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D Mortlock - One of the best experts on this subject based on the ideXlab platform.
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galaxy mass profiles from strong lensing iii the two dimensional broken Power Law Model
arXiv: Astrophysics of Galaxies, 2020Co-Authors: C M Oriordan, S J Warren, D MortlockAbstract:When Modelling strong gravitational lenses, i.e., where there are multiple images of the same source, the most widely used parameterisation for the mass profile in the lens galaxy is the singular Power-Law Model $\rho(r)\propto r^{-\gamma}$. This Model may be insufficiently flexible for very accurate work, for example measuring the Hubble constant based on time delays between multiple images. Here we derive the lensing properties - deflection angle, shear, and magnification - of a more adaptable Model where the projected mass surface density is parameterised as a continuous two-dimensional broken Power-Law (2DBPL). This elliptical 2DBPL Model is characterised by Power-Law slopes $t_1$, $t_2$ either side of the break radius $\theta_\mathrm{B}$. The key to the 2DBPL Model is the derivation of the lensing properties of the truncated Power Law (TPL) Model, where the surface density is a Power Law out to the truncation radius $\theta_\mathrm{T}$ and zero beyond. This TPL Model is also useful by itself. We create mock observations of lensing by a TPL profile where the images form outside the truncation radius, so there is no mass in the annulus covered by the images. We then show that the slope of the profile interior to the images may be accurately recovered for lenses of moderate ellipticity. This demonstrates that the widely-held notion that lensing measures the slope of the mass profile in the annulus of the images, and is insensitive to the mass distribution at radii interior to the images, is incorrect.
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Galaxy mass profiles from strong lensing II: The elliptical Power-Law Model
'Oxford University Press (OUP)', 2020Co-Authors: Cm O’riordan, S J Warren, D MortlockAbstract:We present a systematic analysis of the constraints σγ on the mass profile slope γ obtainable when fitting a singular Power-Law ellipsoid Model to a typical strong lensing observation of an extended source. These results extend our previous analysis of circular systems, Paper I. We draw our results from 676 mock observations covering a range of image configurations, each created with a fixed signal to noise ratio S = 100 in the images. We analyse the results using a combination of theory and a simplified Model which identifies the contribution to the constraints of the individual fluxes and positions in each of the lensed images. The main results are: 1. For any lens ellipticity, the constraints σγ for two image systems are well described by the results of Paper I, transformed to elliptical coordinates; 2. We derive an analytical expression for σγ for systems with the source aligned with the axis of the lens; 3. For both two-image systems and aligned systems, σγ is limited by the flux uncertainties; 4. The constraints for off-axis four-image systems are a factor of two to eight better, depending on source size, than for two-image systems, and improve with increasing lens ellipticity. We show that the constraints on γ in these systems derive from the complementary positional information of the images alone, without using flux. The complementarity improves as the offset of the source from the axis increases, such that the best constraints σγ < 0.01, for S = 100, occur when the source approaches the caustic
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galaxy mass profiles from strong lensing i the circular Power Law Model
Monthly Notices of the Royal Astronomical Society, 2019Co-Authors: C M Oriordan, S J Warren, D MortlockAbstract:In this series of papers, we develop a formalism for constraining mass profiles in strong gravitational lenses with extended images, using fluxes in addition to positional information. We start in ...
Aparna Bhattacharya - One of the best experts on this subject based on the ideXlab platform.
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the exoplanet mass ratio function from the moa ii survey discovery of a break and likely peak at a neptune mass
The Astrophysical Journal, 2016Co-Authors: D Suzuki, D P Bennett, T Sumi, I A Bond, Leslie A Rogers, F Abe, Y Asakura, Aparna BhattacharyaAbstract:We report the results of the statistical analysis of planetary signals discovered in MOA-II microlensing survey alert system events from 2007 to 2012. We determine the survey sensitivity as a function of planet star mass ratio, q, and projected planet star separation, s, in Einstein radius units. We find that the mass-ratio function is not a single Power Law, but has a change in slope at q approx.10(exp -4), corresponding to approx. 20 Stellar Mass for the median host-star mass of approx. 0.6 M. We find significant planetary signals in 23 of the 1474 alert events that are well-characterized by the MOA-II survey data alone. Data from other groups are used only to characterize planetary signals that have been identified in the MOA data alone. The distribution of mass ratios and separations of the planets found in our sample are well fit by a broken Power-Law Model. We also combine this analysis with the previous analyses of Gould et al. and Cassan et al., bringing the total sample to 30 planets. The unbroken Power-Law Model is disfavored with a p-value of 0.0022, which corresponds to a Bayes factor of 27 favoring the broken Power-Law Model. These results imply that cold Neptunes are likely to be the most common type of planets beyond the snow line.
