1111.2043
Discovery of extended VHE gamma-ray emission from the vicinity of the young massive stellar cluster Westerlund 1
HESS collaboration
* Westerlund 1: a compact young star cluster in the MW galaxy--the most massive compact young star cluster known in the entire local group of galaxies. Contains a number of rare, evolved, high-mass stars.
* HESS: uses Cherenkov light from gamma-ray induced particle cascades in the Earth's atmosphere. One of the leading observatories studying very high energy gamma-ray astrophysics.
VHE (E>100 GeV) gamma ray observations to study particle acceleration processes in the vicinity of the young massive stellar cluster Wd1. Resolved wrt HESS PSF. Energy spectrum with an index of Gamma=2.19. Four possible objects coincident: the magnetar, the x-ray binary, the pulsar, and Wd1 itself (which contains the others). In a single-source scenario, Wd1 is the most likely one, where the hadronic parent population would be acceleratved within the stellar cluster. Also evidence for multi-source origin--maybe the pulsar.
1111.2044
The MW and other spiral galaxies
Hammer et al
It claims MW is unlike other spirals in SDSS (only 1.2% are like MW), unlike M31, which is more typical, in terms of its circular velocity (M_K, R_d, V_flat) observations. Speculate that it's probably because of its quiescent history since thick disk formation.
* But it doesn't say what's so different about the MW, in what manner, and why they reach this conclusion. ...oh, it's about 1-2 sigma off from the M,R,V relation. And it's already been established that there hasn't been a major merger at the MW recently (10-11 Gyrs). MW is off of Tully-Fisher relation--it's rotation is faster, compared to what is expected from M and R.
1111.2048
The MW's bright satellites as an apparent failure of LCDM
Boylan-Kolchin, Bullock, Kaplinghat
Aquarius sims show that the most massive subhalos in galaxy-mass DM halos in LCDM are grossly inconsistent with the dynamics of the brightest MW dwarf spheroidal galaxies. LCDM predicts at least ten subhalos with Vmax > 25 km/s, where all dwarf spheroidals observed have 12<Vmax<25 km/s. UV suppression mass??? it's exceeded back to z~10 for these subhalos. Suppression cannot be reproduced by LCDM based model. [...]
1111.2051
Two populations of X-ray pulsars produced b two types of supernovae
Knigge, Coe, Podsiadlowski
Majority of neutron stars produced by two types of SNe: (1) Fe-core collapse supernovae, high-mass star develops a degenerate Fe core that exceeds the Chandrasekhar limit. (2) electron-capture supernovae, associated with the collpase of a lower-mass O-Ne-Mg core as it loses pressure support owing to the sudden capture of electrons by Ne and/or Mg nuclei. These two have been hard to distinguish. Report that a large, well-known class of neutron-star-hosting X-ray pulsars is actually composed of two distince sub-populations with different characteristic spin periods, orbital periods, and orbital eccentricities. The Be/X-ray binaries contains neutron stars that accrete material from a more massive companion star. The two sub-populations are most probably associated with the two distinct types of neutron-star-forming SNe, with electron-capture SNe preferentially producing system with short spin period, short orbital periods and low eccentricity. The split between the two sub-populations is clearest in the distribution of the logarithm of spin period, which is not predicted from theory.
1111.2058
Ubercalibration of the Deep Lens Survey
Wittman, Ryan, Thorman
Describe the internal photometric calibration of the DLS (5 fields by two observatories). Apply "ubercal" approach of SDSS, derive flatfield corrections for all observing runs. Correction of order 0.13 mag in z, and half of that in BVR. Application of correction reduces spatial non-uniformities in corrected exposures to the 0.01-0.02 mag level. Some differences with SDSS discussed.
1111.2059
The evolution of the baryon distribution in the universe from cosmological simulations
Durier, deFreitas Pacheco
Presently most of baryons are in warm-hot intergalactic medium (WHIM, about 43%), while at z=2.5 most of baryons constitute the diffuse medium (74%). Stars and cold gas in galaxies represent only 14% of the baryons at z=0. For z<4 about half of the metals are locked into stars, while fraction present in the WHIM and in the diffuse medium [what's the difference between the two?] increases with decreasing redshift: from 4 to 22% (WHIM) from z=2.5 to 0, 0.6% to 4% in diffuse. Enrichment due essentially to turbulent diffusion mechanism associated to mass motions driven by SNe explosions. At z=0, simulated blue galaxies show correlation of the O abundance in the cold gas with luminosity of the galaxy that agrees well with data derived from HII regions.
1111.2136
Comparison of the diffuse Halpha and FUV continuum backgrounds: on the origins of the diffuse Halpha background
Seon et al
Propose scenario where H alpha BG at high latitudes mostly composed of two components, H alpha photons produced by in-situ recombination at the ionized regions around late OB stars and dust scatter light of the H-alpha photos originated from late OB stars.
* in any case, the Halpha is coming from OB stars.
1111.2214
Observational constraints on the averaged universe
Clarkson, Clifton, Coley, Sung
Universe is not completely isotropic, and this can decouple the geometrical spatial curvature term in the metric from the dynamical spatial curvature in the Friedmann equation. Find only the geometrical spatial curvature is tightly constrained; ability to constrain DE dynamics severely impaired.
* should we take this seriously? Is this a real problem?
