astrophysics
23 posts
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PySM: produce CAR output at the smoothing stage
PySM 3 only builds HEALPix skies. Here is how to produce CAR pixelization output at the smoothing stage with a single spherical harmonic transform, and a validation against the smooth-then-reproject route.
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healpy 1.20.0b1 beta — harmonic_ud_grade for artifact-safe map downgrading
pip install --pre healpy==1.20.0b1 harmonicudgrade changes map NSIDE through spherical-harmonic transforms with pixel-window and beam transfer corrections following Eq. 1 of Planck 2015 X (arXiv:1502.01588).
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healpy harmonic_ud_grade vs skytools change_resolution: A Comparison
A comparison of healpy.harmonic_ud_grade and skytools.change_resolution for HEALPix map resolution changes, highlighting API differences, beam/pixel-window support, direct alm input, and agreement levels.
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harmonic_ud_grade vs ud_grade: A Focused Comparison
harmonic_ud_grade vs ud_grade A Focused Comparison.
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Why 3 pixels per beam? The mathematics of HEALPix resolution matching
Exploring why the Planck convention uses FWHM = 3 x pixel size for harmonic-space map downgrading, with equations from the literature and simulated demonstrations.
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Healpy blm_gauss breaking change analysis
Analyzing the breaking change in healpy's blm_gauss function (1.18.1 to 1.19.0) and its impact on Gaussian beam coefficients.
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Astrophysics Papers Daily Summaries Notebook with the Jetstream LLM Inference Service
Fetch today's astro-ph papers from arXiv, summarize abstracts with llm, and output a Markdown summary. This is an example of using the Jetstream Inference Service, notice that you need first to configure the llm package to access the Jetstream Inference Service via the API
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Interactive 3D plot of a Planck map with Matplotlib
This is an update of my older tutorial Unfortunately I was not able to make Mayavi properly plot the data, rerunning the same code would give a map that looked like uniform noise.
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CFITSIO file writing with checkpointing
I wrote a prototype implementation of writing FITS files in C checkpointing using the FITS flush function so that if the code segfaults, the file is not corrupted, see:
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Simple WCS with astropy modeling and gwcs
Some notes on how to convert a FITS WCS to a WCS from gwcs (Generalized WCS) to be used within the JWST pipeline python import astropy from astropy.io import fits import numpy as np from astropy import units as u
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Advanced pandas with astrophysics example notebook
Taught a lesson today on advanced python and pandas based on an example application in Astrophysics with simulations of data from the Planck Satellite), features also a Binder button to run it yourself. Jupyter Notebook available at: under CC-BY
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Accelerate groupby operation on pixels with Numba
Download the original IPython notebook Astrophysics background
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clviewer, interactive plot of CMB spectra
Today it was HackDay at .Astronomy, so I felt compelled to hack something around myself, creating something I have been thinking for a while after my previous work on Interactive CMB power spectra in the browser
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Planck CMB map at high resolution
Prompted by a colleague, I created a high-resolution version of the Cosmic Microwave Background map in MollWeide projection released by the Planck collaboration, available on the Planck Data Release Website in FITS format.
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Interactive figures in the browser - CMB power spectra
For a long time I've been curious about trying out d3.js , the javascript plotting library which is becoming the standard for interactive plotting in the browser.