Dust extinction map of the Galactic plane based on the UKIDSS survey data

TL;DR

This work tackles the challenge of mapping dust extinction in the Galactic plane where optical surveys underperform due to high column density. It introduces XPNICER, a near-infrared extinction mapping method that fuses PNICER with X percentile background-source selection and leverages Gaia DR3 GSP-Phot intrinsic colors to estimate per-star extinction before constructing 2D maps. The authors apply XPNICER to the UKIDSS/GPS data, delivering high-resolution extinction maps ($30''$–$300''$) over about $1800~\mathrm{deg}^2$, reaching $A_V \sim 30$–$40$ mag with typical per-pixel uncertainty $\sim0.2$ mag and a line-of-sight limiting depth $d_{limit}$ of roughly $2$–$20$ kpc. They validate and contrast their maps against Planck, Green2019, and Zhang2022, highlighting improved resolution and sensitivity to dense dust structures, while acknowledging zero-point and extinction-law systematics. The resulting resources, including uncertainty and background-source density maps, offer a valuable, complementary dust tracer for Galactic studies and star-forming regions, with future gains anticipated from deeper surveys like LSST and JWST under the PROMISE framework.

Abstract

Dust plays a critical role in the study of the interstellar medium (ISM). Extinction maps derived from optical surveys often fail to capture regions with high column density due to the limited photometric depth in optical wavelengths. To address these limitations, we developed the XPNICER method based on near-infrared (NIR) photometric survey data. This method combines the previously established PNICER and Xpercentile techniques, enabling effective mitigation of foreground contamination and improved handling of complex dust structures in the Galactic plane, which thus can provide more accurate extinction estimates, particularly in highly obscured regions. By applying XPNICER to the Galactic Plane Survey from the UKIRT Infrared Deep Sky Survey, we have generated a series of two-dimensional (2D) dust extinction maps that span roughly 1800 deg2 of the Galactic plane (0< l < 110deg and 140< l < 232deg, |b| < 5deg). These maps, with spatial resolutions between 30arcsec and 300arcsec, can trace extinction up to Av ~ 30-40 mag. This new approach offers higher spatial resolution and better detection of high-extinction regions compared to previous large-scale dust-based maps of the Galactic plane, providing an independent and complementary measure of dust column densities.

Figures (12)

• Figure 1: The fraction of reliable cells relative to the total number of cells, denoted as $f_{\mathrm{re}}$, is presented for various cell sizes and $X_0$ configurations in the extinction maps of both the inner and outer Galactic plane. A green solid line marks the threshold of $f_{\mathrm{re}} = 0.95$. Extinction maps with $f_{\mathrm{re}}$ values below this threshold are considered unreliable, as they contain an insufficient number of background sources in some beams.
• Figure 2: The XPNICER extinction maps, associated uncertainty maps, number density maps of background sources, and zero-point offset map obtained using $X_0=$ 80% and $X_1=$ 95% with the spatial resolution of 90 for the Galactic plane area covered by UKIDSS/GPS. The zero-point offset has been subtracted from the extinction map.
• Figure 3: The upper and lower limit of the limiting distance ($d_{\textrm{limit}}$) to which the extinction integrated. Panels a and c show the lower limit ($d_{\textrm{limit,lower}}$) map of inner and outer Galactic plane, respectively. Panel b and d present the upper limit ($d_{\textrm{limit,upper}}$) map of inner and outer Galactic plane.
• Figure 4: Panels a, b, and c display the visual extinction profiles as functions of distance for three sightlines from green2019. The blue points and lines represent these extinction profiles. The minimum and maximum reliable depths ($d_{\textrm{min}}$, $d_{\textrm{max}}$) defined by green2019 are indicated by black dashed vertical lines. Panels a, b, and c illustrate the method used to quantify $d_{\mathrm{limit}}$. As described in the main text, we first estimate the lower and upper bounds of $d_{\mathrm{limit}}$, denoted as $d_{\mathrm{limit,lower}}$ and $d_{\mathrm{limit,upper}}$, respectively. The lower limit ($d_{\mathrm{limit,lower}} = d_{\mathrm{max}}$) is indicated by a vertical black dashed line, while the upper limit is shown by a vertical black dotted line. The horizontal red dotted line represents the integrated extinction ($A_{V, \mathrm{XPNICER}}$) from our XPNICER map along each sightline.In panel a, the horizontal red dotted line intersects the extinction profile from green2019 (shown in blue) within the range [$d_{\mathrm{limit,lower}}$, $d_{\mathrm{limit,upper}}$]. The distance at this intersection is taken as $d_{\mathrm{limit}}$ for that sightline and is marked with a vertical red solid line. In panels b and c, no intersection occurs between $A_{V, \mathrm{XPNICER}}$ and the extinction profiles within the specified range. In these cases, we fit the extinction profile between $d_{\mathrm{min}}$ and $d_{\mathrm{max}}$ (i.e., the section of the blue line bounded by the two vertical black dashed lines) using a linear dust model, as detailed in the main text. The resulting fits are shown as green solid and dashed lines. Where the green dashed line intersects the horizontal red dotted line, we adopt the corresponding distance as $d_{\mathrm{limit}}$, again marked with a vertical red solid line. Panels d and e show the final $d_{\textrm{limit}}$ map in the inner and outer Galactic plane, respectively.
• Figure 5: Zoom-in view of a section in the inner Galactic plane of (a): our $A_V^{60}(X_0=90)$ map; (b): XPNICER extinction map obtained by vvvextmap. We also corrected the zero point offset of this map using the method described in Sect. \ref{['sect:extmap']}; (c): Planck dust map planck-dust-2014; and (d): integrated 3D extinction map obtained by green2019.