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the exoplanet mass ratio function from the moa ii survey discovery of a break and likely peak at a neptune mass
arXiv: Earth and Planetary Astrophysics, 2016Co-Authors: D Suzuki, D P Bennett, T Sumi, I A Bond, Leslie A Rogers, F Abe, Y Asakura, Aparna Bhattacharya, M Donachie, M FreemanAbstract:We report the results of the statistical analysis of planetary signals discovered in MOA-II microlensing survey alert system events from 2007 to 2012. We determine the survey sensitivity as a function of planet-star mass ratio, $q$, and projected planet-star separation, $s$, in Einstein radius units. We find that the mass ratio function is not a single Power-Law, but has a change in slope at $q \sim 10^{-4}$, corresponding to $\sim 20 M_{\oplus}$ for the median host star mass of $\sim 0.6 M_{\odot}$. We find significant planetary signals in 23 of the 1474 alert events that are well characterized by the MOA-II survey data alone. Data from other groups are used only to characterize planetary signals that have been identified in the MOA data alone. The distribution of mass ratios and separations of the planets found in our sample are well fit by a broken Power-Law Model of the form $dN_{\rm pl}/(d{\rm log} q\ d{\rm log} s) = A (q/q_{\rm br})^n s^m \, {\rm dex}^{-2}$ for $q > q_{\rm br}$ and $dN_{\rm pl}/(d{\rm log} q\ d{\rm log} s) = A (q/q_{\rm br})^p s^m \, {\rm dex}^{-2}$ for $q < q_{\rm br}$, where $q_{\rm br}$ is the mass ratio of the break. We also combine this analysis with the previous analyses of Gould et al. and Cassan et al., bringing the total sample to 30 planets. This combined analysis yields $A = 0.61^{+0.21}_{-0.16}$, $n =-0.93\pm 0.13$, $m = 0.49_{-0.49}^{+0.47}$ and $p = 0.6^{+0.5}_{-0.4}$ for $q_{\rm br}\equiv 1.7\times 10^{-4}$. The unbroken Power Law Model is disfavored with a $p$-value of 0.0022, which corresponds to a Bayes factor of 27 favoring the broken Power-Law Model. These results imply that cold Neptunes are likely to be the most common type of planets beyond the snow line.
Alain Blanchard - One of the best experts on this subject based on the ideXlab platform.
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is cosmic acceleration proven by local cosmological probes
arXiv: Cosmology and Nongalactic Astrophysics, 2017Co-Authors: Isaac Tutusaus, Brahim Lamine, Arnaud Dupays, Alain BlanchardAbstract:Context: The cosmological concordance Model ($\Lambda$CDM) matches the cosmological observations exceedingly well. This Model has become the standard cosmological Model with the evidence for an accelerated expansion provided by the type Ia supernovae (SNIa) Hubble diagram. However, the robustness of this evidence has been addressed recently with somewhat diverging conclusions. Aims: The purpose of this paper is to assess the robustness of the conclusion that the Universe is indeed accelerating if we rely only on low-redshift (z$\lesssim$2) observations, that is to say with SNIa, baryonic acoustic oscillations, measurements of the Hubble parameter at different redshifts, and measurements of the growth of matter perturbations. Methods: We used the standard statistical procedure of minimizing the $\chi^2$ function for the different probes to quantify the goodness of fit of a Model for both $\Lambda$CDM and a simple nonaccelerated low-redshift Power Law Model. In this analysis, we do not assume that supernovae intrinsic luminosity is independent of the redshift, which has been a fundamental assumption in most previous studies that cannot be tested. Results: We have found that, when SNIa intrinsic luminosity is not assumed to be redshift independent, a nonaccelerated low-redshift Power Law Model is able to fit the low-redshift background data as well as, or even slightly better, than $\Lambda$CDM. When measurements of the growth of structures are added, a nonaccelerated low-redshift Power Law Model still provides an excellent fit to the data for all the luminosity evolution Models considered. Conclusions: Without the standard assumption that supernovae intrinsic luminosity is independent of the redshift, low-redshift probes are consistent with a nonaccelerated universe.
