Day 123

Tuesday, all saints day here (holiday).  I still want to get more work done.  KiDS politics on the reduction pipeline could get a bit messy---Thomas doesn't want to "compete" with Astrowise, because he knows it's already better.  I have a lot of projects in hand, but I want to be involved with the WL systematic testing with Rachel, on the GREAT08/10 continuation.

1110.6436
The prediction method of similar cycles
Du, Wang


Propose concept of "degree of similarity" (eta) to describe parameters (e.g., maximum amplitude Rmax) of a solar cycle relative to a referenced one, and the prediction method of similar cycles further developed.  Two parameters (solar minimum Rmin and rising rate beta-a), a synthesis degree of similarity (eta-s) is defined as the weighted-average of the eta values around Rmin and beta-a with the weights given by the coefficients of determination of Rmax with Rmin and beta-a, respectively.  The monthly values of the whole referenced cycle can be predicted by averaging the corresponding values in the most similar cycles with the weights given by the eta-s values.  Cycles 14 and 10 are found to be the two most similar cycles of Cycle 24.  As an application, Cycle 24 is predicted to peak around Jan 2013 with a size of about Rmax=83 and end around 2019.


* What is the science in defining "similar cycles"?


1110.6538
Environment dependence of DM haloes in symmetron modified gravity
Winther, Mota, Li


Symmetron is one of three known mechanisms for screening a fifth-force, and thereby recovering GR in dense environments.  Effectiveness of screening depends on both the mass of the object and the environment it lies in.  Using high-resolution N-body simulations find a significant difference, which depends on the halos mass and environment, between lensing and dynamical masses of DM halos similar to f(R) modified gravity.  Symmetron can yield stronger signatures due to a freedom in the strength of the coupling to matter.


1110.6439
Collisions of inhomogeneous pre-planetesimals
Gereshauser, Speith, Kley


Carry out collisions of centimeter-sized dust aggregates of intermediate porosity, vary inhomogeneous distribution at fixed typical clump size; collision outcome categorized according to the four-population model [?].  Show inhomogeneous pre-planetesimals are more prone to destruction than homogeneous aggregates.  Even slight inhomogeneities can lower the threshold for catastrophic disruption.  For a fixed collision velocity, sizes of fragments decrease with increasing inhomogeneity.  Pre-planetesimals with an active collisional history tend to be weaker.  Possible obstacle to collisional growth, and needs to be taken into account in future studies of the coagulation scenario.


* maybe the temperature of the coagulates matters?


1110.6440
Extended excursion set approach to structure formation in Chameleon Models
Li, Efstathiou


* yuck.


Extend excursion set theory to incorporate environmental effects on structure formation; apply method to a chameleon model and calculate observables at various redshifts.  The method can be generalized to study other observables and other models of environmentall dependent interactions [what does this mean?].  Analytic methods described here can be useful in delineating which models deserve more detailed study with N-body simulations.


1110.6441
The rest frame UV to optical colors and SEDs of z~4-7 galaxies
Gonzalez, Bouwens, Labbe, Illingworth, Oesch, Franx, Magee


Derive SEDs of star-forming galaxies from the rest-frame UV to the optical over a wide luminosity range (M_1500~-21 to -18) from z~7 to 4.  Sample contains: ~400 z~4 galaxies to 36 z~7 galaxies.  Medan stacking enables the first comprehensive study of very faint high-z galaxies at multiple redshifts.  At z~4 the faint median-stacked SEDs reach to ~0.06 L* (z=4) and are combined with recently published results at high luminosity L>L* that extend to M_1500 ~ 23.  Use the observed SEDs and template fits to derive rest frame UV-to-optical colors (U-V) at all redshifts and luminosities.  Find: this color does not vary significantly with redshift at a fixed luminosity [well if you pick star-forming galaxies and no red ones, then yea]. The color does show a weak trend with luminosity, becoming redder at higher luminosities, most likely to dust.  At z>~5 find blue colors [3.6]-[4.5] ~ -0.3 mag that are most likely due to rest-frame optical emission lines contributing to the flux in the IRAC filter bandpasses.  The scatter across derived SEDs remains substantial, but results are most consistent with a lack of any evolution in the SEDs with redshift at a given luminosity.  Similarity of the SEDs suggests a self-similar model of evolution over a timespan from 0.7 Gyr to 1.5 Gyr that encompasses very substantial growth in the stellar mass density in the universe (from 4e6 to 2e7 Msun/Mpc^3).


1110.6442
The HST cluster supernova survey: VI. the volumetric Type Ia SNe rate
Barbary et al, for the Supernova Cosmology Project


Present measurement of SN Ia rate out to z~1.6 from the HST CSS survey.  Observations span 189 orbits with ACS; discovered 29 SNe, of which ~20 are SNe Ia.  12 are located in the foregrounds and backgrounds of the clusters targeted in the survey.  Using these new data, derive the volumetric SN Ia rate in four broad redshift bins, finding results consistent with previous measurements at z>1 and strengthening the case for a SN Ia rate that is equal to or greater than ~0.6e-4/yr/Mpc^3 at z~1, and flattening out at higher redshift.  Provide SN candidates and efficiency calculations in a form that makes it easy to rebin and combine these results with other measurements for increased statistics.  Compare the assumptions about host-galaxy dust extinction used in different high-z rate rate measurements, find different assumptions induce significant systematic differences between measurements.


1110.6445
A practical guide to the massive black hole cosmic history
Sesana


Review current understanding of massive black hole formation and evolution.  Overview relevance of MBHs in the hierarchical structure formation paradigm; discuss the main viable channels for seed BH formation at high z and for their subsequent mass growth and spin evolution.  The picture, where MBHs grow through merger triggered accretion episodes, acquiring mass while shining as quasars, is overall robust, but too simplistic to explain the diversity in MBH phenomenology.  Briefly discuss which future observations will help to shed light on the MBH cosmic history in the near future, paying particular attention to the upcoming gravitational wave window.


1110.6446
Star formation and environment in clusters up to z~2.2
Raichoor, Andreon


* Butcher-Oemler effect: a scientific hypothesis suggesting that the cores of galaxy clusters at intermediate redshift (z~0.3) contain a larger fraction of blue galaxies than do the cores of low redshift clusters (Butcher and Oemler 1978).  Studies show BO effect widespread in rich clusters at z>0.2, and is due to vigorous episodes of star formation in a subset of cluster members.  Appears to be confined to rich clusters, similar to Virgo.  (>95% of blue field galaxies brighter than bJ=22.5 are at redshifts less than z=0.5, verifying models predicting no luminosity evolution of the field galaxy population since z=1.  


