Saturday. Sunday.
1311.5092
Testing metallicity indicators at z~1.4 with the gravitationally lensed galaxy CASSOWARY 20
James, .. Steidel, et al
All 5 estimates of metallicity in agreement within factor 2 uncertainty of each mouthed; shows very low C-to-O ratio. The ISM of CSWA 20 only partially covers the SF region as viewed, in particular, absorption lines from neutrals and first ions are exceptionally weak. Find evidence for large-scale outflows of ISM with speeds of up to 750 km/s, similar to the values measured in other high-z galaxies sustaining much higher rates of SF.
1311.5225
Generating merger trees for dark matter haloes: a comparison of methods
Jiang, van den Bosch
Halo merger trees describe the hierarchical mass assembly of dark matter haloes, and are the backbone for modeling galaxy formation and evolution. Merger trees constructed using MC algorithms based on extended PRess-Schechter (EPS) formation are complementary to those extracted from N-body simulations, and have the advantage that they are not trammeled by limited numerical resolution and uncertainties in identifying (sub) haloes and linking theme between snapshots. This paper compares multiple EPS-based merger tree algorithms to simulation results using 4 diagnostics: progenitor mass function (PMF), mass assembly history (MAH), merger rate per descendant halo, and the unevolved sub halo mass function (USMF). In general, algorithms based on spherical collapse yield major-merger rates that are too high by a factor of 2, resulting in MAHs that are systematically offset. Assuming ellipsoidal collapse solves most of these issues, but the particular algorithm investigated here that incorporates ellipsoidal collapse dramatically over predicts the minor-merger rate for massive haloes. The only algorithm in the comparison that yields MAHs, merger rates, and USMFs in good agreement with simulations, is that by Parkinson+ 2008. However, this is not a true EPS-based algorithm as it draws its progenitor masses from a PMF calibrated against simulations, rather than 'predicted' by EPS. Finally, emphasize that the benchmarks used to test the EPS algorithms are obtained from simulations and are hampered by significant uncertainties themselves. In particular, MAHs and halo merger rates obtained from simulations by different authors reveal discrepancies that easily exceed 50 percent, even when based on the same simulation. Given this status quo, merger trees constructed using the Parkinson+ algorithm are as accurate as those extracted from N-body sims.
1311.5226
Cosmological constraints from the anisotropic clustering analysis using BOSS DR9
Linder, Oh, Okumura, Sabiu, Song
Perform a full 2-d anisotropy analysis of galaxy clustering data, fitting in a substantially model independent manner the angular diameter distance D_A, Hubble parameter H, and growth rate ddelta/dln a without assuming a DE model. The results demonstrate consistently with lCDM expansion and growth, hence also testing GR. Also point out the interpretation dependence of the effective redshift, and its cosmological impact for next generation surveys.
1311.5238
Evidence for high-energy extraterrestrial neutrinos at the IceCube detector
IceCube collaboration
All-sky search for high-energy neutrino events interacting within the IceCube neutrino detector conducted between May 2010 and May 2012. Search follows up on the previous detection of two PeV neutrino events, with improved sensitivity and extended energy coverage down to approximately 30 TeV. 26 additional events observed, substantially more than expected from atmospheric backgrounds. Combined, both searches reject a purely atmospheric origin for the 28 events at the 4 sigma level. These 28 events, which include the highest energy neutrinos ever observed, have flavors, directions, and energies inconsistent with those expected from the atmospheric muon and neutrino backgrounds. These properties are, however, consistent with generic predictions for an additional component of extraterrestrial origin.
