Day 438

Sunday.

1305.5840
Unleashing positive feedback: linking the rates of star formation and supermassive black hole accretion
Silk

Pressure-regulated SF is a simple variation on the usual SNe-regulated SFE that controls the global SFR as a function of cold gas content in SF galaxies, and accounts for the Schmidt-Kennicutt law in both nearby and distant galaxies.  Inclusion of AGN-induced pressure, by jets and/or winds that flow back onto a gas-rich disk, can lead under some circumstances to significantly enhanced SFRs, especially at high z and most likely followed by the more widely accepted phase of sF quenching.  Simple expressions are derived that relate SMBH growth, SF and outflow rates.  THe ratios of BH to spheroid mass and of both BH accretion and outflow rates to SFR are predicted as a function of time.  Suggest various tests of the AGN-triggered SF hypothesis.

1305.5914
Massive stars in the galaxies of the local group
Massey

SF galaxies of G act as laboratories for testing massive star evolutionary models.  In this review, briefly summarize what we know about massive star evolution and the connection between OB stars, Luminous Blue Variables, yellow supergiants, red supergiants, and Wolf-Rayet stars.  The difficulties and recent successes in identifying these various types of massive stars in the neighboring galaxies of the LG will be discussed.

1305.6025
Rotating globular clusters
Bianchini, Varri, Bertin, Zocchi

Photometry and 3d kinematics of omega Can, 47 Tuc, and M15, analyzed by means of self-consistent axisymmetric rotating models.  The three clusters are characterized by different relaxation conditions, and show evidence of differential rotation and deviations from sphericity.  The combination of LoS velocities and proper motions allows determination of internal dynamics, morphology prediction, and dynamical distance estimation.  47 Tuc is well relaxed and well interpreted by the model--internal rotation is found to explain the observed morphology.  For M15, a global model is in good agreement with data, including the central behaviour of the rotation profile and the shape of the ellipticity profile.  For the partially relaxed cluster omega Cen, the selected model reproduces the complex 3-d kinematics; in particular the observed anisotropy profile, characterized by a transition from isotropy, to weakly-radial anisotropy, and then to tangential anisotropy in the outer parts.  The discrepancy found for the steep central gradient in the observed LoS velocity dispersion profile and for the ellipticity profile is ascribed to the condition of only partial relaxation of this cluster and the interplay between rotation and radial anisotropy.

1305.6142
Dark-matter admixed white dwarfs
Leung, Chu, Lin, Wong

Study the equilibrium structures of WDs with DM cores formed by non-slef-annihilating DM particles with mass ranging from 1 GeV to 100 GeV, which are assumed to form an ideal degenerate Fermi gas inside the stars.  For DM particles of mass 10 GeV and 100 GeV, find that stable stellar models exist only if the mass of the DM core inside the star is less than O(1e-3) Msun and O(1e-6) Msun, respectively.  The global properties of these stars, and in particular the corresponding Chandrasekhar mass limits, are essentially the same as those of traditional WD models without DM.  Nevertheless, in the 10 GeV case, the gravitational attraction of the DM core is strong enough to squeeze the normal matter in the core region to densities above neutron drip, far above those in traditional WDs.  For DM with particle mass 1 GeV, the DM core inside the star can be as massive as around 0.1 Msun and affects the global structure of the star significantly.  In this case, the radius of a stellar model with DM can be about 2 times smaller than that of a traditional WD.  Furthermore, the Chandrasekhar mass limit can also be decreased by as much as 40%.  Results may have implications on to what extent SNIa can be regarded as standard candles - a key assumption in the discovery of DE.

1305.6154
Comparison of HI and optical redshifts of galaxies - The impact of redshift uncertainties on spectral line stacking
Maddox et al

Redshifts derived from optical spectroscopy and HI spectral line observations agree well, with a negligible systematic offset and a small distribution width.  With simulations, determine how the width of an ideal stacked HI profile depends on these redshift offsets, as well as larger z errors more appropriate for high z galaxy surveys.  The width of the stacked profile is dominated by the width distribution of the input individual profile when the z errors are less than the median width of the input profiles, and only when the z errors become large, ~150 km/s, do they significantly affect the width of the stacked profile.  The z accuracy can be achieved with moderate resolution optical spectra.  Provide guidelines for the number of spectra required for stacking to reach a specified mass sensitivity, given telescope and survey parameters, which will be useful for planning optical spectroscopy observing campaigns to supplement the radio data.

