Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Foreground Extinction to Extended Celestial Objects -- I. New Extinction Maps

G. A. Gontcharov, A. A. Marchuk, S. S. Savchenko, A. V. Mosenkov, V. B. Il'in, D. M. Poliakov, A. A. Smirnov, H. Krayani

TL;DR

The paper addresses the need for accurate foreground extinction estimates toward extended celestial objects by constructing new 2D and 3D maps of $A_ ext{V}$ using Gaia DR3 parallaxes and multi-band photometry for nearly 100 million dwarfs. The 2D map spans the Galactic dust half-layer at $|b|>13^ deg$ with 6.1′ resolution and $σ(A_ ext{V}) \\approx 0.07$ mag, while the 3D map covers up to 2 kpc with a transverse resolution of $3.56$ pc and radial resolution of 50 pc, achieving $σ(A_ ext{V}) \\approx 0.1$ mag. The authors identify and correct major systematics in the input data (isochrone mismatches, metallicity/extinction degeneracy, and selection biases), construct the maps with robust averaging schemes, and validate them against a wide array of extended objects—galaxies, SN Ia, globular and open clusters, and molecular clouds—finding general agreement with literature but notable map-to-map differences likely arising from extinction-law spatial variations. The public data products include comprehensive $A_ ext{V}$ estimates for thousands of extended objects, enabling reliable foreground extinction assessments for extragalactic studies and detailed extinction analyses within the Galactic dust layer. Overall, the work demonstrates that Gaia-based extinction estimates, when properly corrected for systematics, yield highly useful 2D and 3D extinction maps for astrophysical applications, with future Gaia data releases expected to further improve radial resolution.

Abstract

We present a new two-dimensional (2D) map of total Galactic extinction, $A_\mathrm{V}$, across the entire dust half-layer from the Sun to extragalactic space for Galactic latitudes $|b|>13$ deg, as well as a three-dimensional (3D) map of $A_\mathrm{V}$ within 2~kpc of the Sun. These maps are based on $A_\mathrm{V}$ and distance estimates derived from a dataset, which utilizes {\it Gaia} Data Release 3 parallaxes and multi-band photometry for nearly 100 million dwarf stars. We apply our own corrections to account for significant systematics in this dataset. Our 2D map achieves an angular resolution of 6.1~arcmin, while the 3D map offers a transverse resolution of 3.56~pc -- corresponding to variable angular resolution depending on distance -- and a radial resolution of 50~pc. In constructing these maps, we pay particular attention to the solar neighborhood (within 200~pc) and to high Galactic latitudes. The 3D map predicts $A_\mathrm{V}$ from the Sun to any extended object within the Galactic dust layer with an accuracy of $σ(A_\mathrm{V}) = 0.1$~mag. The 2D map provides $A_\mathrm{V}$ estimates for the entire dust half-layer up to extragalactic distances with an accuracy of $σ(A_\mathrm{V}) = 0.07$~mag. We provide $A_\mathrm{V}$ estimates from our maps for various classes of extended celestial objects with angular size primarily in the range of 2--40~arcmin, including 19,809 galaxies and quasars, 170 Galactic globular clusters, 458 open clusters, and several hundreds molecular clouds from two lists. We also present extinction values for 8,293 Type Ia supernovae. Comparison of our extinction estimates with those from previous maps and literature sources reveals systematic differences, indicating large-scale spatial variations in the extinction law and suggesting that earlier 2D reddening maps based on infrared dust emission tend to underestimate low extinction values.

Foreground Extinction to Extended Celestial Objects -- I. New Extinction Maps

TL;DR

The paper addresses the need for accurate foreground extinction estimates toward extended celestial objects by constructing new 2D and 3D maps of using Gaia DR3 parallaxes and multi-band photometry for nearly 100 million dwarfs. The 2D map spans the Galactic dust half-layer at with 6.1′ resolution and mag, while the 3D map covers up to 2 kpc with a transverse resolution of pc and radial resolution of 50 pc, achieving mag. The authors identify and correct major systematics in the input data (isochrone mismatches, metallicity/extinction degeneracy, and selection biases), construct the maps with robust averaging schemes, and validate them against a wide array of extended objects—galaxies, SN Ia, globular and open clusters, and molecular clouds—finding general agreement with literature but notable map-to-map differences likely arising from extinction-law spatial variations. The public data products include comprehensive estimates for thousands of extended objects, enabling reliable foreground extinction assessments for extragalactic studies and detailed extinction analyses within the Galactic dust layer. Overall, the work demonstrates that Gaia-based extinction estimates, when properly corrected for systematics, yield highly useful 2D and 3D extinction maps for astrophysical applications, with future Gaia data releases expected to further improve radial resolution.