1311.5246
2MASS photometric redshift catalog: a comprehensive three-dimensional census of the whole sky
Bilicki, .. Peacock, .. et al
Key cosmological applications require the 3d galaxy distribution on the entire celestial sphere. These include measuring the gravitational pull on the Local Group, estimating the large-scale bulk flow and testing the Copernican principle. However, the largest all-sky redshift surveys --- the 2MRS and IRAS PSCz --- have median redshifts of only z=0.03 and sample the very local Universe. THere exist all-sky galaxy catalogs reaching much deeper --- SuperCOSMOS in the optical, 2MASS in the NIR and WISE in the mid-IR --- but these lack complete redshift information. At present, the only rapid way towards larger 3d catalogs covering the whole sky is through photometric redshift techniques. IN this paper, present the 2MASS photometric redshift catalog (2MPZ) containing 2 million galaxies, constructed by cross-matching 2MASS XSC, WISE and SuperCOSMOS all-sky samples and employing the artificial neural network approach (the ANNz algorithm), trained on such redshift surveys as SDSS, 6dFGS and 2dFGRS. The derived photometric redshifts have errors nearly independent of distance [how far? later it says median z ~ 0.1], with an all-sky accuracy of sigma_z=0.015 and a very small percentage of outliers. In this way, obtain z estimates with a typical precision of 12% for all the 2MASS XSC galaxies that lack spectroscopy. In addition, have made an easy effort towards probing the entire 3d sky beyond 2MASS, by pairing up WISE with SuperCOSMOS and training the ANNz on GAMA redshift data reaching currently to z_med~0.2. This has yielded photo-z accuracies comparable to those in the 2MPZ. These all-sky photo-z catalogs, with a median z~0.1 for the 2MPZ, and significantly deeper for future WISE-based samples, will be the largest and most complete of their kind for the foreseeable future.
1311.5255
The kinetic Sunyaev-Zel'dovich effect from the diffuse gas i the Local Group
Rubin, Loeb
LG of galaxies moves wrt CMB; free electrons in its gaseous halo should imprint large-scale non-primordial temperature shifts in the CMB via the kSZ effect. Model the distribution of gas in the LG halo and using its inferred velocity wrt the CMB, calculating the resulting kSZ signal from the diffuse LG medium. Find that it is dominated by a hot spot ~10 deg in size in the direction of M31, where the optical depth of free electrons is the greatest. By performing a correlation analysis, find no statistical evidence that the kSZ signal from model of the LG halo is embedded in the CMB temperature map measured by the Planck satellite. Constrain the amount of mass in the LG halo by limiting the kSZ temperature shift around the host spot to be smaller than the observed temperature shift in the Planck map. FInd the tightest constraints for models where the halo mass is highly concentrated, with the mass limited to 2-5e12 Msun depending on the value of the halo concentration parameter.
1311.5486
Evaluation of a College freshman diversity research program
Garner et al
Since 2005, Pre-Major in Astronomy Program (Pre-MAP) at UW has made a concentrated effort to recruit and retain underrepresented undergraduates in STEM. Evaluate Pre-MAP in the context of larger UW student population using UW's student database. Evaluate in terms of goals of recruiting a more diverse population than the University , and in terms of a higher fraction of students successfully completing degrees. Find that Pre-MAP serves a higher percentage of underrepresented minorities and equal percentages of women compared to entering freshmen classes at UW. Additionally, Pre-MAP has a higher percentage of degree completion with higher average GPA's and similar time to completing when compared to UW as a whole and other STEM majors, particularly with students that place into lower-level math courses.
1311.5489
The bright optical flash and afterglow from the Gamma-ray burst GRB 130427A
Vestrand et al
The optical light generated simultaneously with the x-rays and gamma-rays during a GRB provides clues about the nature of the explosions that occur as massive stars collapse to form BHs. Report a bright optical flash and fading afterglow from the GRB, and present a comparison with the properties of the gamma-ray emission that show correlation of the optical and >100 MeV photon flux light curves during the first 7k seconds. Attribute this correlation to co-generation in an external shock. The simultaneous, multi-color, optical observations are best explained at early times by reverse shock emission generated in the relativistic burst ejecta as it collides with surrounding material and at late times by a forward shock traversing the circumburst environment. The link between optical afterglow and >100 MeV emission suggests that nearby early peaked afterglows will be the best candidates for studying GRB emission at GeV/TeV energies.
1311.5492
The stellar-to-halo mass relation for Local Group galaxies
Brook et al
Contend that a single power law halo mass distribution is appropriate for direct matching to the stellar masses of observed LG dwarf galaxies, allowing the determination of the slope of the stellar mass-halo-mass relation for low mass galaxies. Errors in halo masses are well defined as the Poisson noise of simulated local group realizations, which is determined using constrained local universe simulations (CLUES). For the stellar mass range 1e7<M*<1e8 Msun, for which likely have a complete census of observed galaxies, find that the stellar mass-halo-mass relation follows a power law with slope of 3.1, significantly steeper than most values in the literature. The steep relation between stellar and halo masses indicates that LG dwarf galaxies are hosted by dark matter haloes with a small range of mass. Methodology is robust down to the stellar mass to which the census of observed LG galaxies is complete, highlighting the importance of pushing the completeness limit to lower masses and larger volumes.
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