1305.6243
Astrochemistry: the issue of molecular complexity in astrophysical environments
De Becker

Overview of astrochemistry, exploring issue of formation of molecules of increasing complexity in particular physical conditions that deviate significantly from those in laboratories.  So far, about 170 molecules have been identified in ISM.  THe presence of this molecular diversity constitutes firm evidence that efficient formation processes are at work in ISM.  Note various astronomical environments and conditions (radiation fields, CRs, low densities, etc.).  Two approaches for molecular complexity: (1) growing complexity starting from the most simple chemical species in IS environments, (2) successive precursors of the most complex species commonly found on Earth, and in particular in our biochemistry.  

1305.6595
Paired galaxies with different activity levels and their supernovae
Nazaryan et al

SNe Ibc are located in pairs with significantly smaller difference of radial velocities between components than pairs containing SNe Ia and II.  Consider this as a result of higher SFR of these closer systems of galaxies.  SN types are not correlated with the luminosity ratio of host and neighbor galaxies in paris.  The orientation of SNe with respect to the preferred direction toward neighbor galaxy is found to be isotropic and independent of kinematical properties of the galaxy pair.  From 56 SNe located in pairs of galaxies with different levels of SF and nuclear activity.  The man distance of type II SNe from nuclei of hosts is greater by about a factor of 2 than that of type Ibc SNe.  

1305.6447
Can structure formation distinguish LCDM from non-minimal f(R) gravity?
Thakur, Sen

Non-minimally coupled f(R) gravity is an interesting approach to explain the late time acceleration of the Universe without introducing any exotic matter component in the energy budget of the Universe, but distinguishing such model with the concordance LCDM model using present observational data is a challenge.  Address whether it can be differentiated from growth of matter over-density g(z) from galaxy surveys.  BG cosmology is insufficient to distinguish different DE models.  Find functional form for f(R) which produces the BG cosmology in LCDM, then calculate the growth of matter over-density g(z) for such f(R) models, and compare with LCDM universe.  Use g(z) sigma_8(z) from different galaxy surveys to reconstruct behavior for g(z) and sigma_8(z) for both the non-minimally coupled f(R) gravity models as well as for the LCDM.  Results show that there is a small but finite window where one can distinguish the non-minimally coupled f(R) models with the concordance LCDM.

1305.6607
The bright end of the exo-Zodi luminosity function: disk evolution and implications for exo-Earth detectability
Kennedy, Wyatt

Present 12um warm dust ("exo-Zodi") LF around Sun-like stars, focussing on the dustiest systems that can be identified by WISE.  Detect 6 new warm dust candidates, 5 of which have unknown ages.  Bright warm dust is more common around young (<120 Myr) systems.  Show that a two component in situ model where all stars have initially massive warm disks and in which warm debris is also generated at some random time along the stars' MS lifetime, perhaps due to a collision, can explain the observations.  However, if all stars only have initially massive warm disks these would not be visible at Gyr ages, and random collisions on the MS are too infrequent to explain the high disk occurrence rate for young stars (neither component can explain the observations on their own).  Cannot rule out an alternative model in which comets are scattered from outer regions because the distribution of systems with the appropriate dynamics is unknown.  Predicts the fraction of stars with exo-Zodi bright enough to cause problems for future exo-Earth imaging attempts is at least ~10%, and is higher for populations of stars younger than a few Gyr.  Applies to old stars as well, because bright systems imply a population of fainter systems that were once bright but are now decaying through fainter levels.   ...  Hot dust in systems can have a cometary origin due to the quirks of the planetary dynamics.

1305.6811
Observation of the cosmic-ray shadow of the Moon with IceCube
IceCube Collaboration

Report observation of a significant deficit of CRs from the direction of the Moon with IceCube detector.  "Moon shadow" used to characterize the angular resolution and absolute pointing capabilities of the detector.  The detection is based on data taken in two periods before the completion of the detector: 2008-2009 with 40 strings, and 2009-2010 with 59 strings.  Using two independent analysis methods, the Moon shadow has been observed to high significance (>6 sigma) in both detector configurations.  THe observed location of the shadow center is within 0.2 degrees of its expected position when geomagnetic deflection effects are taken into account.  Measurement validates the directional reconstruction capabilities of IceCube.

1305.6847
Galactic dynamics using 1/r force without dark matter
Lo

As the title says: instead of 1/r^2 Newtonian, go to 1/r at galactic scales.  Explans galactic morphology and rotation without DM.  [But does it explain Hubble expansion?  Cosmology?]

1305.6859
Dark Matter
Peebles

Exploration of the nature of DM led by direct and indirect detection experiments, to be complemented by advances in the full range of cosmological tests, including judicious consideration of the rich phenomenology of galaxies.  The results may confirm ideas about DM already under discussion.  [An essay.]

