Day 472

Wednesday.
1307.5324
A search for fast optical transients in the Pan-STARRS1 medium-deep survey: M Dwarf Flares, Asteroids, Limits on Extragalactic rates, and implications for LSST
Berger, ... et al

Present a search for fast optical transients (~0.5 hr - 1 day) using repeated observations of the Pan-STARRS1 MDS fields.  Consecutive g/r-band observations, 16.5 min in each filter, by requiring detections in both bands, with non-detections on preceding and subsequent nights.  Identify 19 transients <22.5 mag (S/N>10).  Of these, 11 exhibit quiescent counterparts in the deep PS1/MDS templates identified as M4-M9 dwarfs.  The remaining 8 transients exhibit a range of properties indicative of main-belt asteroids near the stationary point of their orbits.  With identifications for all 19 transients, place an upper limit of R_FOT(0.5hr)<0.12 deg^-2 /day (95% CL) on the sky-projected rate of extragalactic fast transients at <22.5 mag, a factor of 30-50 times lower than previous limits; the limit for a timescale of ~day is R_FOT<2.4e-3 deg^-2 /day.  To convert these sky-projected rates to volumetric rates, explore the expected peak luminosities of fast optical transients powered by various mechanisms, and find that non-relativistic events are limited to M~-10 mag (M~-14 mag) for a timescale of ~0.5 hr (~day), while relativistic sources (GRBs, etc) can reach much larger luminosities.  The resulting volumetric rates are <13 (-10mag), <0.05(`14mag) and <1e-6 Mpc^-3 /yr (-24 mag), significantly above the nova, SNe, and GRB rates, respectively, indicating that much larger surveys are required to provide meaningful constraints.  Motivated by the results of the search, discuss strategies for identifying fast optical transients in the LSST main survey, and reach the optimistic conclusion that the veil of FG contaminants can be lifted with the survey data, without the need for expensive follow-up observations.
1307.5326
The M-sigma relation in simulations of isolated and merging disk galaxies with kinetic or thermal AGN feedback
Barai, Viel, Murante, Gaspari, Borgani

Two modes of coupling the feedback energy from a central AGN to the neighboring gas in galaxy simulations: kinetic - velocity boost, and thermal - heating.  Formulate kinetic feedback models for energy-driven wind (EDW) and momentum-driven wind (MDW), using two free parameters: feedback efficiency epsilon_f, and AGN wind velocity v_w.  New algorithm in SPH code GADGET-3 to prevent the expansion of a hole in the gas distribution around the BH.  Perform simulations of isolated evolution and merger of disk galaxies, of MW mass as well as lower and higher masses.  Find that in the isolated galaxy BH kinetic feedback generates intermittent bipolar jet-like gas outflows.  Infer that current prescriptions for BH subgrid physics in galaxy simulations can grow the BH to observed values even in an isolated disk galaxy.  The BH growth is enhanced in a galaxy merger.  Comparing the [M_BH-sigma_star] relation obtained in simulations with observational data, conclude that it is possible to find parameter sets for a fit in all the models, except for the case with MDW feedback in a galaxy merger, in which the BH is always too massive.  The BH thermal feedback implementation of Springel, DiMatteo & Hernquiest (2005) within the multiphase SF model is found to have negligible impact on gas properties; and the effect claimed in all previous studies is attributed to gas depletion around the BH by the creation of an artificial hole.  The BH mass accretion rate in simulations exhibit heavy fluctuations.  The SFR is quenched with feedback by removal of gas.  The CGM gas at galactocentric distances (20-100)/h kpc are found to give the best metallicity observational diagnostic to distinguish between BH models.  

1307.5374
Solar activity during two millennia as estimated from annual tree rings
Muraki et al

As the title says.  Solar maximum and minimum global effect was 0.17 pm 0.01K, but at 40N/S, maximum effect of 0.5K.  Look for trees with this latitude: find two cycles (12 and 25 years) during the Maunder minimum in the annual growth rate.  Evidence of solar activity found in all samples.  Discovered a correlation between Swiss glacier fluctuation and the growth rate of the Yaku tree ring.