Study star formation in clusters in a zphot~2.2 cluster.  use deep ugrizJHK to estimate photoz's.  Find no evindence of BO effect between z~2.2 and z~0 for galaxies more massive than 1.34e11 Msun.  [how can you do that with one cluster?]  Results show that present-day star formation-density relation is already in place at z~2.2.


1110.6479
Heavy sterile neutrinos, entropy and relativistic energy production, and the relic neutrino background
Fuller, Kishimoto, Kusenko


Explore implications of the existence of heavy neutral fermions (i.e., sterile neutrinos) for the thermal history of the early universe.  Consider sterile neutrinos with rest masses in the 100-500MeV range, with couplings to ordinary active neutrinos large enough to guarantee thermal and chemical equilibrium at epochs in the early universe with temperatures T>1 GeV, but in a range to give decay lifetimes from seconds to minute.  Such neutrinos would decouple early, with relic densities comparable to those of photons, but decay out of equilibrium, with consequent prodigious entropy generation prior to, or during, BBN.  Most of the ranges of sterile neutrino rest mass and lifetime considered are at odds with CMB limits on the relativistic particle contribution to energy density; but some sterile neutrino parameters can lead to an acceptable N_eff.  These parameter ranges are accompanied by considerable dilution of the ordinary background relic neutrinos, possibly an adverse effect on BBN, but sometimes fall in a range which can explain measured neutrino masses in some particle physics models.  A robust signature of these sterile neutrinos would be a measured N_eff not equal to 3 coupled with no cosmological signal for neutrino rest mass when the detection thresholds for these probes are below lab-established neutrino mass values.


* I didn't quite get all the signatures of the sterile neutrinos.  It seems like they exist under  several strict conditions in order to match observations.


1110.6484
Evidence for shocks as the origin of gamma-ray flares in blazars
Aller, Hughes, Aller, Marscher, Jorstad, Hovatta, Aller


Finding supports the idea that oblique shocks in the jet are a viable explanation for activity from the radio to the gamma-ray band in at least some gamma-ray flares.


1110.6491
A conservation-based method for simulating the inspiral of binary black holes
Meiron, Laor


New approach: impose conservation of total energy and angular momentum in scattering experiments, find dissipation forces that are exerted on the BH by the stars, and thus obtain decaying path of the binary from the classical dynamical friction regime down to subparsec scales.  Studied both equal mass and 10:1 mass ratio binaries under various initial conditions, show that while an equal mass binary stalls at a nearly circular orbit, a runaway growth of eccentricity occurs in the unequal mass case.  This effect reduces the timescale for BH coalescence through gravitational radiation to well below the Hubble time, even in spherical and gasless systems formed by dry mergers.


1110.6536
The effect of different observational data on the constraints of cosmological parameters
Gong, Gao, Zhu


BAO and WMAP7 alone does not constrain w well, but together with SN Ia help break denegeracies among the model parameters, and constrain w_a.  


1110.6857
The fundamental surface of quad lenses
Woldesenbet, Williams


In quadruply imaged lens system, the angular distribution of images around the lens center is completely described by three relative angles.  Show empirically that in the 3d space of these angels, spanning 180x180x90 degrees, quads from simple 2-fold symmetric lenses of arbitrary radial density profile and arbitrary radially dependent ellipticity or external shear define a realy invariant 3d surface.  Give fitting formula for the surface using SIS+elliptical lensing potential.  Various circularly symmetric mass distributions with shear up to 0.4 deviate from it by typically rms~0.1 deg, while elliptical mass distributions with ellipticity of up to 0.4 deviate by rms 1.5 deg.  The existence of a near invariant surface [is this relevant?  is there going to be lens with two-fold symmetry?] gives a new insight into the lensing theory and provides a framework for studying quads without any recourse to mass modeling.  As an illustration, show that about 3/4 of the observed galaxy-lens quads do not belong to this surface within observational error, and so require additional external shear or substructure to be modeled adequately.


* so it can tell if the lens for quad images has 2-fold symmetry.


1110.6872
Sgr A* flares: tidal disruption of astroids and planets?


Likely, if the central parsec of the MW has asteroid population per parent star  not too dissimilar from that around stars in the Solar neighborhood. (Sgr A* produces tiny flares that last only hours but occur daily.)


1110.6889
A new model for the Fermi-LAT Extragalactic gamma-ray background
Cavadini, Salvaterra, Haardt


Blasars account for 45% of the total Fermi-LAT EGB.  At low <10GeV and high >50GeV, the blazar contribution falls short to account for the observed BG light.  At E<10GeV, the extragalactic gamma-ray background can be fully explained by considering the additional contribution of star-forming galaxies, where at very high energies, where the absorption due to extragalactic background light dominates, the observed background calls for an additional unknown component.


1110.6735
Effect of the cosmological constant on the bending of light and the cosmological lens equation
Arakida, Kasai


First re-examine the motion of photon in the Schwartschild spacetime, and explicitly describe the trajectory of photon and deflection angle alpha up to the second order in G.  Then extend to the contribution of the cosmological constant Lambda in the Schwarzschild-deSitter or Kottler spacetime.  Contrary to previous arguments, (a) the cosmological constant does appear in the orbital equation of light, (b) bending angle of light alpha does not change its form even if Lambda != 0 since the contribution of Lambda is thoroughly absorbed into the definition of the impact parameter, and (c) the effect of Lambda is completely involved in the angular diameter distance D_A.


* want to read this and try to figure it out.  3 pages, no figure.

1110.6174

The nature of assembly bias - II. Observational properties

Lacerna, Padilla, Stasyszyn

Assembly-type bias: where old galaxies have a higher clustering amplitude at scales r>1Mpc than young galaxies of equal magnitude.  Definition of age: luminosity-weighted stellar age, increases the difference from 25% to a factor of 2 at r~2.5 Mpc.  In contrast, when using the definition based on the Dn4000 index, the clustering amplitude at large scales show a weaker signal-to-noise for the assembly bias detection.  In semi-analytic galaxies, the difference in clustering using the stellar age is similar at distances beyond 3Mpc, but overpredict the assembly bias found in SDSS at smaller scales.  .... measure crowding around objects that traces the assembly bias effect from neighbour galaxies in cylinders in contrast to a smooth density field.

