Forthcoming large photometric surveys for cosmology require precise and accurate photometric redshift (photo- z ) measurements for the success of their main science objectives. However, to date, no method has been able to produce photo- z s at the required accuracy using only the broad-band photometry that those surveys will provide. An assessment of the strengths and weaknesses of current methods is a crucial step in the eventual development of an approach to meet this challenge. We report on the performance of 13 photometric redshift code single value redshift estimates and redshift probability distributions (PDZs) on a common set of data, focusing particularly on the 0.2 − 2.6 redshift range that the Euclid mission will probe. We designed a challenge using emulated Euclid data drawn from three photometric surveys of the COSMOS field. The data was divided into two samples: one calibration sample for which photometry and redshifts were provided to the participants; and the validation sample, containing only the photometry to ensure a blinded test of the methods. Participants were invited to provide a redshift single value estimate and a PDZ for each source in the validation sample, along with a rejection flag that indicates the sources they consider unfit for use in cosmological analyses. The performance of each method was assessed through a set of informative metrics, using cross-matched spectroscopic and highly-accurate photometric redshifts as the ground truth. We show that the rejection criteria set by participants are efficient in removing strong outliers, that is to say sources for which the photo- z deviates by more than 0.15(1 + z ) from the spectroscopic-redshift (spec- z ). We also show that, while all methods are able to provide reliable single value estimates, several machine-learning methods do not manage to produce useful PDZs. We find that no machine-learning method provides good results in the regions of galaxy color-space that are sparsely populated by spectroscopic-redshifts, for example z > 1. However they generally perform better than template-fitting methods at low redshift ( z < 0.7), indicating that template-fitting methods do not use all of the information contained in the photometry. We introduce metrics that quantify both photo- z precision and completeness of the samples (post-rejection), since both contribute to the final figure of merit of the science goals of the survey (e.g., cosmic shear from Euclid ). Template-fitting methods provide the best results in these metrics, but we show that a combination of template-fitting results and machine-learning results with rejection criteria can outperform any individual method. On this basis, we argue that further work in identifying how to best select between machine-learning and template-fitting approaches for each individual galaxy should be pursued as a priority.
We update van den Bergh's parallel-sequence galaxy classification in which S0 galaxies form a sequence S0a–S0b–S0c that parallels the sequence Sa–Sb–Sc of spiral galaxies. The ratio B/T of bulge-to-total light defines the position of a galaxy in this tuning-fork diagram. Our classification makes one major improvement. We extend the S0a–S0b–S0c sequence to spheroidal ("Sph") galaxies that are positioned in parallel to irregular galaxies in a similarly extended Sa–Sb–Sc–Im sequence. This provides a natural "home" for spheroidals, which previously were omitted from galaxy classification schemes or inappropriately combined with ellipticals. To motivate our juxtaposition of Sph and Im galaxies, we present photometry and bulge–disk decompositions of four rare, late-type S0s that bridge the gap between the more common S0b and Sph galaxies. NGC 4762 is an edge-on SB0bc galaxy with a very small classical-bulge-to-total ratio of B/T = 0.13 ± 0.02. NGC 4452 is an edge-on SB0 galaxy with an even tinier pseudobulge-to-total ratio of PB/T = 0.017 ± 0.004. It is therefore an SB0c. VCC 2048, whose published classification is S0, contains an edge-on disk, but its "bulge" plots in the structural parameter sequence of spheroidals. It is therefore a disky Sph. And NGC 4638 is similarly a "missing link" between S0s and Sphs—it has a tiny bulge and an edge-on disk embedded in an Sph halo. In the Appendix, we present photometry and bulge–disk decompositions of all Hubble Space Telescope Advanced Camera for Surveys Virgo Cluster Survey S0s that do not have published decompositions. We use these data to update the structural parameter correlations of Sph, S+Im, and E galaxies. We show that Sph galaxies of increasing luminosity form a continuous sequence with the disks (but not bulges) of S0c–S0b–S0a galaxies. Remarkably, the Sph–S0–disk sequence is almost identical to that of Im galaxies and spiral galaxy disks. We review published observations for galaxy transformation processes, particularly ram-pressure stripping of cold gas. We suggest that Sph galaxies are transformed, "red and dead" Scd–Im galaxies in the same way that many S0 galaxies are transformed, red and dead Sa–Sc spiral galaxies.