1307.5395
Dual haloes and formation of early-type galaxies
Park, Lee

Present a determination of the 2d shape parameters of the blue and red globular cluster systems (GCSs) in a large number of elliptical galaxies and lenticular galaxies (ETGs).  Use a  homogeneous data set of the globular clusters in 23 ETGs from HST.  The position angles of both blue and red GCSs show a correlation with those of the stellar light distribution, showing that the major axes of the GCSs are well aligned with those of their host galaxies.  However, the shapes of the red GCSs show a tight correlation with the stellar light distribution as well as with the rotation property of their host galaxies, while the shapes of the blue GCSs do much less.  These provide clear geometric evidence that the origins of the blue and red globular clusters are distinct and that ETGs may have dual haloes: a blue (metal-poor) halo and a red (metal-rich) halo.  These two haloes show significant differences in metallicity, structure, and kinematics, indicating that they are formed in two distinguishable ways.  The red halos might have formed via dissipational processes with rotation, while the blue haloes are through accretion.

1307.5637
ASTROSAT: some key science prospects
Paul

ASTROSAT is a satellite designed for Optical/UV and a broad X-ray energy range.  With 4 X-ray instruments and a pair of UV-Optical telescopes, ASTROSAT will provide unprecendented opportunity for simultaneous multi-wavelength observations, of highly variable sources (X-ray binaries and AGN).  Largest effective area in the hard X-ray compared to all previous X-ray missions, will enable high time resolution X-ray measurements in the 2-80 keV band with moderate energy resolution.  Here, give a brief summary of the payload characteristics of ASTROSAT, and discuss the main science.  Possibility of aitding gravitational wave experiments.

1307.5639
A sub-parsec resolution simulation of the Milky Way: global structure of the ISM and properties of molecular clouds
Renaud, .. Dekel, et al

Resolution of 0.05pc, hydro-sim, with a self-consistent description of the galaxy comprising live stellar and DM dynamics.  Model: SF and stellar feedback through photo-ionization, radiative pressure and SNe blasts.  Resolution fo the simulation allows to probe the structure of the ISM down to the formation sites of individual stars, at subparsec resolution for a few cloud lifetimes, and at 0.05 pc for about a cloud crossing time.  IN the full galactic context, turbulence cascade and gravitation from the kpc scales are de facto included in smaller structures like molecular clouds, without having to add them artificially.  In this first paper of a series, present the global structures of the ISM.  In particular, the formation of a bar influences the dynamics of the central ~100 pc by creating resonances that regulate the fueling of the central black hole.  At larger radii, the spiral arms host the formation of regularly spaced clouds: beads on a strong and spurs from gravitational and KH instabilities, respectively.  These instabilities pump turbulent energy in the gas, generally in the supersonic regime.  Because of asymmetric drift due to increased velocity dispersion of young stars compared to gas, and to galactic rotation, the SNe explode outside of their dense gaseous nursery, which diminishes the effect of stellar feedback on the structure of clouds.  The evolution of gas clouds is thus mostly due to fragmentation and gas consumption, regulated mainly by supersonic turbulence, while feedback plays a less important role.

1307.5830
Detection of B-mode polarization in the cosmic microwave background with data from the south pole telescope
Hanson, Hooever, et al

Gravitational lensing of the CMB generates a curl pattern in the observed polarization.  This "B-mode" signal provides a measure of the projected mass distribution over the entire observable Universe and also acts as a contaminant for the measurement of primordial gravity-wave signals.  In this letter, present the first detection of gravitational lensing B modes, using first-season data from the polarization-sensitive receiver on the SPTpol.  Construct a template for the lensing B-mode signal by combining E-mode polarization measured by SPTpol with estimates of the lensing potential from a Herschel-SPIRE map of the cosmic IR background.  Compare this template to the B-modes measured directly by SPTpol, finding a non-zero correlation at 7.7 sigma significance.  The correlation has an amplitude and scale-dependence consistent with theoretical expectations, is robust with respect to analysis choices, and constitutes the first measurement of a powerful cosmological observable.

1307.5842
The same frequency of planets inside and outside open clusters of stars
Meibom, et al

Most stars and their planets form in open clusters.  Over 95% of such clusters have stellar densities too low (<100 stars/parsec^3) to withstand internal and external dynamical stress and fall apart within a few 100 million years.  Older open clusters have survived by virtue of being richer and denser in stars (1000 to 10k per cubic parsec) when they formed.  Such clusters represent a stellar environment very different from the birthplace of the Sun and other planet-hosting field stars.  So far more than 800 planets have been found around Sun-like stars in the field.  THe field planets are usually the size of Neptune or smaller.  In contrast, only four planets have been found orbiting stars in open clusters, all with masses similar to or greater than that of Jupiter.  Report observations of the transits of 2 Sun-like stars by planets smaller than Neptune in the billion-year-old open cluster NGC6811.  This demonstrates that small planets can form and survive in a dense cluster environment, and implies that the frequency and properties of planets in open clusters are consistent with those of planets around field stars in the Galaxy.