Day 122

Monday.  Didn't get to see Aaron last night; he didn't get back home till 1:30am this morning.  Mayumi can use some help with cultural differences between Japanese (Asian) and European (Euro-American, as the Japanese call it) in how human relationship are expressed.


1110.6172
Mapping the galactic center with gravitational wave measurements using pulsar timing
Kocsis. Ray, Zwart

Examine nHz GW foreground of stars and BHs orbiting SgrA*. Cusp of stars and BHs generates a continuous GW spectrum below 40 nHz; individual BHs within 1mpc to SgrA* stick out in the spectrum at higher GW frequencies.  The GWs and gravitational near-field effects can be resolved by timing pulsars within a few pc of this region.  [How does this work?]  Observations with the SKA may be expecialy sensitive to intermediate mass black holes (IMBHs) in this region, if present.  A 100ns-10mus timing accuracy is sufficient to detect BHs of mass 1e3 Msun with pulsars at distance 0.1-1pc in a 3 yr observation baseline.  Unlike EM imaging techniques, the prospects for resolving individual objects through GW measurements improve closer to SgrA*, even if the number density of objects increases inwards steeply.  Scattering by the interstellar medium will pose the biggest challenge for such observations.


* What exactly is the pulsar measuring?  It should be showing modification in its pulsar signal time-of-arrival, due to the strong gravitational field.

1110.6173
On the origin of high energy correlations in gamma-ray bursts
Kocevski


Investigate origin of hte observed correlation between GRB's nuFnu spectral peak Kpk, and its isotropic equivalent energy Eiso through the use of population synthesis code to model the prompt gamma-ray emission from GRBs.  [what model of GRB is assumed here?  how are each measured?]  Using prescriptions for the distribution of prompt spectral parameters as well as the population's luminosity function and co-moving rate density, generate a simulated population of GRBs and examine how bursts of varying spectral properties and redshift would appear to a detector on Earth.  Find a strong observed correlation between the source frame Epk and Eiso for the detected population, despite the existence of only a weak and broad correlation in the original simulated population.  The energy dependence of gamma-ray detector's flux-limited detection threshold acts to produce a correlation between the source frame Epk and Eiso for a low luminosity GRBs, producing the left boundary of the observed correlation.  Conversely, very luminous GRBs are found at higher redshifts than the low luminosity ones due to the standard Malmquist bias, causing bursts in the low Epk, high Eiso regime to go undetected because their Epk values would be redshifted to energies at which most detectors become less sensitive.  This previously unexamined effect produces the right boundary of the observed correlation.  The origin of the observed correlation is a complex combination of the instrument's detection threshold, the intrinsic cutoff in the GRB luminosity function, and the broad range of redshifts over which GRBs are detected.  These simulations serve to demonstrate how selection effects caused by a combination of instrumental sensitivity and the cosmological nature of an astrophysical population can act to produce an artificially strong correlation between observed properties.


MPIfR Lunch Colloquium
Geodetic VLBI and the 100m telescope
Axel Nothagel


Geodetic, geophysical and astrometric results from VLBI (Very Long Baseline Interferometry) observations.

Day 121

Sunday.  Got a lot of work done yesterday (managed to get the gg lensing code running after including some fixes).  Aaron flies back from Vancouver tonight.  Hope to get the reply to the MNRAS referee report finished today.

1110.4107

Virial-to-optical velocity ratios of local disk galaxies from combined kinematics and galaxy-galaxy lensing

Reyes, Mandelbaum, Gunn, Nakajima, Seljak, Hirata

* whoa, it's one of mine.

* DM and baryonic mass are 'comparable' within the optical radius

Measure virial-to-optical velocity ratios of disk galaxies measured for disk galaxies at <z>=0.07 and with stellar masses 1e9 Msun < M* < 1e11 Msun.  The ratio of the circular velocity measured at the virial radius of the dark matter halo (~150 kpc) to that at the optical radius of the disk (~10 kpc) is a strong observational constraint: links galaxies to their DM haloes dynamically and constrains the total mass profile of disk galaxies over an order of magnitude in length scale.  For this measurement, combine V_vir derived from halo masses measured with gg lensing, with V_opt derived from the Tully-Fisher relation (TFR) from Reyes et al (2011).  Use similarly-selected galaxy samples from both the lensing and TFR analysis.  For three M_* bins with lensing-weighted mean stellar masses of 0.6, 2.7 and 6.5e10 Msun, find halo-to-stellar mass ratios M_vir/M_*=41, 23, and 26, with 1-sigma statistical uncertainties of around 0.1 dex, and V_vir/V_opt=0.79, 0.72, and 0.79 (Vopt/Vvir~1.3), with 1-sigma statistical uncertainties of around 0.05 in Vvir/Vopt, respectively.  Results suggest that the dark matter and baryonic contributions to the mass within the optical radius are comparable, if the dark matter halo profile has not been significantly modified by baryons.  The results obtained in this work will serve as inputs to and constraints on disk galaxy formation models, which will be explored in future work.  This paper presents a new an improved galaxy shape catalogue for weak lensing that covers the full SDSS DR7 footprint.  


1110.4370
Gravitationally consistent halo catalogs and merger trees for precision cosmology
Behroozi, Wechsler, Wu, Buscha, Klypin, Primack


New method for generating merger trees and halo catalogs.  Keeps track of and supplements "missing" haloes, for self-consistency.  Check for self-consistency, looks good.


1110.4372
The Rockstar phase-space temporal halo finder and the velocity offsets of cluster cores
Behroozi, Wechsler, Wu


New algorithm for identifying dark matter halos, substructure, and tidal features: adaptive hierarchical refinement of fof groups in six phase-space dimensions and one time dimension, which allows for robust tracking of substructure. Fast. Good recovery of halo properties.  Demonstrate conclusively that DM halo cores are not at rest relative to the halo bulk or satellite average velocities; have coherent velocity offsets across a wide range of halo masses and redshifts.  For massive clusters, the offsets can be up to 400 km/s at z=0, and even higher at high redshifts.  Code publicly available.


