter-rotating components. Discuss how results may relate to the failure or success of fully cosmological disk formation simulations.
1203.1221
The IMF from low to high redshift
Greggio, Renzini
Illustrate how IMF affects various properties of galaxies and galaxy clusters. Start by showing small variations of the IMF slope have large effects on the demography of stellar populations, moving the bulk of the stellar mass from one end to the other of the distribution. Then point out how the slope of the IMF in different mass ranges controls specific major properties of galaxies and clusters. Slope of the IMF in different mass ranges controls specific major properties of galaxies and clusters. Below 1Msun, IMF controls the M/L ratio of local ellipticals, whereas between 1 to 1.4 Msun controls the evolution with redshift of such ratio, hence the fundamental plane of elliptical galaxies. Between 1 and 40 Msun, IMF drives the ratio of the global metal mass in clusters of galaxies to their total luminosity. When studying variations in IMF, explore the full consequences.
1203.1225
On the tidal dependence of galaxy properties
Yan, Fan, White
Tidal environment of galaxies from 1+delta(gal): its ellipticity e. Correlation with galaxy properties, color, Dn4000, concentration and size. There is a transition smoothing scale at which correlations/anti-correlations with e reverse. Transition scale at 3rd nearest neighbor of a galaxy with Mr<-20, distribution peaked ago 2 Mpc/h. This scale corresponds to where the correlation between the color of galaxies and environmental density is the strongest. Similar SAM-based simulation show similar behavior to SDSS, although the color-density correlation is stronger in the SAM.
Awesomeness in Engineering:
http://videosift.com/video/Predator-Camera-That-Learns
1203.1242
Sizes, half-mass densities, and mass functions of star clusters in the merger remnant NGC 1316: clues to the fate of 2nd generation globular clusters
Goudfrooij
Mass functions of globular clusters of NGC 1316, hosts a population of metal-rich globular clusters of intermediate age (~3Gyr). For metal-poor (blue) clusters, peak mass of mass function increases with internal half-mass density, where it stays approximately constant with galactocentric distance Rgal. These clusters consistent with a simple scenario in which they formed with a Schechter IMF and evolved by 2-body relaxation. For intermediate-age population (red), The faint end of the power-law luminosity function with Rgal>9kpc is due to many of these clusters having radii larger than the theoretical maximum value imposed by the tidal field of NGC1361 at their Rgal; renders disruption by 2-body relaxation ineffective. Only a few such diffuse clusters found in they inner regions of NGC1316 (tested for completeness). Hypothesize: most red clusters in the low density tail of the initial distribution have already been destroyed in the inner regions of NGC1316 by tidal shocking, and that several remaining low density clusters will evolve dynamically to become similar to 'faint fuzzes' that exist in several lenticular galaxies.
[what is a Schechter IMF?]
1203.1252
Model selection applied to reconstruction of the primordial power spectrum
Vazquez, Bridges, Hobson, Lasenby
Determine preferred shape of primordial spectrum by performing a Bayesian model selection analysis of cosmological observations. First reconstruct spectrum modeled as piecewise linear in log k between nodes in k-space, whose amplitudes and positions are allowed to vary. THe number of nodes together with their positions are chosen by the Bayesian evidence (determine complexity supported by the data, and locate any features present in the spectrum). Additionally consider a set of parameterised models for the primordial spectrum (standard power-law, the LD model, and a simple variant parameterisation). Compare Bayesian evidence for different classes of spectra. Find the power-law parameterisation is significantly disfavored by current cosmo observation; show a preference for the LD model.
1203.1309
Search for annual modulation in low-energy CDMS-II data
CDMS collaboration, et al
Report limits on annual modulation of the low-energy event rate from CDMS at Soudan Underground Lab (modulation due to interaction with WIMPs with masses 10 GeV). Find no evidence annual modulation in the event rate of veto-anticoincident single-detector interactions consistent with nuclear recoils, and constrain the magnitude of any modulation to 98% confidence. For events consistent with electron recoils, no significant modulation is observed
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