Skip to main content

Lund University Publications

LUND UNIVERSITY LIBRARIES

Gaia Focused Product Release: Spatial distribution of two diffuse interstellar bands

Schultheis, M. ; Lindegren, L. LU orcid ; Hobbs, D. LU orcid ; McMillan, P.J. LU orcid ; Robert, G. and Zucker, S. (2023) In Astronomy and Astrophysics 680.
Abstract
Diffuse interstellar bands (DIBs) are absorption features seen in optical and infrared spectra of stars and extragalactic objects that are probably caused by large and complex molecules in the galactic interstellar medium (ISM). Here we investigate the Galactic distribution and properties of two DIBs identified in almost six million stellar spectra collected by the Gaia Radial Velocity Spectrometer. These measurements constitute a part of the Gaia Focused Product Release to be made public between the Gaia DR3 and DR4 data releases. In order to isolate the DIB signal from the stellar features in each individual spectrum, we identified a set of 160 000 spectra at high Galactic latitudes (|b| ≥ 65) covering a range of stellar parameters which... (More)
Diffuse interstellar bands (DIBs) are absorption features seen in optical and infrared spectra of stars and extragalactic objects that are probably caused by large and complex molecules in the galactic interstellar medium (ISM). Here we investigate the Galactic distribution and properties of two DIBs identified in almost six million stellar spectra collected by the Gaia Radial Velocity Spectrometer. These measurements constitute a part of the Gaia Focused Product Release to be made public between the Gaia DR3 and DR4 data releases. In order to isolate the DIB signal from the stellar features in each individual spectrum, we identified a set of 160 000 spectra at high Galactic latitudes (|b| ≥ 65) covering a range of stellar parameters which we consider to be the DIB-free reference sample. Matching each target spectrum to its closest reference spectra in stellar parameter space allowed us to remove the stellar spectrum empirically, without reference to stellar models, leaving a set of six million ISM spectra. Using the star's parallax and sky coordinates, we then allocated each ISM spectrum to a voxel (VOlume piXEL) on a contiguous three-dimensional grid with an angular size of 1.8 (level 5 HEALPix) and 29 unequally sized distance bins. Identifying the two DIBs at 862.1 nm (λ862.1) and 864.8 nm (λ864.8) in the stacked spectra, we modelled their shapes and report the depth, central wavelength, width, and equivalent width (EW) for each, along with confidence bounds on these measurements. We then explored the properties and distributions of these quantities and compared them with similar measurements from other surveys. Our main results are as follows: (1) the strength and spatial distribution of the DIB λ862.1 are very consistent with what was found in Gaia DR3, but for this work we attained a higher signal-to-noise ratio in the stacked spectra to larger distances, which allowed us to trace DIBs in the outer spiral arm and beyond the Scutum-Centaurus spiral arm; (2) we produced an all-sky map below ±65 of Galactic latitude to ∼4000 pc of both DIB features and their correlations; (3) we detected the signals of DIB λ862.1 inside the Local Bubble (≲200 pc); and (4) there is a reasonable correlation with the dust reddening found from stellar absorption and EWs of both DIBs with a correlation coefficient of 0.90 for λ862.1 and 0.77 for λ864.8. (Less)
Please use this url to cite or link to this publication:
author
; ; ; ; and
author collaboration
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Dust, extinction, ISM: lines and bands, Geometrical optics, Signal to noise ratio, Stars, Diffuse interstellar bands, Extinction, Interstellar medias, Interstellar medium: line and band, Lines and bands, Product release, Property, Spectra's, Stellar spectra, Stellars, Spatial distribution
in
Astronomy and Astrophysics
volume
680
article number
A38
publisher
EDP Sciences
external identifiers
  • scopus:85180972502
ISSN
0004-6361
DOI
10.1051/0004-6361/202347103
language
English
LU publication?
yes
id
82b4d2e5-7175-4464-8b8f-e3b4346f4a0a
date added to LUP
2024-03-04 14:02:36
date last changed
2024-03-05 13:57:08
@article{82b4d2e5-7175-4464-8b8f-e3b4346f4a0a,
  abstract     = {{Diffuse interstellar bands (DIBs) are absorption features seen in optical and infrared spectra of stars and extragalactic objects that are probably caused by large and complex molecules in the galactic interstellar medium (ISM). Here we investigate the Galactic distribution and properties of two DIBs identified in almost six million stellar spectra collected by the Gaia Radial Velocity Spectrometer. These measurements constitute a part of the Gaia Focused Product Release to be made public between the Gaia DR3 and DR4 data releases. In order to isolate the DIB signal from the stellar features in each individual spectrum, we identified a set of 160 000 spectra at high Galactic latitudes (|b| ≥ 65) covering a range of stellar parameters which we consider to be the DIB-free reference sample. Matching each target spectrum to its closest reference spectra in stellar parameter space allowed us to remove the stellar spectrum empirically, without reference to stellar models, leaving a set of six million ISM spectra. Using the star's parallax and sky coordinates, we then allocated each ISM spectrum to a voxel (VOlume piXEL) on a contiguous three-dimensional grid with an angular size of 1.8 (level 5 HEALPix) and 29 unequally sized distance bins. Identifying the two DIBs at 862.1 nm (λ862.1) and 864.8 nm (λ864.8) in the stacked spectra, we modelled their shapes and report the depth, central wavelength, width, and equivalent width (EW) for each, along with confidence bounds on these measurements. We then explored the properties and distributions of these quantities and compared them with similar measurements from other surveys. Our main results are as follows: (1) the strength and spatial distribution of the DIB λ862.1 are very consistent with what was found in Gaia DR3, but for this work we attained a higher signal-to-noise ratio in the stacked spectra to larger distances, which allowed us to trace DIBs in the outer spiral arm and beyond the Scutum-Centaurus spiral arm; (2) we produced an all-sky map below ±65 of Galactic latitude to ∼4000 pc of both DIB features and their correlations; (3) we detected the signals of DIB λ862.1 inside the Local Bubble (≲200 pc); and (4) there is a reasonable correlation with the dust reddening found from stellar absorption and EWs of both DIBs with a correlation coefficient of 0.90 for λ862.1 and 0.77 for λ864.8.}},
  author       = {{Schultheis, M. and Lindegren, L. and Hobbs, D. and McMillan, P.J. and Robert, G. and Zucker, S.}},
  issn         = {{0004-6361}},
  keywords     = {{Dust; extinction; ISM: lines and bands; Geometrical optics; Signal to noise ratio; Stars; Diffuse interstellar bands; Extinction; Interstellar medias; Interstellar medium: line and band; Lines and bands; Product release; Property; Spectra's; Stellar spectra; Stellars; Spatial distribution}},
  language     = {{eng}},
  publisher    = {{EDP Sciences}},
  series       = {{Astronomy and Astrophysics}},
  title        = {{Gaia Focused Product Release: Spatial distribution of two diffuse interstellar bands}},
  url          = {{http://dx.doi.org/10.1051/0004-6361/202347103}},
  doi          = {{10.1051/0004-6361/202347103}},
  volume       = {{680}},
  year         = {{2023}},
}