1110.4391
Discovery of a dissociative galaxy cluster merger with large physical separation
Dawson, Wittman, Jee, Gee, Hughes, Tyson, Schmidt, Thorman, Bradac, Miyazaki, Lemaux, Utsumi


Bullet cluster analog at z=0.5: collisional cluster gas has become separated fomr the collisionless galaxies and DM.  Identify cluster using optical and weak lensing observations as part of DLS.  Cluster is a dissociative merger.  System is at least 0.7Gyr since first pass-through.  


1110.4431
A grand rotation curve and DM halo in the MW galaxy
Sofue


Rotation curve of MW constructed, covering a wide range of radius (galactic center to 1Mpc); deconvolved into bulge, disk and halo components by least-squares fitting.  Dark halo component fits well with NFw density profile.  Fit yielded h=16.3 kpc and rho_0=7.37e-3 Msun/pc^3.  Local dark matter density near the sun at R_0=8 kpc is estimated to be 6.8e-2 Msun/pc^3.  Total mass inside the gravitational boundary of the galaxy at R~385 kpc (half distance to M31) is estimated to be M_h~9e11 Msun.  Stellar baryon fraction of 5%.  From the expected baryon fraction of local group, suggest baryons in the form of 1e6K gas fills the dark halo.  This may contribute to the observed X-ray background.


1110.4635
Optimized detection of shear peaks in WL maps
Marian, Smith, Hilbert, Schneider


Use multiply-scaled filters to detect shear peaks down to S/N of 3, and you'll do better in constraining cosmology.


1110.4659
The imprint of the relative velocity between baryons and dark matter on the 21-cm signal from reionization
Bittner, Loeb


Post-recombination streaming of baryons through dark matter keeps baryons out of low mass (<1e6 Msun) haloes coherently on scales of a few comoving Mpc.  Argued that this will have a large impact on the 21-cm signal before and after reionization, because it raises the minimum mass required to form ionizing sources.  Using semi-numerical code, show that the impact of the baryon streaming effect on the 21 cm signal during reionization (redshifts z approximately 7-20) depends strongly on the cooling scenario assumed for star formation, and the corresponding virial temperature or mass at which stars form.  For the canonical case of atomic hydrogen cooling at 1e4 Kelvin, the minimum mass for star formation is well above the mass of haloes that are affected by baryon streaming, and there are no major changes to existing predictions.  For the case of molecular hydrogen cooling, find reionization is delayed by a change in redshift of approximately 2 [from what reference redshift?], and that more relative power is found in large modes at a given ionization fraction.  But the delay in reionization is degenerate with astrophysical assumptions, such as the production rate of UV photons by stars.


* perhaps an interesting way to determine whether baryon streaming relative to DM affects the formation of first stars (ionization sources).


1110.4888
The effects of alignment and ellipticity on the clustering of galaxies
van Daalen, Angulo, White


* ignoring shapes will underestimate clustering on small (~2Mpc) scales, but it shouldn't affect BAO, or other large scale effects, probably {MG}


Effects of halo ellipticity and alignment with LSS on the galaxy correlation function.  The effect of disrupting the alignment with larger-scale structure is a ~2% decrease in galaxy correlation function around r=1.8Mpc/h; sphericalizing the ellipsoidal distributions of galaxies within haloes decreases the correlation function by up to 20% for r<1Mpc/h.  Similar relusts apply to power spectra and redshift-space correlation functions.  Models such as those based on HOD, which adopt a spherically averaged profile for the galaxy distributions within haloes, will therefore significantly underestimate the clustering on sub-Mpc scales.


* must be careful of using HOD to do model fitting on galaxy correlation functions!  {RN}

1110.4894
Gravitational lensing with 3d ray tracing
Killedar, Lasky, Lewis, Fluke


Distance-redshift relation suffers lensing-induced scatter due to (de)magnification due to WL by LSS.  This can be quantified by the magnification probability distribution; predicting requires ray-tracing simulations.  Standard, multiple thin-lens approximation is often used; to quantify the accuracy, developed code that performs ray-tracing without approximation.  The efficiency and accuracy of this computationally challenging approach improved by careful choices of numerical parameters; the results are analyzed for the behavior of the ray-tracing code in the vicinity of Schwarzschild and NFW lenses.  Preliminary comparisons are drawn with the multiple lens-plane ray-bundle method in the context of cosmological mass distributions for a source redshift of z=0.5.


* where the f*** are the results, man?  did they find the magnification probability distribution, or not?  I guess this was simply a code-testing paper, testing just around Schwartzschild and NFW lenses, showing "preliminary comparisons".

1110.4913
The impact of high spatial frequency atmospheric distortions on WL measurements
Heymans, Rowe, Hoekstra, Miller, Erben, Kitching, Van Waerbeke


Precise measurement of PSF across the imaging data important; want to model the high spatial frequency variation properly.  Analyze dense stellar fields imaged at the CFHT to quantify degree of high spatial frequency variation in ground-based imaging PSF and compare results to models of atmospheric turbulence.  Data shows anisotropic turbulence pattern with an orientation independent of the wind direction and wind speed.  Find the amplitude of the high spatial frequencies to decrease with increasing exposure time, as t^-0.5, and find negligibly small atmospheric contribution to the PSF ellipticity variation for exposure times t>180 seconds.  For future surveys analyzing shorter exposure data, anisotropic turbulence will need to be taken into account as the amplitude of the correlated atmospheric distortions becomes comparable to a cosmological lensing signal on scales less than 10 arcminutes.  Effect can be mitigated by correlating galaxy shear measured on exposures imaged with a time separation greater than 50 seconds, for which spatial turbulence patterns are uncorrelated.


* at least 50 second exposure, with multiple exposure to correlate, to minimize psf ellipticity due to atmospheric turbulence correlation; >180 second exposure to make the atmospheric contribution negligibly small.

Day 120

Saturday.  Lots of stuff to get done today, so I can take tomorrow off.  I also need to eat more fresh fruits and vegetables.  My skin looks so old with all the meat and thoroughly-cooked vegetables I've been eating.

1110.5903

Andromeda XXVIII: A dwarf galaxy more than 350 kpc from Andromeda

Slater, Bell, Martin

Discovery of a new dwarf galaxy, Andromeda-the-28th, using data from SDSS DR8, at distance 365 kpc separation.  650kpc away from the sun, absolute magnitude of M_V=-8.5, half-light radius of r_h=210 pc (similar to may other faint Local Group dwarfs).  Unable to determine whether star formation is going on, so don't know if it's a dwarf spheroidal or dwarf irregular.