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is cosmic acceleration proven by local cosmological probes
Astronomy and Astrophysics, 2017Co-Authors: Isaac Tutusaus, Brahim Lamine, Arnaud Dupays, Alain BlanchardAbstract:Context. The cosmological concordance Model (ΛCDM) matches the cosmological observations exceedingly well. This Model has become the standard cosmological Model with the evidence for an accelerated expansion provided by the type Ia supernovae (SNIa) Hubble diagram. However, the robustness of this evidence has been addressed recently with somewhat diverging conclusions. Aims. The purpose of this paper is to assess the robustness of the conclusion that the Universe is indeed accelerating if we rely only on low-redshift ( z ≲ 2) observations, that is to say with SNIa, baryonic acoustic oscillations, measurements of the Hubble parameter at different redshifts, and measurements of the growth of matter perturbations. Methods. We used the standard statistical procedure of minimizing the χ 2 function for the different probes to quantify the goodness of fit of a Model for both ΛCDM and a simple nonaccelerated low-redshift Power Law Model. In this analysis, we do not assume that supernovae intrinsic luminosity is independent of the redshift, which has been a fundamental assumption in most previous studies that cannot be tested. Results. We have found that, when SNIa intrinsic luminosity is not assumed to be redshift independent, a nonaccelerated low-redshift Power Law Model is able to fit the low-redshift background data as well as, or even slightly better, than ΛCDM. When measurements of the growth of structures are added, a nonaccelerated low-redshift Power Law Model still provides an excellent fit to the data for all the luminosity evolution Models considered. Conclusions. Without the standard assumption that supernovae intrinsic luminosity is independent of the redshift, low-redshift probes are consistent with a nonaccelerated universe.
D P Bennett - One of the best experts on this subject based on the ideXlab platform.
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the exoplanet mass ratio function from the moa ii survey discovery of a break and likely peak at a neptune mass
The Astrophysical Journal, 2016Co-Authors: D Suzuki, D P Bennett, T Sumi, I A Bond, Leslie A Rogers, F Abe, Y Asakura, Aparna BhattacharyaAbstract:We report the results of the statistical analysis of planetary signals discovered in MOA-II microlensing survey alert system events from 2007 to 2012. We determine the survey sensitivity as a function of planet star mass ratio, q, and projected planet star separation, s, in Einstein radius units. We find that the mass-ratio function is not a single Power Law, but has a change in slope at q approx.10(exp -4), corresponding to approx. 20 Stellar Mass for the median host-star mass of approx. 0.6 M. We find significant planetary signals in 23 of the 1474 alert events that are well-characterized by the MOA-II survey data alone. Data from other groups are used only to characterize planetary signals that have been identified in the MOA data alone. The distribution of mass ratios and separations of the planets found in our sample are well fit by a broken Power-Law Model. We also combine this analysis with the previous analyses of Gould et al. and Cassan et al., bringing the total sample to 30 planets. The unbroken Power-Law Model is disfavored with a p-value of 0.0022, which corresponds to a Bayes factor of 27 favoring the broken Power-Law Model. These results imply that cold Neptunes are likely to be the most common type of planets beyond the snow line.
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the exoplanet mass ratio function from the moa ii survey discovery of a break and likely peak at a neptune mass
arXiv: Earth and Planetary Astrophysics, 2016Co-Authors: D Suzuki, D P Bennett, T Sumi, I A Bond, Leslie A Rogers, F Abe, Y Asakura, Aparna Bhattacharya, M Donachie, M FreemanAbstract:We report the results of the statistical analysis of planetary signals discovered in MOA-II microlensing survey alert system events from 2007 to 2012. We determine the survey sensitivity as a function of planet-star mass ratio, $q$, and projected planet-star separation, $s$, in Einstein radius units. We find that the mass ratio function is not a single Power-Law, but has a change in slope at $q \sim 10^{-4}$, corresponding to $\sim 20 M_{\oplus}$ for the median host star mass of $\sim 0.6 M_{\odot}$. We find significant planetary signals in 23 of the 1474 alert events that are well characterized by the MOA-II survey data alone. Data from other groups are used only to characterize planetary signals that have been identified in the MOA data alone. The distribution of mass ratios and separations of the planets found in our sample are well fit by a broken Power-Law Model of the form $dN_{\rm pl}/(d{\rm log} q\ d{\rm log} s) = A (q/q_{\rm br})^n s^m \, {\rm dex}^{-2}$ for $q > q_{\rm br}$ and $dN_{\rm pl}/(d{\rm log} q\ d{\rm log} s) = A (q/q_{\rm br})^p s^m \, {\rm dex}^{-2}$ for $q < q_{\rm br}$, where $q_{\rm br}$ is the mass ratio of the break. We also combine this analysis with the previous analyses of Gould et al. and Cassan et al., bringing the total sample to 30 planets. This combined analysis yields $A = 0.61^{+0.21}_{-0.16}$, $n =-0.93\pm 0.13$, $m = 0.49_{-0.49}^{+0.47}$ and $p = 0.6^{+0.5}_{-0.4}$ for $q_{\rm br}\equiv 1.7\times 10^{-4}$. The unbroken Power Law Model is disfavored with a $p$-value of 0.0022, which corresponds to a Bayes factor of 27 favoring the broken Power-Law Model. These results imply that cold Neptunes are likely to be the most common type of planets beyond the snow line.
