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The orange distribution is a quality sample of the redshifts (best point estimates) generated for cosmology by a Bayesian template-fitting code.
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The orange distribution is a quality sample of the redshifts (best point estimate) generated for cosmology by a Bayesian template-fitting code.
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The maximum is z ~ 6, due to the model's input parameters.
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Green represents redshifts that were generated to study galaxies' physical properties by a supervised learning, k-nearest neighbors algorithm.
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The maximum is z ~ 7, again due to model input parameters.
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The maximum is z ~ 7, again due to model inputs.
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Several quality cuts were applied to produce the dotted-line sample, but this still includes a population of problematic galaxies for which the solutions pointed to unrealistically young ages and very high specific star formation rates.
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The green solid line filters those out and represents a quality sample for this redshift estimate.
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Purple represents the spectroscopic redshifts (best point estimates)
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Purple represents the spectroscopic redshifts (best point estimate).
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The dotted line has been filtered for reliable (SPE) galaxy solutions and the maximum is z ~ 5.
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There is a clear bump between about 0.9 < z < 1.8 which results from a combination of the NISP instrument parameters (tuned to detect Halpha) and a model prior that strongly favored solutions in this regime.
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However much more drastic cuts are needed to obtain a trustworthy sample.
@@ -489,7 +501,7 @@ Compare PHZ to PHYSPARAM.
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Here, we reproduce Tucci Fig. 17 (left panel) except that we don't consider the problematic galaxies nor do we impose cuts on magnitude or region (EDF-F).
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```{code-cell}
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# Get the common objects and set axes data x (PHZ) and y (PHYSPARAM).
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# Get the common objects and set axes data (PHZ on x, PHYSPARAM on y).
The template - aperture magnitude difference is fairly tightly clustered around 0 for extended objects (top row) but the outliers are asymmetric (fractions above and below zero are noted).
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We see a positive offset which indicates a fainter template-fit magnitude, as we should expect given that the templates do a better job of excluding contaminating light from nearby sources.
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The offset is more pronounced for point-like objects, likely due to the PSF handling mentioned above, and we are reminded that aperture magnitudes are more reliable here.
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The offset is more pronounced for point-like objects (bottom row), likely due to the PSF handling mentioned above, and we are reminded that aperture magnitudes are more reliable here.
- OBJECT_ID: -600367386508373277. L-type dwarf, spectroscopically confirmed ([Zhang, Lodieu, and Martín, 2024](https://arxiv.org/abs/2403.15288) Table C.2. '04:00:08.99 −50:50:14.4'. Found in Q1 via cone search; separation = 1.6 arcsec).
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- OBJECT_ID: -531067351279302418. Star-forming galaxy at z=5.78, spectroscopically confirmed ([Bunker et al., 2003](https://arxiv.org/abs/astro-ph/0302401). Found in Q1 via cone search; separation = 0.59 arcsec).
- OBJECT_ID: -600367386508373277. **L-type dwarf**, spectroscopically confirmed ([Zhang, Lodieu, and Martín, 2024](https://arxiv.org/abs/2403.15288) Table C.2. '04:00:08.99 −50:50:14.4'. Found in Q1 via cone search; separation = 1.6 arcsec).
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- OBJECT_ID: -531067351279302418. **Star-forming galaxy at z=5.78**, spectroscopically confirmed ([Bunker et al., 2003](https://arxiv.org/abs/astro-ph/0302401). Found in Q1 via cone search; separation = 0.59 arcsec).
@@ -1023,7 +1037,7 @@ for ax, (target_id, (target_name, target_color)) in zip(axes, targets.items()):
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In the left panel (T dwarf), we see that the photo-z PDF produced by the NIR-only branch is very strongly peaked at z=0 with a small secondary bump near z=7, consistent with its placement in the previous figure.
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Recall that PHZ_PHZ_PDF was produced using galaxy models, regardless of the object's class.
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In the middle panel (L dwarf), we see the multi-peaked NIR PDF that was guessed at based on the previous figure.
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In the middle panel (L dwarf), we see the broad and multi-peaked NIR PDF that was guessed at based on the previous figure.
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While the strongest peak is near z=8 (a QSO solution, perhaps?), there are also peaks at z=0 (consistent with a star) and near z=1.75 (consistent with the PHZ (galaxy) solution) which are prominent enough to reduce the probability of z>6 below the 0.8 threshold.
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In the right panel (Galaxy), we see good agreement between the PDFs except at z=0.
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