1110.5904
Optical line emission in brightest cluster galaxies at 0<z<0.6: evidence for a lack of strong cool cores 3.5 Gyr ago?
McDonald


* Perseus A (NGC1275, Caldwell 24): a type 1.5 Seyfert galaxy located ~70 Mpc away.  BCG of the Perseus Cluster of galaxies.  Morphologically a type-cD galaxy.  Contains a massive network of spectral line emitting filaments--dragged out by rising bubbles of relativistic plasma generated by the central AGN.  Gas filaments are cooler than the surrounding intergalactic cloud--how do they persist?  How come it hasn't collapsed to form stars?  Possibly magnetic fields.
* cD galaxy: a subtype of type-D giant elliptical galaxy, which has a large halo of stars.  Found near the centers of some rich galaxy clusters.  ("central dominant galaxies", "supergiant ellipticals")


>30,000 optically-detected galaxy clusters in the range 0<z<0.6: combine these catalogs with the availability of optical spectroscopy of the brightest cluster galaxy from SDSS allows for the observation of evolution of optical line emission in BCGs over this redshift range.  A minimum fraction of BCGs with optical line emission is found at z~0.3, suggesting that complex, filamentary emission in systems (e.g. Perseus A) are a recent phenomenon.  Evidence for an upturn in the number of strongly-emitting systems is reported beyond z>0.3, hinting at an earlier epoch of strong cooling.  Compare evolution of emission line nebulae to the X-ray derived cool core fraction from the literature, and find overall agreement, with the exception that an upturn in strong CC fraction is not observed at z>0.3.  Overall agreement between the evolution of cool cores and optical line emission at low redshift suggests that emission-line surveys of galaxy clusters may provide an efficient method of indirectly probing the evolution of cool cores, and provide insights into the balance of heating and cooling processes at early cosmic times.


* but what about the "disagreement" at z>0.3, where line emission gets stronger, but CC fraction doesn't rise?  Isn't there concern that emission line do not necessarily correlate to existence of CC?

1110.5906
Andromeda XXIX: A new dwarf spheroidal galaxy 200kpc from Andromeda
Bell, Slater, Martin


Discovery of Andromeda-the-29th from SDSS DR8, and confirmed by Gemini North MOS imaging data, appears to be a dwarf spheroidal.  Sky separation is >15 degrees from M31, red-branch tip distance estimate of 730kpc (from the Sun), corresponding to 200kpc distance from M31, it's virial radius.  Absolute magnitude determined by comparison to Draco dwarf spheroidal is M_V=-8.3.  The XXIX's stellar populations appear very similar to Draco's; estimate metallicity for And XXIX of [Fe/H]~-1.8.  Half-light radius is 360pc, and its ellipticty is 0.35, typical of dwarf satellites of the MW and M31 at this magnitude range.

1110.5910
The clustering of X-ray selected AGN at z=0.1
Mountrichas, Georgakakis


Select AGNs at z~0.1 from XMM on SDSS, and cross correlate with the SDSS Main galaxy sample; inferred X-ray AGN auto-correlation function described by a power law with slope gamma~2.0.  Corresponding mass of the DM haloes that host X-ray AGN at z~0.1 is 1e13 Msun/h.  Comparison with high-z show that this mass scale is characteristic of moderate luminosity X-ray AGN out to z~1.  Split AGN sample by rest-frame color shows that X-ray sources in red hosts are more clustered than those associated with blue galaxies, in agreement with results at z~1.  Find host galaxies of X-ray AGN have lower stellar masses compared ot the typical central galaxy of a ~1e13Msun/h DM halo.  AGN hosts either have experienced less stellar mass growth compared to the average central galaxy of this halo mass, or a fraction of them are associated with satellite galaxies.


* taking correlation function of AGN is useful for galaxy physics, but not so much for cosmology, I think.


1110.5913
Dense gas without star formation: the kpc-sized molecular disk in 3C326N
Nesvabda, Boulanger, Lehnert, Guillard, Salome


Discovery of 3kpc disk of 1e9 Ms [???] of dense, warm H2 in the nearby radio galaxy 3C326 N, which shows no signs of on-going or recent star formation and falls a factor of 60 below the Schmidt-Kennicutt law.  Spectroscopy show ro-vibrational H2 lines across all of the disk, with irregular profiles and line ratios consistent with shocks.  Gas is highly turbulent and not gravitationally bound.  If Jet absent, then SF should be happening. Rapid H2 formation boosted by turbulent compression deemed possible with hydrosims, so propose that molecules formed from diffuse atomic gas in the turbulent jet cocoon.  Gas is not self-gravitating, so cannot form molecular clouds or stars while the jet is active, and is likely to disperse and become atomic again after the nuclear activity ceases.  [why? because it's too hot? once it's a molecule, what makes them become atomic again?]  Speculate that very low star-formation rates are to be expected under such conditions, provided that large-scale turbulence sets the gas dynamics in molecular clouds.  Results illustrate that jets may create large molecular reservours as expected in 'positive feedback' scenarios of AGN-triggered star formation, but that this alone is not sufficient to trigger star formation.


1110.5919
Asymmetric dark matter may alter the evolution of low-mass stars and brown dwarfs
Zentner, Hearin


Theories of stellar interiors with puddles of 4~10 GeV DM particles.  


1110.5920
Locations of satellite galaxies in the Two-degree field galaxy redshift survey
Agustsson, Brainered


Compute locations of satellite galaxies in 2dF using 2 selection criteria and 3 sources of photometric data.  Find satellites are located preferentially near the major axes of their hosts, and the anisotropy is detected at a highly significant level.  Locations of satellites that have high velocities relative to their hosts are statistically indistinguishable from locations of satellites that have low velocities relative to their hosts.  [why is this important?]  Satellites with passive star formation [what does this mean?] are distributed anisotropically about their hosts, while the locations of SF satellites are consistent with an isotropic distribution.  These two distributions are, however, statistically indistinguishable [gah].

Day 119

Friday.  Told Mayumi about Aaron.  I thought I gave a nice talk yesterday, but today, I am not so sure.  Being tired in the middle of a talk is not a good thing to do--must keep energy up during the talk.


