Gaia-2MASS 3D maps of Galactic interstellar dust within 3 kpc

Abstract

Gaia stellar measurements are currently revolutionizing our knowledge of the evolutionary history of the Milky Way. 3D maps of the interstellar dust provide complementary information and are a tool for a wide range of uses. We aimed at building 3D maps of the dust in the Local arm and surrounding regions. To do so, Gaia DR2 photometric data were combined with 2MASS measurements to derive extinction towards stars that possess accurate photometry and relative uncertainties on DR2 parallaxes smaller than 20%. We applied to the individual extinctions a new hierarchical inversion algorithm adapted to large datasets and to a inhomogeneous target distribution. Each step associates regularized Bayesian inversions along all radial directions and a subsequent inversion in 3D of all their results. Each inverted distribution serves as a prior for the subsequent step and the spatial resolution is progressively increased. We present the resulting 3D distribution of the dust in a 6 x 6 x 0.8 kpc 3 volume around the Sun. Its main features are found to be elongated along different directions that vary from below to above the mid-plane: the outer part of Carina-Sagittarius, mainly located above the mid-plane, the Local arm/Cygnus Rift around and above the mid-plane and the fragmented Perseus arm are oriented close to the direction of circular motion. The more than 2 kpc long spur (nicknamed the split) that extends between the Local Arm and Carina-Sagittarius, the compact near side of Carina-Sagittarius and the Cygnus Rift below the Plane are oriented along l∼40 to 55 • . Dust density images in vertical planes reveal in some regions a wavy pattern and show that the solar neighborhood within ∼500 pc remains atypical by its extent above and below the Plane. We show several comparisons with the locations of molecular clouds, HII regions, O stars and masers. The link between the dust concentration and these tracers is markedly different from one region to the other.

Local Bubble contribution to the 353-GHz dust polarized emission

“…The distance at which our investigations place the main region of dust-polarization emission is consistent with the thick shell of the LB toward the Galactic caps as revealed by X-ray observations (Puspitarini et al 2014;Liu et al 2017) and recent three-dimensional maps of the local ISM (e.g., Lallement et al 2019;Leike & Enßlin 2019) and the aforementioned estimates. This makes us confident in our claim that the high-latitude dustpolarized emission as observed by Planck at 353-GHz is dominated by the magnetized LB.…”

“…This implies that our conclusion is driven by the northern Galactic hemisphere. However, the LB wall shows prominent chimneys in the north when we consider the 3D extinction maps (e.g., Lallement et al 2019). On the other hand, in the southern hemisphere the 3D extinction maps are more uniform and a continuous wall is more favorable, although there are chimney indications based on the 3D diffuse interstellar-band maps (Bailey et al 2016;Farhang et al 2019).…”

Modeling the magnetized Local Bubble from dust data

“…We first developed an ad-hoc method to determine the LB shell from 3D extinction maps, defining the inner and the outer surfaces of the shell. We applied this method to the most recent 3D extinction maps that allows for a full-sky determination of the distance from the Sun to the surface, namely the maps from Lallement et al (2019) (L19) and from Leike & Enßlin (2019) (LE19).…”

The extended main-sequence turn-off of the Milky Way open cluster Collinder 347

“…For each reference star field CMD, we generated a sample of boxes (Go, (GBP -GRP )o) centred on each star, with sizes (∆(G), ∆(GBP -GRP )) defined in such a way that one of their corners coincides with the closest star in that CMD region. The intrinsic Go magnitudes and (GBP -GRP )o colours where computed from individual E(B − V ) reddenings obtained from the interstellar absorption maps produced by Lallement et al (2019), and the re- (Cardelli et al 1989;Wang & Chen 2019). Lallement et al (2019) used the Gaia DR2 and 2MASS photometric data sets to estimate the extinction towards ∼27 millions carefully selected stars, from which a 3D map of Milky Way interstellar dust within 3 kpc from the Sun was generated.…”

“…3 illustrates the spatial distributions (left panel) and the intrinsic cluster CMD (right panel) of stars with P > 90 per cent, respectively. We have coloured the stars according to the reddening values provided by Lallement et al (2019), which were used to obtain the intrinsic magnitudes and colours. As can be seen, the total differential reddening across the cluster field amounts ∼ 0.14 mag, which represents a spatial reddening variation of ∼ 0.003 mag/pc (= 0.006 mag/arcmin).…”