1810.01511
The leaky pipeline for postdocs: a study of the time between receiving a PhD and securing a faculty job for male and female astronomers
Flaherty
The transition between receiving a PhD and securing a tenure track faculty position is challenging for nearly every astronomer interested in working in academia. Here, use a publicly available database of recently higher faculty (the Astrophysics Job Rumor Mill) to examine the amount of time astronomers typically spend in this transitory state. Using these data as a staring point to examine the experiences of astronomy postdocs, find that the average time spent between receiving a PhD and being hired into a faculty position is 4.9±0.3 years, with female astronomers higgled on average 4.2±0.4 years after receiving a PhD while male astronomers are typically higgled after 5.3±0.4 years. Using a simple model of the labor market, attempt to recreate this gendered difference in time spent as postdoc. Rule out the role of the increasing representation of women among astronomy PhDs, as well as any bias in favor of higher female astronomers in response to efforts to diversify the faculty ranks. Instead, the most likely explanation is that female astronomers are leaving the academic labor market, at a rate that is 3-4 times higher than male astronomers. This scenario explains the distinct higher time distributions between male and female astronomers, as well as the measured percentage of female assistant professors, and the fraction of female applicants within a typical faculty search. These results provide evidence that more work needs to be done to support and retain female astronomers during the postdoctoral phase of their careers.
1810.01624
The XXL Survey XXV. Cosmological analysis of the C1 cluster number counts
Pacaud, et al
Present an estimation of cosmo parameters with clusters of galaxies. Constrain the Omega_m, sigma_8 and w parameters from a stand-alone sample of the X-ray clusters detected in the 50 deg^2 XMM-XXL survey with a well-defined selection function. Analyse the z distribution of a sample comprising 178 high S/N clusters out to a redshift of unity. The cluster sample scaling relations are determined in a self-consistent manner. In a LCDM model, the cosmology favored by the XXL clusters compares well with results derived from the Planck S-Z clusters for a totally different sample (mass/redshift range, selection biases, and scaling relations). However, with this preliminary sample and current mass calibration uncertainty, find no inconsistency with the Planck CMB cosmology. If the w parameter is relaxed, the Planck CMB uncertainties increase by a factor of ~10 and become comparable with those from XXL clusters. Combining the 2 probes allows constraints on Omega_m=0.316±0.060, sigma_8=0.814±0.054, and w=-1.02±0.20. This first self-consistent cosmo analysis of a sample of serendipitous XMM clusters already provides interesting insights into the constraining power of the XXL survey. Subsequent analysis will use a larger sample extending to lower confidence detections and include additional observable information, potentially improving posterior uncertainties by roughly a factor of 3.
1810.00995
Searches for gamma-ray lines and 'pure WIMP' spectra from dark matter annihilations in dwarf galaxies with H.E.S.S.
HESS collaboration
Dwarf spherical galaxies are among the most promising targets for detecting signals of DM annihilations. The HESS experiment has observed five of these systems for a total of about 130 hours. The data are re-analyzed here, and, in the absence of any detected signals, are interpreted in terms of limits on the DM annihilation cross section. Two scenarios are considered: i) DM annihilation into mono-energetic gamma-rays and ii) DM in the form of pure WIMP multiplets that, annihilating into all electroweak bosons, produce a distinctive gamma-ray spectral shape with a high-energy peak at the DM mass and a lower-energy continuum. For case i), upper limits at 95% CL of about <sigma v> <~ 3e-25 cm^3/s are obtained in the mass range of 400 GeV to 1TeV. For case ii), the full spectral shape of the models is used and several exploded regions are identified, but the thermal masses of the candidates are not robustly ruled out.
1810.02322
Dark Energy Survey Year 1 Results: Joint analysis of galaxy clustering, galaxy lensing, and CMB lensing two-point functions
Abbott, et al
Perform a joint analysis of the auto and cross-correlations between 3 cosmic fields: the galaxy density field, the galaxy weak lensing shear field, and the CMB WL convergence field. These 3 fields are measured using roughly 1300 sq. deg. of overlapping optical imaging data from first year observations of the DES and millimeter-wave observations of the CMB from both the SPT SZ survey and Planck. Present cosmo constraints from the joint analysis of the 2pt correlation functions between galaxy density and galaxy shear with CMB lensing. Test for consistency between these measurements and the DES-only 2pt function measurements, finding no evidence for inconsistency in the context of flat LCDM cosmological models. Performing a joint analysis of five of the possible correlation functions between these fields (excluding only the CMB lensing auto spectrum) yields S_8==sigma_8 sort(Omega_m/0.3) = 0.782+0.019-0.025 and Omega_m=0.260+0.029-0.019. Test for consistency between these five correlation function measurements and the Planck-only measurement of the CMB lensing auto spectrum, again finding no evidence for inconsistency in the context of flat LCDM models. Combining constraints from all 6 2pt functions yields S_8=0.776_0.014-0.021 and Omega_m=0.27+0.022-0.016. These results provide a powerful test and confirmation of the results from the first year DES joint-probes analysis.
1810.02342
Dark Energy Survey Year 1 results: tomographic cross-correlations between DES galaxies and CMB lensing from SPT+Planck
Omori, et al
Measure the cross-correlation between redMaGiC galaxies selected from the DES Year-1 data and gravitational lensing of the CMB reconstructed from SPT and Planck data over 1289 sq. deg. When combining measurements across multiple galaxy redshift bins spanning the redshift range of 0.15<z<0.90, reject the hypotheses of no correlation at 19.9 sigma significance. When removing small-scale data points where thermal SZ signal and non-linear galaxy bias could potentially bias the results, the detection significance is reduced to 9.9 sigma. Perform a joint analysis of galaxy-CMB lensing cross-correlations and galaxy clustering to constrain cosmology, finding Omega_m=0.276+0.029-0.030 and S8=sigma_8 sort(Omega_m/0.3) = 0.800+0.090-0.094. Also perform two alternate analysis aimed at constraining only the growth rate of cosmic structure as a function of z, finding consistency with predictions from the concordance LCDM model. The measurements presented here are part of a joint cosmological analysis that combined galaxy clustering, galaxy leaning and CMB lensing using data from DES, SPT and Planck.
1810.02353
Consistent cosmic shear in the face of systematics: a B-mode analysis of KiDS-450, DES-SV and CFHTLenS
Asgari, et al
Analyse 3 public cosmic shear surveys; KiDS-450, DES-SV and the CFHTLenS. Adopting the COSEBIs statistic to cleanly and completely separate the lensing E-modes from the non-lensing B-modes, detect B-modes in KiDS-340 and CCFHTLenS at the level of bout 2.7 sigma. For DES-SV detect B-modes at the level of 2.8 sigma in a non-tomographic analysis, increasing to a 5.5 sigma B-mode detection in a tomographic analysis. In order to understand the origin of these detected B-modes, measure the B-mode signature of a range of different simulated systematics including PSF leakage, random but correlated PSF modeling errors, camera-based additive shear bias and photometric z selection bias. Show that any correlation between photometric-noise and the relative orientation of the galaxy to the PSF leads to an ellipticity election bias in tomographic analysis. This work therefore introduces a new systematic for future lensing surveys to consider. Find that the B-modes in DES-SV appear similar to a superposition of the B-mode signatures from all fo the systematics simulated. The KiDS-450 and CFHTLenS B-mode measurements show features that are consistent with a repeating additive shear bias.
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