1110.5514
Three QSOs acting as strong gravitational lenses
Courbin, Faure, Djorgovski, Rerat, Tewes, Meylan, Stern, Mahabal, Boroson, Dheeraj, Sluse


Found in SDSS, host galaxy masses comparable to the SLACS sample of early-type strong lenses.


1110.5528
Probing dark energy with Alpha shapes and Betti numbers
van de Weygaert, Pranav, Jones, Bos, Vegter, Edelsbrunner, Teillaud, Hellwing, Park, Hidding, Wintrraecken


Weblike patter in the distribution of galaxies and matter: scale dependent Betti numbers (formalize the topological information content of the cosmic mass distribution.  Does not fully quantify topology, but extends the information beyond genus and Euler characteristic.  Richer information, availability of fast algorithms to calculate them).  When measured as a function of scale, they provide a "Betti signature" for a point distribution that is a sensitive yet robust discriminator of structure.  Highly effective in revealing differences in structure arising in different cosmological models, and is exploited towards distinguishing between different dark energy models and may likewise be used to trace primordial non-Gaussianities.  


MPIfR Lunch Colloquium (Nov. 2, 13:00)
Geodetic VLBI and the 100m telescope
Axel Nothnagel


* Geodesy: branch of mathematic dealing with the shape and area of the earth, or large portions of it.


Primary results of geodetic and astrometric VLBI observations: radio telescope coordinates, earth rotation variations, and quasar positions.  Networks of radio telescope simultaneously observe quasars and other extra-galactic radio sources recording the noise patterns emitted by the radio sources.  Geodesists observe many quasars repeatedly for only 40-200 seconds each.  Recordings employed to determine group delay observables in a correlation and fringe fitting process. Data analysis provides variety of highly precise and unique geodetic, geophysical and astrometric results.  Radio source positions define a quasi-inertial reference frame, the only one which is available today.  Radio telescope coordinates and velocities are used to establish and maintain a terrestrial reference from for geodetic and geophysical studies.  Studies of tectonic stability in central Europe studied with Effelsburg 100m telescope.  The enormous size of the telescope requires a detailed analysis of its deformation characteristics.


1110.5738
Self-similar dynamical relaxation of dark matter haloes in an expanding universe
Lapi, Cavaliere


Advanced model of spherical collapse and accretion in an expanding Universe--investigate structure of CDM haloes.  Based on solving time-dependent equations for the moments of the phase-space distribution function in the fluid approximation; approach includes non-radial random motions, and an advanced treatment of both dynamical relaxation effects that takes place in the infalling matter: (1) phase-mixing associated to shell crossing, and (2) collective collisions related to physical clumpiness.  Find self-similar solutions for the spherically-averaged profiles of mass density rho(r), pseudo phase-space density Q(r) and anisotropy parameter beta(r).  Profiles agree with the outcomes of state-of-the-art N-body simulations in the radial range currently probed by the latter; provide specific predictions at smaller radii.  With the self-similar solutions, link the halo structure to its two-stage growth history, and propose the following picture: During the early fast collapse of the inner region dominated by a few merging clumps, efficient dynamical relaxation plays a key role in producing a closely universal mass density and pseudo phase-space density profiles; these are found to depend only weakly on the detailed shape of the initial perturbation and the related collapse times.  The subsequent inside-out growth of the outer regions feeds on the slow accretion of many small clumps and diffuse matter; thus the outsckirts are only mildly affected by dynamical relaxation but are more sensitive to asymmetries and cosmological variance.


* Sounds like it agrees with Neal Delal's halo picture (I want to compare them!).


1110.5634
Conceptual problems in cosmology
Vieira


How could philosophy help cosmologists?  Knowledge-building in cosmology should begin with visions of the reality, then taking technical form whenever concepts and relations in between are translated into a mathematical structure.  Mandatory that the meaning of such concepts be the same for all cosmologists, and any relationship among all of them be tested both logically as well as mathematically.  In other words, improbability of our universe assures to cosmologists a privileged degree of freedom for formulating interpretations and theories.  At the same time, demands for their formulations and conclusions to be considered in the light of data taken from astrophysical observations [i.e., actual, real-life data].  


* Are they stating the obvious?  (given that I didn't transcribe the first-half of this abstract...)

Day 118

Thursday.  Gave the talk today, I think I now have a grasp on how to give talks.  


MPIfR/AIfA Promotionskolloquium
The dusty, molecular envelopes of Red Supergiant stars: VY Canis Majoris as the Archetypal Example
Lies Verheyen


Maser emission of dusty envelopes surrounding red giant stars studied in 88 red supergiants associated with Galactic open clusters.  Detect SiO maser emission at 86 GHz towards 13 sources with the IRAM 30m telescope.  The maser observations allow us to determine the stellar line-of-sight velocity with high accuracy [how?  just like regular spectroscopy with emission lines?].  A comparison of the maser peak flux with previous detections at 43 GHz show that the 86 GHz maser is stronger in 10 out of the 12 red supergiants detected in both transitions.  [What's the relationship between the 43 and 86, aside that one is twice the other's frequency?]  Analysis of the colors indicates detections occur in the reddest sources, supporting a radiative pumping mechanism for the SiO maser.  Model VY CMa asymmetric nebula with 2d radiative transfer code to model the dust continuum spectrum and optical and near-IR images.  Find: VY CMa is surrounded by a dusty disk with surface density proportional to r^-1 which is observed under inclination angle of 55 degrees.  Dust has 1e-3 M_sun mass, and consists of a mixture of (metallic) Fe, Al2O3 (alumina), (Mg,Fe)2SiO4 (olivine, peridot, pretty!) and (Ca,Na)2(Al,Mg,Fe^2+)[(Al,Si)SiO7] (melilite, a solid solution).  The central star is best represented by a black body of 2800K.  The mass of VY CMa is 15 solar masses.  With an interferometer, observe selection of molecular transition in VY CMa's nebula: HCN(1-0), HCO+(1-0), SiS(5-4), NaCl(7-6), NaCl(8-7), SO2(3{1,3}-2{0,2}), SO2(16{2,14}-15{3,13}) and SO2(10{1,9}-10{0,10}).  The interferometric images show that different molecules trace different parts of the envelope.  NaCl is present exclusively in the spherical outflow, while SO2 is found in the bipolar outflow.  Reproduce observed emission by constructing a model of the envelope plus outflow.  The bipolar outflow has an opening angle of 120 degrees, a constant H2 density and the expansion velocity increases linearly from 15 km/s to 45 km/s.