Abstract

We present a new two-dimensional (2D) map of total Galactic extinction, , across the entire dust half-layer from the Sun to extragalactic space for Galactic latitudes deg, as well as a three-dimensional (3D) map of within 2~kpc of the Sun. These maps are based on and distance estimates derived from a dataset, which utilizes {\it Gaia} Data Release 3 parallaxes and multi-band photometry for nearly 100 million dwarf stars. We apply our own corrections to account for significant systematics in this dataset. Our 2D map achieves an angular resolution of 6.1~arcmin, while the 3D map offers a transverse resolution of 3.56~pc -- corresponding to variable angular resolution depending on distance -- and a radial resolution of 50~pc. In constructing these maps, we pay particular attention to the solar neighborhood (within 200~pc) and to high Galactic latitudes. The 3D map predicts from the Sun to any extended object within the Galactic dust layer with an accuracy of ~mag. The 2D map provides estimates for the entire dust half-layer up to extragalactic distances with an accuracy of ~mag. We provide estimates from our maps for various classes of extended celestial objects with angular size primarily in the range of 2--40~arcmin, including 19,809 galaxies and quasars, 170 Galactic globular clusters, 458 open clusters, and several hundreds molecular clouds from two lists. We also present extinction values for 8,293 Type Ia supernovae. Comparison of our extinction estimates with those from previous maps and literature sources reveals systematic differences, indicating large-scale spatial variations in the extinction law and suggesting that earlier 2D reddening maps based on infrared dust emission tend to underestimate low extinction values.

Paper Structure

This paper contains 12 sections, 6 equations, 43 figures, 8 tables.

Table of Contents

  1. Introduction
  2. Data
  3. Systematics
  4. Creating Maps
  5. Validation of Our Extinction Maps
  6. Galaxies and SN Ia
  7. Globular clusters
  8. Open clusters
  9. Clouds
  10. Comparison of 2D maps
  11. Conclusions
  12. Additional comparison of various maps

Figures (43)

  • Figure 1: Moving average of $A_\mathrm{V}$ over 301 data points as a function of absolute magnitude $M_G$ for spatial cones centered around five directions, shown by colored curves: red — North Galactic Pole (NGP), blue — South Galactic Pole (SGP), orange — $(l=180\degr,\ b=+45\degr)$, green — $(l=270\degr,\ b=+50\degr)$, purple — $(l=90\degr,\ b=-60\degr)$. For illustration, the original unaveraged data for the NGP direction are shown as black symbols. The light purple curve represents the systematic trend in the $(l=90\degr,\ b=-60\degr)$ direction corrected using Eqs. (\ref{['correction1']}) and (\ref{['correction2']}).
  • Figure 2: Moving average of $A_\mathrm{V}$ over 301 data points as a function of $|Z|$, after accounting for the dependence of $A_\mathrm{V}$ on absolute magnitude $M_G$, for the same five spatial cones shown in Fig. \ref{['fig:mg0_av.eps']}, indicated by the same colors. The colored straight lines represent the systematic trends corrected using Eqs. (\ref{['second1']}) and (\ref{['second2']}).
  • Figure 3: Absolute magnitude $M_G$ as a function of distance $R$ for stars in our sample located within a $4\degr$ cone around the SGP. The red curve shows the moving average computed over 249 points.
  • Figure 4: Total Galactic extinction $A_\mathrm{V}$ as a function of vertical distance $Z$ for anders2022 dwarf stars within a $4\degr$ cone around the NGP: (a) original values; (b) after applying the $M_G$-dependent correction [Eqs.(\ref{['correction1']}) or (\ref{['correction2']})]; (c) after applying the $|Z|$-dependent correction [Eqs.(\ref{['second1']}) or (\ref{['second2']})]; (d) after applying both corrections; (e) after applying the final correction [Eq. (\ref{['third']})]. The red curve represents the moving average over 249 points. The green line indicates the TGE in the direction of the NGP. The sample is extended to 4.2 kpc for illustrative purposes.
  • Figure 5: Histograms showing the distribution of our 2D map cells and 3D map bins by the number of stars they contain. Cells and bins with higher star counts (up to 410 and 447 stars, respectively) are not displayed for clarity.
  • ...and 38 more figures