1901.06391
The imprint of element abundance patterns on quiescent galaxy SEDs
Choi, Conroy, Johnson
Stellar population synthesis (SPS) models have long struggled to reproduce observed optical through near-IR (NIR) spectral energy distributions (SED) of massive quiescent galaxies. Revisit this issue using a novel approach that combines the diagnostic power of full-spectrum fitting with recently updated stellar spectral libraries. First, perform full-spectrum fitting of continuum-normalized stacked SDSS spectra in bins of velocity dispersion to infer their stelar population properties, such as the elemental abundances and age. Next, use the resulting best-fit parameters to compute ugriz colors, which are then compared to observed colors of the same galaxies. With this approach, one can predict the ugriz SEDs of low and high mass galaxies at the <~0.03 mag level in nearly all cases. Find that the full optical through NIR SEDs of quiescent galaxies can be reproduced only when the spectrum is fit with a flexibility that is able to capture the behavior of the entire optical absorption line spectrum. The models include variations in individual elemental abundances, nebular emission lines, and the presence of young stellar components. The successful predictions of the SED shape from continuum-normalized spectra implies that the continuum information is largely contained in the narrow absorption features. These results also imply that attempts to model broadband photometry of quiescent systems will suffer from potentially significant biases if the detailed abundance patterns are not taken into account.
1901.06495
Rainbow cosmic shear: optimization of tomographic bins
Kitching, Taylor, Capak, Masters, Hoekstra
Address the problem of finding optimal cosmic shear tomographic bins. Generalize the definition of a cosmic shear tomographic bin to be a set of commonly labelled voxels in photometric color space, rather than bins defined directly in redshift. Explore this approach by using a self-organizing map to define them multi-dimensional color space, and define a 'label space' of connected regions on the self-organizing map using overlapping elliptical disks. This allows to find optimal labelling schemes by searching the label space. Use a metric that is the signal-to-noise ratio of a dark energy equation of state measurement, and in this case, find that for up to five tomographic bins, the optimal color-space labelling is an approximation of an equally-spaced binning in z; that is in all cases, the best configuration. Also show that such a redefinition is more robust to photometric z outliers than a standard tomographic bin selection.
1901.07119
Dark Energy Survey Year 1 results: calibration of cluster mis-centering in the redMaPPer Catalogs
Zhang, et al
The center determination of a galaxy cluster from an optical cluster finding algorithm can be offset from theoretical prescriptions or N-body definitions of its host halo center. These offsets impact the recovered cluster statistics, affecting both richness measurements and the WL shear profile around the clusters. This paper models the centering performance of the RM cluster finding algorithm using archival X-ray observations of RM-selected clusters. Assuming the X-ray emission peaks at the fiducial halo centers, and through analyzing their offsets to the RM centers, find that ~75±8% of the RM clusters are well centered and the mis-center offset follows a Gamma distribution in normalized, projected distance. These mis-centering offsets cause a systematic underestimation of cluster richness relative to the well-centered clusters, for which a descriptive model is proposed. The results enable the DES Y1 cluster cosmology analysis by characterizing the necessary corrections to both the WL and richness abundance functions of the DES Y1 redMaPPer cluster catalog.
The imprint of element abundance patterns on quiescent galaxy SEDs
Choi, Conroy, Johnson
Stellar population synthesis (SPS) models have long struggled to reproduce observed optical through near-IR (NIR) spectral energy distributions (SED) of massive quiescent galaxies. Revisit this issue using a novel approach that combines the diagnostic power of full-spectrum fitting with recently updated stellar spectral libraries. First, perform full-spectrum fitting of continuum-normalized stacked SDSS spectra in bins of velocity dispersion to infer their stelar population properties, such as the elemental abundances and age. Next, use the resulting best-fit parameters to compute ugriz colors, which are then compared to observed colors of the same galaxies. With this approach, one can predict the ugriz SEDs of low and high mass galaxies at the <~0.03 mag level in nearly all cases. Find that the full optical through NIR SEDs of quiescent galaxies can be reproduced only when the spectrum is fit with a flexibility that is able to capture the behavior of the entire optical absorption line spectrum. The models include variations in individual elemental abundances, nebular emission lines, and the presence of young stellar components. The successful predictions of the SED shape from continuum-normalized spectra implies that the continuum information is largely contained in the narrow absorption features. These results also imply that attempts to model broadband photometry of quiescent systems will suffer from potentially significant biases if the detailed abundance patterns are not taken into account.
1901.06495
Rainbow cosmic shear: optimization of tomographic bins
Kitching, Taylor, Capak, Masters, Hoekstra
Address the problem of finding optimal cosmic shear tomographic bins. Generalize the definition of a cosmic shear tomographic bin to be a set of commonly labelled voxels in photometric color space, rather than bins defined directly in redshift. Explore this approach by using a self-organizing map to define them multi-dimensional color space, and define a 'label space' of connected regions on the self-organizing map using overlapping elliptical disks. This allows to find optimal labelling schemes by searching the label space. Use a metric that is the signal-to-noise ratio of a dark energy equation of state measurement, and in this case, find that for up to five tomographic bins, the optimal color-space labelling is an approximation of an equally-spaced binning in z; that is in all cases, the best configuration. Also show that such a redefinition is more robust to photometric z outliers than a standard tomographic bin selection.
1901.07119
Dark Energy Survey Year 1 results: calibration of cluster mis-centering in the redMaPPer Catalogs
Zhang, et al
The center determination of a galaxy cluster from an optical cluster finding algorithm can be offset from theoretical prescriptions or N-body definitions of its host halo center. These offsets impact the recovered cluster statistics, affecting both richness measurements and the WL shear profile around the clusters. This paper models the centering performance of the RM cluster finding algorithm using archival X-ray observations of RM-selected clusters. Assuming the X-ray emission peaks at the fiducial halo centers, and through analyzing their offsets to the RM centers, find that ~75±8% of the RM clusters are well centered and the mis-center offset follows a Gamma distribution in normalized, projected distance. These mis-centering offsets cause a systematic underestimation of cluster richness relative to the well-centered clusters, for which a descriptive model is proposed. The results enable the DES Y1 cluster cosmology analysis by characterizing the necessary corrections to both the WL and richness abundance functions of the DES Y1 redMaPPer cluster catalog.
No comments:
Post a Comment