Astronomisches Kolloquium (Oct. 28, 11:00)
The multiphase extraplanar medium in spiral galaxies
George Heald


Evolution of galaxy connected to environment.  Extraplanar region in spiral galaxies is the interface between the star-forming disk and the environment.  The structure and kinematics of the baryonic material in this interface region are vital clues to the relative importance of various processes, such as cold gas accretion and galactic fountains, in determining the history of galaxies.  The strength and morphology of the magnetic fields in these regions may also be crucial to understanding the connection to the intergalactic medium.  Hydrogen acccretion in local galaxies (HALOGAS) survey: deep edge-on spiral gas accretion WSRT observations; reveals the presence of kinematically lagging extraplanar gas, and counterparts to the MW's high velocity clouds. WSRT-SINGS survey: high-quality polarimaetric data for a partially overlapping galaxy sample: leads to a common model of the magnetic field morphology in spiral galaxies.  


1110.5635
Moving mesh cosmology: properties of gas disks
Torrey, Vogelsberger, Sijacki, Springel, Hernquist


Compare structural properties of galaxies formed in SPH GADGET vs. the moving-mesh code AREPO.  Both use identical gravity solvers and same sub-resolution physics, but use very different methods to track the hydrodynamic evolution of gas.  Permits: isolation of effects of hydro solver on formation and evolution of galactic disks.  Fit simulated gas disks with exponential profiles.  Find: cold gas disks formed using AREPO have systematically larger disk scale lengths and higher specific angular momenta than their GADGET counterparts.  Reason for difference: rooted in the inaccuracies of the SPH solver, and calls for a reassessment of commonly adopted feedback prescriptions in cosmological simulations.


* would the feedback prescriptions by Hopkins, Quataert, and Murray help?


1110.5636
Continuum removal in Halpha extragalactic measurements
Spector, Finkelman, Brosch


Point out important source of error in measurements of extragalactic H alpha emission, and suggest ways to reduce it.  Common procedure: take narrow-band and wide-band flux; subtract continuum from the narrowband.  Errors introduced by color effects: can lead to underestimates as large as 40% and overestimates as large as 10%, depending on the underlying galaxy's stellar population and the continuum-subtraction procedure used.  Errors may lead to biases in results of surveys, and to the underestimation of the cosmic star formation rate at low redshifts (the low z points in the Madau plot).  Use single colour measurement to significantly reduce these errors.


* interesting if it affects the Madau plot.


1110.5638
From star-forming spirals to passive spheroids integral field spectroscopy of E+A galaxies
Swinbank, Balogh, Bower, Zabludoff, Lucey, McGee, Miller, Nichol


* E+A galaxy: strong Balmer line absorption and weak OII emission.  "E" == spectra showing characteristics of stellar populations from elliptical galaxies; "A" == Balmer lines typical of spectra associated with "A" type stars.  A.k.a. "K+A" galaxies.


3d spectroscopy of 11 E+A galaxies, which suggests a recent burst of star-formation being triggered, but was subsequently abruptly ended.  Probe spatial and spectral properties of both the young (~1Gyr) and old (few Gyr) stellar populations.  Use H-delta equivalent widths to estimate burst masses be >10% by mass, also consistent with the SFH inferred from the broad-band SEDs.  On average the A-stars cover ~33% of the galaxy image, extending over 2-15 kpc^2, indicating that the characteristic E+A signature is a property of the galaxy as a whole and not due to a heterogeneous mixture of populations.  In ~50% of sample, A-stars, nebular emission, and continuum emission are not co-located, suggesting that the newest stars are forming in a different place than those that formed ~1Gyr ago, and that recent star-formation has occurred in regions distinct from the oldest stellar populations.  10/11 galaxies have dynamics that class them as "fast rotators" with magnitudes and dynamics comparable to local ellipticals and SO's.  Also find correlation between the spatial extent of the A-stars and dynamics: fastest rotators tend to have the most compact A-star populations, providing new constraints on models that aim to explain the transformation of later type galaxies into early types.  Show that there are no obvious differences between the line extents and kinematics of E+A galaxies detected in the radio (AGN) compared to non-radio sources, suggesting that AGN feedback does not play a dramatic role in defining their properties, or that its effects are short.


* A-stars lasts for... how many years?  


1110.5645
Far-infrared properties of Lyman break galaxies from cosmological simulations
Cen


* Lyman break galaxies: typically at z=3~4, uses Lyman break at 912A moving into UV/optical, and using UV/blue drop-outs to efficiently identify high-z objects.


AMR hydro simulations with ultra-high resolution (114h-1pc[?]) and large sample size (>3300 galaxies of stellar mass > 1e9 Msun), show how the stellar light of Lyman break galaxies at z=2 is distributed between optical/UV/FIR bands.  With a single scalar parameter for dust obscuration: can simultaneously reproduce the observed UV luminosity function for the entire range (3-100 Msun/yr) and extant FIR luminosity function at the bright end (>20Msun/yr).  Quantify that galaxies more massive or having higher SFR tend to have larger amounts of dust obscuration mostly due to a trend in column density and in a minor part due to a mass (or SFR)-metallicity relation.  Predict FIR luminosity function in the range SFR=1-100Msun/yr is a power law with a slope about -1.7.  Further predict that there is a "galaxy desert" at SFR (FIR) < 0.02 [...?] in the SFR(UV)-SFR(FIR) plane.  Detailed deistributions of SFR(FIR) at fixed SFR(UV) are presented.  Upcoming observations by ALMA should test this model.  If confirmed, it validates the predictions of the standard CDM model and has important [?] implications on the intrinsic SFR function of galaxies at high redshift.


* Is this discussion limited to the luminosity function of Lyman break galaxies only?  Is it talking about evolution into the z~2 range?