The readily available Pt(0) methyl acrylate complex [Pt{CH2CHC(O)OMe}(PPh3)2] (2) allows access to the known, mixed-valence trinuclear cluster [Pt3(mu-PPh2)3Ph(PPh3)2] (3) in 64% yield. Oxidation of 3 with 2 equivalents of I2 afforded the new trinuclear complex [Pt3(mu-I)2(mu-PPh2)2I2(PPh3)2] (4) whose molecular structure is similar to that of the related compound of empirical formula [Pt3(mu-I)2(mu-PPh2)2Cl0.5I1.5(PPh3)2] ( 5) which has been generated by oxidation of 3 with successively 1 equivalent of I2 and 1 equivalent of C6H5ICl2. In these complexes, the four halogen atoms lie on the same side of the almost aligned platinum atoms and the nearly square-planar coordination planes of the metal atoms adopt a japanese screen, chair-like conformation. The reaction of the dinuclear, metal-metal bonded Pt(I)-Pt(I) complex [Pt2(mu-PPh2)2(PPh3)2] with one equivalent of I2 afforded the Pt(II) complex [Pt2(mu-PPh2)2I2(PPh3)2] (6). The molecular structures of complexes 2 x CH2Cl2, [Pt3(mu-I)2(mu-PPh2)2(I1.3Cl0.7)(PPh3)2][Pt3(mu-I)2(mu-PPh2)2(I1.7Cl0.3)(PPh3)2] x C6H5Cl x 3CH2Cl2 (5A x 5B x C6H5Cl x 3CH2Cl2) and 6 have been established by single crystal X-ray diffraction studies.
Die Lebensmittel Zeitung ist die führende Fach- und Wirtschaftszeitung der Konsumgüterbranche in Deutschland. Wer aktuelle Nachrichten, Analysen und Hintergrundberichte zu Marketingstrategien, Sortiments- und Vertriebskonzepten deutscher und internationaler Handels- und Industrieunternehmen sucht, findet sie in der LZ - oftmals exklusiv. Dabei reicht das Spektrum der Berichterstattung von Food über Nonfood bis hin zu IT und Logistik.
Die Lebensmittel Zeitung ist die führende Fach- und Wirtschaftszeitung der Konsumgüterbranche in Deutschland. Wer aktuelle Nachrichten, Analysen und Hintergrundberichte zu Marketingstrategien, Sortiments- und Vertriebskonzepten deutscher und internationaler Handels- und Industrieunternehmen sucht, findet sie in der LZ - oftmals exklusiv. Dabei reicht das Spektrum der Berichterstattung von Food über Nonfood bis hin zu IT und Logistik.
Die Lebensmittel Zeitung ist die führende Fach- und Wirtschaftszeitung der Konsumgüterbranche in Deutschland. Wer aktuelle Nachrichten, Analysen und Hintergrundberichte zu Marketingstrategien, Sortiments- und Vertriebskonzepten deutscher und internationaler Handels- und Industrieunternehmen sucht, findet sie in der LZ - oftmals exklusiv. Dabei reicht das Spektrum der Berichterstattung von Food über Nonfood bis hin zu IT und Logistik.
Using the M31 PAndromeda Cepheid sample and the HST PHAT data we obtain the largest Cepheid sample in M31 with HST data in four bands. For our analysis we consider three samples: A very homogeneous sample of Cepheids based on the PAndromeda data, the mean magnitude corrected PAndromeda sample and a sample complementing the PAndromeda sample with Cepheids from literature. The latter results in the largest catalog with 522 fundamental mode (FM) Cepheids and 102 first overtone (FO) Cepheids with F160W and F110W data and 559 FM Cepheids and 111 FO Cepheids with F814W and F475W data. The obtained dispersion of the Period-Luminosity relations (PLRs) is very small (e.g. 0.138 mag in the F160W sample I PLR). We find no broken slope in the PLRs when analyzing our entire sample, but we do identify a subsample of Cepheids that causes the broken slope. However, this effect only shows when the number of this Cepheid type makes up a significant fraction of the total sample. We also analyze the sample selection effect on the Hubble constant.
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