Isaac Tutusaus - One of the best experts on this subject based on the ideXlab platform.
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is cosmic acceleration proven by local cosmological probes
arXiv: Cosmology and Nongalactic Astrophysics, 2017Co-Authors: Isaac Tutusaus, Brahim Lamine, Arnaud Dupays, Alain BlanchardAbstract:Context: The cosmological concordance Model ($\Lambda$CDM) matches the cosmological observations exceedingly well. This Model has become the standard cosmological Model with the evidence for an accelerated expansion provided by the type Ia supernovae (SNIa) Hubble diagram. However, the robustness of this evidence has been addressed recently with somewhat diverging conclusions. Aims: The purpose of this paper is to assess the robustness of the conclusion that the Universe is indeed accelerating if we rely only on low-redshift (z$\lesssim$2) observations, that is to say with SNIa, baryonic acoustic oscillations, measurements of the Hubble parameter at different redshifts, and measurements of the growth of matter perturbations. Methods: We used the standard statistical procedure of minimizing the $\chi^2$ function for the different probes to quantify the goodness of fit of a Model for both $\Lambda$CDM and a simple nonaccelerated low-redshift Power Law Model. In this analysis, we do not assume that supernovae intrinsic luminosity is independent of the redshift, which has been a fundamental assumption in most previous studies that cannot be tested. Results: We have found that, when SNIa intrinsic luminosity is not assumed to be redshift independent, a nonaccelerated low-redshift Power Law Model is able to fit the low-redshift background data as well as, or even slightly better, than $\Lambda$CDM. When measurements of the growth of structures are added, a nonaccelerated low-redshift Power Law Model still provides an excellent fit to the data for all the luminosity evolution Models considered. Conclusions: Without the standard assumption that supernovae intrinsic luminosity is independent of the redshift, low-redshift probes are consistent with a nonaccelerated universe.
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is cosmic acceleration proven by local cosmological probes
Astronomy and Astrophysics, 2017Co-Authors: Isaac Tutusaus, Brahim Lamine, Arnaud Dupays, Alain BlanchardAbstract:Context. The cosmological concordance Model (ΛCDM) matches the cosmological observations exceedingly well. This Model has become the standard cosmological Model with the evidence for an accelerated expansion provided by the type Ia supernovae (SNIa) Hubble diagram. However, the robustness of this evidence has been addressed recently with somewhat diverging conclusions. Aims. The purpose of this paper is to assess the robustness of the conclusion that the Universe is indeed accelerating if we rely only on low-redshift ( z ≲ 2) observations, that is to say with SNIa, baryonic acoustic oscillations, measurements of the Hubble parameter at different redshifts, and measurements of the growth of matter perturbations. Methods. We used the standard statistical procedure of minimizing the χ 2 function for the different probes to quantify the goodness of fit of a Model for both ΛCDM and a simple nonaccelerated low-redshift Power Law Model. In this analysis, we do not assume that supernovae intrinsic luminosity is independent of the redshift, which has been a fundamental assumption in most previous studies that cannot be tested. Results. We have found that, when SNIa intrinsic luminosity is not assumed to be redshift independent, a nonaccelerated low-redshift Power Law Model is able to fit the low-redshift background data as well as, or even slightly better, than ΛCDM. When measurements of the growth of structures are added, a nonaccelerated low-redshift Power Law Model still provides an excellent fit to the data for all the luminosity evolution Models considered. Conclusions. Without the standard assumption that supernovae intrinsic luminosity is independent of the redshift, low-redshift probes are consistent with a nonaccelerated universe.