1305.6620
Denoising observational data
Bourdin

Method that conserves most of the instrumental resolution and introduces as few methodical artifacts as possible searched.  Short review of different techniques given here, and a non-local averaging method is applied to Hinode magnetograms and G-band data.  

1035.6654
SZ observations with AMI of the hottest galaxy clusters detected in the XMM-Newton cluster survey
AMI consortium

15 of the apparently hottest XCS clusters that can be observed with AMI.  Detect SZ effect at high significance towards 3 of the clusters, and at lower significance for a further 2 clusters.  Remaining 10 clusters show no clear SZ signal.  Calculate mass and temperature estimates, while for all undetected clusters, determine upper limits on these parameters.  Find that large-scale mean temperatures derived from AMI SZ measurements (and the upper limits from null detections) are substantially lower than the XCS-basd core-temperature estimates.  For clusters detected in the SZ, the mean temperature is, on average, a factor of 1.4lower than temperatures from the XCS.  For clusters undetected in SZ, the average 68% upper limit on the mean temperature is a factor of 1.9 below the XCS temperature.

1305.6923
How to zoom: bias, contamination, and Lagrange volumes in multimass cosmological simulations
Onorbe, ... Bullock, ... Hahn

Performa a suite of multimass cosmolgocial zoom simulations of individual DM haloes and explore how to best select Lagrangian regions for resimulations without contaminating the halo of interest with low-resoluton particles.  Such contamination can lead to significant errors in the gas distribution of hydrodynamical simulations, as we show.  For a fixed Lagrange volume, find that the chance of contamination increases systematically with the level zoom.  In order to avoid contamination, the Lagrangian volume selected for resimulation must increase monotonically with the resolution difference between parent box and the zoom region.  Provide a simple formula for selecting Lagrangian regions (in units of the halo virial volume) as a function of the level of zoom required.  Also explore the degree to which a halo's Lagrangian volume correlates with other halo properties (concentration, spin, formation time, shape, etc.) and find no significant correlation.  There is a mild correlation between Lagrange volume and environment, such that halos living in the most clustered regions have larger Lagrangian volumes.  Nevertheless, selecting haloes to be isolated is not the best way to ensure inexpensive zoom simulations.  Explain how one can safely choose haloes with the smallest Lagrangian volumes, which are the least expensive to resimulate, without biasing one's sample.

1305.6924
Constraining the minimum luminosity of high redshift galaxies through gravitational lensing
Mashian, Loeb

Effects of GL on the source count of high z galaxies as projected to be observed by the Hubble Frontier Fields program and the JWST in the near future.  Modeling the lens as a singular isothermal sphere residing as a redshift of z_L=0.5, explore the radial dependence of the resulting magnification bias and how it varies with the velocity dispersion of the lens, the photometric sensitivity of the instrument, and the redshift of the background source population, and the minimum intrinsic Luminosity of the sources.  Find that gravitational lensing enhances the number of galaxies with redshifts z>10 detected in the angular region theta_E/2 < theta < 2 theta_E by a factor of 5 and 200 when observations are made with JWST and HST, respectively.  Furthermore, find that the bias is sensitive to the minimum intrinsic luminosity of galaxies, transitioning from positive to negative in certain cases when larger values of L_int are assumed.  In those cases where a transition does take place, the upper bounds on L_int to detect a positive magnification bias are 5e27 and 3e27 erg/s/Hz when observing galaxies with redshifts z>8 and z>10 respectively.  GL may therefore offer and alternative way of constraining the value of minimum L of high z galaxies by comparing source counts in blank fields against counts measured behind a FG lens.  

1305.6927
The Magellanic quasars survey. III. spectroscopic confirmation of 758 AGNs behind the Magellanic clouds
Kozlowski, ... Kochanek, .. et al

As the title says.  94% newly identified; 12 years of light curve since OGLE.