1110.5648
The spatial clustering of ROSAT all-sky survey AGNs III. Expanded sample and comparison with Optical AGNs
Krumpe, Miyaji, Coil, Aceves


Compare RASS vs SDSS AGN clustering; 0.07<z<0.50 range.  Meaaasure clustering amplitude through cross-correlation functions with SDSS galaxies, and derive the bias by applying a HOD model directly to the CCFs.  Find no difference in clustering of X-ray and optically-selected broad-line AGNs, as well as for samples with radio-detected AGNs are excluded.  This contrasts low z optically-selected narrow-line AGNs, where radio-loud AGNs are found in more massive halos than optical AGNs without a radio-detection.  [What does this imply?] The typical dark matter halo masses of our broad-line AGNs are 12.4-13.4, consistent with the halo mass range of typical non-AGN galaxies at low redshifts.  Find no significant difference between clustering if X-ray selected narrow-line AGNs and broad-line AGNs.  Confirm weak dependence of the clustering strength on AGN X-ray luminosity at a ~2 sigma level.  Finally, summarize the current picture of AGN clustering to z~1.5 based on three dimensional clustering measurements.


* states the facts on correlation, but doesn't state the implications or significance of these results.

Day 117

Wednesday.  Had 3 telecons yesterday: RCS2, gglens (Rachel), and cluster (Mitra).  Asked Daniela if she wanted to go see the Anime-as-an-Artform exhibition (I have a free ticket voucher, which she can have).  She said she'd go, and will organize if others want to go too.  Okonomiyaki last night was good--now I'm extremely hungry.


1110.5326
Hot Graphite Dust and the infrared spectral energy distribution of active galactic nuclei
Mor, Netzer


IR SED of AGN from Spitzer; 51 narrow-line Seyfert 1 galaxies and 64 broad-line Seyfert 1 galaxies using a three component model: clumpy torus, a dusty narrow line region (NLR) and hot pure-graphite dust located in the outer part of the broad line region (BLR) [why graphite?].  Fit on SF-subtracted SEDs using SF templates that take into account the entire range of possible host galaxy properties.  Find: mid-IR intrinsic emission of NLS1s and BLS1s are very similar regardless of AGN luminosity, with log wavelength downturn at around 20-25 um [what does this imply?].  Present a model of the hot dust component that takes into account the distribution of dust temperature within the clouds and their emission line spectrum; provides a very good fit to the observed near-IR continuum.  Most line emission in this component is dramatically suppressed, except MgII (2798A) and HeI lines that are still contributing significantly to the total BLR spectrum.  We calculate the covering factors of all the AGN components and show that the covering factor of the hot-dust clouds is about 0.15-0.35, similar to the covering factor of the torus, and is anti-correlated with the source luminosity and the normalized accretion rate.


* covering factor: presumably, the fraction of the AGN that is "covered" by the dust torus.


1110.5328
New limits on Early Dark Energy from the SPT
Reichardt, de Putter, Zahn, Hou


Strong upper limit on the early dark energy density of Omega_e < 0.018 at 95% confidence, a factor of three improvement over WMAP data alone.  Show: adding lower-redshift probes of the expansion rate to the CMB data improves constraints on the DE EoS, but not the early dark energy density.  Also explain how the small-scale CMB temperature anisotropy constrains early dark energy.


1110.5329
Slowly-rotating stars and BHs in dynamical Chern-Simons gravity
Ali-Haimoud, Chen


Chern-Simons (CS) modified gravity is an extension to general relativity (GR) in which the metric is coupled to a scalar field, resulting in modified Einstein field equations.  Solve equations numerically for slowly-rotating neutron stars and BHs.  Analytic solution for constant-density non-relativistic object also presented.  Cannot use BH solutions for stars, as previously assumed.  Compared to GR: (i) frame-dragging is reduced because potential is reduced at surface.  (ii) In stars, angular momentum is enhanced.  For large coupling strength, the near-surface dragging becomes screened, and far-zone enhancement saturate at maximum value.  From Gravity Probe B and LEGEOS satellites, a (weak) constraint set to the characteristic CS lengthscale: xi^1/4 <~ 1e8 km.  [what does this lengthscale characterize?]


1110.5331
Galaxy cluster strong lensing: image deflactions from density fluctuations along the line of sight
Host


Suggested explanation for SL position discrepancy (only accurate to within 1~few arcsec) is the additional perturbations of the path of the light ray caused by matter density fluctuations along the line of sight.  Calculate the statistical expectation value for the angular deflections caused by density fluctuations, given the matter power spectrum.  Find about 1 arcsec deflection is indeed possible; also find deflection angle of a particular image is expected to increase with source redshift [why?] and with the angular distance on the sky to the lens [that makes sense].  Images' expected defection angle are highly correlated (because they both pass through the same LSS).  Implies that LoS density fluctuations are asignificant and possibly dominant systematic for SL mass modeling and set a lower limit to how well a scluster mass model can be expected to replicate the observed image positions.  Discuss how the deflections and correlations should explicitly be taken into account in the mass model fitting procedure.  


1110.5335
Proton-Helium spetral anomaly as a signature of CR accelerator
Malkov, Diamond, Sagdeev


Proof of CR acceleration in SNR (supernova remnants) hinges on full consistency of acceleration theory with the observations: direct proof is impossible because of the orbit [CR trajectory] scrambling of CR particles.  PAMELA show deviation between helium and proton CR spectra that is inconsistent with the theory, since latter does not differentiate between elements of untrarelativistic rigidity.  This spectral difference is, in fact, a unique signature of the diffusive shock acceleration (DSA), if one considers initial (injection-) phase of DSA.  Collisionless plasma SNR shocks inject more He2+ relative to protons when they are stronger and so produce harder helium spectra.  The injection bias is due to Alfven waves driven by the more abundant protons, so the He2+ ions are harder to trap by these waves because of the larger gyroradii.  By fitting the p/He ratio to the PAMELA data, can bolster the DSA-case for resolving the century-old mystery of CR origin.


* anyone to verify or reject their claim?  anyone?


1110.5338
Toward a consistent picture for CRESST, CoGeNT and DAMA
Kelso, Hooper, Buckley


As the title says.  CoGeNT and CRESST-II consistent with each other and with CDMS-II, but tension with Xe-based experiments.  DAMA also compatible, but amplitude of observed modulations not quite as high as expected.  Potential resolve if tidal streams or other non-Maxwellian structures are present in the local distribution of DM.


1110.5339
Using CMB lensing to constrain the multiplicative bias of cosmic shear
Vallinotto


Constrain multiplicative bias by exploiting the cross-correlation between WL measurements from galaxy surveys and the ones obtained from high resolution CMB experiments.  Cross-correlation is hown to have the power to break the degeneracy between the normalization of the matter power spectrum and the multiplicative bias of cosmic shear, and to be able to constrain the latter to a few percent. 


* I want to read this.