Spatially-Resolved Spectra of Diffuse Galactic Light using 10.8 M DESI Sky Fibers
Abstract
Using 10.8 million ``blank'' sky spectra from the DESI Year 3 dataset, we measure the diffuse galactic light (DGL) spectrum in the optical at spectral resolution R ∼ 4000 by correlating with far-infrared emission from IRAS. Subdividing the sky into 54 deg2 pixels (HEALPix, NSIDE = 8), we map the variation of the DGL correlation spectrum and nebular emission lines across the DESI footprint in the high-Galactic-latitude sky. The increased data volume over previous SDSS-based analyses enables several new detections in the DGL, including scattering both onto and out of the line of sight from neutral interstellar sodium and potassium. We further detect direct emission from ro-vibrational transitions of molecular hydrogen in the near-infrared with an absolute radiance of 0.65substack+0.13 −0.12×10−9 erg cm−2 s−1 sr−1, roughly consistent with theoretical expectations, but with an apparent ortho-to-para line ratio that is lower by a factor of 0.60substack+0.28 −0.27. We confirm previous detections of extended red emission (ERE) in the DGL and map its spatial variation. Our spatially resolved DGL maps provide important observational constraints for the radiative transfer efforts that are now possible with recent 3D models of the Milky Way.
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BibTeX
@misc{saydjari2026spatiallyresolved,
title = {{Spatially-Resolved Spectra of Diffuse Galactic Light using 10.8 M DESI Sky Fibers}},
author = {Andrew Saydjari and Bruce Draine and Timothy Brandt and Edward Schlafly and Arjun Dey and Douglas Finkbeiner and Jessica Nicole Aguilar and Steven Ahlen and Carlos Allende Prieto and Abhijeet Anand and Florian Beutler and Davide Bianchi and David Brooks and Aurelio Carnero Rosell and Todd Claybaugh and Axelde La Macorra and Peter Doel and Andreu Font-Ribera and Jaime E Forero-Romero and Enrique Gaztañaga and Satya Gontcho A. Gontcho and Gaston Gutierrez and Julien Guy and Klaus Honscheid and Tanveer Karim and David Kirkby and Anthony Kremin and Ofer Lahav and Andrew Lambert and Martin Landriau and Laurent Le Guillou and Aaron Meisner and Ramon Miquel and John Moustakas and Seshadri Nadathur and Enrique Paillas and Will Percival and Ignasi Pérez-Ràfols and Francisco Prada and Corentin Ravoux and Graziano Rossi and Lado Samushia and Eusebio Sanchez and Christoph Saulder and David Schlegel and Michael Schubnell and Ray Sharples and Joseph Harrysilber and Małgorzata Siudek and Gregory Tarlé and Benjamin Alan Weaver and Rongpu Zhou},
howpublished = {HAL},
year = {2026},
month = aug,
doi = {10.48550/arxiv.2608.28740},
eprint = {2608.28740},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05743343v1},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Spatially-Resolved Spectra of Diffuse Galactic Light using 10.8 M DESI Sky Fibers
AU - Andrew Saydjari
AU - Bruce Draine
AU - Timothy Brandt
AU - Edward Schlafly
AU - Arjun Dey
AU - Douglas Finkbeiner
AU - Jessica Nicole Aguilar
AU - Steven Ahlen
AU - Carlos Allende Prieto
AU - Abhijeet Anand
AU - Florian Beutler
AU - Davide Bianchi
AU - David Brooks
AU - Aurelio Carnero Rosell
AU - Todd Claybaugh
AU - Axelde La Macorra
AU - Peter Doel
AU - Andreu Font-Ribera
AU - Jaime E Forero-Romero
AU - Enrique Gaztañaga
AU - Satya Gontcho A. Gontcho
AU - Gaston Gutierrez
AU - Julien Guy
AU - Klaus Honscheid
AU - Tanveer Karim
AU - David Kirkby
AU - Anthony Kremin
AU - Ofer Lahav
AU - Andrew Lambert
AU - Martin Landriau
AU - Laurent Le Guillou
AU - Aaron Meisner
AU - Ramon Miquel
AU - John Moustakas
AU - Seshadri Nadathur
AU - Enrique Paillas
AU - Will Percival
AU - Ignasi Pérez-Ràfols
AU - Francisco Prada
AU - Corentin Ravoux
AU - Graziano Rossi
AU - Lado Samushia
AU - Eusebio Sanchez
AU - Christoph Saulder
AU - David Schlegel
AU - Michael Schubnell
AU - Ray Sharples
AU - Joseph Harrysilber
AU - Małgorzata Siudek
AU - Gregory Tarlé
AU - Benjamin Alan Weaver
AU - Rongpu Zhou
PY - 2026
DA - 2026/08/28
PB - HAL
DO - 10.48550/arxiv.2608.28740
UR - https://hal.science/hal-05743343v1
AB - Using 10.8 million ``blank'' sky spectra from the DESI Year 3 dataset, we measure the diffuse galactic light (DGL) spectrum in the optical at spectral resolution R ∼ 4000 by correlating with far-infrared emission from IRAS. Subdividing the sky into 54 deg^2 pixels (HEALPix, NSIDE = 8), we map the variation of the DGL correlation spectrum and nebular emission lines across the DESI footprint in the high-Galactic-latitude sky. The increased data volume over previous SDSS-based analyses enables several new detections in the DGL, including scattering both onto and out of the line of sight from neutral interstellar sodium and potassium. We further detect direct emission from ro-vibrational transitions of molecular hydrogen in the near-infrared with an absolute radiance of 0.65substack+0.13 −0.12×10^−9 erg cm^−2 s^−1 sr^−1, roughly consistent with theoretical expectations, but with an apparent ortho-to-para line ratio that is lower by a factor of 0.60substack+0.28 −0.27. We confirm previous detections of extended red emission (ERE) in the DGL and map its spatial variation. Our spatially resolved DGL maps provide important observational constraints for the radiative transfer efforts that are now possible with recent 3D models of the Milky Way.
ER -