13035.6931
Structural evolution of early-type galaxies to z=2.5 in CANDELS
Chang, ... Rix, ... Bell, ... et al

Projected axis ratio measurements of 880 early-type galaxies at 1<z<2.5 selected from CANDELS are used to reconstruct and model their intrinsic shapes.  The sample is selected on the basis of multiple rest-frame colors to reflect low SF activity.  Demonstrate that these galaxies as an ensemble are dust-poor and transparent and therefore likely have smooth light profiles, similar to visually classified early-type galaxies.  Similar to their present-day counterparts, the z>1 early-type galaxies show a variety of intrinsic shapes; even at a fixed mass, the projected axis ratio distributions cannot be explained by random projection of a set of galaxies with very similar intrinsic shapes.  However, a two-population model for the intrinsic shapes, consisting of a triaxial, fairly round population, combined with a flat (c/a~0.3) oblate population, adequately describes the projected axis ratio distributions of both present-day and z>1 early-type galaxies.  Find that the proportion of oblate vs triaxial galaxies depends both on the galaxies' stellar mass, and (at a given mass) on redshift.  For present-day and z<1 early-type galaxies the oblate fraction strongly depends on the galaxy mass.  At z>1 this trend is much weaker over the mass range explored here (1e10-11 Msun), because the oblate fraction among massive galaxies was much higher in the past: 0.59 pm 0.1 at z>1, compared to 0.20 pm 0.02 at z~0.1.  In contrast, the oblate fraction among low-mass early-type galaxies (<1e10.5 Msun) increase toward the present, from 0.38pm0.11 at z>1 to 0.72pm0.06 at z=0.

1305.6966
The destruction of protogalaxies by Pop III supernovae: prompt chemical enrichment and supermassive black hole growth
Whalen et al

THe first primitive galaxies formed from accretion and mergers by z~15, and were primarily responsible for cosmological reionization and the chemical enrichment of the early cosmos.  But a few of these galaxies may have formed in the presence of strong UV fluxes that sterilized them of H2, preventing them from forming stars or expelling heavy elements into the IGM prior to assembly.  At masses of 1e8 Ms and virial temperatures of 1e4K, these haloes began to rapidly cool by atomic lines, perhaps forming 1e4-1e6 Ms Pop III stars and, later, the seeds of SMBH.  Modeled the explosion of a supermassive Pop III star in the dense core of a line-cooled protogalaxy with the ZEUS-MP code.  Find that the SN expands to a radius of 1kpc, briefly engulfing the entire galaxy, but then collapses back into the potential well of the DM.  Fallback fully mixes the interior of the protogalaxy with metals, igniting a violent starburst and fueling the rapid growth of a massive BH at its center.  The starburst would populate the protogalaxy with stars in greater numbers and at higher metallicities than in more slowly-evolving, nearby halos.  The SN remnant becomes a strong synchrotron source that can be observed with eVLA and eMERLIN and has a unique signature that easily distinguishes it from less energetic SN remnants.  Such explosions, and their attendant starbursts, may well have marked the birthplaces of SMBH on the sky.

1305.6982
Cluster probes of dark energy clustering
Appleby, Linder, Weller

Cold early DE, with a sound speed much smaller than the speed of light, can give a detectable signature.  Combining cluster abundances with CMB PS can determine the early dark energy fraction to 0.3% and distinguish a true sound speed of 0.1 from 1 at 99% confidence.  Project constraints on early DE from the Euclid cluster survey, as well as the DES, using both current and projected PLanck CMB data, and assess the impact of cluster mass systematics.  Also quantify the importance of DE perturbations, and the role of sound speed during a crossing of w=-1.

1305.7163
The hierarchical origins of observed galaxy morphology
Wilman, et al

Galaxies grow primarily via accretion-driven SF in disks and merger-driven growth of bulges.  These processes are implicit in SAM of galaxy formation, with bulge growth in particular relating directly to the hierarchical build-up of halos and their galaxies.  In this paper, consider several implementations of two SAM.  Focusing on implementations in which bulges are formed during mergers only, examine the fractions of elliptical galaxies and both passive and star-forming disk galaxies as functions of stellar and halo mass, for central and satellite systems.  This is compared to an observational cross-matched SDSS+RC3 z~0 sample of galaxies with accurate visual morphological classifications and M*>1e10.5 M_sun.  The models qualitatively reproduce the observed increase of elliptical fraction with stellar mass, and with halo mass for central galaxies, supporting the idea that observed ellipticals form during major mergers.  However, the overall elliptical fraction produced by the models is much too high compared with the z~0 data.  Since the "passive" -- i.e., non SF-ing -- fractions are approximately reproduced, and since the fraction which are SF disc galaxies is also reproduced, the problem is that the models overproduce ellipticals at the expense of passive S0 and spiral galaxies.  Bulge-growth implementations (tuned to reproduce simulations) which allow the survival of residual discs in major mergers still destroy too much of the disc.  Increasing the lifetime of satellites, or allowing significant disc regrowth around merger remnants, merely increases the fraction of SF disc galaxies.  Instead, it seems necessary to reduce the mass ratios of merging galaxies, so that most mergers produce modest bulge growth in disc-galaxy remnants instead of ellipticals.  [but major mergers can commonly result in disks... I read somewhere]