A guided map to the spiral arms in the galactic disk of the Milky Way

Vallée, J. P.

doi:10.1080/21672857.2017.1379459

Cited by 60 publications

(52 citation statements)

References 140 publications

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“…The pattern for HI column densities, which are higher at x < 8 kpc, do not match CaII and NaI for ISM gas as they do for IV gas. The Sun, at x = 8 kpc, is nestled just outside the the Sagittarius spiral arm of the Milky Way, and the elevated HI column density measurements we measure in that direction can be explained by this feature (Vallée 2016(Vallée , 2017. Figure A.2 shows ISM gas component, which again is directly comparable to the IV component results shown in Figure 11.…”

Section: Discussionsupporting

confidence: 77%

Galactic Gas Flows from Halo to Disk: Tomography and Kinematics at the Milky Way’s Disk–Halo Interface

Bish

Werk

Prochaska

et al. 2019

ApJ

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We present a novel absorption line survey using 54 blue horizontal branch stars (BHBs) in the Milky Way halo as background sources for detecting gas flows at the disk-halo interface. Distance measurements to high-latitude (b > 60 • ) background stars at 3.1 -13.4 kpc, combined with unprecedented spatial sampling and spectral resolution, allow us to examine the 3-dimensional spatial distribution and kinematics of gas flows near the disk. We detect absorption signatures of extraplanar CaII and NaI in Keck HIRES spectra and find that their column densities exhibit no trend with distance to the background sources, indicating that these clouds lie within 3.1 kpc of the disk. We calculate covering fractions of f CaII = 63%, f NaI = 26%, and f HI = 52%, consistent with a picture of the CGM that includes multi-phase clouds containing small clumps of cool gas within hotter, more diffuse gas. Our measurements constrain the scale of any substructure within these cool clouds to < 0.5 kpc. CaII and NaI absorption features exhibit an intermediate-velocity (IV) component inflowing at velocities of −75 km/s < v < −25 km/s relative to the local standard of rest, consistent with previously-studied HI structures in this region. We report the new detection of an inflow velocity gradient ∆v z ∼ 6 − 9 km/s/kpc across the Galactic plane. These findings place constraints on the physical and kinematic properties of CGM gas flows through the disk-halo interface, and support a galactic fountain model in which cold gas rains back onto the disk.

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Section: Discussionsupporting

confidence: 77%

Galactic Gas Flows from Halo to Disk: Tomography and Kinematics at the Milky Way’s Disk–Halo Interface

Bish

Werk

Prochaska

et al. 2019

ApJ

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“…gaiadr2 Sagittarius-Carina spiral arms (see e.g. Hou & Han 2014;Vallée 2017). The latter structure is different from the spur seen by Xu et al (2016) that is mostly further away from our map and may be seen as the prolongation of a third group of clouds starting beyond 1.5 kpc (see Fig.…”

Section: Discussion and Perspectivesmentioning

confidence: 63%

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

Lallement

Babusiaux

Vergely

et al. 2019

A&A

344

365

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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.

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“…This could be an issue for a classical density-wave theory where a constant pitch angle is expected in the different spiral arms at least at the same radius. More complicatedly, Vallée (2018) found an offset between the CO x-axis is the direction of the Galactic rotation, and y-axis is the direction from the Galactic center to the Sun. The location of the Local arm defined with HMSFRs is highlighted by a solid black line and the black dashed lines indicate the width of the arm defined in Section 2.2.…”

Section: Summary and Discussionmentioning

confidence: 99%

Stellar Overdensity in the Local Arm in Gaia DR2

Miyachi

Sakai

Kawata

et al. 2019

ApJ

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Using the cross-matched data of Gaia DR2 and 2MASS Point Source Catalog, we investigated the surface density distribution of stars aged ∼1 Gyr in the thin disk in the range of 90 • ≤ l ≤ 270 • . We selected 4,654 stars above the turnoff corresponding to the age ∼1 Gyr, that fall within a small box region in the color-magnitude diagram, (J − K s ) 0 versus M (K s ), for which the distance and reddening are corrected. The selected sample shows an arm-like overdensity at 90 • ≤ l ≤ 190 • . This overdensity is located close to the Local arm traced by high-mass star forming regions (HMSFRs), but its pitch angle is slightly larger than that of the HMSFR-defined arm. Although the significance of the overdensity we report is marginal, its structure poses questions concerning both of the competing scenarios of spiral arms, the density-wave theory and the dynamic spiral arm model. The offset between the arms traced by stars and HMSFRs, i.e., gas, is difficult to be explained by the dynamic arm scenario. On the other hand, the pitch angle of the stellar Local arm, if confirmed, larger than that of the Perseus arm is difficult to be explained with the classical density-wave scenario. The dynamic arm scenario can explain it if the Local arm is in a growing up phase, while the Perseus arm is in a disrupting phase. Our result provides a new and complex picture of the Galactic spiral arms, and encourages further studies.

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A guided map to the spiral arms in the galactic disk of the Milky Way

Cited by 60 publications

References 140 publications

Galactic Gas Flows from Halo to Disk: Tomography and Kinematics at the Milky Way’s Disk–Halo Interface

Galactic Gas Flows from Halo to Disk: Tomography and Kinematics at the Milky Way’s Disk–Halo Interface

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

Stellar Overdensity in the Local Arm in Gaia DR2

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