Friday.
1805.05481
Image simulations for gravitational lensing with SkyLens
Plazas, Meneghetti, Maturi, Rhodes
Present the latest version of the ray-tracing simulation code Skylens, which can be used to develop image simulations that reproduce SL observations by any mass distribution with a high level of realism. Improvements of the code with respect to previous versions include the implementation of the multi-lens plane formalism, the use of denoised source galaxies from the Hubble eXtreme Deep Field, and the simulation of substructures in lensed arcs and images, based on a morphological analysis of bright nearby galaxies. Skylens can simulate observations with virtually any telescope. Present examples of space- and ground-based observations of a galaxy cluster through WFC/ACS (HST), NIC (JWST), WFI (WFIRST), HSC (Subaru), and the VIS (Euclid).
1805.05741
Search for $\gamma$-ray line signals from dark matter annihilations in the inner Galactic halo from ten years of observations with H.E.S.S
H.E.S.S. Collaboration
Spectral lines are among the most powerful signatures of DM annihilation searches in very high-energy gamma rays. The central region of the MW halo is one of the most promising targets given its large amount of DM and proximity to Earth. Report on a search for a mono energetic spectral line from self-annihilations of DM particles in the energy range from 300 GeV to 70 TeV using a 2d maximum likelihood method taking advantage of both the spectrand and spatial features of signal versus background. The analysis makes use of GC observations accumulated over 10 years with the HESS array of ground-based Cherenkov telescopes. No significant gamma-ray excess above the background is found. Derive upper limits on the annihilation cross section <sigma_v> for mono energetic DM lines at the level of ~4e-28 cm^3 /s at 1TeV, assuming an Einasto DM profile for the MW halo. For a DM mass of 1TeV, they improve over the previous ones by a factor of 6. The present constraints are the strongest obtained so far for DM particles in the mass range 300 GeV-70 TeV. Ground-based gamma-ray observations have reached sufficient sensitivity to explore relevant velocity-averaged cross sections for DM annihilation into 2 gamma-ray photons at the level expected from the thermal relic density for TeV DM particles.
1805.06479
GalWeight: a new and effective weighting technique for determining galaxy cluster and group membership
Abdullah, Wilson, Klypin
Introduce GalWeight, a new technique for assigning galaxy cluster membership. This technique is specifically designed to simultaneously maximize the number of bona fide cluster members while minimizing the number of contaminating interlopers. The GalWeight technique can be applied to both massive galaxy clusters and poor galaxy groups. Moreover, it is effective in identifying members in both the virial and infall regions with high efficiency. Apply the GalWeight technique to MDPL2 & Bolshoi N-body sims, and find that it is >98% accurate in correctly assigning cluster membership. Show that GalWeight compares very favorably against four well-known exist cluster membership techniques (shifting dapper, den Hartog, caustic, SIM). Also apply the GalWeight technique to a sample of twelve Abell clusters (including the Coma cluster) using observations from SDSS. End by discussing GalWeight's potential for other astrophysical applications.
1805.06508
Sex-disaggregated systematics in Canadian Term Allocation Committee telescope proposal reviews
Spekkens, Cofie, Crabtree
Recent studies have shown that the proposal peer review processes employed by a variant of organizations to allocate astronomical telescope time produce outcomes that are systematically biased depending on whether proposal's principal investigator (PI) is a man or a woman. Using CFHT and Gemini Observatory proposal statistics from Canada over 10 recent proposal cycles, assess whether or not the mean proposal scores assigned by the NRC''s Candan Time Allocaiton Committee (CanTAC) also correlate significantly with PI sex. Classical t-tests, bootstrap and jackknife replications show that proposal submitted by women were rated significantly worse than those submitted by men. Subdivide the data in order to investigate sex-disaggregated statistics in relation to PI carrier stage (faculty vs. non-faculty), telescope requested, scientific review panel, observing semester, and the PhD year of faculty PIs. Consistent with the bivalent results, a multivariate regression analysis controlling for other covariances confirmed that PI sex is the only significant predictor of proposal rating scores for the sample as a whole, although differences emerge for proposals submitted by faculty and non-faculty PIs. While further research is needed to explain the results, it is possible that implicit social cognition is at work. NRC and CanTAC have taken steps to mitigate this possibility by altering proposal author lists in order to conceal the PI's identity among co-investigators. Recommend that the impact of this measure on mitigating bias in future observing semesters by quantitatively assessed using statistical techniques such as those employed here.