1111.2275
DM seeding and the kinematics and rotation of neutron stars
Perez-Garcia, Silk
DM (accreted from galactic halo in the inner regions of NS) self-annihilation may affect the [NS's] kinematical properties, e.g., velocity kicks and rotation patterns. Find: if a stable long-loved single or multiple strangelet off-center seed forms, there is an associated change in momentum and torque that may affect the kinematical observables of the star.
1111.2331
Does the hubble redshift flip photons and gravitons?
Edwards
* The redshifted photons "lose energy". that's because the universe is expanding, and not because its' been converged to gravitons.
1111.0989
Weak lensing mass estimates of galaxy groups and the LoS contamination
Spinelli, Seitz, Lerchster, Brimioulle, Finoguenov
Use COSMOS mock shear data to study the shear profile of 165 groups, and investigate the level at which the neighbouring groups can enhance or suppress the shear signal from the main halo. Expected shear field calculated assuming that the haloes follow NFW density profiles [which is not true! There is always individual variety]. On average, the S/N for a detection of the main halo is affected by ~15% * sqrt(ngal/30) wrt the S/N the same halo if it were isolated in the sky. Groups with neighbors that are close in projected distance (<1') are the most affected, but haloes located at larger angular distances also case measurable shear signal (e.g., "uncorrelated LSS"). The average bias in the mass excess estimate of individual groups that is introduced by the external haloes is zero with an rms of 6-72%, depending on the aperture size used. The average uncertainty introduced by LSS is sigma_{gamma_t}~0.006 per component for an aperture size of ~5', which corresponds to 1.8% of the one-component intrinsic ellipticity value. This large scale structure noise error becomes equal to intrinsic ellipticity noise if there are measurements for ~3000 galaxies within a certain aperture, a number that is already achieved by current deep surveys such as COSMOS.
1111.1004
Constraints on modified gravity from SZ cluster surveys
Mak, Pierpaoli, Schmidt, Macellari
Use Fisher matrix approach and adopt self-calibration for mass-observable scaling relation to investigate SZ cluster survey's power of constraining f(R) gravity. Effects should be seen in the mass function, halo bias, matter power spectrum, and mass-observable relation. Number counts only with Planck will reduce fR0 upper limit constraint by a factor of 4; with cluster power spectrum, can push the limit further where number counts don't have constraining power (due to chameleon screening mechanism). Self-calibration mildly worsens constraints, but this depends strongly on the mass threshold of the cluster samples.
1111.1070
Magnificent Magnification: exploiting the other half of the lensing signal
Huff, Graves
Use fundamental plane relation to measure magnification (lensing affects apparent size, but not surface brightness). The "photometric fundamental plane" replaces velocity dispersions with photometric galaxy properties, thus obviating the need for spectroscopic data. Present first detection of magnification on SDSS data. Derived magnification signal is comparable to methods using gravitational shear. Suppress dominant sources of systematic error and discuss modest improvements that may allow this method to equal or even surpass the S/N achievable with shear. Some of the dominant sources of systematic error are substantially different from those of shear-based techniques. Combining the two techniques addresses the major weaknesses of each and provides a substantial improvement over either method used in isolation. Magnification [can] become a necessary measurement tool for the large ground-based surveys intending to measure gravitational lensing.
1111.1184
Testing cosmology with extreme galaxy clusters
Harrison, Coles
Use Extreme value statistics (EVS) to construct confidence regions in the mass-redshift plane for the most extreme objects expected in the universe. Method can potentially rule out concordance cosmology, but also allows to differentiate between alternative models of enhanced structure formation. Compare theoretical prediction with observations, placing currently observed high and low redshift clusters on a mass-redshift diagram and find (if using full sky) that none are in significant tension with concordance cosmology.
1111.1004
Constraints on modified gravity from SZ cluster surveys
Mak, Pierpaoli, Schmidt, Macellari
Use Fisher matrix approach and adopt self-calibration for mass-observable scaling relation to investigate SZ cluster survey's power of constraining f(R) gravity. Effects should be seen in the mass function, halo bias, matter power spectrum, and mass-observable relation. Number counts only with Planck will reduce fR0 upper limit constraint by a factor of 4; with cluster power spectrum, can push the limit further where number counts don't have constraining power (due to chameleon screening mechanism). Self-calibration mildly worsens constraints, but this depends strongly on the mass threshold of the cluster samples.
1111.1070
Magnificent Magnification: exploiting the other half of the lensing signal
Huff, Graves
Use fundamental plane relation to measure magnification (lensing affects apparent size, but not surface brightness). The "photometric fundamental plane" replaces velocity dispersions with photometric galaxy properties, thus obviating the need for spectroscopic data. Present first detection of magnification on SDSS data. Derived magnification signal is comparable to methods using gravitational shear. Suppress dominant sources of systematic error and discuss modest improvements that may allow this method to equal or even surpass the S/N achievable with shear. Some of the dominant sources of systematic error are substantially different from those of shear-based techniques. Combining the two techniques addresses the major weaknesses of each and provides a substantial improvement over either method used in isolation. Magnification [can] become a necessary measurement tool for the large ground-based surveys intending to measure gravitational lensing.
1111.1184
Testing cosmology with extreme galaxy clusters
Harrison, Coles
Use Extreme value statistics (EVS) to construct confidence regions in the mass-redshift plane for the most extreme objects expected in the universe. Method can potentially rule out concordance cosmology, but also allows to differentiate between alternative models of enhanced structure formation. Compare theoretical prediction with observations, placing currently observed high and low redshift clusters on a mass-redshift diagram and find (if using full sky) that none are in significant tension with concordance cosmology.
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