1805.05481
Image simulations for gravitational lensing with SkyLens
Plazas, Meneghetti, Maturi, Rhodes
Present the latest version of the ray-tracing simulation code Skylens, which can be used to develop image simulations that reproduce SL observations by any mass distribution with a high level of realism. Improvements of the code with respect to previous versions include the implementation of the multi-lens plane formalism, the use of denoised source galaxies from the Hubble eXtreme Deep Field, and the simulation of substructures in lensed arcs and images, based on a morphological analysis of bright nearby galaxies. Skylens can simulate observations with virtually any telescope. Present examples of space- and ground-based observations of a galaxy cluster through WFC/ACS (HST), NIC (JWST), WFI (WFIRST), HSC (Subaru), and the VIS (Euclid).
1805.05741
Search for $\gamma$-ray line signals from dark matter annihilations in the inner Galactic halo from ten years of observations with H.E.S.S
H.E.S.S. Collaboration
Spectral lines are among the most powerful signatures of DM annihilation searches in very high-energy gamma rays. The central region of the MW halo is one of the most promising targets given its large amount of DM and proximity to Earth. Report on a search for a mono energetic spectral line from self-annihilations of DM particles in the energy range from 300 GeV to 70 TeV using a 2d maximum likelihood method taking advantage of both the spectrand and spatial features of signal versus background. The analysis makes use of GC observations accumulated over 10 years with the HESS array of ground-based Cherenkov telescopes. No significant gamma-ray excess above the background is found. Derive upper limits on the annihilation cross section <sigma_v> for mono energetic DM lines at the level of ~4e-28 cm^3 /s at 1TeV, assuming an Einasto DM profile for the MW halo. For a DM mass of 1TeV, they improve over the previous ones by a factor of 6. The present constraints are the strongest obtained so far for DM particles in the mass range 300 GeV-70 TeV. Ground-based gamma-ray observations have reached sufficient sensitivity to explore relevant velocity-averaged cross sections for DM annihilation into 2 gamma-ray photons at the level expected from the thermal relic density for TeV DM particles.
1805.06479
GalWeight: a new and effective weighting technique for determining galaxy cluster and group membership
Abdullah, Wilson, Klypin
Introduce GalWeight, a new technique for assigning galaxy cluster membership. This technique is specifically designed to simultaneously maximize the number of bona fide cluster members while minimizing the number of contaminating interlopers. The GalWeight technique can be applied to both massive galaxy clusters and poor galaxy groups. Moreover, it is effective in identifying members in both the virial and infall regions with high efficiency. Apply the GalWeight technique to MDPL2 & Bolshoi N-body sims, and find that it is >98% accurate in correctly assigning cluster membership. Show that GalWeight compares very favorably against four well-known exist cluster membership techniques (shifting dapper, den Hartog, caustic, SIM). Also apply the GalWeight technique to a sample of twelve Abell clusters (including the Coma cluster) using observations from SDSS. End by discussing GalWeight's potential for other astrophysical applications.
1805.06508
Sex-disaggregated systematics in Canadian Term Allocation Committee telescope proposal reviews
Spekkens, Cofie, Crabtree
Recent studies have shown that the proposal peer review processes employed by a variant of organizations to allocate astronomical telescope time produce outcomes that are systematically biased depending on whether proposal's principal investigator (PI) is a man or a woman. Using CFHT and Gemini Observatory proposal statistics from Canada over 10 recent proposal cycles, assess whether or not the mean proposal scores assigned by the NRC''s Candan Time Allocaiton Committee (CanTAC) also correlate significantly with PI sex. Classical t-tests, bootstrap and jackknife replications show that proposal submitted by women were rated significantly worse than those submitted by men. Subdivide the data in order to investigate sex-disaggregated statistics in relation to PI carrier stage (faculty vs. non-faculty), telescope requested, scientific review panel, observing semester, and the PhD year of faculty PIs. Consistent with the bivalent results, a multivariate regression analysis controlling for other covariances confirmed that PI sex is the only significant predictor of proposal rating scores for the sample as a whole, although differences emerge for proposals submitted by faculty and non-faculty PIs. While further research is needed to explain the results, it is possible that implicit social cognition is at work. NRC and CanTAC have taken steps to mitigate this possibility by altering proposal author lists in order to conceal the PI's identity among co-investigators. Recommend that the impact of this measure on mitigating bias in future observing semesters by quantitatively assessed using statistical techniques such as those employed here.
No comments:
Post a Comment